Conductors, insulators, and electron flow

The electrons of different types of atoms have different degrees of freedom to move around. With some types of materials, such as metals, the outermost electrons in the atoms are so loosely bound that they chaotically move in the space between the atoms of that material by nothing more than the influence of room-temperature heat energy. Because these virtually unbound electrons are free to leave their respective atoms and float around in the space between adjacent atoms, they are often called free electrons.

In other types of materials such as glass, the atoms' electrons have very little freedom to move around. While external forces such as physical rubbing can force some of these electrons to leave their respective atoms and transfer to the atoms of another material, they do not move between atoms within that material very easily.

This relative mobility of electrons within a material is known as electric conductivity. Conductivity is determined by the types of atoms in a material (the number of protons in each atom's nucleus, determining its chemical identity) and how the atoms are linked together with one another. Materials with high electron mobility (many free electrons) are called conductors, while materials with low electron mobility (few or no free electrons) are called insulators.

Here are a few common examples of conductors and insulators:
Conductors:

•     * silver
•     * copper
•     * gold
•     * aluminum
•     * iron
•     * steel
•     * brass
•     * bronze
•     * mercury
•     * graphite
•     * dirty water
•     * concrete

Insulators:

•     * glass
•     * rubber
•     * oil
•     * asphalt
•     * fiberglass
•     * porcelain
•     * ceramic
•     * quartz
•     * (dry) cotton
•     * (dry) paper
•     * (dry) wood
•     * plastic
•     * air
•     * diamond
•     * pure water

It must be understood that not all conductive materials have the same level of conductivity, and not all insulators are equally resistant to electron motion. Electrical conductivity is analogous to the transparency of certain materials to light: materials that easily "conduct" light are called "transparent," while those that don't are called "opaque." However, not all transparent materials are equally conductive to light. Window glass is better than most plastics, and certainly better than "clear" fiberglass. So it is with electrical conductors, some being better than others.

For instance, silver is the best conductor in the "conductors" list, offering easier passage for electrons than any other material cited. Dirty water and concrete are also listed as conductors, but these materials are substantially less conductive than any metal.

It should also be understood that some materials experience changes in their electrical properties under different conditions. Glass, for instance, is a very good insulator at room temperature, but becomes a conductor when heated to a very high temperature. Gases such as air, normally insulating materials, also become conductive if heated to very high temperatures. Most metals become poorer conductors when heated, and better conductors when cooled. Many conductive materials become perfectly conductive (this is called superconductivity) at extremely low temperatures.

While the normal motion of "free" electrons in a conductor is random, with no particular direction or speed, electrons can be influenced to move in a coordinated fashion through a conductive material. This uniform motion of electrons is what we call electricity, or electric current. To be more precise, it could be called dynamic electricity in contrast to static electricity, which is an unmoving accumulation of electric charge. Just like water flowing through the emptiness of a pipe, electrons are able to move within the empty space within and between the atoms of a conductor. The conductor may appear to be solid to our eyes, but any material composed of atoms is mostly empty space! The liquid-flow analogy is so fitting that the motion of electrons through a conductor is often referred to as a "flow."

A noteworthy observation may be made here. As each electron moves uniformly through a conductor, it pushes on the one ahead of it, such that all the electrons move together as a group. The starting and stopping of electron flow through the length of a conductive path is virtually instantaneous from one end of a conductor to the other, even though the motion of each electron may be very slow. An approximate analogy is that of a tube filled end-to-end with marbles:

The tube is full of marbles, just as a conductor is full of free electrons ready to be moved by an outside influence. If a single marble is suddenly inserted into this full tube on the left-hand side, another marble will immediately try to exit the tube on the right. Even though each marble only traveled a short distance, the transfer of motion through the tube is virtually instantaneous from the left end to the right end, no matter how long the tube is. With electricity, the overall effect from one end of a conductor to the other happens at the speed of light: a swift 186,000 miles per second!!! Each individual electron, though, travels through the conductor at a much slower pace.

If we want electrons to flow in a certain direction to a certain place, we must provide the proper path for them to move, just as a plumber must install piping to get water to flow where he or she wants it to flow. To facilitate this, wires are made of highly conductive metals such as copper or aluminum in a wide variety of sizes.

Remember that electrons can flow only when they have the opportunity to move in the space between the atoms of a material. This means that there can be electric current only where there exists a continuous path of conductive material providing a conduit for electrons to travel through. In the marble analogy, marbles can flow into the left-hand side of the tube (and, consequently, through the tube) if and only if the tube is open on the right-hand side for marbles to flow out. If the tube is blocked on the right-hand side, the marbles will just "pile up" inside the tube, and marble "flow" will not occur. The same holds true for electric current: the continuous flow of electrons requires there be an unbroken path to permit that flow. Let's look at a diagram to illustrate how this works:

A thin, solid line (as shown above) is the conventional symbol for a continuous piece of wire. Since the wire is made of a conductive material, such as copper, its constituent atoms have many free electrons which can easily move through the wire. However, there will never be a continuous or uniform flow of electrons within this wire unless they have a place to come from and a place to go. Let's add an hypothetical electron "Source" and "Destination:"

Now, with the Electron Source pushing new electrons into the wire on the left-hand side, electron flow through the wire can occur (as indicated by the arrows pointing from left to right). However, the flow will be interrupted if the conductive path formed by the wire is broken:

Since air is an insulating material, and an air gap separates the two pieces of wire, the once-continuous path has now been broken, and electrons cannot flow from Source to Destination. This is like cutting a water pipe in two and capping off the broken ends of the pipe: water can't flow if there's no exit out of the pipe. In electrical terms, we had a condition of electrical continuity when the wire was in one piece, and now that continuity is broken with the wire cut and separated.

If we were to take another piece of wire leading to the Destination and simply make physical contact with the wire leading to the Source, we would once again have a continuous path for electrons to flow. The two dots in the diagram indicate physical (metal-to-metal) contact between the wire pieces:

Now, we have continuity from the Source, to the newly-made connection, down, to the right, and up to the Destination. This is analogous to putting a "tee" fitting in one of the capped-off pipes and directing water through a new segment of pipe to its destination. Please take note that the broken segment of wire on the right hand side has no electrons flowing through it, because it is no longer part of a complete path from Source to Destination.

It is interesting to note that no "wear" occurs within wires due to this electric current, unlike water-carrying pipes which are eventually corroded and worn by prolonged flows. Electrons do encounter some degree of friction as they move, however, and this friction can generate heat in a conductor. This is a topic we'll explore in much greater detail later.

REVIEW:

• In conductive materials, the outer electrons in each atom can easily come or go, and are called free electrons.
• In insulating materials, the outer electrons are not so free to move.
• All metals are electrically conductive.
• Dynamic electricity, or electric current, is the uniform motion of electrons through a conductor.
• Static electricity is an unmoving (if on an insulator), accumulated charge formed by either an excess or deficiency of electrons in an object. It is typically formed by charge separation by contact and separation of dissimilar materials.
•  For electrons to flow continuously (indefinitely) through a conductor, there must be a complete, unbroken path for them to move both into and out of that conductor.

Static electricity

It was discovered centuries ago that certain types of materials would mysteriously attract one another after being rubbed together. For example: after rubbing a piece of silk against a piece of glass, the silk and glass would tend to stick together. Indeed, there was an attractive force that could be demonstrated even when the two materials were separated:

Glass and silk aren't the only materials known to behave like this. Anyone who has ever brushed up against a latex balloon only to find that it tries to stick to them has experienced this same phenomenon. Paraffin wax and wool cloth are another pair of materials early experimenters recognized as manifesting attractive forces after being rubbed together:

This phenomenon became even more interesting when it was discovered that identical materials, after having been rubbed with their respective cloths, always repelled each other:

It was also noted that when a piece of glass rubbed with silk was exposed to a piece of wax rubbed with wool, the two materials would attract one another:

Furthermore, it was found that any material demonstrating properties of attraction or repulsion after being rubbed could be classed into one of two distinct categories: attracted to glass and repelled by wax, or repelled by glass and attracted to wax. It was either one or the other: there were no materials found that would be attracted to or repelled by both glass and wax, or that reacted to one without reacting to the other.

More attention was directed toward the pieces of cloth used to do the rubbing. It was discovered that after rubbing two pieces of glass with two pieces of silk cloth, not only did the glass pieces repel each other, but so did the cloths. The same phenomenon held for the pieces of wool used to rub the wax:

Now, this was really strange to witness. After all, none of these objects were visibly altered by the rubbing, yet they definitely behaved differently than before they were rubbed. Whatever change took place to make these materials attract or repel one another was invisible.

Some experimenters speculated that invisible "fluids" were being transferred from one object to another during the process of rubbing, and that these "fluids" were able to effect a physical force over a distance. Charles Dufay was one the early experimenters who demonstrated that there were definitely two different types of changes wrought by rubbing certain pairs of objects together. The fact that there was more than one type of change manifested in these materials was evident by the fact that there were two types of forces produced: attraction and repulsion. The hypothetical fluid transfer became known as a charge.

One pioneering researcher, Benjamin Franklin, came to the conclusion that there was only one fluid exchanged between rubbed objects, and that the two different "charges" were nothing more than either an excess or a deficiency of that one fluid. After experimenting with wax and wool, Franklin suggested that the coarse wool removed some of this invisible fluid from the smooth wax, causing an excess of fluid on the wool and a deficiency of fluid on the wax. The resulting disparity in fluid content between the wool and wax would then cause an attractive force, as the fluid tried to regain its former balance between the two materials.

Postulating the existence of a single "fluid" that was either gained or lost through rubbing accounted best for the observed behavior: that all these materials fell neatly into one of two categories when rubbed, and most importantly, that the two active materials rubbed against each other always fell into opposing categories as evidenced by their invariable attraction to one another. In other words, there was never a time where two materials rubbed against each other both became either positive or negative.

Following Franklin's speculation of the wool rubbing something off of the wax, the type of charge that was associated with rubbed wax became known as "negative" (because it was supposed to have a deficiency of fluid) while the type of charge associated with the rubbing wool became known as "positive" (because it was supposed to have an excess of fluid). Little did he know that his innocent conjecture would cause much confusion for students of electricity in the future!

Precise measurements of electrical charge were carried out by the French physicist Charles Coulomb in the 1780's using a device called a torsional balance measuring the force generated between two electrically charged objects. The results of Coulomb's work led to the development of a unit of electrical charge named in his honor, the coulomb. If two "point" objects (hypothetical objects having no appreciable surface area) were equally charged to a measure of 1 coulomb, and placed 1 meter (approximately 1 yard) apart, they would generate a force of about 9 billion newtons (approximately 2 billion pounds), either attracting or repelling depending on the types of charges involved. The operational definition of a coulomb as the unit of electrical charge (in terms of force generated between point charges) was found to be equal to an excess or deficiency of about 6,250,000,000,000,000,000 electrons. Or, stated in reverse terms, one electron has a charge of about 0.00000000000000000016 coulombs. Being that one electron is the smallest known carrier of electric charge, this last figure of charge for the electron is defined as the elementary charge.

It was discovered much later that this "fluid" was actually composed of extremely small bits of matter called electrons, so named in honor of the ancient Greek word for amber: another material exhibiting charged properties when rubbed with cloth. Experimentation has since revealed that all objects are composed of extremely small "building-blocks" known as atoms, and that these atoms are in turn composed of smaller components known as particles. The three fundamental particles comprising most atoms are called protons, neutrons and electrons. Whilst the majority of atoms have a combination of protons, neutrons, and electrons, not all atoms have neutrons; an example is the protium isotope (1H1) of hydrogen (Hydrogen-1) which is the lightest and most common form of hydrogen which only has one proton and one electron. Atoms are far too small to be seen, but if we could look at one, it might appear something like this:

Even though each atom in a piece of material tends to hold together as a unit, there's actually a lot of empty space between the electrons and the cluster of protons and neutrons residing in the middle.

This crude model is that of the element carbon, with six protons, six neutrons, and six electrons. In any atom, the protons and neutrons are very tightly bound together, which is an important quality. The tightly-bound clump of protons and neutrons in the center of the atom is called the nucleus, and the number of protons in an atom's nucleus determines its elemental identity: change the number of protons in an atom's nucleus, and you change the type of atom that it is. In fact, if you could remove three protons from the nucleus of an atom of lead, you will have achieved the old alchemists' dream of producing an atom of gold! The tight binding of protons in the nucleus is responsible for the stable identity of chemical elements, and the failure of alchemists to achieve their dream.

Neutrons are much less influential on the chemical character and identity of an atom than protons, although they are just as hard to add to or remove from the nucleus, being so tightly bound. If neutrons are added or gained, the atom will still retain the same chemical identity, but its mass will change slightly and it may acquire strange nuclear properties such as radioactivity.

However, electrons have significantly more freedom to move around in an atom than either protons or neutrons. In fact, they can be knocked out of their respective positions (even leaving the atom entirely!) by far less energy than what it takes to dislodge particles in the nucleus. If this happens, the atom still retains its chemical identity, but an important imbalance occurs. Electrons and protons are unique in the fact that they are attracted to one another over a distance. It is this attraction over distance which causes the attraction between rubbed objects, where electrons are moved away from their original atoms to reside around atoms of another object.

Electrons tend to repel other electrons over a distance, as do protons with other protons. The only reason protons bind together in the nucleus of an atom is because of a much stronger force called the strong nuclear force which has effect only under very short distances. Because of this attraction/repulsion behavior between individual particles, electrons and protons are said to have opposite electric charges. That is, each electron has a negative charge, and each proton a positive charge. In equal numbers within an atom, they counteract each other's presence so that the net charge within the atom is zero. This is why the picture of a carbon atom had six electrons: to balance out the electric charge of the six protons in the nucleus. If electrons leave or extra electrons arrive, the atom's net electric charge will be imbalanced, leaving the atom "charged" as a whole, causing it to interact with charged particles and other charged atoms nearby. Neutrons are neither attracted to or repelled by electrons, protons, or even other neutrons, and are consequently categorized as having no charge at all.

The process of electrons arriving or leaving is exactly what happens when certain combinations of materials are rubbed together: electrons from the atoms of one material are forced by the rubbing to leave their respective atoms and transfer over to the atoms of the other material. In other words, electrons comprise the "fluid" hypothesized by Benjamin Franklin.

The result of an imbalance of this "fluid" (electrons) between objects is called static electricity. It is called "static" because the displaced electrons tend to remain stationary after being moved from one insulating material to another. In the case of wax and wool, it was determined through further experimentation that electrons in the wool actually transferred to the atoms in the wax, which is exactly opposite of Franklin's conjecture! In honor of Franklin's designation of the wax's charge being "negative" and the wool's charge being "positive," electrons are said to have a "negative" charging influence. Thus, an object whose atoms have received a surplus of electrons is said to be negatively charged, while an object whose atoms are lacking electrons is said to be positively charged, as confusing as these designations may seem. By the time the true nature of electric "fluid" was discovered, Franklin's nomenclature of electric charge was too well established to be easily changed, and so it remains to this day.

Michael Faraday proved (1832) that static electricity was the same as that produced by a battery or a generator. Static electricity is, for the most part, a nuisance. Black powder and smokeless powder have graphite added to prevent ignition due to static electricity. It causes damage to sensitive semiconductor circuitry. While it is possible to produce motors powered by high voltage and low current characteristic of static electricity, this is not economic. The few practical applications of static electricity include xerographic printing, the electrostatic air filter, and the high voltage Van de Graaff generator.

REVIEW:

• All materials are made up of tiny "building blocks" known as atoms.
• All naturally occurring atoms contain particles called electrons, protons, and neutrons, with the exception of the protium isotope (1H1) of hydrogen.
• Electrons have a negative (-) electric charge.
• Protons have a positive (+) electric charge.
• Neutrons have no electric charge.
• Electrons can be dislodged from atoms much easier than protons or neutrons.
• The number of protons in an atom's nucleus determines its identity as a unique element.

HFC (hydrofluorocarbon) Refrigerant

HFC - R23 Trifluoromethane
OIL

• Polyol Ester

Used in very low temperature refrigeration systems, typically on the low stage of a multi-stage system. Has properties similar to R-13 and can be used to replace R-13 in an
existing system. R-23 has higher discharge temperatures than R-13, however, and equipment which is not designed to take this into account may suffer related failures.

Polyol ester (POE) lubricants should be used, and it may still be necessary to charge hydrocarbon oil additives to ensure proper oil return. Check with OEM for specific oil and
charging recommendations.
 

HFC - R134a Tetrafluoroethane
OIL

• Polyol Ester

Application Temperature Range
R-134a performance suffers at lower evaporator temperatures. In general it is not applied at temperatures below -10F, and it is not necessarily the most economical overall choice in some other applications. Traditional R-12 type applications have adopted several products as alternatives, including R-134a, R-22, R-404A/R-507, and numerousretrofit blends.

Lubrication
R-134a requires polyol ester (POE) lubricants, primarily for their ability to mix with HFC refrigerants. Traditional mineral oils and alkylbenzene do not mix with HFCs and will cause compressor failures. In addition, automotive air conditioning systems may also use polyalkaline glycol (PAG) lubricants (not typically seen in stationary equipment). Both POEs and PAGs will absorb moisture, and hold onto it, to a much greater extent than traditional lubricants. The moisture will promote reactions in the lubricant as well as the usual problems associated with water (corrosion, acid formation, etc.). The best way to dry a wet HFC system is to use a filter drier - run the system and change the drier - instead of relying on evacuation to clear the water.

Retrofitting Considerations
Equipment built for R-12 will be sized a bit too small compared to equipment built for R-134a. In order to do the same job an R-134a system will need a larger compressor and larger heat exchangers. As a result a system which is retrofit from R-12 to R-134a will have lower capacity (run longer) and will probably develop higher head pressures (not enough condenser area). The lubricant will also need to be flushed and replaced with POE (residual mineral oil content less than 5%).
 

HFC - R404A Blend: 125/134a/143a 24,100,1300
OIL

• Polyol Ester

A blend of R-125, R-143a, and R-134a intended for low and medium temperature refrigeration applications where R-502 was previously used. Most new equipment has been built for R-404A (and R-507 interchangably). It is also possible to retrofit R-502 systems with R-404A. R-404A has slightly lower pressures than R-507 (from the small amount of R-134a
added), and generally both blends have slightly higher pressures than 502. R-404A requires polyol ester (POE) lubricant, which is usually charged into new equipment. If retrofitting existing equipment the original oil must be flushed and replaced with POE.
 

HFC - R407C Blend: 32/125/134a
 OIL

• Polyol Ester

A blend of R-32, R-125, and R-134a which has very similar properties to R-22 in air conditioning equipment. There is a slight decrease in capacity and efficiency, however R-407C can be used in essentially the same equipment to perform the same job with only minor engineering modifications. It can also be used in medium temp R-22 refrigeration systems. R-407C has a 10F temperature glide. New systems built with R-407C must have POE lubricants, and retrofitted R-22 systems would need the residual oil flushed with POE.
 

HFC - R410A Blend: 32/125
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

A blend of R-32 and R-125 which nearly forms an azeotrope, and therefore has extremely low temperature glide and almost no fractionation potential. This blend has about 60% higher pressure than R-22 in air conditioning applications, and therefore should be used only in new equipment specifically designed to handle the pressure. Systems designed for
R-410A will have smaller components (heat exchangers, compressor, etc.) to perform the same cooling job compared to R-22. R-410A will require POE lubricants. Retrofitting
R-22 equipment is not recommended under any circumstances.

A blend of R-125, R-134a and R-600 (butane), intended for retrofitting R-22 air conditioning and refrigeration systems. Runs slightly lower suction pressure and lower discharge pressure than R-22. There will also be a drop in discharge temperature compared to R-22. Lower pressures can affect valve operation or selection of orifice tube. The blend will produce lower capacity than R-22, especially at lower suction temperatures. Addition of hydrocarbon to the blend improves oil return with mineral oil and alkylbenzene oil, however the lubricant may still separate from the refrigerant. In some applications polyol ester (POE) lubricants may be needed.
 

HFC - R422A
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

R-422A is a low temperature retrofit blend with properties very similar to R-404A. It can directly replace R-502, R-402A/B, R-408A, R-404A and R-507. R-22 low-temp systems can also be retrofitted to R-422A with some component changes (TXVs, for example). With increased regulatory pressure on leakage and recordkeeping of ozone-depleting refrigerants, R-422A offers an HFC-based retrofit solution for R-502 and the HCFC-based low temperature blends.

The hydrocarbon component in R-422A helps promote oil return in systems containing mineral oil or alkylbenzene. Although HFC refrigerants won’t mix with these oils, the hydrocarbon addition thins the oil and keeps it moving around the loop. More complicated piping arrangements or large hold-up volumes may still require some oil be changed to POE.
 

HFC - R422B
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

R-422B (NU-22B) is a retrofit blend from ICOR that is designed to match R-22 in air conditioning and refrigeration applications. No system components need to be changed, nor does the oil need to be flushed, when retrofitting to R-422B. Systems that were previously retrofitted to R-417A (NU-22) can be serviced (topped off) or recharged with R-422B, providing a boost in capacity and run-time properties that more closely match R-22.

The hydrocarbon component in R-422A helps promote oil return in systems containing mineral oil or alkylbenzene. Although HFC refrigerants won’t mix with these oils, the hydrocarbon addition thins the oil and keeps it moving around the loop. More complicated piping arrangements or large hold-up volumes may still require some oil be changed to POE.
 

HFC - R422D Blend: 125/134a/600a
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

R-422D is a low and medium temperature retrofit blend for R-22 refrigeration and air conditioning systems. With properties very similar to R-22, components such as TXVs do not need to be changed. In most cases there will also be no need for an oil change, making R-422D the most economical retrofit solution for R-22 refrigeration systems. Because R-422D has a lower discharge temperature, most low temp R-22 systems will no longer engage the liquid injection module. This will result in significant savings in energy use and a boost in capacity compared to running with R-22.

The hydrocarbon component in R-422D helps promote oil return in systems containing mineral oil or alkylbenzene. Although HFC refrigerants won’t mix with these oils, the hydrocarbon addition thins the oil and keeps it moving around the loop. More complicated piping arrangements or large hold-up volumes may still require some oil be changed to POE.
 

HFC - R507 Blend: 125/143a

OIL

• Polyol Ester

An azeotropic blend of R-125 and R-143a intended for low and medium temeperature refrigeration systems. Similar to R-404A in operation, most new equipment has been rated to use either blend. There will be slightly higher pressures and capacity with R-507 compared to R-404A. Retrofit and lubricant comments are similar to those above.
   

HFC - R508B
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

A blend of R-23 and R-116 intended for very-low-temperature refrigeration systems, typically the low stage of a multi-stage system. R-508B has properties similar to R-503 and can be used to replace either R-13 or R-503 in an existing system. The discharge temperature does not increase significantly compared to R-13, in contrast to the increase seen with R-23. POE lubricants should be used, and it may still be necessary to charge hydrocarbon oil additives to ensure proper oil return. Check with OEM for specific oil and charging recommendations.

HCFC (hydrochlorofluorocarbons) Refrigerant

hydrochlorofluorocarbons (HCFCs), a subclass of chlorofluorocarbon (CFC)

HCFC - R22 Chlorodifluoromethane
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

The dominant refrigerant in residential and commercial air conditioning and some very large centrifugal chillers for air conditioning and industrial process cooling. It has also
been used more in refrigeration since the phaseout of CFCs, both as a pure refrigerant and in blends. R-22 is subject to phaseout in new equipment in 2010 and production ends in 2020.

HCFC - R123 Dichlorotrifluoroethane
OIL

• Mineral
• Alkylbenzene

Replaced R-11 in low pressure centrifugal chillers. New R-123 equipment has been engineered with the correct materials of construction and sized properly for the intended job. Retrofitting existing R-11 chillers to R-123 may require replacement of seals, gaskets, and other system components to obtain the correct operation conditions and prevent leaks.

The ASHRAE safety rating for R-123 is B1, which indicates that lower levels for personal exposure are allowed in normal daily operation and service conditions. Extra precautions
and machinery room requirements must be observed (specific requirements are spelled out in ASHRAE Standard 15, Safety Code for Mechanical Refrigeration).

HCFC - R124 Chlorotetraflouroethane
OIL

• Mineral
• Alkylbenzene

Used in refrigeration blends, primarily those used for R-12 type applications. Also used by itself to replace R-114 in chillers or high ambient air conditioning applications, and
for sterilant gas formulations.

HCFC - R401A Blend: 22/124/152a
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

A blend of R-22, R-152a, and R-124, intended for retrofitting R-12 refrigeration systems. The pressure and system capacity match R-12 when the blend is running in a 10F to 20F evaporator, and there is typically an 8F temperature glide in the evaporator. Applications: direct expansion refrigeration and air conditioning systems designed for R-12 or R-500; good success in any size system, minor adjustment of controls needed. Discharge pressure increases compared to R-12, also slight increase in discharge temperature, however the increases are not as severe as some other retrofit blends. There is a drop in capacity at lower temperatures. R-152a content, an HFC, hurts the miscibility with mineral oil. It is recommended to change some of the oil to alkylbenzene unless the system is small and running at higher evaporator temperatures.

HCFC - R401B Blend: 22/124/152a
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

Similar to R-401A except higher in R-22 content. This blend has higher capacity at lower temperatures (matches R-12 around -30F), and also provides a closer match to R-500 at air conditioning temperatures.

HCFC - R402A Blend: 22/Blend: 125/290 27,110
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

A blend of R-22 and R-125 with hydrocarbon R-290 (propane) included to improve mineral oil compatibility. This blend is formulated to match R-502 in evaporator temperature ranges and does not significantly increase discharge temperature in R-502 retrofit situations. Discharge pressure, however, can increase from 25 to 40 psi over pressures seen with R-502. Although the propane was added to improve oil circulation it is still recommended that some mineral oil be removed and replaced with alkylbenzene.

HCFC - R402B Blend: 22/Blend: 125/290
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

Similar components to R-402A but contains more R-22 and less R-125. This lowers the discharge pressure closer to R-502, however the discharge temperature increases
compared to R-502. This is a benefit in ice machines, where the blend is primarily used, because it improves harvest times. Although propane will improve oil circulation it is
still recommended that some mineral oil be replaced with alkylbenzene.

    
HCFC - R403B
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

A blend of R-22 and R-218 with hydrocarbon R-290 (propane) added to improve oil return. Though this product was originally developed as a replacement for R-502, it has come to be used as an alternative for R-13B1 in single-stage, low-temperature systems.

The evaporator will operate in a vacuum when the low side temperature is below -55F. When existing R-13B1 systems are retrofit to R-403B the capillary tube must be replaced
with a longer/more restrictive size. Similar lubricants can be used for R-403B, with any additives the manufacturer may recommend.

HCFC - R408A Blend: 22/Blend: 125/143a
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

A blend of R-22 and R-143a and R-125 intended for retrofitting R-502 refrigeration systems. This blend has the closest pressure/temperature match to R-502 across the
whole operating range of temperatures. One study suggests higher energy efficiency after retrofit compared to running with R-502. Discharge temperature will increase, however in
most applications this will not impact system performance or long term reliability. In severe duty applications, such as transport refrigeration into hot climates, this blend may not
be recommended by the OEM.

HCFC - R409A Blend: 22/124/142b
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

A blend of R-22, R-142b, and R-124, intended for retrofitting R-12 refrigeration systems. The pressure and system capacity match R-12 when the blend is running in a 10F to 20F evaporator, and there is typically 13F temperature glide in the evaporator. Applications: direct expansion refrigeration and air conditioning systems designed for R-12 or R-500; good success in any size system, minor adjustment of controls needed. Discharge pressure and temperature increases compared to R-12, which may be a problem in
very hot ambient conditions. Capacity holds well into lower application temperatures (-30F). R-409A mixes well with mineral oil down to 0F. As a result it may not be necessary to change oil in systems which do not run colder than 0F in the evaporator (below that alkylbenzene should replace some mineral oil).

HCFC - R414B
OIL

• Mineral
• Alkylbenzene

A blend of R-22, R-124 and R-142b with hydrocarbon R-600a (isobutane) added to improve mineral oil miscibility. This blend can be used to retrofit R-12 automotive air conditioning systems as well as stationary refrigeration systems. The pressure and system capacity match R-12 in 45F to 50F evaporators, and the discharge pressure in hot condensers is only 5 to 10 psi higher than R-12 (a benefit in automotove AC and warmer refrigeration environments). The temperature glide runs about 13F in the evaporator. The addition of isobutane to this blend significantly improves mineral oil compatibility, particularly for high viscosity oils used in auto AC.

HCFC - R416A
OIL

• Mineral
• Alkylbenzene
• Polyol Ester

An R-134a based blend, with R-124 to cut pressure and hydrocarbon R-600 (butane) to improve oil return. This blend matches R-12 pressures at condenser temperatures, and pressures in the evaporator will need to be a few psi lower than R-12 to maintain proper temperature. There is a low temperature glide. Although the blend does not mix with mineral oils the addition of hydrocarbon thins the oil for satisfactory oil return. Systems will experience a loss of capacity, especially at lower temperatures. 

CFCs (chlorofluorocarbon) Refrigerant

A chlorofluorocarbon (CFC) is an organic compound that contains carbon, chlorine, and fluorine, produced as a volatile derivative of methane and ethane

CFC - R11 Tricholorofluoromethane

OIL

• Mineral
• Alkylbenzene

Used in large, low pressure centrifugal chillers. This type of chiller provides a very large amount of chilled water for air conditioning purposes (office buildings, hotels, etc.) at the lowest operating cost compared to any other type of air conditioning system.

R-11 centrifugal chillers operate in a vacuum on the low side. Air which leaks into these systems must be purged, and traditionally this meant that some refrigerant would be lost along with the air. New purge technology and better maintenance practices have reduced
R-11 losses in these systems.

R12 Dichlorodifluoromethane
OIL

• Mineral
• Alkylbenzene

Widely used in a variety of applications from small hermetic refrigeration systems up through large, positive pressure chillers. It has been the long-time industry standard for
automotive air conditioning, high/medium/low temperature refrigeration, and many other commercial and industrial applications.

CFC - R13 Chlorotrifluoromethane

OIL

• Mineral
• Alkylbenzene

Very low temperature refrigeration systems typically operate in two or more stages (cascade type sytems). It would be nearly impossible to achieve low temperatures in a single stage with an inexpensive compressor. The traditional cascade system has a low temperature stage which uses the lower boiling point gas, such as R-13 or R-503, and a high stage which typically uses R-12, R-22, or R-502.

The high stage evaporator provides the correct condensation temperature for the low stage so that compressors in both stages can run at "normal" pressures.

CFC - R13B1

OIL

• Mineral
• Alkylbenzene

Very low temperature refrigeration systems typically operate in two or more stages (cascade type sytems). It would be nearly impossible to achieve low temperatures in a single stage with an inexpensive compressor. The traditional cascade system has a low temperature stage which uses the lower boiling point gas, such as R-13 or R-503, and a high stage which typically uses R-12, R-22, or R-502.

The high stage evaporator provides the correct condensation temperature for the low stage so that compressors in both stages can run at "normal" pressures.

CFC - R113 Thrichlorotrifluoroethane

OIL

• Mineral
• Alkylbenzene

R-113 is used in commercial and industrial air conditioning and industrial water chillers. It is typically employed in an R-11 centrifugal chiller to generate less capacity to better match load conditions. R-113 was widely used as a solvent before being phased out by regulations. It is not possible to use solvent grade 113 for refrigeration purposes because of contaminants or additives used for solvents.

CFC - R114 Dichlorotetrafluoroethane

OIL

• Mineral
• Alkylbenzene

Used in positive pressure centrifugal chillers for air conditioning and industrial process cooling, as well as for air conditioning in very high ambient temperature conditions.
Its very good chemical stability makes it useful in highly corrosive applications, such as for shipboard chillers. Good high temperature stability along with lower vapor pressures
make it a good choice for high ambient air conditioning, for example in steel mill cranes.

CFC - R500 Blend: 12/152a

OIL

• Mineral
• Alkylbenzene

AZEOTROPE: a mixture of two or more refrigerants in which the liquid and vapor have same composition at equilibrium. In addition, the resulting pressure of the mixture is either higher or lower than the pressure of any of the components. Azeotropes behave like pure component refrigerants because there is no change in boiling temperature or shift in composition during phase change, equipment operation, or leakage.

Designed to be a "higher capacity" R-12 type refrigerant, R-500 found some use in air conditioning and dehumidifier equipment and in positive pressure centrifugal chillers.

CFC - R502 Blend: 22/115

OIL

• Mineral
• Alkylbenzene

AZEOTROPE: a mixture of two or more refrigerants in which the liquid and vapor have same composition at equilibrium. In addition, the resulting pressure of the mixture is either higher or lower than the pressure of any of the components. Azeotropes behave like pure component refrigerants because there is no change in boiling temperature or shift in composition during phase change, equipment operation, or leakage.

Developed for use in low temperature refrigeration (the evaporator pressure stays out of vacuum down to -40F). R-502 offers lower discharge temperature and improved capacity compared to R-22. Commercial refrigeration systems can perform low temperature refrigeration in a single stage with relatively inexpensive compressors.

CFC - R503

OIL

• Mineral
• Alkylbenzene

Very low temperature refrigeration systems typically operate in two or more stages (cascade type sytems). It would be nearly impossible to achieve low temperatures in a single stage with an inexpensive compressor. The traditional cascade system has a low temperature stage which uses the lower boiling point gas, such as R-13 or R-503, and a high stage which typically uses R-12, R-22, or R-502.

The high stage evaporator provides the correct condensation temperature for the low stage so that compressors in both stages can run at "normal" pressures.

FAQ An update on refrigerant blends and how to use them

Can I add an HFC or HCFC refrigerant blend on top of the CFC charge in my system?
There is no chemical or legal reason why you can't add an HFC or HCFC refrigerant blend on top of an existing CFC charge, but you'll be left with a mixture of refrigerants with no Pressure Temperature (PT) chart or table of properties to tell you how it should behave. You may also have problems with lubrication or safety if the resulting mixture has a higher pressure than the original refrigerant. Finally, you'll lose the value of the pure CFC refrigerant, and instead create a recycle/reclaim liability in the form of mixed refrigerants.

Do I need to change the oil in my system when I retrofit to a blend?
To begin, HFCs (134a and 404a / 507) MUST have the mineral oil flushed out and replaced with polyolester (POE). Most manufacturers recommend less than 5% residual mineral oil, and in some cases down to 1%. With the retrofit blends (401A, 401B, 402A, 402B, 408A, 409A, and similar blends) the answer isn't as clear. With one exception, compressor manufacturers recommend that some of the mineral oil be changed to either alkylbenzene (AB) or POE (usually 50% or more). On the other hand, some refrigerant manufacturers have made conflicting claims that "no oil change is needed." These are based on oil-refrigerant miscibility tests or measuring oil return in actual systems.

The main concern about lubricant choice is protecting the compressor, which means providing for oil return from the system. The two factors that will affect oil return are chemical mixing of refrigerant and oil and physical system design which promotes "mechanical" oil return. Smaller, warmer-evaporator systems will generally show better oil return than larger, colder-evaporator systems.

Because we generally can't change the system design on a retrofit, the best way to improve oil return is to change the less miscible mineral oil to the more miscible AB or POE. This is true even with R-502, which often has oil return problems. Generally, the more mineral oil changed, the better the oil return.

Given the properties of the refrigerant/oil-type mixture, and after reviewing the system design, the contractor or technician should be able to decide how much, if any, of the oil should be changed.

Why are there so many refrigerant blends? Why don't the chemical producers get together to supply one or two refrigerant blend options?
Each refrigerant manufacturer has tried to differentiate itself by blending a technically better alternative refrigerant. Actually, most blends fall into a few categories and types. There are CFC-12 retrofit blends, and R-502 retrofit blends. The CFC-12 type blends either match CFC-12 in automotive A/C (hot) conditions, or refrigeration conditions. A few "low-temp" CFC-12 blends are available as well. Then there are the longer-term HFC blends for CFC-12, R-502, and HCFC-22 applications. The blends in any given category/ temperature range are very similar in properties, behavior, and they all present the same challenges such as fractionation (composition change).

Will a perfect drop-in be developed? A refrigerant blend that requires no oil change, no glide, or fractionation? Something that has better capacity and efficiency, and that won't require adjustments to the system?
No. We've mixed it all and haven't found a perfect blend. Each blend has advantages and disadvantages which must be balanced to pick the best overall choice for your specific application. Although certain blends can be used in some applications with little or no changes, you should at least check the glide, oil miscibility, and performance properties for problems.

What is the proper charging method for refrigerant blends? If I charge by liquid, won't I slug my compressor?
In a cylinder, a zeotropic blend will have a different vapor composition sitting above the bulk of the liquid. If you remove this vapor, you will: 1) take the wrong composition refrigerant out of the cylinder, and 2) leave behind the wrong composition refrigerant for future use. Liquid must be removed from the cylinder in order to avoid this fractionation effect. Somewhere between the cylinder and the compressor the liquid refrigerant should be flashed to vapor to avoid slugging. This can be done, for example, by just cracking open the valve on the gauge set while charging.

If I am putting in the whole refrigerant bottle, can I feed vapor then?
You can feed vapor, however, at any point in time the compressor will be seeing the wrong composition gas. At first the vapor will be rich in the higher pressure, higher capacity component. This will cause high discharge pressure and temperature, high motor amps, etc. As the cylinder empties, the compressor will see the lower capacity gas which is left behind, changing the operating conditions the other way.

It will take some time for the "locally fractionated" gas to get mixed back into the original composition. Besides, if you need to charge the whole bottle, it's faster to put it in as a liquid.

If a blend leaks out of the system, will I need to pull the remaining charge and recharge, or can I top-off the existing charge after repairs?
It depends. Studies were done a few years ago to show how higher glide blends behave during leakage and they showed significant fractionation, which affected the properties of the blend. When the system was topped off, the properties came back close to original. The cycle was repeated to see how many times the system could leak before topping off became a problem (the recommendation was not more than five). These studies were done on containers at rest, which promotes the worst case of fractionation.

Another study was performed recently on a system running full time, then cycling normally (2/3 on, 1/3 off), which found that the blend did not fractionate when the refrigerant is moving around inside, and not much fractionation occurred when cycling. Low-glide blends didn't show much fractionation in any case.

What this means is that running systems found to be low on charge have probably not fractionated the blend much, and can be repaired and recharged directly. If the system has been off for a long period (more than a day) and found to have leaked (worst case is about half the charge), it's probably better to pull what's left and charge with fresh, unless very little is gone, or very little is left. Low-glide blends won't cause any fractionation-related problems.

Why do bubbles appear in the sight glass when I use a blend? Does this mean I don't have enough refrigerant?
There are several reasons for bubbles in the sight glass. If one of the traditional refrigerants showed vapor in the sight glass it often meant there wasn't enough liquid refrigerant being fed to the valve, and more refrigerant was added to the system.

Blends could show flashing for the same reason, however, they can also flash when there is plenty of liquid in the receiver. Ironically, this liquid in the receiver could be causing the problem, particularly when the equipment is in a hot environment. Blends will come out of the condenser slightly subcooled - at a temperature below the saturated temperature of the blend at the existing high side pressure.

Yet when the blend sits in the receiver, it can "locally fractionate," or change composition slightly by shifting one of the components into the vapor space of the receiver. This will effectively produce a saturated liquid in the receiver, at the same pressure you had before, which flashes when it hits the expanded volume of the sight glass. In most cases these bubbles will collapse when the blend gets back into the tubing which feeds the valve, and the system will operate just fine.

Check other system parameters such as pressures, superheat and amperage to confirm whether you have the right charge. Don't rely solely on the sight glass.

What do "bubble point" and "dewpoint" mean?
A single component refrigerant always had a "boiling point." Zeotropic blends change composition when they boil or condense, and therefore have a continuously changing boiling point. The most useful temperatures to know are where the boiling starts and ends. Bubble point and dewpoint are terms used in the chemical industry to define these two temperatures.

Bubble point is the temperature where the saturated liquid starts to boil off its first "bubble" of vapor. (Picture a pot of liquid with the first bubbles starting to appear.) It is also called the "liquid side temperature/ pressure relationship." Dewpoint is the temperature where saturated vapor first starts to condense, or the last drop of liquid evaporates. (Picture a room full of vapor with a few drops forming on the ceiling.) This is also called the "vapor side temperature/ pressure relationship."

Why are there two columns on a PT chart, and how are they used?
The two columns on the PT chart give the liquid and vapor pressures at the listed temperatures. Single component refrigerants and azeotropic blends have bubble points and dewpoints equal to each other, and we simply call this the boiling point. When there is only one column on the PT chart, lowglide blends would have very similar numbers in the two columns, and often the PT chart will only have one column as well for them.

How a two-column PT chart is used is straightforward. Most times you're interested in knowing the saturated temperature of the refrigerant at the system pressure, so you can compare it to a measurement you're making on the system (for example, to check a superheat or subcool setting). Simply keep track of the condition of the refrigerant where you're measuring, and cross-reference the same side of the PT chart.

Superheat measurements check the line temperature of superheated refrigerant vapor coming out of the evaporator versus the saturated vapor temperature, so you would use the vapor side of the PT chart.

Subcool measurements check the temperature of subcooled liquid refrigerant coming out of the condenser versus the saturated liquid temperature, so you would use the liquid side of the PT chart.

ALTERNATIVE REFRIGERANT TERMINOLOGY

Alkyl Benzene Oil - A synthetic refrigeration oil commonly known as Zerol.

Alternative Refrigerant - any of a number of refrigerants or refrigerant mixtures designed to replace the current CFC or HCFC refrigerants.

Azeotrope - A mixture made up of two or more refrigerants with similar boiling points that act as a single fluid. The components of azeotropic mixtures will not separate under normal operating conditions and can be charged as a vapor or liquid.

CFC Refrigerant - CFC refers to the chemical composition of the refrigerant. ChloroFluoroCarbon indicates that the refrigerant is comprised of Chlorine, Fluorine, and Carbon. Common CFC refrigerants are R11, 12,13,113,114, and 115.

Drop-In Replacement - An alternative refrigerant that can be installed directly into an existing system with minor equipment changes. Most interim alternatives fall into this category.

Ester Oil - A general term that applies to a family of synthetic refrigeration oils based on the chemistry of polyol esters. Ester oils are generally regarded as the oil to use with most of the alternative refrigerants. Ester oils are generally compatible with existing mineral oils, and system components. Ester oils are slightly hygroscopic and should be in non-porous containers.

Forane - Atochem trade name for alternative refrigerants.

Global Warming Potential - Global warming occurs when solar energy penetrates the atmosphere and the resultant infrared energy from the earth's surface is absorbed by certain gases and not allowed to leave. This process is commonly known as the greenhouse effect. Refrigerants are normally rated on a scale from 1 to 10.

HCFC Refrigerant - HCFC refers to the chemical composition of the refrigerant. HydroChloro-Fluoro-Carbon indicates that the refrigerant is comprised of Hydrogen, Chlorine, Fluorine, and Carbon. Common HCFC refrigerants are R22.

HFC Refrigerant - HFC refers to the chemical composition of the refrigerant. HydroFluoroCarbon indicates that the refrigerant is comprised of Hydrogen, Fluorine, and Carbon. Common HFC refrigerants are R134a.

High Pressure Refrigerants (HP) - A term used for some alternative refrigerants designed to operate in the low temperature (-35° F to 0° F) range.

Hygroscopic - A tendency for refrigeration oils to absorb moisture from the atmosphere.

Interim Replacements (SHORT TERM) - Any of a number of refrigerants intended to serve as an intermediate solution during the transition from CFC to HFC refrigerants. Most interim replacements contain HCFC refrigerants like R22.

Klea - I.C.I. Company trade name for alternative refrigerants.

Long Term Replacements - Alternative refrigerants that are considered to have no adverse affect on the stratospheric ozone layer. Most long term replacements are HFC compounds.

Medium Pressure Refrigerant (MP) - A term used for some alternative refrigerants designed to operate in the medium temperature (0° F to 4° F) range.

Mineral Oil - Refrigeration oil currently in use but is not compatible with most of the alternative refrigerants. Refrigerant conversions often require. a procedure for the removal of existing mineral oil because of the incompatibility with alternative refrigerants.

Near Azeotrope - A mixture made up of two or more refrigerants with different boiling points that, when in a totally liquid or vapor state, act as one component. However, when changing from vapor to liquid or liquid to vapor, the individual refrigerants -evaporate or condense at different temperatures. Near-azeotropic mixtures have a temperature glide (see below) of less than 10° F and should be charged in the liquid state to assure proper mixture (non-azeotropic) composition.

Ozone Depletion Potential (ODP) - This is a relative indication of the effect of the chlorine in CFC's on breaking down the ozone layer. It is measured on a scale from 0 to 1 with 0 being non-depleting and 1 being the highest depleting.

P.A.G. Oil - A general term that applies to a family of synthetic oils based on the chemistry of Polyalkyline Glycols. The primary application of P.A.G. oils will be for automotive air conditioning.

Suva - DuPont Company trade name for alternative refrigerants, replaces the Freon trade name.

Temperature Glide - the temperature difference that occurs between the vapor state and liquid state during evaporation or condensation at constant pressure, i.e. the temperature in the evaporator and condenser is not constant. Temperature glide occurs in near-azeotropic and zeotropic mixtures.

Zeotrope - A mixture made up of two or more refrigerants with different boiling points. Zeotropic mixtures are similar to near-azeotropic mixtures with the exception of having a temperature glide greater than 10° F. Zeotropic mixtures should be charged in the liquid state.