Chillers

Introduction

Chillers are a key component of air conditioning systems for large buildings. They produce cold water to remove heat from the air in the building. They also provide cooling for process loads such as file-server rooms and large medical imaging equipment. As with other types of air conditioning systems, most chillers extract heat from water by mechanically compressing a refrigerant.

Chillers are complex machines that are expensive to purchase and operate. A preventive and predictive maintenance program is the best protection for this valuable asset.

Learn more about establishing a Best Practice O&M Program.

Chillers commonly use more energy than any other piece of equipment in large buildings. Maintaining them well and operating them smartly can yield significant energy savings.

 Chiller and associated HVAC systems

Types of Chillers

Mechanical Compression
During the compression cycle, the refrigerant passes through four major components within the chiller: the evaporator, the compressor, the condenser, and a flow-metering device such as an expansion valve. The evaporator is the low-temperature (cooling) side of the system and the condenser is the high-temperature (heat-rejection) side of the system.

 The refrigeration cycle

Mechanical Compressor Chillers

Mechanical compression chillers are classified by compressor type: reciprocating, rotary screw, centrifugal and frictionless centrifugal.

Reciprocating: Similar to a car engine with multiple pistons, a crankshaft is turned by an electric motor, the pistons compress the gas, heating it in the process. The hot gas is discharged to the condenser instead of being exhausted out a tailpipe. The pistons have intake and exhaust valves that can be opened on demand to allow the piston to idle, which reduces the chiller capacity as the demand for chilled water is reduced. This unloading allows a single compressor to provide a range of capacities to better match the system load. This is more efficient than using a hot-gas bypass to provide the same capacity variation with all pistons working. Some units use both methods, unloading pistons to a minimum number, then using hot-gas bypass to further reduce capacity stably. Capacities range from 20 to 125 tons.

 Reciprocating compressor

Rotary Screw: The screw or helical compressor has two mating helically grooved rotors in a stationary housing. As the helical rotors rotate, the gas is compressed by direct volume reduction between the two rotors. Capacity is controlled by a sliding inlet valve or variable-speed drive (VSD) on the motor. Capacities range from 20 to 450 tons.

Screw compressor

Centrifugal: The centrifugal compressor operates much like a centrifugal water pump, with an impeller  compressing the refrigerant. Centrifugal chillers provide high cooling capacity with a compact design. They can be equipped with both inlet vanes and variable-speed drives to regulate control chilled water capacity control. Capacities are 150 tons and up.

Centrifugal compressor

Frictionless Centrifugal: This highly energy-efficient design employs magnetic bearing technology. The compressor requires no lubricant and has a variable-speed DC motor with direct-drive for the centrifugal compressor. Capacities range from 60 to 300 tons.

Turbocor© frictionless centrifugal compressor

Absorption Chillers

Absorption chillers use a heat source such as natural gas or district steam to create a refrigeration cycle that does not use mechanical compression. Because there are few absorption machines in the Northwest U.S., this document covers only mechanical-compression chillers. You can learn more about absorption chillers at the Energy Solutions Center.
Key Components of Mechanical Compression Chillers
Evaporator

Chillers produce chilled water in the evaporator where cold refrigerant flows over the evaporator tube bundle. The refrigerant evaporates (changes into vapor) as the heat is transferred from the water to the refrigerant. The chilled water is then pumped, via the chilled-water distribution system to the building’s air-handling units.

The chilled water passes through coils in the air-handler to remove heat from the air used to condition spaces throughout the building. The warm water (warmed by the heat transferred from the building ventilation air) returns to the evaporator and the cycle starts over.
 
Compressor
Vaporized refrigerant leaves the evaporator and travels to the compressor where it is mechanically compressed, and changed into a high-pressure, high-temperature vapor. Upon leaving the compressor, the refrigerant enters the condenser side of the chiller.
Condenser

Inside the water-cooled condenser, hot refrigerant flows around the tubes containing the condenser-loop water. The heat transfers to the water, causing the refrigerant to condense into liquid form. The condenser water is pumped from the condenser bundle to the cooling tower where heat is transferred from the water to the atmosphere. The liquid refrigerant then travels to the expansion valve.

The refrigerant flows into the evaporator through the expansion valve or metering device. This valve controls the rate of cooling. Once through the valve, the refrigerant expands to a lower pressure and a much lower temperature. It flows around the evaporator tubes, absorbing the heat of the chilled water that’s been returned from the air handlers, completing the refrigeration cycle.

Controls
Newer chillers are controlled by sophisticated, on-board microprocessors. Chiller control systems include safety and operating controls. If the equipment malfunctions, the safety control shuts the chiller down to prevent serious damage to the machine. Operating controls allow adjustments to some chiller operating parameters. To better monitor chiller performance, the chiller control system should communicate with the facility’s direct digital control (DDC).
Safety Issues

Chillers are typically located in a mechanical equipment rooms. Each type of refrigerant used in a chiller compressor has specific safety requirements for leak detection and emergency ventilation. Consult your local mechanical code or the International Mechanical Code for details.

The EPA has enacted regulations regarding the use and handling of refrigerants to comply with the Clean Air Act of 1990. All personnel working with refrigerants covered by this act must be appropriately licensed.
Best Practices for Efficient Operation

The following best practices can improve chiller performance and reduce operating costs:

Operate multiple chillers for peak efficiency: Plants with two or more chillers can save energy by matching the building loads to the most efficient combination of one or more chillers. In general, the most efficient chiller should be first one used.

Raise chilled-water temperature: An increase in the temperature of the chilled water supplied to the building’s air handlers will improve its efficiency. Establish a chilled-water reset schedule. A reset schedule can typically adjust the chilled-water temperature as the outside-air temperature changes. On a centrifugal chiller, increasing the temperature of chilled water supply by 2–3°F will reduce chiller energy use 3–5%.

Reduce condenser water temperature: Reducing the temperature of the water returning from the cooling tower to the chiller condenser by 2–3°F will reduce chiller energy use 2–3%. The temperature setpoint for the water leaving the cooling tower should be as low as the chiller manufacturer will allow for water entering the condenser. The actual leaving tower water temperature may be limited by the ambient wet bulb temperature.

Purge air from refrigerant: Air trapped in the refrigerant loop increases pressure at the compressor discharge. This increases the work required from the compressor. Newer chillers have automatic air purgers that have run-time meters. Daily or weekly tracking of run time will show if a leak has developed that permits air to enter the system.

Optimize free cooling: If your system has a chiller bypass and heat exchanger, known as a water-side economizer, it should be used to serve process loads during the winter season. The water-side economizer produces chilled water without running the chiller. Condenser water circulates through the cooling tower to reject heat, and then goes to a heat exchanger (bypassing the chiller) where the water is cooled sufficiently to meet the cooling loads.

Verify Performance of hot-gas bypass and unloader: These are most commonly found on reciprocating compressors to control capacity. Make sure they operate properly.

Maintain refrigerant level: To maintain a chiller's efficiency, check the refrigerant sight-glass and the superheat and subcooling temperature readings, and compare them to the manufacturer’s requirements. Both low-level and high-level refrigerant conditions can be detected this way. Either condition reduces a chiller’s capacity and efficiency.

Maintain a daily log: Chiller O&M best practices begin with maintaining a daily log of temperatures, fluid levels, pressures, flow rates, and motor amperage. Taken together, these readings serve as a valuable baseline reference for operating the system and troubleshooting problems. Many newer chillers automatically save logs of these measurements in their on-board control system, which may be able to communicate directly with the DDC system. Below is an example of a daily log that can be adapted for use with your chiller.

Best Practices for Maintenance

Compared to a major chiller failure, a sound preventive and predictive maintenance program is a minor cost. Implementing a best-practice maintenance plan will save money over the life of the chiller and ensure longer chiller life. For more information on this topic go to Best Practice O&M Program.

Substandard operating practices frequently go unnoticed and become the accepted norm. Training personnel in both maintenance and operating practices is the best prevention. Many chiller manufacturers offer training for building operating engineers in operating and maintaining their chillers.

To effectively maintain chillers, you must 1) bring the chiller to peak efficiency, and 2) maintain that peak efficiency. There are some basic steps that facilities professionals can take to make sure their chillers are being maintained properly. Below are some of the key practices.
Reduce Scale or Fouling

Failure of the heat exchanger tubes is costly and disruptive. The evaporator and condenser tube bundles collect mineral and sludge deposits from the water. Scale buildup promotes corrosion that can lead to the failure of the tube wall. Scale buildup also insulates the tubes in the heat exchanger reducing the efficiency of the chiller. There are two main preventive actions:

Checking water treatment: Checking the water treatment of the condenser-water open loop weekly will reduce the frequency of condenser tube cleaning and the possibility of a tube failure.

Learn more about Operation and Maintenance of Cooling Towers.

Checking the water treatment of the chilled-water closed loop monthly will reduce the frequency of evaporator tube cleaning and the possibility of a tube failure.

Inspecting and cleaning tubes: The tubes in the evaporator and condenser bundles should be inspected once a year, typically when the chiller is taken offline for winterizing. Alternately, for systems that operate all year to meet process loads, tube scaling and fouling can be monitored by logging pressure drop across the condenser and evaporator bundles. An increase in pressure from the inlet to the outlet of 3–4 PSI indicates a probable increase in scale or fouling requiring tube cleaning.
Inspect for Refrigerant Leaks

If possible, monitor the air-purge run timer. Excessive or increased air-purge time may indicate a refrigerant leak. If an air-purge device is not installed, bubbles in the refrigerant sight-glass may also indicate refrigerant leak. Gas analyzers can also be used to identify refrigerant leaks.

The table below provides a checklist for maintenance tasks.

Maintenance Schedule for Chillers
Description	Comments	Maintenance Frequency
Fill out daily log	Check all setpoints for proper setting and function. Make sure there are no unusual sounds and the space temperature is acceptable.	Daily (4x)
Chiller use/sequencing	Turn off or sequence unnecessary chillers	Daily
Check chilled water reset settings and function	Check settings for approved sequence of operation at the beginning of each cooling season	Annually
Check chiller lockout setpoint	Check settings for approved sequence of operation at the beginning of each cooling season	Annually
Clean evaporator and condenser tubes	Indicated when pressure drop across the barrel (tube bundle) exceeds manufacturer's recommendations, but at least annually.	Annually
Verify motor amperage load limit	Motor amperage should not exceed manufacturer's specification	Annually
Compressor motor and assembly	Conduct vibration analysis: Check all alignments to specifications. Check all seals. Lubricate where necessary.	Annually
Compressor oil system	Perform analysis on oil and filter. Change if necessary. Check oil pump and seals Check oil heater and thermostat Check all strainers, valves, etc.	Annually
Electrical connections	Check all electrical connections and terminals for full contact and tightness	Annually
Check refrigerant condition	Add refrigerant if low. Record amounts and address leakage problems.	Annually
Check for condenser and evaporator tube corrosion and clean as needed.	Indications include: poor water quality, excessive fouling, and age of chiller. Eddy current testing may be done to assess tube condition.	As needed

HVAC Jobs and Careers

High Performance HVAC Jobs and Careers

hvac careers, hvac jobs, hvac booksSo you want to become an HVAC Technician and want to know how to find a successful career in HVAC? It’s not easy but here’s some help for you. First of all you need a good foundation of the basics and it would help if you understood the different types of HVAC jobs you can find by pursuing a career in HVAC. The HVAC education foundation will take you very far. To get this HVAC foundation you need to study and read. Burn those HVAC books up and study so that you can understand basic HVAC principles. Take some courses at the local university or trade school and find yourself a job working for an HVAC company. The HVAC books will help you with theory in temperature relationships (Basic physics) and electrical theory which is important to understand if you want go far in the field of HVAC.

There are different jobs within HVAC that you will to know about to give you a better idea of what you want to do within the HVAC job field. There the HVAC installation technicians. These HVAC technicians install the HVAC systems for residential and commercial applications. These HVAC technicians must understand electrical and mechanical things. From the circuit breaker box to the HVAC equipment they are installing they need to understand how to run the wire, what size of wire to use, and the proper breaker to use for the job. It is not a bad idea to check with an electrician or experienced HVAC technician before sizing wires for an installation job. An HVAC installer must also work with sheet metal and duct work for forced air systems an install piping for refrigeration, hot water and chilled water systems. It is important to know the right type of sheet metal to use for the duct work and the right kind of pipe to use for the refrigeration hot water and chilled water systems. An HVAC theory book will help you understand the different types of piping and sheet metal available and what to use in certain HVAC installation applications.

Another job within the HVAC field is the HVAC service technician. These HVAC technicians need to have a very good understanding of the whole system, how it operates, the HVAC control sequence of operation, and how to deal with customers many of which can be difficult to deal with especially if their HVAC equipment is not working properly. Many HVAC service technicians start off their HVAC career as HVAC installers and work their way into HVAC service. The build their HVAC knowledge foundation at a trade school and by working to install the systems and ask a lot of questions about the systems they are working with and installing. This gives them the knowledge and experience to service and repair the HVAC equipment they are responsible for maintaining. As an HVAC service technician it will also be good to understand troubleshooting techniques because it will be necessary to solve problems with the HVAC equipment if you want an HVAC career as an HVAC service technician.

Other HVAC jobs within the HVAC career field include HVAC sales and HVAC management jobs. These jobs are usually filled by the experienced HVAC service technicians and HVAC installers who work hard to learn all they can learn in HVAC. A good HVAC career starts with learning all you can on HVAC basics and taking some courses at your local university. Get yourself an HVAC manual and start studying.

Mesothelioma

Mesothelioma is a rare type of cancer that primarily affects the lining of the lungs, but can also affect the heart and abdomen. Approximately 2,000 to 3,000 cases of mesothelioma are diagnosed each year in the United States, comprising around 3 percent of all cancer diagnoses. This cancer occurs about four times more frequently in men than in women and all forms of mesothelioma, except for benign mesothelioma, are terminal since there is no cure.

The life expectancy for mesothelioma patients is generally reported as less than one year following diagnosis, however a patient’s prognosis is affected by numerous factors including how early the cancer is diagnosed and how aggressively it is treated.

Mesothelioma is caused by asbestos exposure  which occurs when fibers are inhaled or ingested into the body and become lodged in body cavities, causing inflammation or infection. Asbestos is a naturally-occurring fibrous substance that was widely used in the 20th century in a number of different industries. When the public became aware of the hazards associated with the mineral, warnings were issued in the mid-1970s and use of the product began to decline.

More than 30 percent of those diagnosed with mesothelioma are veterans. Please visit the page on asbestos for additional information about the mineral.

Mesothelioma Types

There are five known types of mesothelioma. The four listed below are malignant cancers, and benign mesothelioma is a non-cancerous condition.

Pleural Mesothelioma:  This type of mesothelioma develops in the lining of the lungs, known as the pleura. It is the most common form of malignant mesothelioma, with around 75 percent of cases being pleural in origin.

Peritoneal Mesothelioma: Comprising approximately 20 percent of mesothelioma cases, this form of mesothelioma develops in the lining of the abdominal cavity, known as the peritoneal membrane.

Pericardial Mesothelioma: This form of mesothelioma develops in the lining of the heart, known as the pericardium. Approximately 5 percent of all mesothelioma cases are pericardial.

Testicular Mesothelioma: Testicular mesothelioma develops in the tunica vaginalis of the testicles and is the rarest form of the cancer.

Mesothelioma Symptoms

Symptoms of mesothelioma often do not appear for 20 to 50 years after initial exposure to asbestos occurred. Mesothelioma symptoms often resemble less-serious conditions, which can make a diagnosis of mesothelioma difficult. Below is a list of several common symptoms mesothelioma patients may experience.

Pleural Symptoms: Shortness of breath, chest pain, persistent cough, fatigue, lumps under the skin on the chest

Peritoneal Symptoms: Weight loss, abdominal pain and swelling, bowel obstruction, nausea

Pericardial Symptoms: Heart palpitations, irregular heartbeat, chest pain, difficulty breathing, night sweats

Testicular Symptoms: Painful or painless testicular lumps

After a patient begins to demonstrate mesothelioma symptoms and a diagnosis occurs, the next step is often exploring applicable treatment options to create the best treatment plan possible. Treatment options range from surgery to chemotherapy

Mesothelioma Diagnosis

The process of mesothelioma diagnosis usually begins with a review of a patient’s medical history followed by a physical examination.

If a problem is suspected, a doctor may request several diagnostic tests. These typically include medical imaging scans such as:

    * X-rays
    * CT scans
    * PET scans
    * MRI scans

A combination of these tests is often used to determine the location, size and type of the cancer. Biopsy procedures are often requested following an imaging scan to test samples of fluid and tissue for the presence of cancerous cells.

Mesothelioma Treatments

The most common mesothelioma treatments recommended by doctors for patients include surgery, chemotherapy and radiation  therapy. Patients often undergo multiple treatments to combat the disease, which is known as multimodality therapy. The combination of aggressive treatments helps to combat the cancer in various ways, helping to improve the patient's life expectancy.

Experimental procedures, such as immunotherapy, photodynamic therapy and gene therapy are also utilized by mesothelioma patients. However, since these treatments are still in the experimental stage, they are typically only available through clinical trials.

Recent clinical trials on mesothelioma have investigated photodynamic therapy and immunotherapy, both finding resutls that warrent further research. Patients who participate in a clinical trial contribute to the discovery of a mesothelioma cure through testing up-and-coming procedures and medications.
Mesothelioma Legal Issues

he dangers of asbestos exposure were known long before any efforts were made to protect workers. Thousands of American workers were exposed to asbestos during the 20th century, and were often unaware of the hazards of exposure.

Companies that produced asbestos-containing products or used these products on a daily basis are liable for their negligence in failing to protect their workers. If you or a loved one has developed mesothelioma or another asbestos-related disease as a result of asbestos exposure

Mesothelioma Life Span

The life span of those diagnosed with mesothelioma is typically poor due to the severe latency period associated with the disease. In most cases, patients do not experience symptoms until at least 20 years have passed since the initial exposure to asbestos occurred, resulting in a late diagnosis. Another reason for the poor life span is the fact that there is no definitive cure. However, many patients elect to undergo treatment to combat the cancer, improve their quality of life and relieve symptoms.
Improving Life Span

The average life span for a newly-diagnosed mesothelioma patient ranges from four to 18 months. While treatments are commonly used to help with symptoms and provide comfort, they can also be utilized to prolong the length of a patient’s life.  One such treatment is radiation therapy, which is used to slow the spread of the cancerous tumor. This particular type of treatment can also be used during chemotherapy, another common treatment option, and after surgery.

If mesothelioma cancer is diagnosed in the early stages of development, surgery to remove the tumor may be an option, but may not prevent the cancer from coming back. Other treatments that may be helpful for mesothelioma patients are alternative therapies, including acupuncture, massage, meditation, hypnosis, yoga and aromatherapy. Outside of traditional remedies for treating mesothelioma, patients may be interested in participating clinical trials that test new drugs and treatments.

Smoking cigarettes is something all mesothelioma patients should avoid after being diagnosed. Multiple studies have shown that smoking cigarettes can significantly decrease the life span and weaken the patient’s ability to fight the disease. Smoking cigarettes has also been proven to block air passages, making breathing even more difficult. Those diagnosed with mesothelioma are strongly encouraged by doctors to stop or not smoke cigarettes as it can make their condition worse.

The life span of a mesothelioma patient is largely determined by the age, health and type of mesothelioma cancer. While pleural mesothelioma is the most common, other forms of mesothelioma that can result from exposure to asbestos include peritoneal and pericardial mesothelioma. The latency period for these diseases can range between 20 and 50 years. Those who suspect they have been exposed to asbestos should seek routine medical checkups for asbestos-related diseases.


Mesothelioma Survival Rates

When a patient learns of a mesothelioma diagnosis, the questions that often follow may concern typical survival rates for mesothelioma patients. In general, approximately 10 percent of mesothelioma patients will live for at least five years after they are diagnosed with the cancer. According to medical research, the average survival for a mesothelioma patient is approximately four to 18 months after diagnosis.

Understanding the average mesothelioma survival rate can be complicated because various factors influence the data. Survival rate may be influenced by the level of the cancer’s development (stage), the size of the tumor, whether or not surgery may be preformed and the age and general health of the patient, among other contributing conditions.

For example, a patient diagnosed with mesothelioma in stage one (the earliest developmental stage of the cancer), whose general health is otherwise good, may be a candidate for surgery. If the surgery is successful and the patient responds favorably to additional treatments, their survival may far surpass average survival rates.

Reading statistical information about survival rates can be discouraging to mesothelioma patients and their loved ones. It is important to remember that research and studies are being conducted internationally to help in the fight against mesothelioma. Treatment options continue to improve and exciting developments continue to surface, providing hope to mesothelioma patients everywhere.

While there is currently no cure for mesothelioma, many patients elect to undergo treatment following diagnosis to combat further development and ease the symptoms of the cancer. The most popular treatment options utilized by mesothelioma patients include surgery, chemotherapy and radiation.

Many patients also find hope through participation in a clinical trial. Clinical trials are conducted to test up-and-coming treatments and medications before they are deemed safe and effective for the general public. All potential treatment options and medications must go through the clinical trial process before they are approved for widespread use. For additional information about clinical trials currently in progress, please click here to receive a complimentary comprehensive packet.

Alternative therapies are also frequently used by mesothelioma patients. Acupuncture, massage, supplements, meditation and yoga are among the list of alternative therapies that many patients have noted have provided relief and comfort. Although medical documents typically note the survival rate for a mesothelioma patient is less than one year after diagnosis, it is important to remember that many physicians have patients who survive significantly longer than this, with the occasional patient surviving for many years.
Mesothelioma Death Rate

Approximately 2,000 to 3,000 people are diagnosed with mesothelioma each year. Since the cancer is rare, many patients and their loved ones are not sure what the cancer is and what exactly a mesothelioma diagnosis entails. Questions about prognosis and the mesothelioma death rate often surface.

Number of U.S. Malignant Mesothelioma Deaths 1999 - 2005

Characteristic	1999	2000	2001	2002	2003	2004	2005	Total
Total	2482	2530	2505	2570	2621	2656	2704	18068
Age
25-34	4	6	7	10	7	11	6	51
35-44	33	34	39	40	38	42	34	260
45-54	138	131	144	106	148	121	118	906
55-64	388	372	361	380	386	400	438	2725
65-74	818	814	748	764	715	674	735	5268
75-84	888	918	942	975	1028	1097	1014	6862
85+	213	255	264	295	299	311	359	1996
Sex
Male	1993	2043	2019	2126	2122	2140	2148	14591
Female	489	487	486	444	499	516	556	3477
Race
White	2353	2398	2405	2447	2481	2535	2561	17180
Black	104	109	75	99	109	97	114	707
Other	25	23	25	24	31	24	29	181

Mesothelioma Mortality Rate

According to the Centers for Disease Control and Prevention (CDC), the malignant mesothelioma death rate in the United States from 1999 through 2005 totaled 18,068 people. The death rate increased from 2,482 deaths in 1999 to 2,704 in 2005, an increase of 222 deaths.

Men are diagnosed with mesothelioma more often than women, and males comprised 80.8 percent of mesothelioma deaths during this timeframe (a total of 14,591). White people comprised 95.1 percent of mesothelioma deaths, totaling 17,180.

Age influenced the mortality rate, as those 75 years old and older comprised the majority of the patients who passed away from mesothelioma (8,858 total deaths). Deaths in patients age 44 or younger totaled 311, or 1.7 percent.

During the time period addressed in the CDC’s study, the state mesothelioma death rate was greater than the national death rate of 13.8 per one million people per year. In six states the mesothelioma death rate was greater than 20 per one million people per year.

The mesothelioma death rate was highest in Maine at 27.5 percent (173 total), followed by Wyoming (22.2 percent, 50 deaths), West Virginia (21 percent, 182 deaths), Pennsylvania (20.8 percent, 1,210 deaths), New Jersey (20.2 percent, 814 deaths) and Washington (20.1 percent, 558 deaths).

Research and extensive studies are conducted daily to improve treatments for mesothelioma patients and search for a cure for the cancer. Through medical advances and developments in clinical trials, more options will continue to be available to combat mesothelioma and improve the mesothelioma death rate in the United States.