Heating, ventilation, and air condition (HVAC)) systems rely on refrigerants to provide cool air to houses and other buildings. A refrigerant is a liquid that picks up heat by evaporating at a low temperature and pressure. The refrigerant also gives up heat at a higher temperature and pressure. This guide provides a concise history of refrigerants in HVAC systems, including an explanation of refrigerants that were used in the past, but are now illegal. Also presented in the guide is a procedure for checking the refrigerant level for an air conditioning system. In order to purchase refrigerant and repair systems that contain ozone-depleting refrigerants, a person must have an EPA refrigerant usage certification. HVAC refrigerants can be found at home improvement stores, but they can also be purchased online on eBay. The site has a wide variety of refrigerants that can be purchased at discount prices. Refrigerants used in early HVAC systems included sulfur dioxide, methyl chloride, and ammonia.

These chemicals provided adequate cooling, but were hazardous because of their toxicity and flammability. In the 1930s, chlorofluorocarbon (CFC) was used as a safe alternative. In the 1950s, hydrochlorofluorocarbons (HCFC) were also introduced as refrigerants. While not toxic or particularly flammable, it was discovered that the use of CFC (and HCFC, to a lesser extent) in HVAC systems was contributing to the depletion of the ozone layer. The Montreal Protocol, an international environmental treaty, was established in 1987. It set target dates for phasing out the use of CFC and eventually HCFC in HVAC systems. The phase-out of CFC was completed in 1996. Many of the CFCs were replaced by HCFCs, which have a lower ozone-depletion potential (ODP). The phase for HCFCs was set from 2004 to 2030 (2040 in developing countries). The replacement refrigerant material is hydrofluorocarbons (HFC), which has a zero ODP. Concerns with the use of HFC led to the Kyoto Protocol in 1997. HFC was shown to have global-warming potential (GWP) and the protocol set to reduce use of greenhouse gases in developed countries.

In the United States, the Clean Air Act was issued to phase out production and importing of CFCs and HCFCs. Hydrofluoroolefins (HFO) are the next family of refrigerants because they have minimal environmental impact.ac repair slc ut As noted above, in order to buy refrigerants and fix HVAC systems that use ODP refrigerants, a person needs EPA certification. rooftop hvac units maintenanceA 608 certification allows people to buy any refrigerant sold in a HVAC/R store in containers of 20 pounds or greater. lowes central air conditioner pricesA 609 certification allows a person to buy any refrigerant solid in an automotive supply store in any size container. Stores usually sell R-12, R-134a, and replacement blends for R-12. There are a number of refrigerants currently in use.

The following table provides some details: Used in older units; Not very energy efficient; very little environmental impact R-22 and R-410A are the most common refrigerants used in air conditioning systems, but both are being slowly phased out (as noted above). One of the ways a person can maintain his or her air condition system is to check the refrigerant level. This is also called air conditioning charging. Prior to charging the air conditioner, a routine maintenance should be performed in which the air filter,, blower wheel, evaporator coil, and condenser coil should be clean. Refrigerant added to a dirty air conditioner can cause damage to the unit. There are a number of specialized tools required for charging an air conditioner. Gauges for measuring operating pressures are used. The gauges include a manifold with a low and high pressure gauge and hoses to connect to the system's ports. The gauges also contain a scale that measures pressure and temperature.

An infrared thermometer or thermocouple-based meter can be used to measure pipe temperature will also be needed. Prior to charging the air conditioner, the unit should be shut off. Hoses from the gauge manifold can be attached to the pressure points of the system. Generally, the low pressure hose is blue and connected to the suction line on the larger of the two pipes. The high pressure hose is red and connected to the liquid line, the smaller of the two pipes. Run the unit for 15 minutes and check the various temperature and pressure gauges. Based on the measurements, one can check the unit's guide for superheat and subcooling for a given outdoor temperature. Superheat is added to the refrigerant to cause the temperature of the refrigerant to rise above its saturation temperature. Refrigerant is removed from the system to increase the superheat. Subcooling is the opposite of superheat; it is added to the refrigerant to cause the temperature of the refrigerant to fall below its saturation temperature.

Refrigerant is added to the system to increase subcooling. The amount of superheat is calculated by measuring the suction line temperature and taking away the low pressure gauge temperature reading. The amount of subcooling is calculated by measuring the liquid line temperature and subtracting the high pressure gauge reading. Refrigerant should be added slowly in small amounts. If more than a little refrigerant is needed, there may be a leak. There are a number methods used to detect refrigerant leakage in HVAC systems. Sometimes, leaks are visible to the naked eye, including a visible line break, the presence of oil, and a vapor cloud of refrigerant. The follow methods can also be used to detect leaks. This method is often used on new systems before refrigerant is added. Dry nitrogen is used to increase pressure, which is monitored with a pressure gauge for several hours. This method is time consuming but quite reliable. On existing systems, refrigerant must be shut down prior to the test.

Service ports can also be the source of the leak, so they should be checked after attaching the gauge hoses. The isolation method is used in conjunction with the standing hold method when parts of the system are not easily accessible. The refrigerant piping system is opened, then resealed. A pressure test is then applied to the system to evaluate sources of leakage. While bubbling liquid solutions are a time consuming and often messy method of detecting leaks in HVAC systems, they can provide very specific leakage points whereas other methods just point to general areas. The solutions are applied via spray, dabber, brush, or immersion. The solutions bubble up when placed on a leak site. Small, chlorinated refrigerant leaks of less than an ounce per year can be detected using a halide torch. Air is drawn over a copper element, which is heated by a hydrocarbon fuel. If vapors of halogenated refrigerant are present, the flame changes color from blue to bluish green. If you are an authorized HVAC repair person, then you can go to eBay to find sources of HVAC refrigerant.

To find the refrigerant, you can do a search by typing "HVAC refrigerant&" into the text box found on most pages. If you can add the type of refrigerant (see table above), you will get more focused search results. Phrases can be searched on eBay by adding quotes around the keywords. This will narrow search results by only looking for exact phrase typed in the text box. When buying HVAC refrigerant, you can be more confident in your purchase by doing a few minutes of research on the seller. On every product page, you can find seller information, including the seller's user name, the number of transactions the seller has participated in, and the rate of positive feedback.. This box will also let you know if the seller is top-rated as determined by eBay. By clicking on the seller's name, you can see more detailed feedback including ratings of item description accuracy, communication timeliness, and shipping information. While refrigerant for HVAC systems should not be purchased unless the user has the appropriate certification, once those papers are obtained there is a lot of information about refrigerant that should already be known by repair persons.