To begin working in the HVAC industry you will need to pass the Environmental Protection Agency (EPA) HVAC certifications. These certifications are often referred to as the EPA 608 certifications and this is the start of the Discover-HVAC.com course.
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Text Stephen Peters August 2016, updated November 2019
The Environmental Protection Agency (EPA) section 608 type 2 certification covers high pressure Heating, Ventilation, and Air Conditioning (HVAC) appliances. This is the Discover-HVAC.com type 2 course which typically follows the core course.
To pass the exam a technician must correctly answer 70% of the 25 questions in the test (i.e. 18 correct questions), as well as have passed the proctored core exam for a type 2 certification. To gain a universal certification the Type 1, Type 3, as well as the core exams must be passed. The type 2 exam is a proctored test which for most students means taking the test in a classroom but some companies are offering online proctored tests.
Medium, high, and very high pressure appliances containing more than 5lbs of refrigerant are covered by the type 2 certification. Factory sealed appliances containing less than 5lbs of refrigerant are covered by the type 1 certification, and MVAC appliances by the EPA section 608 certification.
Medium pressure refrigerants have a pressure between 30 - 155 psig at their liquid phase temperature of 104°F.
High pressure refrigerants have a pressure between 155 - 340 psig at their liquid phase temperature of 104°F.
Very high pressure refrigerants have a pressure above 340 psig at their liquid phase temperature of 104°F.
Before searching for a refrigerant leak in an appliance a technician must first suspect a leak. There are several tell tale signs that a system has developed a leak when it is inspected by a technician. The first signs are often the problems with the operation of the unit reported by the end user, such as warm airflow in cooling mode or cold airflow in heat pump mode.
On an initial inspection the technician may find the air being discharged from the condenser is close to ambient temperature. There may be ice build up on the evaporator or copper refrigerant lines. Oil may be present on fittings and pipework, or may have been sprayed on nearby surfaces.
Once gauges have been connected the system may be showing low refrigerant pressures on both the low and high side. The superheat value may be high and the subcooling value may be too low.
Leak testing should always be performed before charging or recharging a system with refrigerant. Typical places to find leaks are valves and flare fittings. Tubing can develop pinhole leaks if it is in contact with anything it can rub against. Receivers can rust and develop leaks. Non-hermetic compressors can leak at the rotating shaft seal or head gasket, with a shaft seal oil leak being a common fault if the system has not been running for some time. Evaporator and condenser coils can corrode and leak, as can expansion devices and filter dryer assemblies.
If the system is not charged with refrigerant either because the technician is performing the initial commissioning or the system has just been repaired and does not contain any refrigerant it should be pressurized with nitrogen to test for leaks. If an electronic refrigerant detector is to be used a trace amount of refrigerant should be added to the system. Electronic refrigerant detectors are designed to detect specific refrigerants and will not detect nitrogen leaking.
An electronic detector can be used to trace leaks in a system charged with nitrogen and trace amounts of refrigerant or a fully charged appliance. A halide torch can also be used to accurately detect the location of a refrigerant leak as the torch flame turns green when refrigerant is present. Fluorescent dyes can be added to the system if they are compatible with the refrigerant. Once added they leave a stain which glows under ultraviolet light at the leak location.
The bubbles from soapy water brushed or sprayed onto the leak area can be used to pinpoint the exact location of leak. Newer commercially available bubble solutions stick to the leak area for longer and form a highly visible foaming layer over the leak.
Appliances containing a refrigerant charge of over 5 lbs where refrigerant is being removed must have records kept for a minimum of three years with the following information:
Appliances containing a refrigerant charge of 50lbs or over must have records kept for a minimum of three years for the following information:
Since the 1st January 2019 EPA regulations for large systems changed. Appliances containing 50lbs or more of a regulated refrigerant must have an annual leak test. If a leak is detected the leak must be repaired within 30 days if the annual leak rate is over 10% of the refrigerant charge. Once the leak has been repaired and tested another follow on leak test must be completed within ten days.
The thirty day repair deadline can only be extended for the following reasons:
Should an appliance charged with a regulated refrigerant have a chronic leak of 125% or more of the full refrigerant charge in one year the owner must report this to the EPA. The report must include details of the leak detection and repair actions made by the qualified technicians working on the appliance. The owners report must be submitted by March 1st of the subsequent year.
Comfort cooling (otherwise known as air conditioning) has a new leak threshold rate since 1st January 2019 as part of the recent EPA "final rule" update. The new rate is 10% lowered from the previous threshold rate of 15%.
Both IPR and commercial refrigeration also have a new leak threshold rate since 1st January 2019 as part of the recent EPA "final rule" update. For commercial refrigeration the new rate is 20% lowered from the previous threshold rate of 35%. IPR refrigeration has a new threshold of 30% lowered from the previous threshold rate of 35%. If an appliance serves both IPR use as well as other uses it should be considered to be an IPR appliance only if 50% of system capacity serves IPR use. If an appliance used for IPR or commercial use contains a charge of 500 pounds or more of refrigerant it must be leak tested every three months unless a refrigerant leak monitoring system is installed, or it has kept under the leak rate for successive four quarters.
To calculate leak rate you will need to work out the total system charge. This is typically completed when the system is commissioned, however if the documentation of this is not available or you are commissioning the appliance you will need to know how to calculate the total quantity of refrigerant the system can contain. Typically the appliance manufacturer will provide data sheets showing charge values for condensers, evaporators, and receivers. Charge values for both the liquid and suctions lines will need to be calculated from a piping charge calculation table based on the refrigerant, line size, and length of pipe.
Since January 1st 2019 leak rates must be calculated for appliances containing 50 lbs or more of refrigerant. The EPA has set out two allowable methods of calculating the appliance leak rate, the annualizing method, and the rolling average method. These calculations must be retained for three years and since these calculations are used when calculating the leak rate must be available for technicians who are performing new leak rate calculations.
The annualizing leak rate calculation is defined by the EPA as follows:
| Leak rate (% per year) | = | Pounds of refrigerant added | × | 365 days/year | × | 100% |
| 365 days/year | Shorter of #days since refrigerant last added or 365 days |
When using the annualizing method the first refrigerant addition in 2019 the second term would be 365/365 i.e. 1. Subsequent additions would be 365 divided by either the number of days since the last refrigerant addition or 365, whichever is the shortest.
The rolling average leak rate calculation is defined by the EPA as follows:
| Leak rate (% per year) | = | Pounds of refrigerant added over past 365 days | × | 100% |
| Pounds of refrigerant in full charge |
Using the rolling average method in 2019 the dividend would be the lowest amount of either pounds of refrigerant added since January 1st 2019 or the last successful followup test. In 2020 and beyond the dividend would be the amount of refrigerant added since the shorter of 365 days or the last successful followup verification test.
Before attempting to recover refrigerant a technician should read the appliance data plate and check for any refrigerant retrofit labels. As there have been many refrigerant blends introduced following the phaseout of CFC and HCFC refrigerants it is important to identify the type of refrigerant charge in the appliance. If a technician is unsure what the refrigerant type is in a system they can check with a pressure temperature (P/T) chart as explained in the core section.
Refrigerants can pose a significant safety risk to both the technician as well as the end user. Technicians should ensure they are familiar with the safety sections of the core exam and ensure recovery equipment is not damaged and is being operated correctly. They should also retain the material safety data sheets (MSDS) for any refrigerants they are working with.
Hermetic compressors rely on the flow of refrigerant through the compressor case for cooling. Never run a hermetic compressor when the system is under a vacuum as this is highly likely to cause the compressor to rapidly overheat and fail. Never run a compressor when the discharge service line is closed as this too will cause rapid compressor failure.
Whenever an appliance is opened for repair the filter drier should be replaced. Filter driers will remove any moisture drawn in to a system but have a finite life and are considered a consumable part. A strong smell present during refrigerant recovery is a common sign of a compressor that has burnt out. Compressor bun outs can contaminate the oil which should be tested with a test kit.
If the appliance is fitted with a moisture indicating sight glass which will change colour if the system contains moisture in the refrigerant. If the sight glass is iced it can be cleaned with isopropyl alcohol which is frequently used in cold climates as an icing inhibitor. Crankcase heaters are also found in compressors used in cold climates to prevent refrigerant foaming in the oil especially during system starting.
Should a large appliance contain a significant amount of water when it is being evacuated with a high capacity vacuum pump some of the water may freeze within the system. Nitrogen introduced to the system during the evacuation will increase the pressure until all of the water has been removed and prevent it from freezing.
High pressure in the discharge line can be an indication there are noncondensibles in the system, which is frequently caused by air in the system. The system must be fitted with at least one pressure relief valve.
The American Society of Heating Refrigerating and Air conditioning Engineers (ASHRAE) standard 15 Safety standard for refrigeration systems requires a refrigerant sensor with alarm in equipment rooms where refrigerant may concentrate. The alarm should sound at a refrigerant concentration level no higher than the threshold limit value (TLV) time weighted average (TWA).
In the test inches of mercury (HG) are used as a measurement of pressure. Inches of mercury is really a measure of distance as it is used in HVAC applications. It relates to the displacement of a mercury column by atmospheric pressure. Today it is considered a crude measurement and while you will need to know a variety of measurements in Hg measurements in microns of mercury are more commonly used in industry. The main reason for the test using Hg is that the original legislation was written in the past when measurements in Hg were more common.
Large systems are normally fitted with a liquid line service valve allowing charging via the liquid line for faster charging. Large systems often are fitted with service valves for pumping down the appliance to allow for even faster liquid line charging.
If the appliance has a liquid to liquid heat exchanger there is a risk of freezing the heat exchanger when charging through the liquid line. To prevent this begin charging with refrigerant vapour until the system pressure reaches a temperature higher than 32 degrees as indicated by a pressure temperature chart. Once this has been achieved charging can begin through the liquid line.
The Clean Air Act require refrigerant recovery and recycling equipment be tested to ensure it meets EPA requirements. To enable equipment to be tested the EPA has approved the Air Conditioning, Heating, and Refrigeration Institute (AHRI) and Underwriters Laboratories (UL) to certify recovery and recycling equipment. Certified equipment should have a label stating "This equipment has been certified by AHRI/UL to meet EPA's minimum requirements for recycling and/or recovery equipment intended for use with [type of appliance]."
Technicians do not need to certify to the EPA that they have acquired recovery and recycling equipment nor do they need to certify they are complying with the Clean Air Act requirements as they used to.
Before using recovery equipment to reclaim a refrigerant charge the technician should ensure the machine has been purged of any residual refrigerant from the last job the machine was used on. Service valves should be checked to ensure they are correctly set before connecting hoses and starting to recover refrigerant. Recovery equipment should be fitted with quick connect couplers for use with self sealing hoses to minimize refrigerant releases
Reclamation equipment needs periodic maintenance, which includes oil and filter changes. Recovery equipment filters should ideally be changed each time the machine is used, and at a bare minimum each time the type of refrigerant is changed to avoid contaminating the system being worked on with a mix of refrigerant. As recovered refrigerant can often contain significant amounts of contaminants such as water, oil, acids, and brazing spatter filter changes can significantly lengthen the life of recovery equipment. Technicians should also check the oil level on the recovery equipment before using it.
When using an empty recovery cylinder ensure the cylinder has been fully evacuated before transferring refrigerant to it.
Recovery equipment which contains a hermetic compressor relies on the flow of refrigerant through the compressor for cooling. As with appliances using hermetic compressors pulling a vacuum for a long time with this type of device can cause the compressor to overheat.
Recovering refrigerant in the vapour phase will minimize loss of oil from the system. Vapour recovery accounts for 75-80% of the recovery process time so recovery machines with high vapor recovery rates will take less time to recover refrigerant.
Liquid refrigerant recovery is much faster than vapour recovery, but can remove more oil from the appliance. Liquid recovery is ideal for large systems which are often designed with this in mind. Liquid recovery is however the first step in recovery as any remaining refrigerant vapour must be condensed and recovered once all of the liquid has been reclaimed. Ensure that no liquid remains trapped between the service valves after transferring liquid refrigerant.
Once the recovery cylinder contains more than five pounds of refrigerant it can be chilled in a bucket of ice water to lower the cylinder pressure. This will speed up the recovery process.
Technicians recovering HFC refrigerants must now use equipment solely dedicated to these refrigerants. This means that a dedicated set of gauges, hoses, vacuum pump, recovery machine, oil containers, and recovery cylinders must only be used with these refrigerants.
When performing recovery on a large appliance a high capacity recovery machine with integral water cooling may be used to speed up refrigerant transfer times. These must be connected to a constant potable or municipal water source with an accessible water drain.
If a large appliance has a receiver or storage tank, refrigerant should be transferred to the tank before recovery. On systems where the condenser is lower than the receiver the refrigerant should be removed from the condenser outlet as the lowest part of the system.
In a large system with a parallel rack of compressors such as those commonly found in food retail refrigeration isolate the compressor with an open equalization valve before recovery.
Once a sufficient level of vacuum has been reached the technician should wait for a few minutes to see if the system pressure rises. If so there may be residual refrigerant either in the oil or a remote part of the system. Under a vacuum oil dissolved in the compressor oil will gradually emerge as refrigerant vapour which can be recovered normally.
If the system has a leak which makes it impossible to achieve a vacuum before repair then it is acceptable to reduce the system pressure to atmospheric pressure (i.e. 0 psig). A proper vacuum level must be reached before recharging after the repair.
When an appliance contains more than 15 pounds of refrigerant the system cannot be recovered using a system dependant method and an independent recovery machine must be used.
Any service, repair or maintenance that involves removing the compressor, condenser, evaporator, or auxiliary heat exchanger is considered to be a major repair by the EPA.