In-house maintenance personnel who regularly service, repair or replace packaged terminal air-conditioning units should be aware that newer PTAC units may use a flammable refrigerant. This makes safety and proper refrigerant handling more important than ever.
The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) assigns safety classifications to refrigerants based on toxicity and flammability data submitted by the refrigerant’s producer. For flammability, there are three main classifications: class 1, for refrigerants that do not propagate a flame; class 2, for refrigerants of low flammability; and class 3, for highly flammable refrigerants.
For many years, R-410A was the refrigerant of choice for PTAC units. R-410A is a class 1 refrigerant and is considered virtually non-combustible. However, R-410A (and some other refrigerants) are being phased out in favor of more environmentally friendly products. In the case of PTACs, most new and future units are likely to be using R-32, which is a class A2L refrigerant (with the “A” indicating low toxicity, the “2” being the flammability classification, and with the “L” indicating the refrigerant’s low-burning velocity).
Changing How Service Work is Done
Douglas Mackemer, national director of strategic institutional product management at Carrier Enterprise, a distributor of HVAC and refrigeration equipment in 31 states, said working with flammable refrigerants—even those with a low-burning velocity such as R-32—changes the behavior of how service work and installation is performed.
“The first thing for maintenance staff to be aware of is what kind of unit they're working on and what the refrigerant is. That seems like a basic thing, but it’s more important than ever,” Mackemer said.
Also be aware that the tools used to work on such systems, such as refrigerant recovery machines or vacuum pumps, must be certified for use with A2L refrigerants.
A major change when working on these PTAC will be the need to purge the system with nitrogen after removing and recovering the refrigerant.
“In the past, you could just evacuate and recover the refrigerant,” Mackemer said. “Now one of the requirements is that you must use nitrogen to purge the system to clear out any remaining refrigerant before you start any repairs or service work on it.”
Sensors and Safeguards
Mackemer noted that there are additional safeguards and sensors built into equipment that use a mildly flammable refrigerant, including a built-in sensor that will shut the system down and turn a fan on to dilute any concentration of leaking refrigerant.
“These sensors should not be bypassed,” he cautioned. “They should remain connected for everyone’s safety.”
Maintenance staff are also likely to need a new gauge set to accurately represent the system’s pressure/ temperature references, and will need to be aware that some manufacturers of R-32 equipment are changing the thread pattern for the hoses and recovery equipment from right-handed to left-handed.
“That’s done to ensure awareness and call attention to the fact that something is different about the equipment,” Mackemer explained.
Look for the Label
Awareness is the key to safety, agrees Marc Lopez, senior technical support representative, Friedrich Air Conditioning Co. Fortunately for maintenance personnel, equipment containing flammable refrigerant will be well-labeled.
“There’s usually going to be a big sticker identifying the refrigerant type on the outside of the unit and another one inside where the process tubes are,” he said.
Once the type of refrigerant has been determined, it’s up to the service personnel to take the warnings seriously and follow the proper procedures. And don’t let Lopez hear you dismissing the danger.
“You can call it ‘mildly’ flammable, and it’s true that R-32 is not as flammable as the R-290 (propane) that is being used as a refrigerant in some small systems such as those found in beverage vending machines,” he said. “But the switch from flammability class 1 to flammability class 2 means you are now working with a flammable substance and should use caution accordingly.”
This is especially true if you’re working on a unit that is in a confined space. In order to catch fire, the concentration of R-32 to oxygen must be between 14 percent and 31 percent.
“If you’re working on these units in a confined area, the risk increases,” Lopez warned.
Beyond that, the major change maintenance techs will need to be aware of is the need to purge the unit with nitrogen while evacuating the R-32.
Lopez explained that Friedrich recommends three to five minutes of nitrogen flush and evacuation, and then another three to five minutes of nitrogen flush.
“The first flush is mandated, the second flush is a ‘best practices’ recommendation,” he said. “Basically the idea is you’re flushing nitrogen through the system to make sure the A2L refrigerant is completely out of the system before you begin removing any components. And at Friedrich, we suggest for added safety that even after flushing, you cut the components out with a tubing cutter, not a torch.”
Additional Safety Tips
Additional tips and best practices from Friedrich include:
- Verify all tools, vacuum pumps and recovery equipment are A2L compatible by checking with the tool manufacturer.
- Do not share hoses and gauges with different refrigerants.
- Do not mix refrigerants in recovery cylinders.
- Completely flush and clean recovery equipment after use.
- Always pressure test the system to manufacturer’s specs or industry standards.
- Always perform nitrogen sweeps before evacuation.
- Triple evacuate systems to below 500 microns.
- Always charge the unit to manufacturer’s specs.
- Maintain a focus on safety. When working with refrigerants be alert for potential ignition sources, ensure proper ventilation to avoid asphyxiation in confined spaces, protect against skin burns, and wear eye protection.
PTACs are durable, dependable and versatile units used widely throughout the hospitality industry, and nothing about these new refrigerants and updated maintenance procedures will change that. Just remember to be aware of the refrigerant type, your surroundings, and to use the proper tools—with safety being the best tool of all.