So far, the EPA has opened the door for only allowing hydrocarbon (HC) refrigerants in small refrigeration and HVAC systems.
Small systems obviously hold less of it, so they remain less hazardous if they happen to develop a leak. That makes sense.
The EPA further stipulates that those systems shall only be NEW equipment that's designed and manufactured specifically for its use. Only SNAP approved refrigerants are allowed. Therefore - R12a, R22a and others that have been produced and marketed as alternate replacement refrigerants for existing systems (conversions) that are not designed to use HC refrigerants...will remain illegal.
Little by little, we WILL see more acceptance of the LEGAL variations of hydrocarbon refrigerants for use in larger HVAC systems (such as residential CENTRAL HVAC units) here in the U.S. Before you saw it coming, that time will be here.
Not for drop-ins or a conversions, though. That's not gonna happen. That will sill REMAIN illegal.
The use of HC refrigerants in larger HVAC systems will only be NEW ones - from the factory, and with specific INSTALLATION requirements as per standards (yet) to set forth by our U.S. government.
So, the companies installing these systems must be on-board as well.
Like I'd said before, Australia and Europe are already using it for for larger HVAC systems - but with restrictions spelled out by THEIR regulatory organizations. So, I was inspired to take a look at what those restrictions are. I took a look at the British Refrigeration Association’s Guide to Flammable Refrigerants, which appears to be the standards they must abide by.
Australia's guide is v-e-r-y similar.
Here's what I found. This is a VERY generalized, not-all-inclusive summary:
Installation Design Factors:
Employment of acceptable hydrocarbon refrigeration/HVAC systems is based upon certain preliminary usage factors. The intended use of the conditioned-space, the size of that space, the system design's (remote vs integral), the refrigerant charge quantity...and other factors. Some scenarios simply aren’t suitable for using a system employing a flammable refrigerant. For those applications that ARE suitable, these specified design features are incorporated to minimize flammability hazards -
- Systems must adhere to prescribed limits to the quantity of refrigerant charge that employ a class A3 refrigerant, with limiting factors based upon installation location of equipment (above ground vs below ground), square footage of conditioned area and type of space usage (based on occupancy classifications: i.e., are people living & sleeping there, or is it just storage rooms).
- Ignition sources are to be minimized by using electrical switch/component isolation boxes and specially engineered electrical components designed to be spark-proof.
- The HVAC units are required to be located in a room that's free of open flame-heated units such as boilers, furnaces and water heaters.
- Refrigerant piping is to be installed so that it's encapsulated by sheathing or dedicated pipe ducting for proper containment, routing and ventilation of any flammable refrigerant leaks to the outdoors or back to the machine room. The containment medium is to be sealed to any walls it passes through to prevent leakage/fire into an occupied space.
- A machine room containing a system must have a low level ventilation system that maintains a static atmospheric pressure at a LOWER level than the pressure within adjoining living spaces to prevent the flammable refrigerant vapor from migrating into neighboring living spaces.
- Should a flammable refrigerant leak occur, combustible gas sensors must be in place to provide notice to occupants through an alarm system and to also activate high level, emergency mechanical ventilation of the machine room containing the HVAC unit.
Tools and equipment used for maintenance/repairs:
- Tools should be rated for use or have been suitably tested for use with flammable refrigerants.
- Flammable gas detector - for monitoring the air in the work area.
- Electronic leak detector - one which must be safe and sensitive to the flammable refrigerant.
- Recovery machines – most standard HFC types have not been assessed for use with flammable refrigerants, so approval must be sought from the manufacturer before using a standard HFC recovery machine with any flammable refrigerant – they may be safe to use with flammable HFCs but not HCs.
- More accurate scales - necessary when charging small, critically charged systems with some flammable refrigerants such as HCs. An accuracy of ±5 g (0.18 oz) is often necessary.
- A dry powder or CO2fire extinguisher - must be available at the location.
- .A suitable ventilation fan - should be used when working inside if there is insufficient natural ventilation.