FUEL-GASES versus FLAMMABLE REFRIGERANTS

There are dramatic differences between the gas being fed to your gas grill or gas stove…when compared to a flammable refrigerant put into a HVAC system that's not designed for it:

PRESSURES:

• Gas heated appliances (stoves, ovens, grills, water heaters, gas furnaces) are fed their gas fuel at a pressure of less than ½ psi. Gently blow on your hand. That's about the same.  Additionally, that fuel-gas is supplied to your home already in a vapor form.
  
• Depending on the location of a leak in a HVAC system and whether the system is running, the flammable refrigerant can potentially leak out into your home at well over 200 psi.  Depending on the operational state of the equipment, THAT leak might be at a location in the system that spews the volatile refrigerant out in a LIQUID form.
  • Even if it's NOT running and the system is static, the pressure can still be over 100 psi. That's far more than the pressure from your water hose to wash a car with.

STATE OF MATTER:

• As stated, your natural gas or propane heated appliance is fed to your home in a vapor form.  It's brought in that way into your living/storage space in the safest form it can be for use by your appliances.  Your appliances are designed to shut it off if there's a problem.
  
• Once AGAIN, depending on the location of a leak in a HVAC system and whether the system is running, a propane-based refrigerant may leak out into your home in a liquid form.  As such, its in a dangerously and highly concentrated form.  Once let out from the highly pressurized lines of a refrigeration cycle, it would immediately flash into a vapor and expand as it's exposed to atmospheric pressure.
  • With a boiling point of -44°F at atmospheric pressure, the flammable refrigerant vapor has an expansion rate of 1:270. As such, it would rapidly emanate as a vapor into the indoor space that it's leaking, pass under doorways and into other rooms.
    

SPECIFIC GRAVITY AND HEAT VALUE:

• Your gas appliance probably uses natural gas. Natural gas is lighter than air and is therefore easily dissipated and escapes through whatever ventilation points that are in the room. Also worth noting is that the heat value of natural gas is around 1000 Btu/cu. ft. of vapor.
• The flammable refrigerant R22a is propane-based. Propane is heavier than air and 1.5 times as dense. Therefore, if it leaks out into your home, it will form a pool of flammable vapor on the floor. Also, propane has a heat value of around 2500 Btu/cu. ft. of vapor, making it 2.5 times the heat energy level of natural gas.

PLUMBING CONSTRUCTION:

• A natural gas line leading into a home is primarily black pipe, which is very thick and rigid so it can (by design) take an inordinate amount of abuse to PREVENT leaks. A section of stainless-steel, flexible tubing may terminate that gas feed to your gas appliance. That's the only truly vulnerable section of gas line, but that short section generally installed out of harm's way.
  • Worth noting is, per NFPA and mechanical codes, copper tubing CANNOT be used for delivery of fuel gases within buildings. There's a reason for that – to prevent fires and explosions!
• The flexible copper tubing that comprises an AC system line-set may run a total of over 100′ in some homes, routed up and around and through garages, voids in walls, etc. – ultimately leading to an air-handler in a garage, attic, crawlspace or hallway closet.
  • Copper can be easily punctured by sharp objects. However, HVAC systems have a FAR greater chance of developing a leak somewhere due to system vibration, corrosion, a bump from a heavy object stored near it, a failed braze joint, etc.
  • You can't predict a when or if a leak will occur…nor the size of it. And as a reminder – per NFPA and mechanical codes, copper tubing CANNOT be used for delivery of fuel gases within a building.

SAFETIES:

• Most gas heated appliances have safety systems incorporated so that a fuel gas is proven to properly ignite. Essentially, if those systems don't PROVE that a proper flame has occurred, then the fuel gas is automatically shut off. If a highly unusual situation arises where the fuel gas otherwise leaks from a line or a fitting, you would be duly warned of such a leak since you could SMELL it.
• Your R22 or R410a HVAC system has NO type of safety devices that could prevent or detect leakage of a flammable refrigerant from its system and into your home.
  • You will NOT be able to SMELL the flammable refrigerant if it has leaked out into your home or garage.  WHY is THAT?  Well…
    

FUEL GASES ARE ODORLESS:

• Natural gas and propane are odorless. However, a pungent, sulfur-based odorant (mercaptan) is added to natural gas and LP during production to facilitate easy detection in case of a leak.
  • This requirement was mandated world-wide shortly following the tragic New London TX school explosion that occurred on March 18, 1937. That tragedy took the lives of nearly 300 children.
• Propane being produced and sold as a refrigerant does not meet the same standards. The manufacturers of R22a may claim they put an odorant in it (a pine scent?…REALLY?), but that scent would be quickly flushed out in the refrigeration cycle.
  • So, if the flammable refrigerant leaks into your home, UNLIKE a natural gas leak, you would not be able to smell it.

So these characteristics of a flammable, propane-based refrigerant….coupled with putting it into a system that's not designed for containment of a potentially explosive substance leaking out…surrounded by potential ignition sources like a gas water heater, electrical switching devices, etc…plus the likelihood that the system it's put into will be by a “do-it-yourselfer” who bought it on-line and will probably NOT go to the trouble of properly marking/labeling the system to indicate the flammable refrigerant has been put in it…leads to any number of scenarios where someone may get hurt, a fire may get started or an explosion may occur.