About a year ago, maybe less, I had a customer call in with a no heat on her Goodman air to air heat pump. The warranty had just run out and the problem had been occurring for some time. As Goodman has had issues with leaking service valves and the refrigerant level was low, I assumed those were to blame as there were leaks. The problem was that I was back in a week with the same issue. I found a loose nut on the metering device (the expansion valve), tightened it up and filled the system yet again. I also noticed that this was an R-410A system mated to an old Williamson low boy furnace with a belt driven blower, but did not put two and two together.
The unit failed AGAIN and my boss at the time did something else about it outside of my knowledge.
Funny thing was that I was called to a higher end system, still a Goodman heat pump, but it kept going off on high pressure. Because of the issue of putting gauges on same, releasing R-410A, and messing up the charge, I went down to the furnace (as this was a hybrid system, but with a new Goodman furnace with a direct drive blower). The filter was plugged solid and I put a new one in. The heat pump went on without a hiccup and I charged the customer 89 dollars and advised her to change the filter monthly.
So what's the point? R-22 is still being sold in green jugs to service older equipment and fill those units that are still made, but shipped dry for legal reasons. You see, R-22 is no longer available in a precharged system as this is being phased out due to eating up the ozone layer. This is because it's a Hydrochloroflorocarbon. The chlorine binds with the O3 or Ozone molecule changing into oxygen (O2) and Chlorine Monoxide (Cl O). R-22 is a lot more forgiving in certain situations as the pressures used are lower than those of R-410A, which is a Hydroflourocarbon or HFC. With these higher pressures mean some differences in engineering, but the installer world hasn't quite caught up. Special fittings, flares, tools and techniques are called for to prevent problems and one issue with a heat pump is that the indoor coil is going to be the condenser in the winter. Plugged filters, slow blower speeds and dirty coils will cause the pressures inside the coil to skyrocket; sometimes in excess of 500 pounds a square inch. Anything not brazed and only threaded will work loose in short order and this is what happened to the first customer. Her old Williamson furnace wasn't up to the task of moving the air needed and the coil sprung leaks as a result.
If you're considering a hybrid heating and cooling system, mainly an air to air heat pump, don't cheap out and keep your 20 plus year old furnace. You need to replace BOTH pieces of equipment, unless the furnace is less than 10 years old and has a direct drive motor. Otherwise you risk hours of frustration and unnecessary repair bills. If the installer says you can use a belt driven blower with an R-410A heat pump, get another installer. Belt driven furnaces in a residential system cannot move the volume of air needed to keep this system operating correctly. Maranatha!