Quote:
Originally Posted by bill498326
Does this mean that the coil in the indoor unit is filled with non condensible gas that prevents good heat transfer?
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Possibly. What sort of heat are you getting out of it when it is wound up to maximum?
Quote:
Originally Posted by bill498326
How does one use dry ice to take the place of a recovery machine?
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So glad you asked!.
Dry ice sublimates at approximately 77 Degrees C. R410a (Or R22 or Propane) is a liquid at atmospheric pressure at somewhere around 45 degrees C (give or take for the differing gasses).
You take the recovery cylinder and vac it out, then pack it in a cooler with dry ice and wait for it to get really cold (I wrapped the cooler with towels and filled it with alcohol to aid the heat transfer). Simply hook it up to the patient and open the valves. The refrigerant will naturally migrate to the bottle as it wants to condense in the coldest part of the system. Eventually (might take an hour or so) you will note the system pressure ventures toward a vacuum, and you're done.
Now, your system pressure may well not venture into vacuum as you have a snot load of nitrogen in there, and it takes more than dry ice to condense that, but it should pull all the R410a out.
To be honest, if you hook a vacced out bottle up to the liquid line you'll probably suck 2/3rds of the charge out before it even starts to get cold. When I recover my big unit here now, I hook up a vacced bottle to the liquid line and start 'er up in cool mode. The system practically flushes the refrigerant right into the bottle. It leaves much less to pull out for the painstaking (relatively) vapor recovery.
All temperatures given here are rough approximations from memory, however they're close enough that the principle works. I've recovered 3 systems doing it this way (before I bought a recovery machine).