T&T: Air conditioning compressor Temp.

[Steve Sipe]

Ken Williams wrote:
> Greetings,
> Marine Air Systems 16,000 btu air conditioner. (about 10 years old). Don't use
> it too much, but when I turned it on today, it sounds fine and seems to be
> running fine. But the compressor case is 225 degrees on the Pyrometer. To hot
> to touch! Seems excessive to me. Well vented and clean. What do you think?
> Thanks!
>   
Sounds like it might be low on charge. Check your delta-T (difference 
between evaporator entering/leaving air in cooling), it should be 20F or 
close. Check the suction line (largest one) at the compressor, it should 
be sweating or cold to touch, in the 35-40F range. All values are 
relative, not absolute. Your compressor derives motor cooling from the 
refrigerant flowing through it, if the refrigerant charge has absorbed 
as much heat as it can (superheat) by the time it gets to the 
compressor, the compressor has no means to dissipate its heat, so it 
goes out through the case. Very hard on it. There has to be enough 
refrigerant in the system to absorb the amount of heat the evap coil can 
transfer with enough capacity to absorb the heat from the compressor. 
The condenser circuit then gives up the accumulated head as the 
refrigerant condenses back into a liquid. The compressor's job is to 
take the low pressure superheated gas & compress it into high pressure, 
the condenser can then remove the heat as it condenses it.

End of lesson.

Short version: Dimes to donuts it's undercharged.

Steve Sipe