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View Full Version : How cold should A/c lines be


Doug Crf
Aug 28, 2005, 11:23 PM
On my a/c system in my house the line with the insulation on it is cool but not cold.Is the system may be low on freon?
I noticed the evaporator air intake filter was not sealed very good but even if the evaporator is dirty should'nt the line still be more than just cool,I know on some of the trucks I work on the evaporator could have like a sheet of dust on it totally pluging it and the line coming out of the evaporator would still be very cold,It would not cool the inside of the cab at all but you could tell that the freon charge is very good.
On the truck ac systems the low and high side are separated at the inlet of the evaporator with an orfice tube or a expansion valve and that is where the freon changes from liqued to gas,Is that the same as for home units or does the freon change from liqued to gas out side the house by the compresser.Any help would be apricated. Woops on the spelling.
Thanks Doug :confused:

labman
Aug 29, 2005, 06:24 AM
How cold is cold? In a home A/C, the Freon changes back to a gas as it enters the A-coil through an expansion valve in the furnace. I would be more concerned with the air coming out the vents. As long as it is cold enough to cool the house in a reasonable time, it should be OK.

Doug Crf
Aug 29, 2005, 12:25 PM
How cold is cold? In a home A/C, the Freon changes back to a gas as it enters the A-coil through an expansion valve in the furnace. I would be more concerned with the air coming out the vents. As long as it is cold enough to cool the house in a reasonable time, it should be OK.

I stuck a thermometer in one of the vents close to the unit and it got down to about 62 deg is that considered cold for coming out of a vent.
Thanks doug

hvac1000
Aug 29, 2005, 07:05 PM
Most home central a/c units are designed for a 20 degree TD.(total differential from the outside to the inside air. The temperature will change with the temp outside. You also have to consider humidity etc in the calculations. I would suggest a HVAC course at one of your local trade schools so you can better understand how a a/c system works. There are to many variables.