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AU_Prospector 06-03-2008 01:46 PM

strange sounds from A/C unit

I have a central air/heat pump unit in my attic which cools the upstars portion of my home. There is a pair of copper lines which go to the fans unit outside. One is insulated and the other bare. I assume these are the coolant lines. When the A/C first starts running I hear the coolant running in these lines. I also hear a gurgling sound coming from the attic box blower unit. This is definetly coolant gurgling and increases in sound to that of a full boil. After a few minutes all of these sounds subside.

Are these noises normal? The coolant lines run inside of an interior wall down to the crawl space where they exit to the outside fan unit. I havent listened closely, but near as I can tell the larger unit which controls the lower level temp does not make these sound. That unit however is in the crawl space and not readily accessable.


kok328 06-06-2008 04:53 PM

Make sure both the evaporator and condensor coils are clean, along w/the air filter. If you don't move enough air across these two coils, the unit won't have the capability to convert from gas to liquid and back again. I suspect your hearing freon in the form of liquid going through the A/C lines.

glennjanie 06-06-2008 06:12 PM

Hello Matt:
Acessibility is the answer. You can hear the upstairs unit because it is more readily accessible. The refrigerant is supposed to come in through the small line in liquid form, go to the "A" coil which has a metering device to regulate the flow of liquid to gas, pick up the heat and take it out to the compressor by the large line. The large line may be cool to frosty, this is perfectly normal.

AU_Prospector 06-08-2008 01:39 PM

Thanks Glenn,

Just to follow up with my temps on this unit.

Outdoor air temp. 94 F Outdoor blower unit is always shaded. Large line is only cool and has condensation on it, I guess about 60 F. Small line is warm but not hot, I guess 100 - 105 F. I dont have a temp gun so I cannot measure this accurately.

After running the unit for 10 mins, indoor temp at the air intake 78 F.
Register temp closest to attic unit is 64 F.
Register temp furthest away is 66 F.
All registers are ducted through attic which is 106 F.

Are these temps okay? I was thinking of getting a tech out to check the pressure and top off the coolant if needed. Home is 6 years old and has not been serviced since it was built. Dont want to throw away money if these temps are in the normal range. All lines, coils and radiator fins are intact and clean as far as I can see without taking anything apart. Unit has brand new air filter. This is a paper filter and would definetly restrict some airflow, but thats what a filter does, right?


Very much appreciated.

glennjanie 06-09-2008 12:48 PM

Hello Matt:
Your temps are within the acceptable range. The refrigerant simply compresses to a liquid, gives up the heat outside, evaporates inside to pick up more heat and is compressed to a liquid again. It is a closed system and no gas is consumed or wears out unless there is a leak. If you had a leak it would eventually stop working at all.
I don't have much patience with the A/C servicemen who put their gauge on the 'lo side' line and say "It just needs a little gas"; they haven't learned how to take the gauge hose off the 'high side' without freezing their hand, so they just don't hook it up. Meanwhile, the condenser coil gets a little dirtier each year and adding gas makes it appear to be working right when the pressures are going out of control and, someday, it will begin to leak a lot!
Remember the quote of a good service man is "Clean first, gas last (only if it needs it)".

AU_Prospector 06-11-2008 05:55 PM

Thanks Glenn!
I will save my money for when it actually quits working (hopefully that never happens).


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