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-   -   reduced cooling after condenser fan failure (http://www.diychatroom.com/f17/reduced-cooling-after-condenser-fan-failure-113160/)

technic 08-06-2011 02:39 PM

reduced cooling after condenser fan failure
 
Earlier this week I noticed that my a/c unit outside sounded different, and found that the condenser fan was not on. I spun it with a screw driver and it spun freely but did not start up, and noticed that the fan motor felt very hot so I turned off the power to the unit for awhile and tried it again and the fan came on. After awhile it was off again but this time with power going to it it would not spin freely and it was buzzing. I decided to try to replace the capacitor first which was not the problem, it continued to stop. I ended up installing a universal condenser fan from grainger which matched the specs of my old one but had a slightly different wiring configuration. Now that the condenser fan is working properly The air conditioning is not quite as cold as it was before. setting my thermostat to 70 before would have the a/c running around 50% of the time, now it is running 100% and can't quite cool down to 70 (lowest is 71) which I can live with. The temperature at the floor registers of the output air is 58* and the intake air is 71* but the outside temp today is only 85* here in the Midwest so I'm more worried about those 100*+ days that we get.

My question is: do home a/c compressors have high pressure relief valves on them or did my compressor overheat and is now less efficient?

beenthere 08-06-2011 04:36 PM

Compressors have internal relief valves. Are you sure the new condenser fan motor is spinning the right way.

technic 08-06-2011 06:39 PM

Quote:

Originally Posted by beenthere (Post 701780)
Compressors have internal relief valves. Are you sure the new condenser fan motor is spinning the right way.

at first i actually did have it spinning the wrong way, there are two connectors coming out of the motor to switch polarity, I first set it to clockwise because to me the blade was spinning clockwise, then I realized that it was actually spinning counter clockwise to the face of the motor so I switched it. I'm an automotive mechanic and I work on a/c in vehicles all the time and I know that those compressors sometimes have external relief valves that will purge freon if the pressure gets too high which is usually the case when a fan fails causing the pressures to rise due to the increased temps.

beenthere 08-06-2011 07:18 PM

You said the new motor matched the specs of the old motor. Did you go by HP, or by amp draw. Also, is the new motor longer then the old motor.

technic 08-06-2011 07:50 PM

Quote:

Originally Posted by beenthere (Post 701849)
You said the new motor matched the specs of the old motor. Did you go by HP, or by amp draw. Also, is the new motor longer then the old motor.

my old motor had these specs:
hp 1/6
volt 208/230
rpm 825
amp 1.1
hz 60
frame 48y
thermally protected
mfg no m97 c
pt no 10584308

I actually ordered this part number from a website, then got an e-mail from them saying it was backordered, so I called to find out how long it would take and they said 10-14 days, so i cancelled the order.

this is the motor I ordered:
http://www.grainger.com/Grainger/wwg...N=0&sst=subset

I cut the shaft to the same length as the old motor and both motors are the same physical size

beenthere 08-06-2011 07:56 PM

May just be low on charge, and just a coincidence that it is showing up now.

technic 08-06-2011 08:18 PM

Quote:

Originally Posted by beenthere (Post 701868)
May just be low on charge, and just a coincidence that it is showing up now.

It's pretty comfortable, it's much better now than trying to sleep with no a/c at all, I'll have to wait until later this week when it is supposed to get hotter again to see how it performs, if I'm not happy with it then, I guess I'll have to have a tech come out and check the freon. As a service professional I'm pretty wary of hiring other service professionals because I have seen and heard of some pretty shady practices.

yuri 08-06-2011 08:36 PM

Did you position the fan blade on the shaft in the same position as B4. If it is higher or lower then it won't suck air properly and will result in the coil/freon temps being higher and reduced capacity. Notice Beenthere asked you if the new motor is longer? If it is the blade may be lower. Sly fox he is.:laughing:

It does have an internal relief valve, it will sound like a rifle shot when it goes off and a very high pitched scream/whistle. In very rare situations they may not reseat properly but I have never run into that. May be an urban myth or trade story.

technic 08-06-2011 09:10 PM

Quote:

Originally Posted by yuri (Post 701902)
Did you position the fan blade on the shaft in the same position as B4. If it is higher or lower then it won't suck air properly and will result in the coil/freon temps being higher and reduced capacity. Notice Beenthere asked you if the new motor is longer? If it is the blade may be lower. Sly fox he is.:laughing:

It does have an internal relief valve, it will sound like a rifle shot when it goes off and a very high pitched scream/whistle. In very rare situations they may not reseat properly but I have never run into that. May be an urban myth or trade story.

up, made sure to swap the fan blade over exactly how it was on the old motor. I have no idea how long it was running without a fan, I noticed it when I came home from work and it had been over 100* that day, so the purge valve could have gone off.

REP 08-07-2011 01:02 AM

If you look down at the fan blade and motor you will notice That each blade will have a pitch to it.
That means that one side of each blade will have a high side and a low side.
If the rotation is correct it will be turning in the direction of the low side.
The low side will be scooping air and moving it to the high side as it turns.
The fan blade should be located in the middle of the fan shroud.Up too high in the shroud or down too low will rob CFMs that your condenser needs to cool off,lowering the effiency of the whole system.


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