AC not cooling sometimes


  #1  
Old 05-25-10, 06:11 PM
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AC not cooling sometimes

I have two York Air Conditioners (one for the first floor, and another one for the second floor). The problem is with the AC for the second floor.

Most time that AC works fine. However the AC does not blow the cool air sometimes. I can hear and feel the air flow (but air is not cool). I checked the outside unit, and found the fan in the outside unit was not running. If I turn off and then turn on the AC by using the thermostat, the fan in the outside unit will run and the AC will blow the cool air (after the AC restarted).

I noticed that this problem happens mostly when other major electricity consumption units (like another AC, dryer, or/and water heater…) are running in the house.

My air conditioner model: York Affinity 5T, and the thermostat model: Honeywell TH6110D.

Any help would be appreciated.
 
  #2  
Old 05-25-10, 08:36 PM
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How old is that fan ? ALso check the terminal of the fan to see if you have power at the terminal when the fan is not working.
 
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Old 05-26-10, 07:40 AM
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Both the outdoor and indoor units of AC are 4 years old (from 2006). I will check the power at the terminal of the fan when it happens again.

Thank you!
 
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Old 08-10-10, 06:27 PM
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I had a service tech check that AC. But the AC worked fine when he was checking it. He didn’t find anything wrong with that AC, but only changed a filter.

But sometimes I still need to turn off and turn on for starting the outdoor unit fan. Recently, I found that this problem might be related with the power voltage. Normally, the voltage of the power outlet in my house is around 118 V. When this problem happens, the voltage of the power outlet in my house is around 114 V (the power voltage for AC should be also lower than normal time).

Is the power voltage the cause of this problem? If so, can the AC be adjusted for working in the lower voltage?

Thank you!
 
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Old 08-10-10, 06:53 PM
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Check the voltage at the contactor load and line sides with the unit running. Also, at the breaker box.

114V is too low. But check across the 240-V bus, too. Then call the utility company. They are obliged to provide 240V +/- at the meter (beyond that, it's your problem).

The utility can boost the voltage by changing a transformer tap or by installing capacitors.
 
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Old 08-17-10, 06:12 PM
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Thanks for your advice! I checked the 240-V bus. It is normally around 237V, but sometimes it drops to 230V. When it is around 230V, this problem happens more likely.

I called the utility company, and the utility sent some people over to check the voltage. They measured both 120-V and 240-V buses, and the voltage on 120-V bus was 116V and the voltage on 240-V bus was 233V at that time. They said these voltages are “good”.

Now, should I update my house electrical system to boost the voltage on 240-V bus to 240V +/-, or ask AC services to adjust the AC for the lower working voltage?
 
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Old 08-18-10, 07:52 AM
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Originally Posted by dddiy
Now, should I update my house electrical system to boost the voltage on 240-V bus to 240V +/-, or ask AC services to adjust the AC for the lower working voltage?
I don't know what you could do inside your house to "boost" the voltage at the service panel buses. Only the utility could do that - and it seems that is not going to happen.

There is no way to adjust your A/C to run at a lower voltage. Check the compressor nameplate, but chances are it is dual rated for both 208/230V (or any voltage in between). Have you checked the voltage on the load side of the condenser unit? That's what you need to check.

I don't think the the voltage is what is causing your problem.
 
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Old 08-18-10, 01:58 PM
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One more thought.

First, when the fan quits, does the compressor stop too? That might suggest a bad or weak contactor (located inside the condenser unit). When the unit stops, check the voltage on the load and line sides of the contactor. Then, you can try pushing the contactor manually closed with a stick.

Also, check the 24-V control voltage at the contactor when there is a call for A/C.
 
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Old 08-18-10, 06:44 PM
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Thanks for pointing out the direction for me.

When the fan doesn’t run, the compressor doesn’t run either. Sometimes I need to turn it off and then turn back on the AC several times to start the outdoor unit. Sometimes when I turned on the AC thermostat, the outdoor fan started, rotated several times, and then stopped.
 
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Old 08-18-10, 07:09 PM
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Sounds like it could be the contactor. Please complete the other tests I suggested.
 
  #11  
Old 08-25-10, 10:26 AM
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could be the low voltage wiring or the tstat itself. Need to see if the low voltage drops out at the contactor when it is not pulled in. I am betting that a squirrel has chewed on your tstat wiring causing a intermittent short.
 
 

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