humming from compressor - http://www.hvacmechanic.com/ Forums
Original message
| ebrown
 |  "humming from compressor"
, posted Sat 31 May 16:05  
i was on a service call today for a panel that had noise comming from it. after looking around and playing with the breakers i noticed that a 50amp double pole breaker was the culprit. i turned the breaker off than back on that is how i noticed. the breaker makes a noise as its engaged. i installed a new breaker and got the same result so i went to look at the ac unit. i turned the 50amp ac breaker off and the ac unit was still humming. i am trying to find out what would cause something like this to happen? could it be the compacitor is bad? if not than please advice.
only the strong will survive
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Replies:
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| burnerman
| "Re(1):humming from compressor" , posted Sun 1 Jun 15:48
had this happen once the noise you hear at unit is the themostat engaged calling for cooling the capacitor was the culpert on my job drawing too many amps as another mentioned before me you are on the right track
royboy
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| Jojo98
| "Re(1):humming from compressor" , posted Sun 1 Jun 02:14
Exactly what is your trade, and what type of service call were you on?
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| | ebrown
| "Re(2):humming from compressor" , posted Mon 2 Jun 06:13
i am a electrical contractor. some one called me out because there breaker triped and upon reengaging the breaker it had a strange noise coming from it.
only the strong will survive
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| theduke03
| "Re(1):humming from compressor" , posted Sat 31 May 16:17
There is no such thing as a compacitor. However the compressor is locked and drawing high amps. Could be caused by a faulty capacitor or the compressor itsself.
"My dad was the most feared furnace fighter in Northern Indiana."
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| | ebrown
| "Re(2):humming from compressor" , posted Sat 31 May 16:35
yeah i know its a capacitor got stupid for a minute. hey but thanks for the info. what would cause the compressor or capacitor to do this? how can i narrow it down to the one causing the problem?
only the strong will survive
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| | theduke03
| "Re(3):humming from compressor" , posted Sat 31 May 16:42
Is compressor connected to a dual capacitor(3 terminals) or not(2 terminals). If a dual cap then disreguard the fan terminal. Shut off unit and remove the wires from capacitor. Set ohmmeter to highest scale. Check ohms on the 2 terminals. If cap is good you will see ohms drop towards 0; then rise back up towards infinity. Then switch terminals and repeat. If ohms do not change then cap is open or shorted and needs to be replaced. If cap is good then I suggest adding a "hard start kit" to the unit to help that compressor start.
"My dad was the most feared furnace fighter in Northern Indiana."
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| | ebrown
| "Re(4):humming from compressor" , posted Sat 31 May 17:02
would this also cause the breaker to make noise as its engaged. i have never seen are herd of this happening.
only the strong will survive
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| | Houston204
| "Re(5):humming from compressor" , posted Sat 31 May 20:14
It could cause excessive amperage.
If you are in the profession, I recommend a fieldpiece or some other meter capable of measureing the microfarad reading. I have seen 7.5 microfarad capacitors reading 2MFD and unable to sustain operation.
"Tip of the Day" Remember to remove power first.
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