Should a Central Ac Compressor Pull Tab Be Continuous

1. Compressor pulling high amps

   Alright guys,

   Looking for a little help on a problem unit I am dealing with. First call was to replace the dual cap due to condensing fan not running. Replaced the cap, but the compressor was off on open thermal protection. Cooled down compressor with water, and then let compressor sit while I took another service call. Came back in a few hours and compressor and outdoor fan spun right up and all looked well. A couple hours later the homeowner called to tell tell me that the unit was off again. I went back the next day to find the factory start capacitor blown. Replaced the start capacitor with a 5-2-1 of equal capacitance. Started compressor and found the compressor running 42A. The RLA obviously being much lower at 18A. I did not change the contactor but it appears to be in fair condition when I ohm it out, and the contactor pulls in without hesitation when the thermostat calls. The compressor is not shorted to ground and has no open windings. The windings ohm at:
   C to S - 1.4
   C to R - .9
   S to R - 2.1

   One of the other technicians condemned the compressor, but other than the high amp draw the compressor would not indicate any problems. The voltage at the disconnect is 235V and there is a drop of 10V when starting the compressor. Should I be looking for another problem (i.e. breaker, contactor) before I go condemning then compressor? Or could the compressor have been FUBAR'd when it ran without a condensing fan and then without a start cap. By the way this is an American standard recip in a 4 ton Meristar condensing unit.

   Many thanks in advance,

   tranger

   ---

2. I would start by checking voltage at each leg to ground, then voltage at main panel.
   Not sure, but I get a hunch that incoming power may be an issue.

   "The only true wisdom is in knowing you know nothing" Socrates
   

   ---

3. Originally Posted by tranger03

   Alright guys,

   Looking for a little help on a problem unit I am dealing with. First call was to replace the dual cap due to condensing fan not running. Replaced the cap, but the compressor was off on open thermal protection. Cooled down compressor with water, and then let compressor sit while I took another service call. Came back in a few hours and compressor and outdoor fan spun right up and all looked well. A couple hours later the homeowner called to tell tell me that the unit was off again. I went back the next day to find the factory start capacitor blown. Replaced the start capacitor with a 5-2-1 of equal capacitance. Started compressor and found the compressor running 42A. The RLA obviously being much lower at 18A. I did not change the contactor but it appears to be in fair condition when I ohm it out, and the contactor pulls in without hesitation when the thermostat calls. The compressor is not shorted to ground and has no open windings. The windings ohm at:
   C to S - 1.4
   C to R - .9
   S to R - 2.1

   One of the other technicians condemned the compressor, but other than the high amp draw the compressor would not indicate any problems. The voltage at the disconnect is 235V and there is a drop of 10V when starting the compressor. Should I be looking for another problem (i.e. breaker, contactor) before I go condemning then compressor? Or could the compressor have been FUBAR'd when it ran without a condensing fan and then without a start cap. By the way this is an American standard recip in a 4 ton Meristar condensing unit.

   Many thanks in advance,

   tranger

   Sounds like it has an open run capacitor.

   ---

4. Run cap is new and I have checked it multiple times thinking the same thing. Still shows correct capacitance (35).

   ---

5. Originally Posted by tranger03

   Run cap is new and I have checked it multiple times thinking the same thing. Still shows correct capacitance (35).

   Try the live test on it. Capacitance equals the start winding amps times 2653 divided by the volts across the capacitor terminals. If nothing else just get an amp reading on the start winding. A coworker was getting similar numbers a few weeks back. The compressor plug had a burned connector in it. The start winding wasn't getting power. It would kick over with a hard start kit intermittently, but would run high amps, bog down, and stall.

   ---

6. I'll try that. Thanks medic.

   ---

7. hmm i wonder is the hard start kit dropping out of the circuit

   ---

8. I would change the contactor just to see if it helps. You can always reinstall the old one if not. Good luck..

   ---

9. What are your refrigerant pressures? High head can also produce high amperage, as the motor is working harder.

   ---

10. Could be overcharged system or plugged condenser(most common), or these two combined. And many more reasons for compressor to overheat and trip on safety(voltage problems, wrong/bent fan blades etc etc, too many to list). For example last week I had a 5 ton straight AC was pulling 35A, rated 30.2 max, compressor sounded horrible and tripped breaker. Turns out it was a plugged filter-dryer(some contractor moved condensing unit due to renovations and apparently didn't use nitrogen while brazing, so filter got partially plugged). There was only 2 degrees temp drop accross it though, kind of hard to detect, and very hard to blow air thru it after I cut it out. On top of that, system was overcharged. After replacing filter and charging by weight amps were like 24A(80% of rated), no problems with system(so far).

    Last edited by Frosty_VA; 08-21-2013 at 10:42 AM. Reason: mistake

    ---

11. Still need operating pressures, still need to re-check capacitor, is fan spinning correct rotation?

    ---

stichwhipar1984.blogspot.com

Source: https://hvac-talk.com/vbb/threads/1380391-Compressor-pulling-high-amps

Share this post