View Full Version : rooftop comp.
06-30-2006, 02:52 PM
i have a unit (rooftop) that fried the fuses. i ohmed comp. and it seems fine is there any other way to check comp. or could there be something else that caused that to happen
06-30-2006, 03:54 PM
When you say ohmed, you also mean checked it for ground, I assume? If its not open, shorted, or grounded, it could have just been a bad fuse or power surge. Check for loose wires. Some people use a megaohm meter that can detect very suble shorts. If it checks out with your meter and is not drawing excessive amperage, its probably ok.
06-30-2006, 04:18 PM
check the fuses & disconnect to see if they're running hot when the unit is running with an infared thermometer if fuse clips or knives not making good contact they will preheat fuses causing to plow prematurely
06-30-2006, 05:17 PM
I would say remove coil wires for the compressor, ensure everything else works correctly. Disconnect CCH, reconnect compressor and try to run it, if it blows the fuses (quickly) you could have a mechanical break in the compressor. The condensor fan runs off of the same contactor, if it has only 1 fan, verify it's operation seperate from the compressor first.
06-30-2006, 09:49 PM
what was the line tag voltage of the unit,and how many fuses did it fry
07-01-2006, 02:06 AM
Carbon tracking between legs or lines
07-01-2006, 08:21 AM
if the flash guard aren't installed on the contactors....on a start that arc/flash jumpimg on the start can blow the fuses especially on 460/480 3 phase with the larger tonnages.
07-01-2006, 08:29 PM
Check the condenser fan motors, the evaporator motor, the CCH, Transformers, circuit board for shorts etc. Burnt wiring. Anything that you get voltage thru.
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