dkpd1581
| Joined: | Sun Dec 17th, 2006 |
| Location: | Atlanta, Georgia USA |
| Posts: | 199 |
| Flavorite Brew: | a free one |
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Verify 208/230 VAC to transformer.
Verify transformer is tapped for correct incoming voltage. Transformers set at 230 VAC tap but being supplied with only 208 VAC will not produce a LV signal of at least 22 VAC to run LV system. Retap as necessary.
Check to see if there is 24 VAC coming out of the transformer - if not find reason why the high side windings are open or 3-5 amp fuse is blown.
If 24 VAC is coming out of the transformer and through the 3-5 amp circuit, follow it through the LV circuits - going into board and not out is possible bad board. Out of board but not to contactor - possible limit switch open (HP manual reset, LP auto reset defective).
No board - follow through relay coils - coils open replace relay. Coils good but contacts do not change state - replace relay.
24 VAC to contactor coil of compressor and/or fan contactor relay but no change of state in contacts same as above. If contacts change state but full voltage registered across closed contacts means the contact surface is bad or obstructed. Clean contacts or replace as necessary.
24 VAC circuit is closed and completing a proper path, contactors change state, and zero voltage is registered across closed contacts, check OL switch on compressor, check physical connections in HV circuit, compressor windings for shorts to ground, partially shorted windings, open windings.
If compressor tries to start but is unable to, pulls locked rotor amps and quits, check the capacitor and verify that its within 10 percent of name plate value - if not replace. If all else is good install a hard start capacitor.
If compressor tries and fails to start with all the above, you may have a physically locked up compressor and a last effort is to strike the compressor head on start up in an attempt to dislodge the seizure.
Try this and let us know what happens.
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