keep losing the primary of my transformer

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keep losing the primary of my transformer

Postby jnicholas1 » Sun Dec 26, 2010 1:08 am

I have a ruud heat pump 1.5 ton with electric backup. The other day it blew the primary in the transformer. I put another one it it and when the sequencers kicked on the amerage went up quite a bit. I changed one of my sequencers. I engauged both of them but only found a small resistance on one set of the contacts. put it back together and about half a day later it did it again. Any ideas on where the overcurrent is coming from? The three element ran with 12.3 amps in them and the primary of the transformer had .35 amps
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- keep losing the primary of my transformer

Postby nomadpeo » Fri Jan 14, 2011 11:58 am

measure total transformer secondary current in heat mode with just the heat pump running. do the same in emergency heat mode. the transformer should be capable of handling all those loads combined if there is a need for aux heat. the transformer's limit is approx 1.7 amps (40 va / 24 v). if the current draw is approaching that number, you need to energize each low voltage load one at a time and isolate the one drawing too much current. if the wires outside are suspect, call for heat and measure current on the common wire outside while jiggling the wire bundle. if you see a spike occur, separate the wires and find the insulation break. if a direct short occurs while performing this test, something should chatter in the unit also. a 3 amp fuse will catch a short, but if the current hovers between 1.7 and 3.0, you may still lose a transformer. that would indicate a low voltage load beginning to deteriorate and intermitent rising current. if a load is failing in such a manner, it should also get hot. sometimes a mechanical hangup in a relay can cause current to rise.
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