keep losing the primary of my transformer

[jnicholas1]

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 * The three element ran with 12.3 amps in them and the primary of the transformer had .35 amps

[jnicholas1]

if I have a short in the low voltage wouldn't the secondary of the transformer *

[jnicholas1]

okay I wasn't picturing that in my mind but you are right. I will take your advice and add a fuse to the secondary while I try to find the short. A three amp fuse should be plenty for a 40va transformer.

[hvaclover]

In cases where trans are not factory protected by a fuse I find it handy to mini breakers instead of fuses.

[nomadpeo]

you might try the following 'divide and conquer' approach.

- install a 3 amp fuse in transformer secondary.

- measure and record total secondary current in heat pump mode only (call for heat 1 degree above room temp).

- measure and record total secondary current in emergency heat mode only.

- measure and record total secondary current in heat pump plus aux heat mode ( run heat 5 degrees above room temp). the transformer should be able to handle all this current and the current should not exceed 1.6 amps (40va / 24v)

you can then run heat in each mode separately. if there is a current spike, the fuse may blow and you can focus on outside or inside.

if it is determined the problem is occurring outside, install a fuse in the common wire outside and jiggle the wire bundle. if the fuse blows, look for a break in insulation outside.

the current limit for the 40 va transformer is approx 1.7 amps (40va / 24 v). a direct short will blow a 3a fuse. an increase to 2 amps, however may take out another transformer. ultimately, you may need to look for an overheating relay or sequencer.

[nomadpeo]

purpose would be to locate the problem.