On Tue, 12 Apr 2011 10:40:02 -0700, John Robertson
wrote:



Yes, the thread got too long. If you saw the photo, and know the
primary went open on 3 transformers, it sure looks like a problem on the
primary side. If the load was too much, those wires on the secondary
side would most likely have been at the very least discolored from the
heat.

Tony

Yes, I looked at the pictures (rather poor resolution). The failure
looks like a connection issue because there is no evidence of windings
overheating. If the output was shorted the transformer would burn up -
assuming it could sink enough current, but it would be unlikely to flare
at one spot. This is a pretty standard 115VAC transformer, I've seen
many of them...

If someone tried to pump 5000 volts into the transformer then possibly
you could get an arc like that to the transformer frame, so that would
mean a serious miss-wiring of the furnace where the igniter somehow was
connected to the primary of the transformer and then turned on.

Hard to see that happening as the transformer powers the logic board
that would enable the igniter to fire up!

John :-#)#
And the FACT that the furnace in question uses a hot plate ignitor
further removes that scenario from any semplance of possibility