An odd situation with a retrofit of two old downflow Lennox duracurve units with that nasty seven relay pack for twinning. Popped in a pair of Trane TDX furnaces.
After a year of no probs... all of a sudden (and to no surprise) the boards have that dastardly issue of burn marks on the back of the boards at a pack of resistors nesltled snuggly on the center of the board.
Normally, you'd get a series of intermettent 'false' problem codes, easily determined by the 'offending' part, is in-fact operating normally.
We replaced both 'burned boards'... but get a intermittent fault code of nine flashes. Both ignitors have been replace. And the Thermostat was replaced with a digital H/W T5000 non-programmable. And for good measure, an isolating relay was installed to further alleviate T-stat probs.
Is there anyone out there that is familiar with the Twinning of Trane Downflow furnaces and their potential anommolys?
Application: Two 120,000 btu. Common return, common supply. Heating a small gymnasium. Heat load is correct.
All installation requirements met. Common 120vac as per request for both furnaces. Solid 18/2 solid core stat wire. L1 - C = 123VAC, N1 - C = 1.3VAC, 3.2 MicroAmps flame signal on both furnaces. Gas pressures, and all conceivable tests were administered. But please feel free to overstate the obvious. It's a 100 miles out, and a pain in the arse to go to every other day.
Thanks in advance.