DIYbanter - View Single Post - OT

am (Laurie Forbes) wrote in message ...
This group is knowledgeable about so many topics I though I'd ask
about a problem I'm having with a Trane high efficiency (condensing,
model TUX080) furnace installed in my house. Every once in a while,
the furnace gets stuck in the cool-down part of the heat cycle wherein
the flame is out and the blower keeps running until the microprocessor
is manually reset by turning the power off/on. This is particularly
annoying when it happens in the middle of a cold night as it's usually
discovered because the house gets cold and one has to get up to reset
it. The processor is flashing an error message but, with the help of
the dealer, I've checked out the suggested fault possibilities to no
avail (ignitor, voltage level or grounding problem).

Anyhow, the dealer also mentioned that line voltage noise and spikes
can also glitch the processor so I am thinking of installing a surge
suppressor in the line input. One way would be to use a suppressor
typically used for electronic equipment such as computers but they are
plug in rather than permanent wired. Any comments on using such a
device (by installling a plug in the furnace line and plugging it into
the suppressor) would be appreciated, or, any other suggestions.

Another possibility I don't want to think about is an intermittant
processor board problem (a replacement board is nearly $500 CAN with
no assurance that it will correct the problem).

TIA for any help............

Laurie Forbes

Since it gets stuck in the same state each time, could be a "self
induced" power spike rather than an external one. For example, the
spikes resulting when the control board actuates the draft motor, the
gas solenoid or the fan motor. The draft motor comes to mind first as
its "off" spike happens when the furnace cycles off - with the fan
still running until it cools down.

Are there any accessories wired into the system, like an electronic
air cleaner or humidifier? Might try disconnecting those before
messing with the furnace.

There are a bunch of sensors in that style furnace - flame sensor,
over-temp sensor, draft sensor, I don't know what else. Takes only
one to make it stop working, but your description of the problem
indeed does not sound like a sensor related problem.

If you have A/C (or a heat pump), dirty evaporator coils can reduce
air flow to where the furnace shuts off on the over-temp. Dirty or
wet combustion supply air can clog or corrode the burners to where not
all will light and it shuts off on account of the flame sensor.
These are examples of things you can fix yourself with a suitable
shape brush.

Bob