On Tue, 16 May 2006 23:57:46 +1000, Mastic not@thisaddress wrote:

Hi All

To cut a long story short I have no 24V to run the solenoid on the gas
modulating valve, chasing the wires back there is a transformer and
some printed circuit boards so I think the burnt wires shorted and
fried the solid state thingo.
Problem is it's old heater, no parts or etc available for it.
So I need a generic wiring diagram if anybody know where one can be
got off the web.
Is the 24V AC or DC? The gas modulating valve has several electrical
terminals on it but I think it only needs the wires to the actual
solenoid, am I right?

Since I'm not psychic, and you provided no clues as to make or
model...

Concentrate on figuring out the make and model of the gas valve,
that's the critical component. You might have to go through catalogs
to be sure. The wiring is really simple once you figure out the
terminals - there's 24V to run everything, and on an old furnace like
that a 40VA transformer is probably plenty.

There is one circuit that goes to the thermostat and back to the gas
valve for 'call for heat'. The fan is not directly controlled by the
stat (unless you hit the manual switch) it is started by the Fan/Limit
thermostat at the top of the firebox. There is a relay to kick the
120V to the fan motor, usually right next to the transformer.

And if the fan fails it gets hotter in there, the Limit part kicks
in and breaks the 'call for heat' circuit to the gas valve. Some of
those are manual reset.

Depending on the age of the unit, there may be a few 'flame rollout'
safety switches to cut the burner in the event of a plugged flue. And
we'll leave the subject of "How to sense that the pilot light is out"
for later, because there are a dozen different ways to do it.

-- Bruce --
--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
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