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

Hi All
I have a home gas central heating unit mounted on the outside
wall of my garage and blowing/sucking through a couple of grills in
the garage wall. Nice, it has worked well for the last 10 years to
heat the 10,000 square foot garage.
Sadly it recently died and tried to cremate itself but only succeeded
in burning some of the wiring.
No problem I thought, I just replace the cremated wires clean the
burner and away it goes again.
Wrong!
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?
Thanks in Advance

David

Get the numbers off the controller and/or gas valve and go to an HVAC
supply place. The controllers for such things are all made by a very
few manufacturers -- Johnson Controls, Honeywell, RobertShaw, etc.
There are "generic" controls available, generic meaning that they can
be adapted to about any heater or furnace. . It'll cost about $100.
(Don't ask what factory cost on those things are -- it'd spoil your
day! )

The control runs off of 24 VAC from the transformer, does a number of
functions that relate to ignition, flame proving and safety.

Check the heat exchanger in your furnace before you invest much. If
it's suspicious it'd be better to bite the bullet and replace the
whole works.

I replaced a controller in my heater last winter, but I'll be
replacing the whole heater this year during the warmer weather when
it's easy to do. That heater is 25 years old, doesn't owe me a thing.
The gas valve is occasionally intermittent, and a whole new heater
costs only about $50 more than a new gas valve.

Sheesh! Factory cost on those valves is pocket change. It's
entirely automated -- raw materials go in one end of a huge machine,
finished valves come out the other. The rest must be lawyerproofing.

Don't they have to pay for the machines and factory space?

I mean, if it really comes down to it, the cost of the materials of
just about anything may be really cheap on the molecular level. But
the process of putting it all together the way you want adds to the
cost.

Don Foreman wrote:

Sheesh! Factory cost on those valves is pocket change. It's
entirely automated -- raw materials go in one end of a huge machine,
finished valves come out the other. The rest must be lawyerproofing.

On Wed, 17 May 2006 09:52:47 -0500, Mike Berger
wrote:

Don't they have to pay for the machines and factory space?

I mean, if it really comes down to it, the cost of the materials of
just about anything may be really cheap on the molecular level. But
the process of putting it all together the way you want adds to the
cost.

Sure, but "factory cost" includes all costs associated with producing
a product including factory burden or overhead, which includes
amortization of capital investment.