Wiring Diagram for Gas Hung Heater

Does the limit switch have open terminal? Sounds like the fan is wired to high cut off, rather than wired to fan.

Christopher A. Young Learn more about Jesus

After we got the pilot light sorted (it was clogged) we fired the thing up and determined that the fan switch isn't working. So, I went out today and got a new fan switch, and replaced the old one.

It _still_ doesn't work, but I can hear a distinct "click" from the heater when the fan switch _should_ be working. But the fan doesn't come on until the limit switch engages and turns the gas off. So I suspect that my new fan switch is working just fine, but there's something else wrong with the unit.

Given that the former owner of the property would have enthusiastically torn into this thing either to fix it or "improve" it, I can't count on things just being broken -- I have to accept the fact that things may be put together wrong, etc.

So -- my Google Fu completely failed me in turning up a service manual or schematic for this thing. Can anyone point me to a wiring diagram? Failing that, can anyone give me a rundown on how these things go together, where to find the limit switch, and that sort of nifty stuff?

Am I correct in assuming that if I identify the 120V wires across the fan switch and simply short them out, that the fan should come on? For that matter, I assume that with the fan _off_ I should see 120V across the appropriate terminals of the fan switch? (I'm suspecting broken or incorrect wiring here, which is why I'm asking these questions).

Thanks in advance.

Dayton is a house brand for Grainger's. See if they still have the manual on file.

enthusiastically

Check the flame sensor.

enthusiastically

enthusiastically

Sounds like you have stabding pilot system.

The fan is SUPPOSED to come on if the high limit cut off activates.

enthusiastically

Calls for heat flame comes on high limit turns flame off fan comes on

And you suggest to check the flame sensor? I think we view things differently.

Christopher A. Young Learn more about Jesus

Check the flame sensor.

Sound like you gad a code id yor dose? Stabding pilot?

Hmm. What makes you think his device has a standing pilot? Same thing told you to check the flame sensor? Which I doubt it has one, other than a thermocouple.

Christopher A. Young Learn more about Jesus

Sounds like you have stabding pilot system.

High limit cut off is supposed to turn off the burner. This is a safety design. Normally, a high limit cut off will never get used. Only if the fan is not running for some reason.

Fan comes on, at a lower setting. This is how the furnace operates, normally.

We sure learned different information. Me, I think you're mistaken.

Christopher A. Young Learn more about Jesus

The fan is SUPPOSED to come on if the high limit cut off activates.

The limit switch also turns the fan on , and it's temperature-adjustable . Look for little adjustable pointers on the face that rotates ... one's for the fan , one's for gas valve hi temp cutoff . It could also be the relay that powers the fan , which is energized by the limit switch .

The author of this web page has not inspired my confidence.

Christopher A. Young Learn more about Jesus

Sounds like you have stabding pilot system.

(top posting fixed)

The service guy told me that the limit switch both turns the burner off, and forces the fan to turn on, so that the heat exchanger gets some cooling if the fan switch is broken.

So the behavior is normal for a broken fan switch -- it's just that fixing the fan switch doesn't fix the @$#% behavior.

I couldn't find it on their web page. Suggestions?

I dunno if there is one -- I'm told the fan switch is a time delay gizmo.

Email? Snail mail? Phone call? They have very little tech data on their website.

That would mean it gets power when the flame comes on The delay is so that it warms up some and doesn't blow cold air.

There can't be a lot involved in wiring the switch to fan. Check for continuity and power.

-jim

Yea, I think it's down to that. I really prefer to have a schematic. Even if it's wrong, if it's Official it makes me feel better -- kind of like having my favorite blanky, I guess.

Ha. That got me going. At least it showed me the general direction of where to look for the limit switch (the wiring of which was hidden).

It must have been a loose connection, because after I went into Full Engineer Mode and measured everything every which way with my voltmeter, then took a couple of connections apart to visually inspect them (without finding problems), it worked fine when I turned it on again to look for problems.

So -- a qualified yippie. I never like problems that go away by themselves; I'm always afraid they're just sleeping and not dead.

enthusiastically

If the flame stays lit till the exchanger overheats then the flame sensor is okay.

There may be a second Klixon to delay the fan till the exchanger warms up.

As long as your high limit is killing the gas like it should then you should be able to get by until you properly troubleshoot the unit by forcing the fan to operate by jumpering connecting G to W

Just beware that if you do this, the burner will also operate if you turn the thermostat to "fan only"