Honeywell Gas Wall Furnace turns off after only 30-45 seconds


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Old 11-24-09, 02:22 PM
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Angry Honeywell Gas Wall Furnace turns off after only 30-45 seconds

I have a 750mV Honeywell gas wall furnace. It got moved from one wall to another. Every since the move and reconnect, the heater has stopped working. The only thing that changed from the original install is that I got a new Honeywell thermostat. It is the RTH 111. It says it's compatible with the mV system.

So, when I first tried to light the pilot, everything went just fine but after the flames came on, the heater would click and everything would go out. I did some research and then when trying to re-light the pilot, realized that it wouldn't stay lit.

My research then said to replace the thermopile. I took it out (it looked toasted) and went out and replaced it with a new one. The new one lights the pilot just fine and it stays lit. Again, I went through the process of trying to get the heater to work.

I turned on the thermostat to the highest setting, lit the pilot, turned the gas on and it worked for about 30-45 seconds. The flames come on beautifully and the heat starts (there's no blower) and then it clicks and shuts off pilot and all.

I have seen that there is a possibility that my thermopile is overheating. So, then I went to the pilot adjust screw and turned it clockwise to see if I could get the pilot flame down just a little. I turned it clockwise quite a bit and I still can't get the heater to stay on.

Should I keep turning some more until it works or is there a possibility that something else might be wrong? I don't see a flame sensor that needs to be cleaned. The only parts to this heater are the gas valve unit, the pilot and the thermopile.

Is there a possibility that I have the thermopile wired wrong?

As of now, the there are only three terminals on the gas valve. Upper right, lower right and lower left. The pilot is pre-connected. I have the thermostat white wire on the bottom left and the red (I believe it's the hot) wire on top right. I have the thermopile's red (hot wire) to the top right and ground to the bottom right.

Can anyone please help? I'm in northern CA and it's getting pretty cold at night. Space heaters don't do much except waste electricity.

A huge thanks in advance!
 
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Old 11-24-09, 03:44 PM
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You apparently have a millivolt control system.

The most common reason for these not to work is a dirty pilot burner and dirty pilot orifice. Describe the pilot burner flame. It should look like a small blowtorch.

If it has a yellow flame, or is easily blown around like a candle flame, the pilot burner need to be disassembled and cleaned and the pilot orifice removed and cleaned, or replaced.
 
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Old 11-24-09, 03:45 PM
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Why did you change the thermostat? Since you said yourself that this is when your problem started, then the thing to do would be to rehook up the old one and see. Hopefully you did not throw it away.

Is the new thermostat mechanical or digital? If digital and Mv compatible, are there dip switches inside that have to be set?
 
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Old 11-24-09, 06:23 PM
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Check and make sure you haven't pinched the tstat wires between the sheetmetal somewhere in the furnace.
I see you are in Salinas, why not call PG&E?
 
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Old 11-24-09, 06:41 PM
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Most thermostats are designed for use with 24 VAC circuits, and wont work with millivolt systems.

Post the make and model number of the thermostat you are using and perhaps we can tell you if you have the proper type.
 
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Old 11-28-09, 11:12 PM
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continuing to work on the problem

The thermostat is the Honeywell RTH 111. It said on the package that it would be compatible with millivolt systems. It is a digital one.

I changed the thermostat because the old mechanical one was pretty worn out but now I'm thinking that maybe I should go back and get a new one of those.

The pilot flame is blue and looks like a blowtorch. It stays lit when I first light the pilot.

A contractor set up the new digital thermostat but I went back to double check how it was set up. Since my old thermostat only had two wires, it required a jumper and it looked like everything was set up correctly.

MBK3...I had no idea I could call PG&E for this. I should do that.

I do however hear a click when the furnace turns off. I also noticed that the gas turns off completely. I researched and the Honeywell website said it could possibly be my thermopile overheating and engaging a safety switch inside.

My problem with this is that there is a fixed place for the pilot and thermopile. I have also tried playing around with the pilot flame making allowing more or less gas to go through and I still can't get it to stay on.

I guess I'll have to make an appointment with PG&E. I'm just hoping I can avoid replacing the whole thing.

Thanks for the tips!

Is there anything else I should do??
 
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Old 11-29-09, 12:24 AM
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How are the terminals on the gas valve labeled?

For example, they might be labeled pg/th, th and pg.
 
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Old 11-29-09, 08:51 AM
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Top left is TH, top right is PP, bottom left is TH and bottom right is PP.
 
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Old 11-29-09, 11:43 AM
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I presume that one of the TH and PP terminals are connected together electrically?
 
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Old 11-29-09, 12:46 PM
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Yeah, the top ones are connected together. The top TH has a hardwired pilot to it as well.

I did change the thermostat today to the mechanical ones but it hasn't fixed the problem.
 
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Old 11-29-09, 02:14 PM
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By a hardwired pilot, I'm guessing you mean that one of the wires to the pilot generator is connected to that top pair of terminals, which we'll call the TH-TP terminal.


With the thermostat turned down to the lowest setting, measure the DC millivolts between the TH-TP and TP terminals.

Turn the thermostat up to 80 degrees, and take that measurement again.

Also with the thermostat turned up measure the millivolts between TH and TP.

I'm presuming the connections for your thermostat are between TH-TP and TH, and the gas valve is turned to the ON position, not the PILOT position.
 
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Old 11-29-09, 02:24 PM
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Also, when you light the pilot, keep the thermostat turned down to a minimum setting for 5 minutes or so. It takes some time for the pilot generator to heat up enough to provide sufficient power to hold the magnet and operate the gas valve.

Turn it up too quickly and the magnet will tend to drop out and the burner may not light.


That's probably not the problem, though.
 
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Old 11-29-09, 06:59 PM
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If the generator has clips on the end, cut them off. Scrap the wires to brighten them and connecto gas valve. The reason i mention this, I have found many that have poor connection thru the clips, and when removed the voltage is increased.
As I mention in another post, check to make sure the tstat wires are not pinched where they leave the furnace.
Also, when PG&E arrives make sure he/she uses their meter and not just peek around.
Are there any splices in the t'stat wire you are aware of?
Please advise us after PG&E has made the call.
 
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Old 11-30-09, 08:38 AM
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Sounds as if your thermopile is wired in series with an eco or vent safety switch. You said the furnace had been moved. I suspect the furnace is improperly vented and is spilling flue gasses at the draft diverter causing a safety to overheat. Hence the click. Have seen elbows added to the venting too close to the furnace cause problems like you describe.
 
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Old 12-01-09, 08:43 PM
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Got it to work...kind of

So after all the running around, I didn't have to look for pinched wires or check the voltage on the gas valve. I removed the front cover of the furnace in order to get the gas valve without any obstructions.

The heater turned on beautifully and stayed on. When I put the cover on the heater, it suddenly clicked off. Voila! It must be a venting thing.

So now, in order to have the heater running, I have to keep the grill cover off the heater. I guess I finally know what the problem is.
 
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Old 12-01-09, 10:23 PM
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Originally Posted by soccermaniac723
So now, in order to have the heater running, I have to keep the grill cover off the heater. I guess I finally know what the problem is.

Well no, you don't. You are merely guessing again. You prefer your guesses to a systematic way of isolating the actual problem.
 
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Old 12-02-09, 04:41 PM
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How many tests back and forth did you do - with the grill on, then off, then on, then off, etc., etc.,....to rule out a coincidence.

If not a coincidence, make sure the grill does not push on wires, gas valve, or anything else inside. The grill cover is not damaged/bent inward, is it?

Then let us know if this is the only grill that can be installed on that wall furnace - to rule out that say(if there are 2 grills) an upper cover is put where a lower cover should be. (One of my tenants did that with a mobile home furnace!)

Also tell us if the grill has a filter attached to it.

Also tell us about how many square inches of slots ( or whatever type openings), allow air to enter the furnace through that cover.

This is most interesting. Hope you did not leave us for good, since by you thinking you fixed it, if that indeed occured, you really only found a symptom of some other underlying cause.
 
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Old 12-02-09, 05:56 PM
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I tested the heater back and forth with and without the grill and it seems that it was mere coincidence. The grill is in perfect condition. I just wish the contractor that had done the work originally hadn't been so unprofessional in the end otherwise I would get him to come out and fix it.

Another thing, when the heater did turn on and stay on, it seems like the valve was stuck in that position because it would not respond to the thermostat. It would not turn off so I had to manually shut off the gas valve.

I am going to take the multimeter and do the testing on it that SeattlePioneer told me to do. When I got the heater to work, I was so happy that I wasn't willing to do any more testing but since it was temporary, it's time I go about it in a methodical way.

SeattlePioneer, it's not that I don't use a systematic way but I'm a grad student and my finals are taking a big of precedence over this for now. I will, however, measure the voltage and let everyone know the results.

I also have PG&E coming over next week so they might help me with the problem if it still exists then.

Thanks everyone for the suggestions though. I really appreciate it.
 
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Old 12-04-09, 09:36 AM
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Smile

Originally Posted by SeattlePioneer
By a hardwired pilot, I'm guessing you mean that one of the wires to the pilot generator is connected to that top pair of terminals, which we'll call the TH-TP terminal.


With the thermostat turned down to the lowest setting, measure the DC millivolts between the TH-TP and TP terminals.

Turn the thermostat up to 80 degrees, and take that measurement again.

Also with the thermostat turned up measure the millivolts between TH and TP.

I'm presuming the connections for your thermostat are between TH-TP and TH, and the gas valve is turned to the ON position, not the PILOT position.
Hello everyone,

I didn't have the chance to measure the millivolts myself but a repairman just did this morning. He said that there weren't enough millivolts read at the terminals and concluded that the gas valve needed to be replaced.

I don't have the guts to go too far with d.i.y. repairs because I don't have much time or expertise to do it but I thought I would let everyone know that the gas valve is being replaced and it should fix the problem.

I did inspect the unit and there were no wires pinched. I went into the attic and it looks like the venting was done well and did not have any sharp turns in it. Since the heater only has a few components, I ruled everything else out before thinking it was the gas valve.

Also, what helped was going to a D.I.Y. chat room and learning how the heater worked.

I'm really glad this forum exists. Thanks everyone especially Seattle Pioneer.
 
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Old 12-04-09, 11:03 AM
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Originally Posted by soccermaniac723

I didn't have the chance to measure the millivolts myself but a repairman just did this morning. He said that there weren't enough millivolts read at the terminals and concluded that the gas valve needed to be replaced.


Ummm. Normally you decide that the gas valve is bad when the normal amount of millivolts are present and it still wont do what it's supposed to do.

A lack of adequate millivolts suggests that the problem is elsewhere, such as a bad switch, electrical connection, pilot flame or pilot generator.

However, we'll hope the diagnosis is correct and a new gas valve solves the problem.
 
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Old 12-04-09, 04:54 PM
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Did the Serviceman indicate what reads he had, on your service report?
 
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Old 12-04-09, 05:59 PM
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Originally Posted by SeattlePioneer
Ummm. Normally you decide that the gas valve is bad when the normal amount of millivolts are present and it still wont do what it's supposed to do.
That's what I thought too. I kept reading and rereading that post over and over, out of disbeleif at either the repairman, or soccer got the story from the repairman backwards somehow.
 
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Old 12-05-09, 07:43 PM
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I'm sorry everyone, I had the diagnosis backwards. I had to ask again what the readings were. I believe he said he read about 350mV from the thermopile but the second valve wouldn't open.

Anyway, once the valve got replaced, the heater worked like a champ and responded to the thermostat and everything. I tuned it on and off a few times to make sure everything was working correctly.

I always read some posts and think some people just don't make sense and in this case it was me. Sorry about the mix-up.
 
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Old 12-06-09, 12:01 PM
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Thanks for coming back on and clearing it up.
 
 

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