# Lennox Superior Fireplace Problem



## bob22 (May 28, 2008)

Try going to:
http://www.lennoxhearthproducts.com/products/fireplaces/gas/
download the manual for your fireplace insert; it has troubleshooting advice.
I'm 99.9% sure it isn't your wall switch.


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## yuri (Nov 29, 2008)

I would replace the wall switch. they use a millivolt system (3/4 of a volt or less) and those light switches cost $1-2 and do wear out or get corroded. make sure you have bare copper and tighten the wires nice and snug on the new switch. voltage is so low it cannot hurt you so you don't have to turn anything off. just don't touch them to anything metal or the gas valve will shut down.


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## kcrossley2 (Dec 17, 2006)

Since the fireplace uses a millivolt system should I purchase a special wall switch or just get a standard one?


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## yuri (Nov 29, 2008)

standard one. get a new one and not some used one or sitting in a damp basement or garage one. takes VERY little resistance to stop a millivolt system.


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## kcrossley2 (Dec 17, 2006)

Okay, thanks!


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## how (Feb 26, 2011)

I find that often the pilot flame is partially restricted enough to not envelope the thermopile adequately. This reduces the dcv so that minor resistance stops the fireplace from working. You can try tapping the metal beside the pilot assembly with a large screwdriver while the pilot is burning and the vibration plus the pilot gas pressure will often dislodge any obstructing debris. You will notice the pilot flame becoming larger if you are successful. If the fireplace then fires up, the wall switch will not need to be changed.

Of course perhaps opening up the fireplace to access the thermo pile is more trouble than a wall switch change but should be kept in mind if the wall switch change doesn't correct the problem.


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## kcrossley2 (Dec 17, 2006)

Good suggestion. What does a thermopile look like?


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## how (Feb 26, 2011)

If you look at your pilot flame, the powerpile will be bathed by the pilot flame and be about the same width as a cigarette. When tapping the metal around the pilot assembly, don't accidently hit the little pilot igniter or you may damage it.
Bobs suggestion for downloading your manual is worthwhile for showing how to access the pilot(if you need to) as well as showing what the parts are what.


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## kcrossley2 (Dec 17, 2006)

What does the thermopile do and how does that differ from the thermocouple?


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## how (Feb 26, 2011)

A thermocouple produces a fraction of the power a thermopile does. A thermopile is a collection of thermocouples that produces enough voltage from the pilot flame to run your gas valve, safety limit controls and thermostat/on-off switch.


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## kcrossley2 (Dec 17, 2006)

I started up my Lennox gas fireplace today (Model LMDV-4035CNM) and I'm having the same problem as last year. According to the troubleshooting guide in the owner's manual I'm supposed to do the following:

Check thermopile with millivolt meter. Take reading
at thermopile terminals of gas valve. Should read
325 millivolts minimum with optional wall switch
“OFF.” Replace faulty thermopile if reading is below
specified minimum.

This particular gas fireplace has a SIT Millivolt Natural Gas Valve. There are three terminals labeled TPTH, TP, and TH. Using a voltmeter, where do I place the leads to measure the voltage?


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## kcrossley2 (Dec 17, 2006)

Okay, I just tested the TPTH and the TP terminals and I'm getting 460mv with the wall SWITCH OFF and 200mv with the wall switch on. 

The weird thing is if I hold the voltmeter leads on the two terminals, the voltage with the SWITCH OFF will slowly rise from 460mv to 492mv. If I hold the voltmeter leads on the terminals with the SWITCH ON the voltage will drop from 200mv to 186mv. I waited about 10 minutes and the SWITCH ON voltage stabilized around 183mv. So far the fireplace remains lit. I'll keep an eye on it and see what happens.

What does this indicate?


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## kcrossley2 (Dec 17, 2006)

Still having problems. Bumping this old thread for help.


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## beenthere (Oct 11, 2008)

Replace that switch.


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## yuri (Nov 29, 2008)

U R only as good as your weakest link in a MV system and any device with open contacts is the weakest link. Replace da switch.


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## kcrossley2 (Dec 17, 2006)

Already did. No effect.


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## yuri (Nov 29, 2008)

A new healthy powerpile should produce 700-750 MV with no load or wires attached to it. Below 650 and I replace them. When testing them DO NOT hold the wires with your fingers or your body drains the current. Use alligator clips on your probes. If the pilot burner is dirty and the flame not strong enough it won't heat the generator hot enough and the MVs drop. If you have excessive draft on the burner it can disturb the flame too and that is not easy to discuss or fix w/o me being there.


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## kcrossley2 (Dec 17, 2006)

yuri said:


> A new healthy powerpile should produce 700-750 MV with no load or wires attached to it. Below 650 and I replace them. When testing them DO NOT hold the wires with your fingers or your body drains the current. Use alligator clips on your probes. If the pilot burner is dirty and the flame not strong enough it won't heat the generator hot enough and the MVs drop. If you have excessive draft on the burner it can disturb the flame too and that is not easy to discuss or fix w/o me being there.


Thanks for your post Yuri. I don't believe this is a draft issue, because we've never had any problems before now. I'm beginning to suspect that either the orifice is dirty, like you mentioned, or the Thermocouple may be a problem. I read (please correct me if I'm wrong) that if the Thermopile is defective usually the pilot light won't stay lit, which it does.

How do I clean the orifice?


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## yuri (Nov 29, 2008)

The thermopile gets progressively weaker until hit hits the dropout point which may be 2-300MV and B4 that happens the burner won't go on so that info is wrong. The pilot will hold at 300MV but it needs the extra power to literally open the valve, There are 2 valves, pilot and main.

You would need to remove the whole pilot burner and CAREFULLY disassemble it and clean it. I would get a Pro to do it because you could end up with a gas leak at the fittings on the burner and at the valve if you don't seat them and test them with soap properly etc. The logs need to be set properly and the main burner etc or CO can be produced. People have died from CO from leaky or poorly burning fireplaces. Now you are entering dangerous territory.:whistling2:


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## kcrossley2 (Dec 17, 2006)

Sounds good. Perhaps I should call in a pro.


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## yuri (Nov 29, 2008)

Reread my previous post as I added to it.

Yeah, we had a tragedy in Ontario a few yrs ago where a woman survived but her kids and hubby died from a leaky fireplace. Sad part was she was a nurse ( should have been aware of CO symptoms?), thought they had flu symptoms for several days and turns out it was the fireplace poisoning them. I use a CO sniffer after working on them.


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## kcrossley2 (Dec 17, 2006)

We do have a CO alarm plugged in right next to the fireplace for that very reason. We also have a second one in our laundry room. When it comes to gas I don't take any chances, which is why I'll likely call in the pros.


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## yuri (Nov 29, 2008)

The problem with CO detectors is that not all of them detect small continuos amounts which can slowly poison you. They are meant for major events/chimney blockages etc. For under $50 you cannot always get that sensitivity and accuracy. Pro units cost $200-1000 or more and need calibrating.


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## kcrossley2 (Dec 17, 2006)

Well, at least it's something. I wonder if the gas company will come out and check for leaks?


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## yuri (Nov 29, 2008)

Some do. Ours does and they have very expensive properly calibrated testers that can read 1 ppm down to 1% accuracy. Read the specs on your HDepot unit and the guaranteed sensitivity is the issue plus they lose sensitivity with age, good for 5 yrs somewheres I read.


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## beenthere (Oct 11, 2008)

kcrossley2 said:


> We do have a CO alarm plugged in right next to the fireplace for that very reason. We also have a second one in our laundry room. When it comes to gas I don't take any chances, which is why I'll likely call in the pros.


Get low level CO detectors.


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## kcrossley2 (Dec 17, 2006)

A neighbor suggested using compressed air to clean out the gas outlets. What do you think?


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## yuri (Nov 29, 2008)

You gotta be kidding? Did we not discuss the safety issues? I don't condone DIYers taking apart actual gas burners or doing anything to them that can affect the flame or combustion. Fireplaces can be worse than furnaces as they are actually in your living area. A furnace can spill fumes and they get sucked back up into the chimney thru a draft diverter, not so with a fireplace.


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## kcrossley2 (Dec 17, 2006)

yuri said:


> You gotta be kidding? Did we not discuss the safety issues? I don't condone DIYers taking apart actual gas burners or doing anything to them that can affect the flame or combustion. Fireplaces can be worse than furnaces as they are actually in your living area. A furnace can spill fumes and they get sucked back up into the chimney thru a draft diverter, not so with a fireplace.


Relax Yuri. I'm not taking anything apart. I'm simply cleaning out the fireplace with a vacuum cleaner and compressed air. Plus I'm removing the embers (rock wool), vermiculite, and decorative stone. The best case scenario is the cleaning works. The worst case scenario is at least the fireplace will be cleaned when the service tech arrives. 

Does that make you feel better?


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## yuri (Nov 29, 2008)

Yeah, as long as a Pro checks the flame and other safety issues. I am concerned about all the other readers who might be tempted to do something unsafe with theirs. Don't blow into the burners or debris may clog the orifices/slots and make things worse.:yes:

Getting ready to eat some Thanksgiving turkey and get fat on carbs and al the goodies today.


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## kcrossley2 (Dec 17, 2006)

yuri said:


> Don't blow into the burners or debris may clog the orifices/slots and make things worse.:yes:


Okay, will do. Thanks for your help. I'll make sure to post a postscript on this issue so others can benefit from my experience.


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## yuri (Nov 29, 2008)

That would be good. After that Ontario tragedy fireplaces are not to be fooled around with. They do make low level CO detectors and I hear they run $200 and up. Senco makes them. Google them and read the specs.


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## kcrossley2 (Dec 17, 2006)

Well it appears that the cleaning worked! The fireplace has been running for about a half hour and it hasn't cut-off. Plus, it turns on immediately. Last season, it took me several tries before the gas would ignite. 

On another note, is there anything wrong or dangerous with adding some additional glowing embers (rock wool) to the fireplace? It came with some, but not very much.


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## yuri (Nov 29, 2008)

As long as you don't block the burner ports it should be okay. You can buy them from a fireplace store.


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## kcrossley2 (Dec 17, 2006)

An interesting thing happened this morning. If you've been following this thread, you know that I thought I had finally fixed my Lennox gas fireplace. It's been lighting and staying lit fine for weeks.

Since it's getting colder here (47 degrees), I decided to check all of my HVAC equipment, including the fireplace. I flipped the wall switch this morning and nothing. At first, I thought it was due to the change in weather. But I noticed I didn't hear that familiar click of the wall switch activating the SIT Millivolt Gas Valve. I began to suspect the wall switch, like others have suggested, but then I remembered that I already replaced that a few months back. 

Then it occurred to me to check the leads going into the SIT Millivolt Gas Valve. I removed and reconnected both, flipped the wall switch and the fireplace fired up. I never thought the connectors could get dirty, but that seems to have been part of the problem. How does one clean these connectors?

Thanks again for everyone's help with this problem. :thumbsup:


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## yuri (Nov 29, 2008)

actually that is the most common problem with them beside weak generators, I take them off and sand them with 400 or 800 grit emory paper or scrape them clean with a sharp screwdriver until I see bare metal. Sandpaper is better. The cleaning probably did not solve it but it was a coincidence it fired up. Most likely it is those poor connections.


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## kcrossley2 (Dec 17, 2006)

yuri said:


> actually that is the most common problem with them beside weak generators, I take them off and sand them with 400 or 800 grit emory paper or scrape them clean with a sharp screwdriver until I see bare metal. Sandpaper is better. The cleaning probably did not solve it but it was a coincidence it fired up. Most likely it is those poor connections.


Okay, I'll try that later today. Thanks Yuri.


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