# Lennox Whisper Heat G20 series occasionally pops when igniting



## hvaclover (Oct 2, 2008)

Should have replaced all burners at the same time if that indeed is the problem.

Lennox might have a diff policy, however. Did he show you or say why the burners needed replacing? As I recall those were stainless steel burners.


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## Tator1076 (Dec 22, 2009)

CubsWin said:


> I have a 14 year old Lennox Whisper Heat G20 gas furnace that has been giving me problems since last winter. I had a technician come out in the fall to clean and repair the unit. He cleaned everything out and replaced the flame sensor, but the furnace continued to "pop" (sounds like a build up of gas igniting) when igniting. After a couple return visits, the technician replaced one of the burners (and also the pilot module for another clicking issue) and thought that would resolve my problem, but the furnace is still popping occasionally on ignition. I would say that it has some degree of pop on about 1 out of every 5 times that the furnace comes on, with some of them being small and others being loud enough to startle nearby people or my dog.
> 
> I called the technician back again and he said he would most likely need to replace one or both of the other burners to resolve this problem, but that he didn't see any noticeable problems with them. Does that sound like a reasonable solution to have to replace all my burners? The technician seems very knowledgeable and has done other work for me in the past, but before I spend the money on 2 more burners is there something else that he is overlooking that would be a more likely cause of this type of behavior?


 


You Need a New gas valve!!!!! I work on Lennox over 17 years now and some reason the gas valve on Whisper heat will open fast over time. It is needs to be 3.5 coming out of it and now I bet it like over 5.0. This is very important tio get replace. If you have to call another Lennox dealer.


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## Tator1076 (Dec 22, 2009)

Note Flame sensor should never be replace. All it need to be is clean. When a company replace it all the time its a scam.


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## CubsWin (Dec 28, 2007)

Thanks for all the feedback so far. The technician replaced the one burner because that was the one that he saw with delayed ignition. After thoroughly cleaning it out twice, he indicated that he would have to replace it although he couldn't "see" anything physically wrong with it.

As for the gas valve, how difficult is it to determine whether that is the problem? I'm assuming it is something that I wouldn't want to do myself, but is that a standard check for a service technician to make? He has done everything since my first visit as free callbacks, so I'm not afraid to have him come check the gas valve if that is the likely culprit.


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## hvac122 (Dec 10, 2007)

Tator1076 said:


> Note Flame sensor should never be replace. All it need to be is clean. When a company replace it all the time its a scam.


What? If a flame sensor is reading low it does need to be replaced. Or if it was cleaned with sandpaper it could ruin it. Do you know how to check a flame sensor?

To the OP has the heat exchanger been checked? I believe that is a duracurve chamber and they are prone to crack which could cause delayed ignition.


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## hvaclover (Oct 2, 2008)

hvac122 said:


> What?* If a flame sensor is reading low it does need to be replaced. Or if it was cleaned with sandpaper it could ruin it. Do you know how to check a flame sensor?*
> 
> To the OP has the heat exchanger been checked? I believe that is a duracurve chamber and they are prone to crack which could cause delayed ignition.


That's why steel wool should be used to clean a sensor. Only time I ever replaced one is when I broke it during an anual inspection on a furnace


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## yuri (Nov 29, 2008)

The furnace I love to hate and the Pulse. The gas valve may need replacing. I have 31 yrs on Lennox. :wink:That particular Honeywell valve develops a short between the PV and MV terminals internally. Turns on the MV AND PV and spark at the SAME time. Like turning on a gas BBQ, open lid and throw a match in. Some of those burners warp and the heat exchanger may warp. They are very finicky as there is a gas scoop inside the burner and if anything goes out of alignment that can cause delayed ignition. 95% of the time it is the valve, 5% the burners. You can clean a whisperheat sensor but the pilot burner needs replacing after 10 yrs. Hood gets warped and corroded and the current needs to pass thru it back to the board. Same thing with S86 units.


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## SKIP4661 (Dec 3, 2008)

I agree with the valve also. Have experienced the same and the new valve cured it.


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## Tator1076 (Dec 22, 2009)

Like I post. I work n Lennox for along time and some reason that furnace has a promblem with gas valves. I do remember one time lennox put it on recall on some units


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## autotrans (Mar 24, 2010)

I have the same POPing problem....I have had the heat exchanges replaced under warranty (exchanges only 20 year warranty) labour was $1000 on each.. We have 2 furnaces. .... they also changed the the burners..... still POPing. Over a one week period there were 3 separate explosions, happens late at night or early morning. Now they say it is a leaky gas valve that has to be replace, waiting for a cost on it....... I have also read that the ignition board might be a problem.... Never had any problems over 20 years on the first set of Lennox.

Anyone have a cost on the gas valve?


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## User75130 (Mar 14, 2010)

The porcelain on that flame sensor cracks easily, and may be why it needed to be replaced.

The other techs here nailed it, gas valve.

You can measure the manifold pressure and pull the MV wire off the gas valve. If the burners fire or the manifold pressure is above 3.5"wc you'll need to replace it. Either problem will cause your symptoms. I would charge $383 for the valve and labor + $89 service call.

Replace the furnace, you replcaced far to many parts already.


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## hvaclover (Oct 2, 2008)

Tech X said:


> The porcelain on that flame sensor cracks easily, and may be why it needed to be replaced.
> 
> The other techs here nailed it, gas valve.
> 
> ...


You guys in Ontario are with in a few bucks of what the better one man shops here in the Detroit suburbs charge. Well from what I see of the quality of work our Ontario colleagues do it's worth every Looney.


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## cdncowboy (Sep 28, 2010)

My G20 is still doing it!! Replaced Gas valve, new circuit board. This thing is dangerous and junk!! Have spent enough money on repairs that I could have gotten a better furnace, but now into it for too much and still not working right. Wonder if a lawsuit for when it blows up my house will get Lennox's attention!!


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## beenthere (Oct 11, 2008)

Are you running on nat gas, or propane?


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## cdncowboy (Sep 28, 2010)

It is natural gas. I was told the burners need cleaned and re-aligned, just some more money and this was from a non-lennox heating guy, he also said that the fact that the other guy changed the gas valve just shows that he didn't have a clue. Pre-ignition is usually something to do with the pilot gas not getting to all the burners through the crossovers, either from mis-alignment or dirty crossovers.


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## Jass (Feb 1, 2011)

*Lennox Whisper Heat - G20*

I have 18 year old Lennox whisper heat, and it has been acting up from 1.5 years.

It pops
Sensor turn on but the rest of the burners does not get on and then the fan runs, and goes off. Sometimes it will turn on nicely and sometimes it does. Problems noticed more in the extreme cold weather

Last year the furnace company change the sensor 2 times, changed the ignition modular and the problem was on and off

For last 2 days it was completely dead. I called another furnace company, the guy said the previous ignition that was changed last year not good and needs to be changed. He also thought there was wiring problems and he fixed it according him the way it should be and after he left the problem is still there but still it missed its tries. Sometime all the burners will come on and immediately goes off.

I have spent lots of money on this and not sure what else to do.

Please let me know it is the circuit board, gas value or the burner’s needs to be changed. 

Thanks
Jess


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## R.V Doctor (Oct 2, 2020)

CubsWin said:


> I have a 14 year old Lennox Whisper Heat G20 gas furnace that has been giving me problems since last winter. I had a technician come out in the fall to clean and repair the unit. He cleaned everything out and replaced the flame sensor, but the furnace continued to "pop" (sounds like a build up of gas igniting) when igniting. After a couple return visits, the technician replaced one of the burners (and also the pilot module for another clicking issue) and thought that would resolve my problem, but the furnace is still popping occasionally on ignition. I would say that it has some degree of pop on about 1 out of every 5 times that the furnace comes on, with some of them being small and others being loud enough to startle nearby people or my dog.
> 
> I called the technician back again and he said he would most likely need to replace one or both of the other burners to resolve this problem, but that he didn't see any noticeable problems with them. Does that sound like a reasonable solution to have to replace all my burners? The technician seems very knowledgeable and has done other work for me in the past, but before I spend the money on 2 more burners is there something else that he is overlooking that would be a more likely cause of this type of behavior?


Ok - so when your unit starts from a cold state you should hear a gentle Woosh as the burners light. I just finished serviceing my unit and discovered its the gas valve that makes a pretty loud click when it opens to ignight the start pilot then another loud click to open the main valve and light the burners. Now - you have to know that hot gases will be alot more audiable when they ignight if the furnace is relighting from a hot state. have you looked at the burners when they are running of the condition of the flame / the entire flame should be blue in colour with no orange colour other than dust will cause this condition - a poping sound from flame would indicate a blocked burner from debree of scale or carbon build up causing restriction. Another possibility is the burner may be separating due to age as it gets hot the guide baffle may be warped and is making a popping sound as the metal is expanding, Lastly the heat exchanger should be inspected for cracks from old age if the flue exaust ports are a tan in colour then you have good combustion and clean burning - but if they are black with soot then there is a over rich mixture from a incomplete burn from a restriction somewhere or the orfices are the wrong size for type of fuel being used - complete service and inspection is needed then


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## roughneck (Nov 28, 2014)

Please note the dates on this thread. It’s been almost 10 years since the last post.
And 13 years since the OPs original post.


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