Lennox - intermittent ignition failure


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Old 02-14-09, 10:38 AM
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Lennox - intermittent ignition failure

I have a Lennox GSR14 series furnace that has recently and gradually developed a problem starting up. If the thermostat calls for heat within less than 15-20 minutes of last run, I hear the purge blower come on and ths gas valve clicks followed by a click from the ignition switch but no ignition, and after a few tries the unit locks out. I've spent over $400 on service calls with no improvement from replacing both the spark plug and the flame sensor. I can tell you that after a long enough waiting time and a reset, the unit will ignite properly and run for as long as it needs to run (has never shut down prematurely and is always followed by the typical blower cool down period), but lately I notice that the needed downtime before a successful start up is getting longer, requiring 30 minutes or more since last run period. Not against another service call, but the unit is 22 years old and the techicians seem to be in the dark. I'd rather consider a new unit than throwing good money after bad....if that's more appropriate.
 
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Old 02-14-09, 11:30 AM
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Does the initial pulse lit by the spark light? Or do you get no ignition at all when it's not working properly?
 
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Old 02-14-09, 11:48 AM
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Seems like no ignition at all. The only evidence that system is attempting to respond to thermostat is the sound of the purge blower followed by click from gas valve, followed by click from ignition switch/box,...then nothing. Definitely no evidence that there's any initial lite. But, after some downtime and a reset, then a normal ignition and run.
 
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Old 02-14-09, 11:55 AM
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The manual for your furnace is at
http://hvacpartsshop.net/GSR14_Series.pdf

It looks like your furnace is getting to step 6 on page 13 of the manual, but the gas isn't lighting.

I'd start by verifying that the gas for the burner is actually turning on and that the spark is good and robust.



If that's the case, I'd remove, clean and inspect the burner orifice, pictured in Figure 17 of page 12 and Figure 14 of page 10.

I'd be especially suspicious that the burner orifice or the burner spacer plate need cleaning and being the cause of lack of combustion.

Frankly, I'd recommend against a DIY job on this furnace. I'd print out the manual so that it's available for a repairman and see if you can shop around for someone familiar with this type of furnace.

Unfortunately, these pulse furnaces are something of an odd duck and it may be difficult to find someone with much experience with it. Still, with the manual a GOOD, COMPETENT repairman ought to be able to use general gas combustion theory to identify the combustion problem that is likely preventing the furnace from lighting off.

I'm guessing that you didn't have the manual available when your repairmen were there earlier? If not, a degree of puzzelment about what to do with this furnace isn't especially surprising.
 
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Old 02-14-09, 12:59 PM
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Thank you for the manual link and the advice. Those sound like good things to look at although I'm not sure that I understand why there would be no ignition problem if the unit has been off for 30 minutes or so. This failure has only been occuring if there is a new call for heat within 15-20 minutes of the previous shutdown. Is there any reason to suspect that a valve wouldn't open wide enough or a spark wouldn't be robust enough as a function of not enough cool down time between runs? The time between runs is a definte factor. I'm not qualified to DIY, but when I have another guy back, I want to give him as many leads as possible...plus the manual. Thanks, again for your help!
 
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Old 02-14-09, 01:09 PM
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You want to be able to test and check as many likely sources of a problem as possible.

Verify that the spark is good and that the gas valve is actually opening are both essential to have combustion, so checking is worthwhile, in my opinion.

Assuming you have a good spark and gas, then dirty burner parts are the next most likely thing to cause a problem, so disassembling, cleaning and inspecting those burner parts would be the next likely thing to check.


After that ---- well, there are lots of things flapping and moving around in the furnace, and all of them would have to be checked and inspected for cleanliness and proper operation.

Personally I'd hope for the dirty burner orifice to be the problem.
 
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Old 03-02-09, 04:55 PM
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Hi, Seattle Pioneer,...or anyone else,
I was wondering if you would take one further look at this thread now that I've retrieved the unit's manual and read it in detail. I've looked at all components that a non-repairman can reasonably inspect without causing a new problem. I even actually noticed that one of the hoses coming off the pressure differential unit was almost separated from its connector/adaptor, but that turned out to be of no consequence to my problem. My bottom line is this,...the failure is very predictable and VERY time-dependent which leads me to believe that some component that is particulary subject to overheating is the possible culprit and preventing the unit from igniting despite the activation of the purge blower, gas valve and (apparently) the ignition control. The unit cycles reliably until the thermostat program call for an increased heat level early in the morning (wake setting) and then later in the afternoon (return setting). In both cases, the unit does indeed promptly ignite and runs for the entire time (~30 minutes) that it needs to raise the house temp, but after those particular run times which are their longest of the day, the unit will try, but not ignite for the subsequent call,..unless at least 30 minutes of downtime have elapsed. It simply locks out after a few tries. At that time, breaking and reestablishing the demand puts it back into a successful start-up. I don't mean to dismiss the advice to clean this or that, but some of the disassembly instructions appear like something a novice should not attempt. Plus I'm hung up on why the problem would be so predictably limited to the instances noted above and be fine for the many, many other ignitions throughout the day and night. Almost seems like some relay or electronic component needs some time to cool down after the longer runs. One thing that I want to still do that you advised is to observe the spark. The ignition control is clicking during the failed attempts just as it does during successful ones, but maybe the spark is just not happening. Actually, the control feels a bit warm to the touch and is mounted on the chamber's inner wall. I assume that if I remove the small access panel to the inner chamber, I can safely observe it. If it doesn't spark, I can recall repair service and he can take it from there as well as I can get on his case a little for maybe not having done that on previous visits. But, in the event he ruled that out and/or if I can indeed see it sparking, what else can be evaluated that is so predictably time-dependent? I read in the manual that "proper gas/air mix is required for ignition on the first attempt,...If there is slight deviation, within tolerance, the unit will try 4 more times and then lock out" requiring the reset that I am used to. If it's not the ignition spark, is there a time-dependent factor that would affect the gas/air mix so predictably? I am more than willing to arrange service to have burner and/or gas orifice cleaned, but I also want to be prepared to suggest other logical things (and provide the manual) since each guy so far has seemed to be at a loss.
Thanks for any further advice.
 
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Old 03-04-09, 07:24 PM
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Originally Posted by rdenn
It simply locks out after a few tries. At that time, breaking and reestablishing the demand puts it.

You have an intermittent problem. That means something is probably on the edge of working properly, but not quite. It will probably continue to get worse over time.

Intermittent problems are the bane of repairman, but a GOOD repairman doesn't throw up their hands when a problem doesn't sit there and want to be diagnosed.

options are:

1) replicate the problem. RUN the beast for a half hour and then shut it off and see if you can observe the problem.

2) Test all the conditions that are testable and might contribute to or cause the problem. This might be such things as the gas supply pressure, burner manifold pressure, pressure on the pressure switch, voltage being supplied to the circuit board and gas valve and so on.

3) Complete the regular maintenance work needed for the equipment. There is a reasons why maintenance work needs to be done, and often enough if it isn't done THINGS QUIT WORKING!

It sounds like there is only one thing you might be able to check yourself, and that's whether gas is coming out of the pilot burner when the spark is turned on and the pilot isn't lighting. If that gas is coming out, it should light off the spark. If it isn't probably 90% of the time it's because the pilot burner and pilot orifice need to be cleaned.

Unfortunately, it sounds like you have had lazy or incompetent repairman who have simply thrown up their hands and prfessed to be helpless when the furnace lit normally for them. It can take time, skill and energy to diagnose intermittent problems --- and your repairman haven't had it in them.

At a minimum they should have cleaned the pilot burner and the pilot orifice, or replaced it. 90% of the time that would probably solve the problem. The only excuse I can offer them is that perhaps you didn't describe the problem you observed with clarity --- but even then, cleaning the pilot is a no brainer for someone half way interested in earning their fee.
 
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Old 03-04-09, 07:55 PM
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You did not put the serial number up.. how old is this unit and when was the last time a pressure test was done on it? And I do not mean the duct test.. there is a pressure test kit for this unit to test the Heat Exchanger.. you will need to find a Lennox dealer with one.
The heat exchanger had problems on this unit.. If it fails the pressure test.. and most do... Lennox will provide you with a FREE G51MP furnace(they do not make the Heat Exchanger any longer) you have to pay the install.. I would get the pressure test done.. This furnace had a lifetime warranty on the heat exchanger.


The Original Lennox Pulse Furnace Press Release is given Below

Original appearance at: Pulse Inspection Program Hotline 1-800-537-4341 [OBSOLETE NUMBER][Try 1-800-9-LENNOX (1-800-953-6669)]

Lennox Heats Up Call For Consumers To Schedule Furnace Inspections - Sep 10, 1997

(DALLAS) -- Lennox Industries officials said that with cooler temperatures approaching, it is urgent that owners of Lennox Pulse furnaces installed before 1990 have those furnaces inspected.

Lennox, one of North America's leading residential and commercial heating and air conditioning equipment companies, will continue its Pulse furnace inspection program which began in April, 1997 and has already garnered over 25,000 consumer calls. The inspection program is a response to dealer reports of increased instances of corrosion in some Pulse furnace heat exchangers in units installed before 1990.

With all high-efficiency condensing furnaces, a combination of factors -- such as impurities in fuel or combustion air -- can cause corrosion of key components which could lead to potentially dangerous leaks. Furnaces which are inadequately inspected or improperly maintained can develop problems, including the possibility of carbon monoxide leaks that could be fatal.

According to Bob Schjerven, president and chief operating officer for Lennox Industries Inc., "Consumer response to the Pulse furnace inspection program has been terrific, but we need to reach everyone. We're urging all Pulse furnace owners, before they turn their thermostats from cool to heat, to call our 800 number and schedule a furnace inspection and a safety check with an independent Lennox dealer."

With each inspection, trained service technicians will perform the recommended 17-point Pulse furnace service check, conduct a visual inspection, and complete a pressure test of the unit's lifetime warranted heat exchanger. While Lennox is subsidizing participation in the inspection program, there may still be some cost to Pulse owners. Factors such as the location of the furnace, the condition of the furnace, and service unrelated to the inspection will determine the actual cost of the inspection.

If the warranted heat exchanger needs replacing, Lennox will provide a new heat exchanger at no cost to the owner. While labor costs for replacements are generally not part of the Pulse furnace warranty, Lennox will pay a reasonable allowance to the dealer for installation costs as part of this inspection program. There may be some costs to the owner, depending on the area of the country, type of installation, work required by local code requirements, and any other service required not related to the heat exchanger.

For those owners whose pre-1990 Pulse furnace has a heat exchanger which requires replacement, Lennox will provide, through the local independent Lennox dealer and at the owner's option, a $400 rebate on a new Lennox Pulse furnace. The Pulse furnace inspection program runs through July 1, 1999.

Lennox will also provide a free AIM Safety carbon monoxide detector, one of the highest quality detectors available, as part of the inspection program.

"Lennox has long been involved in a consumer carbon monoxide awareness program unrelated to this Pulse furnace inspection," explains Schjerven. "Since currently there is no device on the market that effectively shuts a furnace down if there is a carbon monoxide leak, it is important to install a carbon monoxide detector as a safeguard, in addition to annual maintenance and inspections."

Scheduling inspections: Homeowners can schedule a furnace inspection and safety check with an independent Lennox dealer by calling 1-800-537-4341. For convenience, the 800 number is staffed 24 hours a day, seven days a week. A Pulse furnace can be identified by its name on the door.

To determine whether your Pulse furnace should be inspected under this program:

1. Check for the Pulse name on the door. If the unit is a Pulse 21 furnace, it was manufactured after 1990 and is not part of this inspection program. However, as with all furnaces, annual inspections are still required.

2. Otherwise, remove the front door and look for the product identification stickers. These stickers are usually placed on the inside cabinet wall on the left side of the furnace.

3. Write down the model number that appears on the sticker (either G14 or GSR14, followed by a series of numbers and letters).

4. Write down the serial number on the product identification sticker (four numbers, followed by a letter, then five more numbers).

5. Call 1-800-537-4341 and have the model number and serial number ready.

All Furnaces Need Yearly Inspection

To maintain safety, efficiency, and reliability, Lennox recommends owners have their heating systems inspected at least once a year. The owner can extend the life of the furnace and help stop inefficient combustion and leaks, which could result in serious injuries, by:

1. Inspecting the filter monthly. Dirty filters can cause inefficient operation and could result in premature heat exchanger failure.

2. Watching for leaks and signs of deterioration. If found, call a certified service technician.

3. Insisting on a combustion efficiency test as part of the annual inspection.

Founded in 1895, Lennox Industries Inc. is an international manufacturer of air conditioning and heating equipment for residential and commercial applications. The company markets its products through a network of over 5,000 independent dealers.
 
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Old 03-05-09, 06:16 AM
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Also anyone reading this.. If you have a Pulse 21 furnace it also now falls under this guidline.. replaced 3 of 6 on one office this winter that failed the pressure test. Lennox supplied 3 G51MP furnaces and the customer paid the labor.
 
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Old 03-05-09, 12:39 PM
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Thanks guys, I will follow up. With regard to the heat exchanger warranty. I thought the lifetime replacement only applied to original owner, but was limited to 20 years if not the original owner. I'm not original owner and unit is 22 years ols.
 
 

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