Burners won't stay lit


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Old 01-21-09, 08:57 AM
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Burners won't stay lit

I am having trouble with my new Goodman natural-gas condensing furnace (1 year old). I'm at work now, but will post the model number when I get home. Here is what's happening:

1. Call for heat from T-stat
2. Draft inducer motor starts up
3. Glow strip heats up
4. Gas valve opens
5. Burners light
6. Main blower motor turns on
7. Burners flare out after aprox. 15 seconds
8. Steps 3 - 7 repeat

After reading other discussions on this topic I'll check for a dirty flame sensor when I get home, but I don't think my furnace has one (if that's possible).

A few other clues:

*Condensate drain system has been acting up recently. Pressurized air was blowing up through the condensate line into the drain trap and splashing water all over. I realized I had not installed an outlet for air blowing out of the coil box into the condensate lines and doning so seemed to take care of the problem.

*Occassionally the buners will stay lit and the furnace will run properly

* Occasionally the furnace locks out after 3 attempts and I get a single flashing trouble code from the LED. Other times Steps 3 - 7 just keep repeating.

* The filter is clean

* T-stat is a new honeywell dial style and seems to be working properly. Not digital.

Thanks for your help...It is cold here in MN with only an oil filled electric heater to keep us warm...
 
  #2  
Old 01-21-09, 09:35 AM
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It could be a flame sensor that needs cleaning.

I'd be more suspicious of the pressure switch opening and shutting off the burners.

Look around the furnace for a list of the diagnostic codes and what the blinking light is identifying as the problem. It could be signaling a pressure switch problem or not detecting the burner flame lighting, which might be the flame sensor problem.

Also, perhaps you can describe this air flow out through the condensate line --- that doesn't sound right. Furthermore, if air is blowing out that line it might cause the pressure switch to open, causing your burner problem.

I have never heard of a furnace blowing air out of the condensate line before. Usually there would be a trap or other device to prevent that. I can't say that's definitely a defect though. Perhaps someone else can comment on that.
 
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Old 01-21-09, 10:08 AM
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I should probably mention I have a concentric vent installation.

Regarding the condensate issue...the air was blowing up from the drain line and escaping outside of the furnace at the trap. The pressurized air comes out of the A-frame box (downflow unit)...I installed an open T at the near the connection to the A-frame box that seems to have solved the problem.


Ok, current plan for me is as follows:

1. clean flame sensor (if I have one)
2. inspect exhaust and intake vents for obstructions
3. inspect hose and pressure switch
4. inspect draft inducing blower

Here are the symptoms listed in the troubleshooting guide for the single flash reading:

• Furnace fails to operate.
• Integrated control
module diagnostic LED
is flashing ONE (1) flash.

Here are the possible causes from the troubleshooting guide:

• Failure to establish flame.
Cause may be no gas to
burners, front cover
pressure switch stuck
open, bad igniter or igniter
alignment, improper
orifices, or coated/oxidized
or improperly connected
flame sensor.

• Loss of flame after
establishment. Cause may
be interrupted gas supply,
lazy burner flames
(improper gas pressure or
restriction in flue and/or
combustion air piping),
front cover pressure
switch opening, or
improper induced draft
blower performance.
 
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Old 01-21-09, 10:32 AM
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That rather broad list of possible problems associated with one diagnostic code means the problem might be either a pressure switch opening or a defect in detecting the burner flame, which could be a flame sensor that needs cleaning.
 
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Old 01-21-09, 05:05 PM
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Well...I do have a flame sensor. I cleaned it off and the furnace seems to be operating properly now. There was just a little corrosion. I find myself a little skeptical that I have completely solved my problems...only time will tell I suppose.

Thanks for your help. This site is a great resource.
 
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Old 01-21-09, 05:33 PM
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Condensate water can come out the condensate drain hose(s) designed for this, and also in conjunction with condensate water still in the inducer assembly, that will exit the exhaust pipe. In both cases the water converges at the trap.

The trap is built so water has to go to the bottom where there may be a pickup tube that is submerged in the water in the bottom of the trap, that then allows the water to flow out that pickup tube and into the drainhose that goes to the drain. There may be a vented tee at that trap assembly that allows water to spill out of it if say the hose that goes to the drain or condensate pump, (if you have one) were to get plugged. The trap with that pick up tube in it, or some other trap configuration, is designed so that exhaust gases can never come out the drain tube, or an associated tee fitting, that goes to the drain or condensate pump, since these gases would contain carbon monoxide. If you feel air coming out that tee, or from any other source at around your trap area, you either do not have water in the trap as you should, to block those gases, or you have an inadequate designed trap system. All exhaust air is to go up the vent pipe, and not come out from anywhere else!
 
 

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