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Old 12-12-2009, 03:57 PM   #1
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Comfortmaker ignition issues


I am the sorry owner of a COMFORTMAKER ENVIRO PLUS 90 forced air furnace, Model # GUK075N12C1. The unit is supplied by my LP tank. The heat exchangers sooted and were replaced with new exchangers.. The igniter and flame sensor unit is new also. When I start the furnace, the inducer fan starts, the igniter heats and when there is ignition, the right flame nozzle is nice and blue, but the center and left nozzle is an ugly, rolling yellow flame. I suspected the inducer, got a tachometer and the fan is spinning 3480rmp with a motor tag rating of 3450rpm, so I should have the air draw the furnace needs. I have cleaned out both the inlet air and exhaust air pvc pipes, so there are no restrictions to air flow. One thread referred to a "COMBUSTION RING" at the air inlet of the inducer fan body. What is this ring made of and what does it look like? If it is missing, then there is a possiblity that I am not getting the draw I need. Only problem with that idea is that my pressure switch picks up... I am also going to measure my supply and manifold gas pressures at the "SmartValve", since I am either not getting enough air flow or too much LP as the yellow color indicates a rich mixture. I sure would like some help on this, it's cold here in Gods Country Wisconsin.

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Old 12-12-2009, 05:02 PM   #2
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Comfortmaker ignition issues


How long ago was the heat exchanger(s) replaced? Did they replace the secondary/ coil heat exchanger or only the top primary cells. May be sooted up again? Did all 3 burners burn correctly after the exchanger replacement?


Last edited by yuri; 12-12-2009 at 05:58 PM.
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Old 12-13-2009, 12:06 AM   #3
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Comfortmaker ignition issues


The primary AND the secondary heat exchangers were replaced on Friday Dec. 11th. Following the exchanger replacement, I monitored the status of the flame and shut the furnace off after approx. 10 seconds of run time. That same lousy yellow, rolling flame was present at the center and left burner with the right burner a nice blue color.
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Old 12-13-2009, 09:03 AM   #4
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Comfortmaker ignition issues


There may be a air/vacuum and draft leak on those 2 cells where they attach to the secondary exchanger. Was the entire exchanger replaced as 1 unit or several pieces? If one unit that shouldn't happen. There is a plastic orifice plate behind the inlet to the inducer where it attaches to the collector box. They can break and affect the draft. However the furnace is designed to prove the correct amount of draft for proper combustion with the pressure switches. Check the orifices to those 2 burners with a paper clip. Apparently spiders can build egg pouches/nests in the manifold in the off season, no joke.
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Old 12-13-2009, 09:19 AM   #5
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Comfortmaker ignition issues


YURI, That plastic orifice plate you refer to located at the inlet to the inducer, is that integral to the inducer?? Is it attached to the inducer or could it fall off? The inducer mounts to the collector box. There is a foam o-ring that sets in a groove on the collector box, but I see no separate plastic orfice plate. Please describe the plate. BTY I have 2" wc vacuum thru the inducer with everything piped up for normal operation. I also checked the burner nozzles and they are clear and clean.
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Old 12-13-2009, 09:33 AM   #6
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Comfortmaker ignition issues


That plate is seperate and a cheap piece of plastic with a tiny tit or 2 sticking out that mates with the inducer housing from the ones I have seen. HOWEVER there are LOTS of different versions of that furnace. There would be a small hole in the inducer where the tit should stick in. Some inducers have a specific hole size to the inducer for the size of furnace but most use 1 size of inducer for 3 models and attach a orifice instead.
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Old 12-13-2009, 11:08 AM   #7
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Comfortmaker ignition issues


If the baffle was not there, and belonged there. You wouldn't have a lazy yellow flame. And it would effect all burners/cells.
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Old 12-13-2009, 12:09 PM   #8
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Comfortmaker ignition issues


Thats what I was thinking but it is a wild guess. The pressure switch proves enough draft in a proper setup. Could have a swirl effect in the collector box and draw harder thru one cell. One of my dumb co-workers forgot to put an orifice in a G26 and it sucked so hard it throttled the gas valve back. Took some intense thinkin on my part and manometer work to cipher that one out.

Last edited by yuri; 12-13-2009 at 12:22 PM.
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Old 12-13-2009, 06:28 PM   #9
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Comfortmaker ignition issues


I appreciate the feedback to my post...Since my inducer satisfies the pressure switch, let's switch to a gas supply line of thinking. Later tonight I am going to measure my supply gas pressure at the main gas valve. If that is the .5psi it is suppose to be, is there a way that the SmartValve could let too much LP through which would cause the rich mixture I see happening? The main gas is solenoid operated, so it is either ON or OFF, not modulating. So...how could I be getting too much LP for my mixture if the supply pressure is correct? Thanks
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Old 12-13-2009, 06:37 PM   #10
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Comfortmaker ignition issues


Lp supply pressure should not be .5PSIG.

Above 12" the sudden shutting off of the valve can cause a pressure increase above 14" and harm the valve or just keep it from opening the next time.

Your gas valves regulator could be off.
Your manifold pressure should only be 10.5"wc at the most.

I know your hoping its a gas valve or other small problem. But its doubtfull. Since a gas valve allowing more pressure in then needed would effect all burners.
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Old 12-13-2009, 07:28 PM   #11
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Comfortmaker ignition issues


Look at what could affect thoughs burners only as said before check the orfices to the burners. Dont just poke them out remove them and look. also check the burners themselves to make sure they are not dirty. I suspect it is the orfices.
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Old 12-13-2009, 07:49 PM   #12
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Comfortmaker ignition issues


May also be that the inside of the manifold pipe to the orifices has debris or spider web inside and reducing the flow. Hard to believe it can happen but we had someone here with that scenario not long ago.
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Old 12-14-2009, 07:51 PM   #13
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Comfortmaker ignition issues


Tonight is used a Magnihelic gauge and I have 12" wc at the inlet to the gas valve. I ordered a new restrictor plate for the inlet to the inducer. I removed the mainfold, removed the burner orifices and cleaned them all. Did not see any appreciable debris, but I imagine it would not take much. I will measure the manifold gas pressure after I get the restrictor installed. All feedback is appreciated.
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Old 12-14-2009, 08:16 PM   #14
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Comfortmaker ignition issues


Why not measure it now?
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Old 12-14-2009, 08:39 PM   #15
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Comfortmaker ignition issues


Quote:
Originally Posted by yuri View Post
May also be that the inside of the manifold pipe to the orifices has debris or spider web inside and reducing the flow. Hard to believe it can happen but we had someone here with that scenario not long ago.
Happens all the time and I know cause I am a dealer for ICP.

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