Trane XV90 furnace- partial ignition


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Old 01-16-15, 05:54 AM
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Trane XV90 furnace- partial ignition

Hey guys,

I've learend quite a bit about my furnace from reading this forum over the last several weeks.

I have a Trane XV90 natural gas furnace with 4 burners. A few weeks ago I noticed I could hear it struggling to ignite. Inducer would come on, gas valve opens, burners all ignite and then extinguish in about 2-4 seconds of the valve opening. I initially thought it was the flame sensor after reading into it. I replaced the part and it worked fine for weeks. Recently it has been acting up again. I poked around a bit more and opened the combustion chamber to watch what was happening. Burners 1 and 2 (closest to gas valve) light, but 3 and 4 do not. Burner 4 is the one with the flame sensor.

Burner 3 just happens to be under the outside air intake grate and has rust build up. I'm assuming this is from either condensation and/or water infiltration obviously. Upon further reading I have learned that the pilot runners carry the flame to the subsequent burner down the gas tube. Burners 3 and 4 usually light ok while the combustion cover is off, I believe this is due to the way airflow changes and carries the flame. I plan to clean the burners of the rust and debris but I also want to order a set to have on standby. I do notice an uneven flame along the pilot runners between burner 3 and it's adjacent burners in comparison to 1 and 2 which look normal.

Questions
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1) My main question is - what dictates the BTUs? When I google "trane xv90 burner tubes" I get part number BNR01077. Is it the gas orifice that determines the BTU and the burner tube just propagates the flame?

I just don't want to order the incorrect item and change the rating of the burners. Any advise is appreciated.

2) Is it safe to keep the combustion cover off in the meantime, or should this always be on. It is averaging -15*C to -20*C here. For now I have set the thermostat to 27*C hoping this will keep the furnace on while I'm not home - unless some sort of logic tells it to shut off after being on too long.

Thanks
 
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Old 01-16-15, 07:23 AM
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So I found my exact model number on the furnace chassis. Does anyone know if the burners are replaceable without removing the gas tube?
 
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Old 01-16-15, 11:50 AM
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Welcome to the forums.

You found the exact model number and didn't share it with us
XV-90 is just a group number.

The burners very rarely need replacement. Usually they just need to be cleaned. If you get the right brushes you can clean them in place.

As far as your burner removal question.... after I see the model I'll let you know.
 
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Old 01-16-15, 02:39 PM
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The furnace model is TUY080R9V3W5. I got home and took out the burners. It was actually a fairly simple process. I went at them with a welding brush and got them ice and clean. I moved the dirtiest one to position 4. I ordered 3 new burners this morning and I'll keep them on hand for any future failure. Even after brushing them there is still a lot of corrosion and pitting. I put it all back together and the flames ignited without any issue.
 
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Old 01-16-15, 04:34 PM
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Corrosion and pitting !?!? How old is the furnace ?
By the model it's a 52kBTU on low and 80kBTU on high furnace.

Those burner tubes are like $25 each.
 
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Old 01-16-15, 08:22 PM
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Based on the service card attached it was installed around 2008. I've been in the house for a year. I think the previous owner set up a sprinkler in their flower bed right near the furnace intake pipe outside. There are other small signs of excess water to the exterior concrete foundation. It's the only way I can explain excess rust on the single burner directly under the intake screen.

The pilot runners on two of them were really plugged up with deposits and rust.


Thanks for the info
 
 

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