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jespo27 02-24-2013 12:35 PM

Heil Propane Furnace NTN6125KJA2 Burner problem
My furnace is propane with a 5 stage burner. My problem is that 2 of the burners do not send the flame all the way into the heat exchanger.
Burners 1, 3 & 5 on assembly are fine , good jet of blue flame going right down the heat exchanger. but burners 2 and 4 are not going as far down heat exchanger as 1,3 & 5 burners. The flames of 2 & 4 hit the sides of heat exchanger and flame has minor accumulation just around the wall of exchanger.
A friend throttled back propane from supply but flame was now yellow but was not hitting sides. I didn't like that so I figured it was better to have a little flame that wasn't going in properly than to be using the inefficient and dangerous yellow flame.
I've replaced the 5 stage burner assembly and igniter and limit switches (300 degree).
I suspect the manifold orifices feeding burners 2 & 4 may be bad but not sure. I've seen replacement orifices being sold with numbers stamped on them (for different flow rates?) but none seem to be spec'd for propane. If it is orifices, are LP and propane orifices different?
What am I missing?

yuri 02-24-2013 01:05 PM

1) propane orifices are definetly different as the gas pressure thru them is different
2) now you need to set the manifold pressure with a manometer and NOT by eye/flame color or you can damage/overfire the unit
3) I have heard that bugs/spiders can get in those orifices and partially block them. sounds weird but true in some areas
4) if you are getting flame disturbance and I suspect you are then the heat exchanger is probably cracked and that one may have compression rings/rivets holding it together which are popped open. you should get an experienced Heil tech to check the heat exchanger properly for cracks and popped rivets and set the gas pressure properly. I cannot describe how to PROPERLY check that heat exchanger as it is a complex process and experienced techs know exactly where they crack etc.
5) it is now dangerous to use if you adjusted the gas pressure and should be setup and checked by a Pro.

jespo27 02-24-2013 01:18 PM

Thanks Yuri. The gas pressure was adjusted by only slowly closing the main shut off gate valve that feeds propane to the furnace. No sophisticated pressure adjustments were made. From what I read I think a cracked heat exchanger may be correct. What if I capped the 2 problem orifices? and ran furnace on 3 burners instead of 5 .

yuri 02-24-2013 02:05 PM

then you will warp the heat exchanger and crack it 4 sure. uneven amount of heat in the chambers will warp and crack it, they all need to be warm and at the same temp.

jespo27 02-24-2013 02:15 PM

At the price of a new heat exchanger around $500 plus labor, maybe a new unit would be a better play. this one is over 11 years old. your thoughts? any recommendations for a new LP furnace mfg?

beenthere 02-24-2013 03:42 PM

The heat exchanger would be under warranty since its only 11 years old.

But now is the time to find out what size furnace you really need. Yours is probably over sized. A load calc would tell you the correct size. Yours may have racked because its over sized, and the duct system connected to it is under sized for it.

yuri 02-24-2013 04:26 PM

Yep. No point in throwing good $$ after bad. 125,000 BTU furnace is huge.

jespo27 02-24-2013 06:37 PM

thanks for info. I checked paperwork and warranty is for original owner. so no proof of purchase. I'm third owner of home. also home is in so. san diego area and home is around 3000sq ft. single story , no bsmt and propane heater is in garage.From what I researched , it looks like a 45,000 BTu unit would be adequate for my needs. Why a 125,000BTU was installed, I do not know. Maybe original builder thought bigger was better. Any ideas for good website to purchase new unit.

beenthere 02-24-2013 06:44 PM

Do you have central A/C. If so what size is it.

jespo27 02-24-2013 06:51 PM

nope, no a/c only propane heater

jespo27 02-25-2013 11:35 AM

Does anyone have a recommendation for a new propane furnace (no a/c) to buy in San Diego area? Any preferable brand ?
From what I researched my single story 2500 sq ft house should be ok with a 25,000 -30,000 BTU furnace.

beenthere 02-25-2013 04:45 PM

One brand is about the same as the other. Installed properly they all last about the same time.

jespo27 02-25-2013 05:24 PM

thanks beenthere

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