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Old 03-02-2012, 07:10 AM   #1
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Random Flame rollout on Gas Furnace


Hi Folks,
I'm new to the DIY chat site but not new to doing handywork of all sorts. I guess you could say i'm a jack of all trades contractor.

I've recently installed a Lenox 80% efficiency furnace in my workshop. It came out of a guys house and i got a good deal on it. The furnace has a draft inducer fan and the unit is hung horizontally. I cheated and stuck the 4" vent right out the side wall (away from combustibles of course). For the first few months it was working perfect then one day it randomly started to produce flame roll outs. I think this started shortly after I hooked up ductwork but I'm not 100% sure.

What happens is this. 'Stat calls for heat. Draft fan kicks on, igniter clicks, gas valve opens and "woosh" we have a nice blue flame that gently fires up. After a minute the room blower kicks on. A few minutes go by, the heat exchanger builds temperature and the gas shuts off. Room blower still runs, thermostat still calling for heat. As the heat exchanger cools the gas fires back up no problem. This cycle happens a few times while its running. Every so often when lighting the flame rolls out. The unit thankfully senses this, waits a few seconds and tries again and succeeds no problem.

This is hanging in my shop near the ceiling and I don't like the idea of flame rollout. Any ideas what could be happening? This only seems to happen when its hot and sporadically at that. I had thought the heat exchanger might be cracked but if it was wouldn't this be a constant problem not intermittent? I cleaned out the turbulators and checked the ignitor. No apparent problems there. The draft fan appears to be working as well.

As I said prior, this is just vented through my sidewall. OK it may not be right or to code but it worked for two months prior no problem. Is there any logical reason I shouldn't vent out the sidewall? I have a pretty good feeling that even if I ran the vent through the roof it wouldn't change anything.

I'm at a loss now and need any help I can get. I can't let me shop get below 32 as I have freeze-damageable items in there.

Thanks in Advance,
Albe

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Old 03-02-2012, 07:41 AM   #2
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Random Flame rollout on Gas Furnace


could be a crack...or a plugged heat exchanger..could be the venting is not factory spec.

what type of work do u do in shop? important to know.

does the furnace have a filter u change every month?

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Old 03-02-2012, 07:58 AM   #3
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could be a crack...or a plugged heat exchanger..could be the venting is not factory spec.

what type of work do u do in shop? important to know.

does the furnace have a filter u change every month?
Would a cracked exchanger cause sporadic rollout? It only happens when hot and not all the time. Venting definitely is not factory spec but the heater has only been hooked up for a month and a half.

I spray paint and cut lumber in the shop but again I just put the heater in and the shop itself is new as well so there isn't much dust to begin with if any. I tried cleaning out the turbulators and that hasn't done anything.

The furnace filter will get changed but as of now it's only a month or so old. Could a clogged filter be the culprit overheating the heat exchanger?

Thanks!
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Old 03-02-2012, 08:24 AM   #4
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Random Flame rollout on Gas Furnace


painting is the worst thing a furnace can be subjected to.

I am thinking you exchanger is partially plugged or cracked from the chemical usage in your shop.

If it's an older furnace the heat ex metal could be very thin and your shop environment did it in.

Either way looks like you need a pro to come look at it to determine weather or not it has a crack or is plugged.

Just out of curiosity, why did the original owner replace it?

FYI< never buy a used furnace..u don't know WHAT problems u will inherit.
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Old 03-02-2012, 08:26 AM   #5
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Can u post a pic of the venting and the burner section?

Maybe another pro can give his opinion .....
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Old 03-02-2012, 10:25 AM   #6
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Random Flame rollout on Gas Furnace


Just curious.
When you say your painting..Does that mean you are also running an exhaust fan in the garage. If so, is the roll out when the exhaust fan is on?
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Old 03-02-2012, 11:07 AM   #7
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Just curious.
When you say your painting..Does that mean you are also running an exhaust fan in the garage. If so, is the roll out when the exhaust fan is on?
I'll have to get a picture tonight. No the rollout is happening without an exhaust fan. Did I also mention its hanging from the ceiling? It was working fine and all of the sudden started sporadically when I hooked up ductwork.
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Old 03-02-2012, 12:18 PM   #8
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Random Flame rollout on Gas Furnace


Take the flue out the roof like its supposed to be and I bet the problem goes away. Does rely on flu draft to work properly.
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Old 03-02-2012, 12:23 PM   #9
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Random Flame rollout on Gas Furnace


On second thought are you sure it's a flame rollout tripping and not the limit switch? if I remember correctly all lennox units use manual reset roll out switches
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Old 03-02-2012, 01:01 PM   #10
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Random Flame rollout on Gas Furnace


What is the complete model #. You should vent it properly into a B vent thru the roof. Sudden winds etc can cause the burner to pulsate/lift off the flame etc when not connected to a proper chimney. It is designed for a chimney and some back pressure of the chimney. w/o it you are on your own. If you ever have a fire and the ins company and fire inspector see your venting then I doubt they are going to be real happy with you or pay a claim if you get my drift. An open burner furnace is a BAD idea in any shop with wood dust or fumes as it will not burn cleanly and will carbon up the heat exchanger as well as the obvious ignition of fumes or dust from the burner. An electric heater is a better idea and just requires occasional blow out with a compressor. I have seen spontaneous combustion from sawdust and been thru 2 garage fires so you don't really want that experience.
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Old 03-02-2012, 01:11 PM   #11
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What is the complete model #. You should vent it properly into a B vent thru the roof. Sudden winds etc can cause the burner to pulsate/lift off the flame etc when not connected to a proper chimney. It is designed for a chimney and some back pressure of the chimney. w/o it you are on your own. If you ever have a fire and the ins company and fire inspector see your venting then I doubt they are going to be real happy with you or pay a claim if you get my drift. An open burner furnace is a BAD idea in any shop with wood dust or fumes as it will not burn cleanly and will carbon up the heat exchanger as well as the obvious ignition of fumes or dust from the burner. An electric heater is a better idea and just requires occasional blow out with a compressor. I have seen spontaneous combustion from sawdust and been thru 2 garage fires so you don't really want that experience.
Thank you! I'm aware of the fire hazards and paranoid of burning the place down but I only do small carpentry stuff in there and plan on putting in an exhaust fan/dust collector. While this still doesn't eliminate fire hazards completely it's better than nothing. I don't plan on cutting with heat on anyway and I have a garage door for when I need to do big runs. Thankfully it hasn't been too cold here in NJ. I only went with gas out of convenience and fast heat.

I know it's supposed to go through b vent but didn't want to cut open the new roof. Any reason why going out the side wall and up is bad? Does that not create enough draft?
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Old 03-02-2012, 01:14 PM   #12
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Random Flame rollout on Gas Furnace


You can run it out the sidewall and up as long as you use B vent. Then you have to mount it to the wall and that is a hassle and does not look good. After that most people build a chase around it for cosmetics so it is a lot more work, cost and hassle but it can be vented out the wall. The gas inspectors frown on sidewall venting and it is rarely done. Get me the complete model # and I can access the install manuals for it to see if they allow that or not.
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Last edited by yuri; 03-02-2012 at 01:18 PM.
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Old 03-02-2012, 01:31 PM   #13
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Random Flame rollout on Gas Furnace


Its probably a venting problem but could be a faulty limit. I would most definately have it vented corectly in a fume rich environment.
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Old 03-02-2012, 02:36 PM   #14
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Still curious why the OPs used furnace was replaced before he bought it ...
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Old 03-02-2012, 02:57 PM   #15
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Random Flame rollout on Gas Furnace


Depending on the model that furnace MAY NOT be approved for sideways/horz use and may be a serious fire hazard.

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