fumey furnace

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  #1  
Old 10-29-03, 12:06 PM
jersey
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fumey furnace

could anyone give me alist of reasons a furnace would have back pressure. im aware of the obvious plugged flue or combustion chamber that needs cleaning. my roof jack is 4 yrs old and is clear,and so is the cap. the combustion air tube is clear also and is taking in fresh air from outside. i have a new heat exchanger because the original cracked after only 4 yrs. i also purchased a new burner assembly ,so i basically have a new furnace. the only problem is fumes that are backing up right where the transformer hinge is. i can feel it blowing on my hand and also smell a kerosene/dirty smell. had about 4 different techs out and the problem is that they are immuned to fumes and say they dont smell anything. the unit starts fine with no noises or hesitations. also can someone tell what color the tips of the flame in the combustion chamber should be if youre burning kerosene. i have a cmf 80 po conv downflow miller furnace with a beckett burner and its a closet installation in a mobile home. thank you for any replies.
hi, i posted last week about furnace with back pressure. didnt get a chance to respond to questions until now. ed, you asked if my barometric damper was ok and i had to do research to find out what it was and i dont have one. i checked my furnace literature and it says dont install a stack damper in the vent system. i burn kerosene because we have a outside tank. weve used it for 10 years,and our neighbors use it too. the last tech put a nozzle with the next size lower gph but the same angle. i usually use 60 80. i dont know if he moved the nozzle set out of the air tube any. the 2nd to the last tech set the unit at co2 13% smoke-0 draft -02 at breach. i bought a new burner because that tech said my pump was bad and i already needed an inlet air box because it was cracked. i figured the price of them changing those parts and maybe needing a transformer in another year came out to almost the price of a new burner. got it for 394$. air filter is clean and there is no other fan to the outside. kfield, you said my draft maybe out of adjustment,how would i go about adjusting it? also, how would i make sure the 'z' dimension is correct? jay, yes i have a new vent and no it isnt undersized. i only have a 7 foot ceiling so the vent pipe isnt very long. the fumes are pretty bad after awile of running. we have to open a window in every room. when the furnace first starts even before the fan starts you can feel a light wind of fumes by the burner. after a half hour my mouth tastes like an ashtray. thank you for your responses. paid a lot of money in techs and parts. they want 70 bucks just to come out and we live in the country. sorry if this to long.
 
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  #2  
Old 10-29-03, 12:31 PM
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I would suggest using a Delavan .559 mh nozzle and making sure fuel pump pressure is at 100psi. I hope when you got the burner you got the mobile home air tube setup. With the F0 burner head and the large static plate. If you did not then you are pushing too much air into the fire and causing your problem. If you do have those parts, you have to find out where the odor is coming from. Does your furnace draw intake air from around the exhaust stack or does it draw from underneath? As I said in an earlier post, the air you feel coming out from around the hinge should be fresh air. It has not yet been down the tube and into the fire. Unless you are redrawing products of combustion from the concentric type of intake/exhaust pipe. The most likely place to get odors is from a poorly sealing sight door on the front of the furnace. If it isn't coming out there, you have another problem all together. I suggest that you get a list of things you want checked by a tech and get one out there or be prepared to burn out another heat exchanger. We can answer questions for you all day but if you have a mismatched burner for your furnace, you are asking for trouble. Especially for the Miller mobile home units.

Ken
 
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Old 10-29-03, 02:34 PM
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oil burner

Im with Ken all the way on the burner. Still like to know why you use the kerosene instead of #2 fuel oil on a gun burner.Dont it cost you more? Have out side tanks get down to -5Fo and they work. Have to keep the water out of them for sure ED
 
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Old 10-30-03, 12:56 AM
jersey
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kfield, thankyou for the information and your time. im calling nordyne to check into the things you mentioned tomorrow. i was wondering what the fo in fo burner head meant? also, i checked my literature with the exploded view of my burner and couldnt find the static plate but i did find a escutcheon plate. are they the same thing? to answer your question i am drawing combustion air through a flexible tube from underneath. the only thing is the new cmf furnace is sitting on the old moc base. the company that installed the cmf said that was acceptable as long as i cut a hole in it which i did. i noticed that the barrel part of the roof jack and vent tube and where it connects to the heat exchanger has a slight slant to it. do you think this could be stressing the heat exchanger and giving me a improper seal at the sight door? do the majority of the leaks come from failure from the thermo paper material? thanks again.
 
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Old 10-30-03, 06:15 AM
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Beckett makes a special burner tube for the mobile home furnaces. It has a welded flange and a 4 or 4 1/2" tube with an 'F0' head. The F0 head has no retention slots around the outside. All the others have slots. It is important not to mix and match burner parts on those furnaces. The combustion area is small and since the furnace sits in the middle of the house, there is no tolerance for excess noise or odor.

I didn't think Miller approved of a new furnace on the old base but I don't think it would cause the problem you are having if you kept the old one.

I can't say what the deal is with the slanted heat exchanger. If everything is tight, it should not leak. If the sight door does not seal, you should be able to see that by the way it closes.
 
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Old 10-31-03, 12:05 AM
jersey
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burner head

hello once again kfield and thanks again for the info. unfortunately nordyne didnt return my call today, but hopefully they will tomorrow. it dawned on me after reading your last reply that i had actually saved the old burner assembly from my old moc unit. i dont know how old it is but the burner head is indeed one solid piece. i compared it to the 4 year old burner assembly that im going to use for parts and the burner head has slots or fins that circle around. i also noticed two cracks along side of the fins. would it be safe to say that this was definitely my problem? i bought the furnace from a mobile home distributor.
 
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Old 10-31-03, 06:19 AM
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I would suggest going to a Beckett distributor and purchasing the 4 1/2" mobile home burner tube assembly. That is the only combination that will work properly in your furnace. Do NOT use the F3 head which you described. The cracks were not the source of the odors. I would also suggest reducing the nozzle size to the smallest that will heat the house. It could be .50 or even .40. If you still have odor with the .559 mh nozzle, it is the only change I can think of to experiment without causing any more trouble. I am assuming that the new heat exchanger was installed properly and is sealed completely. If you have any doubts, you might recheck your work. Does your furnace have the secondary heat exchanger that wraps around the blower? If so, is that new or old? Has it been checked for perforation?

It just seems to me like you are having way too much of a problem with that furnace.
 
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