I have a Bryant model 388E furnace with a model AFG oil burner installed
under the house in the crawl space in 1993. The furnace has operated well
until recently it has started giving off a slight smell of smoke when it
fires off. After the fan starts the smell dissipates quickly until the next
startup. A carbon monoxide detector mounted directly on a register reads
zero so it is not dangerous, just annoying. The furnace has been serviced
yearly since it was installed.
I have put off getting it fixed since the normal serviceman says he is very
busy and my own opinion is that the repair might require the house to be
without heat for a considerable time and this is a bad time of year for
that. In addition the serviceman seems to have no idea how to proceed with
A likely cause for the smell is either a cracked heat exchanger or a bad
gasket. I note from the papers that came with the furnace that the heat
exchanger is removeable and is also warranted against defects for as long as
I own the furnace. The installing contractor has gone out of business and I
expect the small print in the warranty essentially voids it anyway.
Perhaps someone on this group can advise me if the heat exchanger for this
furnace is still available from Bryant as a repair part. If it is not
available or repairable it seems likely that a complete furnace replacement
might be required and I would need to start thinking in that direction now.
Not good. It could be a simple thing, like a dirty exchanger...or a clogged
stack...or a leaking gasket around the burner head...
Or...it could be a cracked heat exchanger.
If you have a CO detector that came from Home Depot, Lowes...etc...its going
to read zero until you get a reading that is high enough to be read, by the
cheap unit, and, its a fact that none of the units sold there read until
there is a possiblity of a dangerous level building.
In other words, that is a false sense of security you have there.
And things break.
Then you need to find someone that knows what he is doing, and fast.
Do NOT put that off any longer. If he cant figure out how to fix it, or how,
or where to start looking, there is a damn fine chance that he didnt know
how to service it right either.
If thats the case, I would look real hard at a crack in the exchanger due to
under, or overfiring, or a heat rise that was too high.
As stated before.
The installer means squat. He can install it today, and go out of the trade
in the morning, and anyone that is licenced and insured in teh business can
install a heat exchanger for you under warranty, PROVIDED the heat exchanger
Labor is not covered under that warranty, so you are going to have to pay
Thanks for your reply.
I tested the CO detector with a candle and I found it would detect and
register CO levels as low as 10 parts per million so I am confident the
furnace is not putting dangerous levels of the gas into the house.
I observed the furnace operation for a few cycles. I found that it would
ignite somewhat violently, slamming the draft regulator vane shut, then
almost instantly a good draft was formed in the pipe and the vane opened
about 1/3. I assume this is normal operation. I could detect no diesel or
smoke smell around the furnace at all. I think the starting pressure forces
a puff of exhaust into the air plenum somehow, and the smoke rises slowly up
the heat pipes. After about 5-10 seconds this can be smelled at the
registers. When the fan comes on this is completely dissipated in a second
or two. When the furnace is opened so the heat exchanger can be viewed
there may be a soot trail that will indicate where the smoke is coming from.
I am, of course, not experienced in this and value your expert opinion.
It is good to know that a replacement heat exchanger is available. Buying a
new one and paying for the installation is certainly less expensive than
installing a new furnace. It is a major job maneuvering one in and out of
that crawl space.
You may be right about the technical qualifications of the serviceman who
has been working on the unit. However oil furnaces are kind of scarce
around here (pacific northwest) and I doubt there are many really good oil
furnace experts locally. I had some difficulty finding a serviceman 10
years ago. If I were to buy another furnace, I think I would go for a heat
pump rather than oil, especially considering the price I paid for my latest
oil delivery (yesterday).
Thanks again for your help
It's possible that none of the answers have hit it. It sounds like you
have a puffback problem or delayed ignition. What that means is that the
burner doesn't light the second the oil begins spraying out of the nozzle
and there's a slight "cloud" of oil in the chamber. Once that "cloud"
comes around where the spark from the electrodes can touch it off...POOF!
This would account for the slamming of the draft regulator. Once the
fire has lighted it runs fine. Have a competant burner man check it.
Although you've had it serviced regularly, it's possible something got in
to the burner tip (nozzle) and is causing the pattern of the nozzle to be
off center enough to cause this problem. If it was the heat exchanger,
you'd smell burned oil all through you house and there would be soot near
the registers too. A good burner man can check this out with a draft
gauge. He places it in the burner area over the fire and when the forced
air fan comes on, it'll usually peg the needle, indicating a force of air
being introduced to the combustion chamber. Again...a good burner man
can check this out.
You are probably right about delayed ignition. I have had the furnace man
out twice recently. The smell was more like diesel oil initially, but after
he adjusted the burner it changed to more of a smoke like smell. I notice
it is getting like diesel again now. In any event, there shouldn't be any
transfer between the fire side to the air side in the furnace. So it is
likely there is some sort of defect in the heat exchanger. That was why I
wanted to know if replacement exchangers were still available.
The repairman never uses any instruments to adjust the furnace, so I expect
he is not one of the experts you recommend. Most of the home heating
systems in this area are either electric or natural gas and I expect the oil
furmace experts have long ago gone into other trades or retired. The oil
furnaces were replaced when the price of fuel oil went sky high about 15
years ago. I paid $1.66/gal for the last delivery. Diesel fuel at the pump
with the road tax is cheaper.
I will look around for a competant repairman although I don't really know
how to find one.
Thanks for your help
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