This is about a Bryant gas-fired downflow forced-air furnace, about 20
years old. It sits atop the A/C evaporator box.
It's the kind where there is an inducer (exhaust) blower. The inducer
function gets proved via a pressure switch, sends power to the pilot
valve and a thermostat switch heated by the pilot which when cold sends
it a spark generator and when heated sufficiently, to the main gas valve.
I was trying to run down a problem that I think stems with that pilot t-
switch (or maybe with the pilot flame itself) as the main gas frequently
gets cut off while heat is still be called for. It keeps shutting off
then quickly restarting. I don't know if that issue is related to what I
The burners are like four blow torches feeding into the heat exhanger.
Around the exchanger inlet by the third burner, I noticed some cracking
and burned metal.
I thought uh oh. This could be bad.
So I ran the blower alone to check it out. As this is a downflow, the
blower is blowing down through the exchanger and with the A/C coil under
acting as a resistance, the air through the exhanger will be somewhat
pressurized. With the blower running I put a lit candle near each entry
into the heat exchanger. No sign of wind. No fluttering. Just a nice
gentle pull on the flame *into* the HE probably because it was still hot
and creating a slight chimney effect.
Whew, I thought.
Then I went back to my issue. While watching the burner operate I
noticed that the flame on the third burner which started out looking like
the others started to change a bit. I'd seen this difference before and
thought maybe the gas flow was slightly impeded so I made sure the
orifice was clear. Well, I started staring into the heat exhanger
opening that it was feeding into and started seeing weird motions of the
gas flame. I got to thinking that the HE might have a crack that is
opening under heat.
So I immediately killed the heat, kept the blower going and got the
candle and sure enough the flame blew around a little bit when held by
the third opening. I think there is little doubt that there is a heat
So I need a new furnace. Right away.
I know this cannot be ignored. The question is whether I need them out
ASAP in the morning or I have a couple days to weigh proposals.
Before you answer:
Because this is a downflow and because the A/C coil means the HE is
pressurized on the air side, it's not going to suck in fumes through the
crack. In theory it could blow fumes out of the furnace into the room
but I think I would see that when the flame is no longer being drawn into
the HE. The crack is small enough not to overcome the inducer and
general upflow of the hot gases.
There is a CO detector just outside the furnace closet.
Is this a busy time for HVAC because it's cold or a slow time because
people are more concerned with Christmas shopping?
On Sun, 01 Dec 2013 01:04:42 -0600, Big Giant Head
If this is true, and I'm not saying it's not, wouldn't it be best for
everyone to always use a furnace with the blower blowing into the HE
area? Yet I know they're not all like that.
(I don't think downflow specifically means what you say, or the
placement of the AC coils, but the fact that the blower blows into the
HE does seem to mean it won't suck fumes in. Others blow from the fan
to the rooms, meaning they are sucking from the HE, right?) .
I'm going to need a new furnace someday, and I would think one that
did that could fit where the current one is.
fwiW, about 10 years ago when I got my first CO detector, or when I
was starting to wonder if it was still good, I called its 800 number,
maybe First Alert, and asked a few questions not covered in the
One was whether I could put it right by the furnace. (I have no
closet. I had in mind about 3 feet away, or for a few minutes 8
inches away) and she said not to. The trouble is she was probably
reading from a script. I think I asked if it would overload the
detection mechanism and ruin the CO detector, and I doubt she knew the
answer to that, but even if she did, her answer didn't cover it.
Hmmm. Maybe your instructions include just outside the closet. If
mine had, I would have fogotten by now.
Then comes the question, is that the location of first and greatest
CO? If the ducts are leaking, maybe, but otherwise, wouldn't it be
the closest air output duct to the furnace.
On Sunday, December 1, 2013 3:44:54 AM UTC-5, micky wrote:
If what's true? That he has a blower that forces air past the
heat exchanger? That it pressurizes it? Even if they are not all
like that, everyone I've seen, and that's a lot of them, have the
blower forcing air into the heat exchanger, not pulling it out.
It may exist, but I've never seen a furnace like that.
On Sun, 01 Dec 2013 01:04:42 -0600, Big Giant Head
If you called the gas company, they would tag it out of service
immediately. I honestly don't know if you have a few days or not, but
I'd call someone first thing in the morning.
One of our tenants in our building at work is a 3 man HVAC company.
They have been busy for the past month or so. First couple of days of
summer heat or winter cold gets them hopping for a few days, but this
is now more normal busy as opposed to emergency.
On Sunday, December 1, 2013 7:37:48 AM UTC-5, Ed Pawlowski wrote:
One thing that's not stated is where it is, how cold it is and how much
the furnace really needs to run. If it were me, I'd get it replaced ASAP,
but I would still get several quotes. In the mean time, for a few days,
I would buy an additional CO detector for the living area and I would only
run the furnace under supervision. Meaning fire it up a few times during
the day while you are there. And I wouldn't run it at night, when going to
It's cold enough that it needs to run regularly. But who knows how long
it's been this way. Nevertheless, I will not wait on this. I will visit a
couple of vendors we have used in the past get some ballpark pricing
information about makes and types and invite them out to see and give a
I think the possibility that it could suck fumes through the crack is
almost nil especially with an A/C coil (and probably a dirty one at that---
more dirt gets past the filters than one would expect) providing resistance
and causing the HE to be pressurized on the air side. So if the crack
suddenly enlarged massively it would blow fumes out where the flame is
going in. At present there is not even a hint of that. The difference in
the flame that I noticed is extremely subtle. What I could see looking
into the HE (and that's not to say that there's stuff I am not seeing) is
putting just a little wisp of flicker in the flame at the bottom of that
With burner off and inducer stopped, while the HE was still hot, the candle
test I described was just a slight flicker; enough to show there was a
problem. Bet if I powered up the inducer it would suck the candle flame
But a couple more CO detectors might be cheap insurance.
In the meantime I guess I will try to find original paperwork and see if by
some chance there was a lifetime HE warranty. Not that it would help
without labor. I highly doubt it anyway.
BTW, is there any type of furnace in this category (gas, downflow) that is
quieter? This machine replaced a 1957 Rheem with traditional cast iron
burners, continuous pilot, which barely made a sigh while running; only the
blower made noise when it came on. The new high(er) efficiency (by 1985ish
standards) with inducer, blow torch burners is so loud on burners alone
that one barely hears the increased noise when the blower kicks in. It
lives in a hall closet so it was a revelation how much noisier it was. One
gets used to everything but it would sure be nice to get something a few dB
On Sun, 01 Dec 2013 09:56:18 -0600, Big Giant Head
Are you going to tell them you need a new furnace, or are you going to
call their repair division and see if he says you need a new furnace?
If you tell them you need a new one, that's what they'll sell you,
even if some smaller repair will fix it.
How old is your furnace?
IIRC, you say you cleaned that jet, but did you do a good job? Is it
possible the hole is too big now?
I don't know anything about furnaces beyond my previous post that
relates to your particular problem. Is the test with the candle the
industry-approved test, or one of your own? What is the industry
test? Maybe a repair guy could do that for you?
I think a bit of both. I will inquire about getting a new furnace because
the old one is having issues which is true. And then mention my diagnosis
and how I came to my conclusion. I certainly welcome having a pro check it
out before buying a new one but I don't want them getting into a panic and
wanting to set me up with whatever they have sitting there if a more
appropriate unit takes one more day. I would explain why I feel safe to
operate it a few more days. They can agree or disagree but I tend to think
that potential liability issues would have them insist that I turn the
thing off immediately.
Quite true. Who knows...maybe they will say this model had a HE that has 4
separate sections bolted together and the bolts need tightening. But I
seriously doubt that.
I have a feeling that once I tell them how I tested it they're going to
just say, yup, cracked HE...get a new furnace. No need for more tests.
And while that *is* probably the right answer, there's no way to know if
they aren't giving it because that lets them sell a furnace AND agree with
the customer and make the customer feel smart about averting a serious
I was thinking 20+ years but I saw something on it that said 1985 so more
like 28. Will know for sure when I find the paper work but close to 30 is
probably about right.
Nah...the flame did not change in size. I only prodded it with a wire and
then put a canned air tube against it. The business about the flame
changing shapes as things warmed up is what caused me to look more closely
and see the oddities within the bottom part of the HE, probably where air
is getting in and then do the candle test over again while the HE was hot.
I don't know what test pros use but I think with blower on, burner &
inducer off, holding a candle in front of the one HE inlet and seeing it
get subjected to air movement is indicative of something.
Can a tech tag something out of service to where it would be illegal to
then use it?
I think he was just wondering if something I did caused the flame to look
different. But that's only what drew my attention. The difference in the
flame was so subtle you'd barely notice. Not sure how to describe it since
the shape remained the same. Maybe like the flame seemed a bit hollow
compared to the others. But what I saw the flame doing in the bottom of
the HE is what caused me to pull out the candle for a 2nd test, one while
the HE was still hot.
Anyway, it does sound like you're satisfied that my test did indeed confirm
a bad heat exhanger. Gracias.
On Sun, 01 Dec 2013 22:15:55 -0600, Big Giant Head
Thinking it's a cracked heat exchanger doesn't mean it is a cracked
heat exchanger. Duh.
Do you believe everything you think?
He's one guy who likes to show off. Don't take him too seriously.
You can always do that at the end of his visit, after he's told you
what he thinks.
First I would want his diagnosis and you can ask him how he reached
it. You can always mention your diagnosis and your way of reaching
it at the end, too, but if I were you I wouldn't just say how you
reached your conclusion but ask him what he thinks of your method.
His answer might be revealing.
You're talking about something related, the part about blowing out
combustion air rather than sucking it in. Since that is directly
related to cracked HE, I wouldn't bring that up until last either.
That way YOU won't be causing his panic if there is any. He and his
own diagnosis will be causing it. If not his own diagnosis, maybe
not a real pani but his desire to get you moving, so he can sell a
But you're going to let 3 people come out before you buy, so you'll
have the chance to hear three opinions, if you don't tell them first
what you think it is.
I doubt he would do that. He might give you the choice of going a day
or two more without heat versus getting what he might call the less
good furnace! If you are without heat, don't try heating the house
from a gas stove, CO risk iirc, but you can warm it up substantially
by boiling water on the stove. Boil a great big pot until it's almost
dry, the humidity will go up**, and the house will feel 5 degrees
warmer, or more. Run an all hot shower into a stoppered tub, with the
bathroom door open and that will humidify the bedroom area even
faster. Remove the soap fromr the soap dish or it will be washed
away, and don't let the tub overflow. The overflow hole never seems
even nearly fast enough. A couple people here claim that boiling
water, etc. does't work, but it does, very well.
An electric blanket will keep you warm sleeping and more clothes will
keep you warm when you are awake. My blanket goes up to 9 but I've
never had it above 2.
**Houses tend to be dry in the winter, which makes people feel colder
(summer or winter). Even if you have a humidifier on your furnace,
since your furnace wouldn't be running in this scenario, neither will
Then what makes you think they will agree with you? And much more
important, what has this got to do with whether you give them your
opinion before they give you theirs?
I rarely have anyone work on my house -- it doesn't need anything or I
can do it -- but I've had at least one crooked chimney sweep who
low-balled on the cleaning price and then came to my house and claimed
I needed 800 dollars of new flue between my furnace and chimney, just
about 14 feet or less.
And I have a friend, not a sweep, who has told me how he overcharges
people who don't know better. I didn't know what to say and I hope he
didn't notice I didn't say anything.
Make them tell you what you need. Don't give them big ideas. It's
going to be easy for even a partly honest company to say you need a
new furnace based on the age of yours alone. It will be easier yet
if you say you think you do too, and easier still if you say that
before they've given their opinion.
Maybe it will turn out in this case that you do need a new furnace,
but you have to abandon your desire to tell a repairman what you think
the problem is**, especially when the solution to that problem is the
most expensive fix out there. **It sounds a little bit like you
want to show him how smart you are, so that he can confirm it.
Whether you're smart or not, now is not the time for that.
Auto repair is another place where people, especially men, including
me, have an idea of what they think is wrong and they often tell the
repair guy what to replace, instead of waiting for him to tell the
customer what he thinks needs replacing.
On Monday, December 2, 2013 2:05:04 AM UTC-5, micky wrote:
He provided reasonable evidence that it is.
It's not what I *think*. He provided a deductive process.
I like to show off? As opposed to what? Give stupid answers, like you?
You implied that a furnace where the blower forces air through the heat exchanger, applying positive pressure, instead of sucking it through, is
an oddity. I've seen a lot of furnaces and have yet to see one designed
that way. Not to say that they don't exist, but your incredulity about
the fact that he has a furnace where the house air is blown throught the
heat exchanger, says you don't know WTF you're talking about.
Maks sure to tell him micky finds it odd that the air handler
blower forces air throught the heat exchanger, instead of
applying negative pressure. I'm sure that will impress the tech.
He's not talking about blowing combustion air. He's talking about
the air handler blowing air. Try reading what he wrote.
Since that is directly
If you accept the validity of his test method. I'll ask you the same
I asked the OP.. Was his test an industry-accepted test, or even an
industry-acknowledged test? Or is it his own test with no history
that shows it's accurate.
I don't understand why the last sentence quoted means anything to
you. He's concluded there's a crack, but his statement about
enlargiing massively is conditional. It starts with "if" and relies
on his prior conclusion that there is a crack.
To the OP, I don't want it to seem that my advice to get the repairmen
to give their opinion first was conditional on you're being right
about the crack. Whether there is a crack or not, you should make the
repairman go first. You didn't invite him to your house so you could
talk to him,, but so that he could look at the furnace and talk to
On Monday, December 2, 2013 10:24:23 PM UTC-5, micky wrote:
Why don't you google it and find out?
The thing that goes with that strategy is that if you know
you have a cracked heat exchanger on a 20 year old furnace,
you can call up 3 companies for quotes on a new furnace and they
are generally free. If you want
to call up companies and ask for a repairman to come out to
check out and evaluate your furnace, then expect a service bill. And then
maybe a second visit by the guy who quotes installing a new furnace.
I got some quotes on a new furnace (various models of Carrier). This was a
sales guy who seemed to have some level of technical knowledge but not a
tech. I did tell him my suspicions.
If I call another outfit and have a technician come out to "evaluate" the
furnace do I prompt him in some way or just hope any tech working on a 26
year old furnace (I've looked up the age finally) would give the HE a
PS: I started a separate thread regarding efficiency options in the
replacement selection, presuming that's necessary and happening.
On Tuesday, December 3, 2013 1:53:39 AM UTC-5, Big Giant Head wrote:
Personally, I wouldn't play games and have a service guy
waste his time. I'd just tell him that you suspect the heat
exchanger may be cracked. And be there when he's looking at it.
If he confirms it, have him show you how he knows it's cracked.
I'd also find out the cost of having the inspection done upfront.
Suppose you follow the advice some have given, which I guess is
to just say "I want my furnace checked and serviced". Suppose
he gets done, hands you a bill for $150, and says it's OK?
Then what? Ask him when he's giving you the bill if he checked
the heat exchanger? And if he says yes, then what? You gonna
sleep OK at night? Call another tech for another $150? I'd
want the tech focused on what you think is the serious problem.
To me, what some are suggesting is like taking your car for service
and instead of telling them that the front brakes are making
a noise, just asking them to check out your car for fear they
are going to sell you a brake job.
IDK what the various procedures, laws are, etc. But I wouldn't
be suprised that some places that if they find it's cracked,
they might be required to notify the gas company, which might
then red tag it, etc., so you might want to be prepared for that.
First sales person said it's not official unless his tech says so. He
didn't say what the ramifications of that would be. I think I'm confident
enough in what I saw with the test candle flame and what the gas flame is
doing at the bottom of the HE in that one section that if I do go ahead and
replace it without a tech checking it out first, I am not going to be up
nights wondering if it was really necessary.
And no one around here, many of whom are skilled in the trade, have said my
conclusion has a high probability of being wrong.
Mild temperature today. Little furnace usage.
Second vendor will visit tomorrow. Would have been today if not for yet a
different homeowner disaster, this one involving a sewer line clogged in
two different places, and lots of wet towels and so forth. It took two
professionals and a lot of gear a couple of hours to make that right. When
it rains it pours. What comes after fire and water? Do I even want to
Don't laugh but last night I found out what comes after fire and water.
It's ice. I opened up the side-by-side fridge and noticed a half inch of
ice at the bottom of the freezer side. Obviously defrost condensate
overflowing the catch tray. Why is the question.
It's all cleaned up now but whether there was really a foreign matter clog
in the drain line that takes water to the bottom or it just froze up for
some reason (poor air circ from being overstuffed perhaps) I do not know.
Drain tube running freely now.
At least I know the defrost system seems to be working well so there's
For what it's worth, when I bought the house I live in now in 2009, the
furnace that was in it (dating to either 1969 or the early 1980s, I
don't remember for sure) had a cracked heat exchanger, per the home
inspector. His advice was that if I wanted to run the furnace during
the day while I worked on the house, that would be OK, but not to sleep
here with the furnace running.
I think the previous owner knew he was living with an old furnace,
because the house was generously equipped with smoke and CO detectors.
All of the houses I have lived in have had the furnace out of the living
area, so I haven't paid too much attention to how much noise they make.
I recall the new gas furnace that my parents got in the mid-90s being
louder than the mid-60s original when running, but not so bad I couldn't
A new high-efficiency furnace will probably have a "sealed" burner box,
which IMHO cuts down on the noise from the burner a little bit. It will
also probably have the two-3"-PVC-pipes intake and exhaust system,
rather than the one-6"-metal-pipe exhaust, so you might be thinking
about where you want the pipes to go.
There are some tax credits available for furnaces and air conditioners
of a certain minimum efficiency. Right now I think they expire at the
end of December 2013. The HVAC companies will know about them and will
give you the right paperwork for it. I got the 2009 version of those
credits; the installer wrote me a letter that basically said "your model
123 furnace and model 456 air conditioner that we installed at 789 Foo
Street on 31 June 2009 meets the requirements", and if I remember right,
I included one extra form and a copy of that letter with my tax return.
http://www.energystar.gov/index.cfm?c=tax_credits.tx_index has the
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