I belong to a little brick bungalow in the midwest US built in 1954. Original
forced-air (galvanized ductwork) heating, 2-yr-old Heil 80% furnace.

Lying in bed, very quiet, furnace begins heat cycle. About 15 seconds after
the burners fire, I hear a big POP. Very consistently. Every night.

I know that the furnace heat makes the sheet metal expand, and a certain
amount of noise (creaks, squeaks, etc) is to be expected, but this one sounds
too loud.

Walked the length of the ductwork, tapped each joint with a mallet, inspected
everything. No apparent problem.

Still I get the big POP.

Anything with 50-year-old galvanized ductwork that I should be looking for?

Thx,
Peetie

On Jan 14, 8:28 pm, Peetie Wheatstraw
wrote:
I belong to a little brick bungalow in the midwest US built in 1954. Original
forced-air (galvanized ductwork) heating, 2-yr-old Heil 80% furnace.

Lying in bed, very quiet, furnace begins heat cycle. About 15 seconds after
the burners fire, I hear a big POP. Very consistently. Every night.

I know that the furnace heat makes the sheet metal expand, and a certain
amount of noise (creaks, squeaks, etc) is to be expected, but this one sounds
too loud.

Walked the length of the ductwork, tapped each joint with a mallet, inspected
everything. No apparent problem.

Still I get the big POP.

Anything with 50-year-old galvanized ductwork that I should be looking for?

Thx,
Peetie

Not sure if it is the sound you are talking about but some forced air
furnaces will cause the sheet metal to suddenly shift out when the fan
starts. Similar to what a balloon does when you blow air into it but
just enough to make a "Whoomp" sound when the sudden air pressure is
turned on.

In that case, it is usually the larger pieces of sheet metal near the
furnace that connects the furnace to the cold air return that make
that sound.

David

On Wed, 14 Jan 2009 19:14:25 -0800 (PST), hibb wrote:

Not sure if it is the sound you are talking about but some forced air
furnaces will cause the sheet metal to suddenly shift out when the fan
starts. Similar to what a balloon does when you blow air into it but
just enough to make a "Whoomp" sound when the sudden air pressure is
turned on.

Just from the force of the air ...

In that case, it is usually the larger pieces of sheet metal near the
furnace that connects the furnace to the cold air return that make
that sound.

I don't think that's it.

Mea Culpa: I did a poor job of describing it yesterday.

I measured again last nite. The burners fire, the blower kicks in,
and about 40 seconds later, I get the big POP!

I 'm pretty sure it has to do with increasing temp in the supply
(not return) ducts.

Thx,
Peetie

"Peetie Wheatstraw" wrote in message
...
On Wed, 14 Jan 2009 19:14:25 -0800 (PST), hibb wrote:

Not sure if it is the sound you are talking about but some forced air
furnaces will cause the sheet metal to suddenly shift out when the fan
starts. Similar to what a balloon does when you blow air into it but
just enough to make a "Whoomp" sound when the sudden air pressure is
turned on.

Just from the force of the air ...

In that case, it is usually the larger pieces of sheet metal near the
furnace that connects the furnace to the cold air return that make
that sound.

I don't think that's it.

Mea Culpa: I did a poor job of describing it yesterday.

I measured again last nite. The burners fire, the blower kicks in,
and about 40 seconds later, I get the big POP!

I 'm pretty sure it has to do with increasing temp in the supply
(not return) ducts.

Thx,
Peetie

my furnace does the opposite. i get the loud POP when the blower shuts off.

--
C.D

On Fri, 16 Jan 2009 09:08:15 -0500, "C.D" wrote:


I measured again last nite. The burners fire, the blower kicks in,
and about 40 seconds later, I get the big POP!

I 'm pretty sure it has to do with increasing temp in the supply
(not return) ducts.

Thx,
Peetie

my furnace does the opposite. i get the loud POP when the blower shuts off.

Immediatly? Before it's had any time to cool off?

On Jan 14, 8:28*pm, Peetie Wheatstraw
wrote:
I belong to a little brick bungalow in the midwest US built in 1954. Original
forced-air (galvanized ductwork) heating, 2-yr-old Heil 80% furnace.

Lying in bed, very quiet, furnace begins heat cycle. About 15 seconds after
the burners fire, I hear a big POP. Very consistently. Every night.

I know that the furnace heat makes the sheet metal expand, and a certain
amount of noise (creaks, squeaks, etc) is to be expected, but this one sounds
too loud.

Walked the length of the ductwork, tapped each joint with a mallet, inspected
everything. No apparent problem.

Still I get the big POP.

Anything with 50-year-old galvanized ductwork that I should be looking for?

* Thx,
* Peetie

If it's happening "Very consistently. Every night" then grab a
sleeping bag and sleep next to the furnace one night, halfway to the
bedroom the next, etc.

Seems like within a few days, you know exactly where the noise
originates and then be able determine the actual cause.

"Peetie Wheatstraw" wrote in message
...
On Fri, 16 Jan 2009 09:08:15 -0500, "C.D" wrote:


I measured again last nite. The burners fire, the blower kicks in,
and about 40 seconds later, I get the big POP!

I 'm pretty sure it has to do with increasing temp in the supply
(not return) ducts.

Thx,
Peetie

my furnace does the opposite. i get the loud POP when the blower shuts
off.

Immediatly? Before it's had any time to cool off?

yep.

--
C.D

On Jan 16, 1:59*pm, DerbyDad03 wrote:
On Jan 14, 8:28*pm, Peetie Wheatstraw
wrote:





I belong to a little brick bungalow in the midwest US built in 1954. Original
forced-air (galvanized ductwork) heating, 2-yr-old Heil 80% furnace.

Lying in bed, very quiet, furnace begins heat cycle. About 15 seconds after
the burners fire, I hear a big POP. Very consistently. Every night.

I know that the furnace heat makes the sheet metal expand, and a certain
amount of noise (creaks, squeaks, etc) is to be expected, but this one sounds
too loud.

Walked the length of the ductwork, tapped each joint with a mallet, inspected
everything. No apparent problem.

Still I get the big POP.

Anything with 50-year-old galvanized ductwork that I should be looking for?

* Thx,
* Peetie

If it's happening "Very consistently. Every night" then grab a
sleeping bag and sleep next to the furnace one night, halfway to the
bedroom the next, etc.

Seems like within a few days, you know exactly where the noise
originates and then be able determine the actual cause.- Hide quoted text -

- Show quoted text -

You *could* have a damper in the duct that opens in closed. Common in
commercial buildings, I've never seen one in residential but that
doesn't mean there isn't one.

But if I had to guess, I'd say the most likely cause is something
called snap-through, pop-through, a couple of other terms. A slightly
convex surface can be stable in two configurations, and under air
pressure (more likely) or temperature (less likely) changes can pop
through to the other. You can probably play with a beverage can and
reproduce it.

If that's what it is, it is harmless.

go down there and search for the pop during operation.

----------------------------------------------------------------
http://www.minibite.com/america/malone.htm

On Jan 16, 9:19*pm, TimR wrote:
On Jan 16, 1:59*pm, DerbyDad03 wrote:





On Jan 14, 8:28*pm, Peetie Wheatstraw
wrote:

I belong to a little brick bungalow in the midwest US built in 1954. Original
forced-air (galvanized ductwork) heating, 2-yr-old Heil 80% furnace.

Lying in bed, very quiet, furnace begins heat cycle. About 15 seconds after
the burners fire, I hear a big POP. Very consistently. Every night.

I know that the furnace heat makes the sheet metal expand, and a certain
amount of noise (creaks, squeaks, etc) is to be expected, but this one sounds
too loud.

Walked the length of the ductwork, tapped each joint with a mallet, inspected
everything. No apparent problem.

Still I get the big POP.

Anything with 50-year-old galvanized ductwork that I should be looking for?

* Thx,
* Peetie

If it's happening "Very consistently. Every night" then grab a
sleeping bag and sleep next to the furnace one night, halfway to the
bedroom the next, etc.

Seems like within a few days, you know exactly where the noise
originates and then be able determine the actual cause.- Hide quoted text -

- Show quoted text -

You *could* have a damper in the duct that opens in closed. *Common in
commercial buildings, I've never seen one in residential but that
doesn't mean there isn't one.

But if I had to guess, I'd say the most likely cause is something
called snap-through, pop-through, a couple of other terms. *A slightly
convex surface can be stable in two configurations, and under air
pressure (more likely) or temperature (less likely) changes can pop
through to the other. *You can probably play with a beverage can and
reproduce it.

If that's what it is, it is harmless.- Hide quoted text -



I think it's also called "oil canning" and is not anything to worry
about, but can be annoying.
Mark

On Jan 16, 10:19�pm, wrote:
On Jan 16, 9:19�pm, TimR wrote:





On Jan 16, 1:59�pm, DerbyDad03 wrote:

On Jan 14, 8:28�pm, Peetie Wheatstraw
wrote:

I belong to a little brick bungalow in the midwest US built in 1954.. Original
forced-air (galvanized ductwork) heating, 2-yr-old Heil 80% furnace..

Lying in bed, very quiet, furnace begins heat cycle. About 15 seconds after
the burners fire, I hear a big POP. Very consistently. Every night.

I know that the furnace heat makes the sheet metal expand, and a certain
amount of noise (creaks, squeaks, etc) is to be expected, but this one sounds
too loud.

Walked the length of the ductwork, tapped each joint with a mallet, inspected
everything. No apparent problem.

Still I get the big POP.

Anything with 50-year-old galvanized ductwork that I should be looking for?

� Thx,
� Peetie

If it's happening "Very consistently. Every night" then grab a
sleeping bag and sleep next to the furnace one night, halfway to the
bedroom the next, etc.

Seems like within a few days, you know exactly where the noise
originates and then be able determine the actual cause.- Hide quoted text -

- Show quoted text -

You *could* have a damper in the duct that opens in closed. �Common in
commercial buildings, I've never seen one in residential but that
doesn't mean there isn't one.

But if I had to guess, I'd say the most likely cause is something
called snap-through, pop-through, a couple of other terms. �A slightly
convex surface can be stable in two configurations, and under air
pressure (more likely) or temperature (less likely) changes can pop
through to the other. �You can probably play with a beverage can and
reproduce it.

If that's what it is, it is harmless.- Hide quoted text -

I think it's also called "oil canning" and is not anything to worry
about, but can be annoying.
Mark- Hide quoted text -

- Show quoted text -

I had this problem a LONG time ago Added a couple drywall screws to
elminate it.

That must be over 20 years ago. Time flies.

On Sat, 17 Jan 2009 05:47:31 GMT, (John Normile) wrote:


"Peetie Wheatstraw" wrote in message
...
I measured again last nite. The burners fire, the blower kicks in,
and about 40 seconds later, I get the big POP!

I 'm pretty sure it has to do with increasing temp in the supply
(not return) ducts.

Thx,
Peetie

I had a furnace that made a poping noise, similar to what you
describe. It was on a fairly new unit and was found to be a broken
heat exchanger. It was leaking CO2 into the house.

Fairly new and broken HE? I assume 'twere under warranty.

I gotta CO detector: no apparent problem.

On Fri, 16 Jan 2009 20:34:11 -0500, "C.D" wrote:


"Peetie Wheatstraw" wrote in message
.. .
On Fri, 16 Jan 2009 09:08:15 -0500, "C.D" wrote:


I measured again last nite. The burners fire, the blower kicks in,
and about 40 seconds later, I get the big POP!

I 'm pretty sure it has to do with increasing temp in the supply
(not return) ducts.

Thx,
Peetie

my furnace does the opposite. i get the loud POP when the blower shuts
off.

Immediatly? Before it's had any time to cool off?

yep.

Even more curious than my little problem.

Hope it doesn't keep you awake at nite.

"Peetie Wheatstraw" wrote in message
...
On Fri, 16 Jan 2009 20:34:11 -0500, "C.D" wrote:


"Peetie Wheatstraw" wrote in message
. ..
On Fri, 16 Jan 2009 09:08:15 -0500, "C.D" wrote:


I measured again last nite. The burners fire, the blower kicks in,
and about 40 seconds later, I get the big POP!

I 'm pretty sure it has to do with increasing temp in the supply
(not return) ducts.

Thx,
Peetie

my furnace does the opposite. i get the loud POP when the blower shuts
off.

Immediatly? Before it's had any time to cool off?

yep.

Even more curious than my little problem.

Hope it doesn't keep you awake at nite.

nah...but now i'm worried about the CO2.

--
C.D

On Sat, 17 Jan 2009 18:36:15 -0500, "C.D" wrote:


"Peetie Wheatstraw" wrote in message
.. .
On Fri, 16 Jan 2009 20:34:11 -0500, "C.D" wrote:


"Peetie Wheatstraw" wrote in message
...
On Fri, 16 Jan 2009 09:08:15 -0500, "C.D" wrote:


I measured again last nite. The burners fire, the blower kicks in,
and about 40 seconds later, I get the big POP!

I 'm pretty sure it has to do with increasing temp in the supply
(not return) ducts.

Thx,
Peetie

my furnace does the opposite. i get the loud POP when the blower shuts
off.

Immediatly? Before it's had any time to cool off?

yep.

Even more curious than my little problem.

Hope it doesn't keep you awake at nite.

nah...but now i'm worried about the CO2.

CO2 is carbon dioxide (in which we swim, all our lives).

You are worried about CO (carbon monoxide).

Buy a detector. Not too expensive.

On Jan 16, 9:49*pm, wrote:
*go down there and search for the pop during operation.

----------------------------------------------------------------http://www.minibite.com/america/malone.htm

Or set a trap.

Spray the duct with something that will crack when it moves. This is
commonly done to check for vibrations in machinery. I can't remember
what is used anymore, maybe some kind of shellac?

It occurs to me that if you can see a galvanized metal duct, it is not
insulated. Bad idea.

I did have to chase every duct-line and vent.

The kitchen vent was partially closed. Looks like that duct was bent
funny back in 1954 and the plasterer plastered up into the dent. With the
vent panel partly open, evidently the expanding something was binding
the panel causing it to pop.

That vent won't close 100%, but with it wide open, no more pop.

Not the first time I've tracked a problem that had it's roots in the
original construction.

Thx,
Peetie

On Wed, 14 Jan 2009 19:28:52 -0600, Peetie Wheatstraw wrote:


I belong to a little brick bungalow in the midwest US built in 1954. Original
forced-air (galvanized ductwork) heating, 2-yr-old Heil 80% furnace.

Lying in bed, very quiet, furnace begins heat cycle. About 15 seconds after
the burners fire, I hear a big POP. Very consistently. Every night.

I know that the furnace heat makes the sheet metal expand, and a certain
amount of noise (creaks, squeaks, etc) is to be expected, but this one sounds
too loud.

Walked the length of the ductwork, tapped each joint with a mallet, inspected
everything. No apparent problem.

Still I get the big POP.

Anything with 50-year-old galvanized ductwork that I should be looking for?

Thx,
Peetie