"EXT" wrote:

-snip-
Also check for exhaust fans in kitchen and/or bathroom that may be working
and/or a dryer may also be adding to negative pressure in the house. Any
one of these things coupled with heavy humid air reducing draft or multiple
equipment may create the negative pressure. You need to experiment to
identify the cause. You may need to add some "make-up" air supply to the
area of the furnace/water heater to replace the air being removed.


Good points-- I hadn't thought about negative pressure. If the OP
has central A/c it could very well be causing some negative pressure
there. And it would be worse on hot/humid days.

Jim

Mikepier wrote:

Sorry for posting late, but for some reason, I saw no new posts for
about a week on this group.

Google sucks for Usenet access. Get yourself an offline reader and a
free server- You'll thank yourself.

Anyway,I found my problem. It was my attic fan. Hard to believe since
I live in a split and the attic fan is 2 stroies upon the other side
of the house with adequate ventilation from the roof vents. I don't
know if getting a slower motor would help, but the motor I have on
there now is 4 amps.


That's step one-- you've located the culprit and it is negative
pressure. For the summer, a cracked window in the basement should
cure it. I might consider a backwards dryer vent [something a
little more elegant is likely out there] to keep that pressure from
going negative.

I do have central air, but when I shut it off, the draft on the water
heater was still no good. Thats what made me think about the attic
fan.
I have a CO detector in the furnace room just in case.

If you have a good digital one it will tell you what the highest level
of CO has been. I'd check it weekly for a while to see if it has
been spiking just under the set-off level. Because CO is a
cumulative poison, you want to keep close track of it over the long
haul.

Jim

willshak wrote:

What kind of attic fan are you talking about? The kind that is installed
in a gable end vent of the attic or in the roof, or a whole house fan
that exhausts air from the living area into the attic?

I agree that we should know what we're talking about before we
speculate.

There is no way that a typical gable or roof attic fan can exhaust air
from a room two stories down and on the opposite side of the house,
unless you have no soffit vents in the attic, and even then, the attic
door(s) would limit the suction from the rest of the house.

My speculation previously was based on the attic fan ['whole house
fan?'] in my house. It is a big bruiser right over the drop
down staircase. The drop down staircase is near the top of the
stairway to upstairs. If you open the door at the bottom of those
stairs while the drop-down is down, it will blow your hat off.

My drop-down isn't real tight- and I crack it a bit in the summer to
help cool the upstairs. [on the 2-3 days a year I use the AC I close
it.]

If a house was buttoned up tight, and there was insufficient gable
venting, [old houses rarely have enough] I can picture negative
pressure in the basement.

I can't think of another reason the two would be connected- and the OP
seems to have made the connection.

Hey Mike- got a barometer? I'm not sure it would work, but I'd
have to do the experiment. I suppose a quicker [but not nearly
as fun] way would be to see what happens when the fan is running, but
a few windows are open so no negative pressure can build up.

Jim

On Wed, 10 Aug 2011 09:05:28 -0700 (PDT), Mikepier
wrote:



The water heater is vented through an exterior brick chimney. The
attic fan is on the opposite side of the house.


You just put that water heater in, right?
Think you posted pictures and we were talking here about vent
placement.
Did the old heater have 4" vent pipe?
How many inches did you stick in the chimney?
Did you put in under the furnace vent instead of side by side or
under?
I think I said my 4" water heater vent was a few inches directly over
the 8" furnace vent. I checked just now and that's how it is.
Don't know if this means anything, but something to consider since as
I recall you changed the setup.

--Vic

On Aug 10, 4:11*pm, Vic Smith wrote:
On Wed, 10 Aug 2011 09:05:28 -0700 (PDT), Mikepier

wrote:

The water heater is vented through an exterior brick chimney. The
attic fan is on the opposite side of the house.

You just put that water heater in, right?
Think you posted pictures and we were talking here about vent
placement.
Did the old heater have 4" vent pipe?
How many inches did you stick in the chimney?
Did you put in under the furnace vent instead of side by side or
under?
I think I said my 4" water heater vent was a few inches directly over
the 8" furnace vent. *I checked just now and that's how it is.
Don't know if this means anything, but something to consider since as
I recall you changed the setup.

--Vic

I had an open "chimney from my basement thru two floors into the attic
from a chase where all the plumbing ran from the basement to the upper
floors. I could feel cold air coming into the basement in the
wintertime. The solution was to put lots of insulation at the top of
the "chimney" to stop the airflow. With an attic exhause fan in one
gable end, I am sure that if the insulation had not been packed
tightly at the top of the "chimney, I would have had negative pressure
in the basement.

The fan I have is similiar to this:

http://www.broan.com/display/router....oductID=100667

And here are pictures of my water heater

https://picasaweb.google.com/mikeroc...eat=directlink

I tried another test yesterday.WIth the attic fan on, I turned on my
water heater and noticed the area around the flue was hetting hot. I
opened a basement window, then the area was not hot anymore. I guess
this reconfirms the fact there is negative pressure in my house.