A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...TM0Q87VFEGEJM8

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

Mikepier wrote:
A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...TM0Q87VFEGEJM8

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

If you have negative air pressure in your attic, why don't you simply
add a few more vents? There are probably eaves where a vent could be
added reducing the pressure.

As far as controlling the speed of the fan motor, I think DC motors are
better suited for such control. Of course you could reduce the AC to an
AC motor, but it can present problems for the motor.

On Aug 22, 9:35*am, Mikepier wrote:
A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...k2_dp_sr_1?pf_....

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

Open a window.

On Aug 22, 9:47*am, Ken wrote:
Mikepier wrote:
A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...k2_dp_sr_1?pf_....

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

* * * * If you have negative air pressure in your attic, why don't you simply
add a few more vents? *There are probably eaves where a vent could be
added reducing the pressure.

* * * * As far as controlling the speed of the fan motor, I think DC motors are
better suited for such control. *Of course you could reduce the AC to an
AC motor, but it can present problems for the motor.

That's the problem, I think I have adequate vents. I have 2 roof
vents, and a gable vent. I'm not sure if adding another vent would fix
it.

Air over fan motors are cooled by the air the fan pulls. Slowing one
down in a place out of sight is a scary proposition even when
thermally protected.
I am guessing the living area is air conditioned otherwise you would
just open access to the attic .

Finding a slower replacement motor might be a better option.

On Mon, 22 Aug 2011 06:35:14 -0700 (PDT), Mikepier
wrote:

A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...TM0Q87VFEGEJM8

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

Without getting to that point, I'd say that the desirability of those
fans is that they move vast amounts of air. I wouldn't slow that
process down.

The problem is in the basement. I'd address it there. If
leaving a window open isn't an option, then a small vent bringing some
outside air in would cure it.

If you've got a furnace down there, it is even more important. *It*
will also benefit from an unrestricted amount of air for combustion.

Jim

Ken wrote:

A few weeks ago I posted a problem with too much negative air
pressure in my house caused by my attic fan.

If you have negative air pressure in your attic, why don't you simply
add a few more vents? There are probably eaves where a vent could be
added reducing the pressure.

There's a couple things going on here.

Normally, an attic space is supposed to be sealed from the house and air
isin't supposed to move between the attic and interior house air space.
Now, sometimes people put a fan in the ceiling to pull air from the
house and push it into the attic, which is useful to pull cooler
exterior air into the house to cool it down in the evening when there
isin't enough of a breeze to accomplish that. The OP doesn't say where
the fan is placed. The picture he shows is typical of a roof-mounted
fan, but I suppose could also be a house exhaust fan.

So if this is a roof-mounted fan, then the house shouldn't experience a
negative air pressure, and any air infiltration into the attic should be
sealed. It's hard to imagine that there wouldn't be enough soffit or
gable-end venting to allow proper attic air flow and air balance.

If this is a house exhaust fan that's exhasting air into the attic, then
it's normal to expect a negative air pressure in the house if you don't
open any windows to allow proper air balance. The whole point of having
a house exhaust fan is that you must allow exterior (outside) air into
the house to balance the airflow.

As far as controlling the speed of the fan motor, I think DC motors
are better suited for such control. Of course you could reduce the
AC to an AC motor, but it can present problems for the motor.

I have a ceiling fan that's connected to an ordinary wall-mounted dimmer
switch (mainly to dim the lights that are part of the fan unit) but the
dimmer does change the fan's RPM along with the brightness of the
lights.

The downside of having a speed-controlled AC motor is RF noise created
by the controller or dimmer that gets injected into your power lines and
can mess up AM radio and sometimes OTA tv reception.

The solution is not to put a speed controller on the fan motor. The
solution is to allow proper air balance.

"Mikepier" wrote in message
...
A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...TM0Q87VFEGEJM8

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

Are you talking too much negative pressure inside the thermal envelope? If
so, the problem is your thermal envelope isn't _tight_. Slowing down the
attic fan isn't the solution to fixing the envelope problem.

This is a roof mouted fan, not a whole -house fan.

I don't have issues with my furnace since in the cold weather, the
attic fan is off anyway. Its my water heater I have issues with.

I have a pull-down attic stairs in the second floor hallway. I know
it's not 100% sealed, but for the most part its pretty tight.

On Mon, 22 Aug 2011 06:54:32 -0700 (PDT), Mikepier
wrote:

On Aug 22, 9:47Â*am, Ken wrote:
Mikepier wrote:
A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...k2_dp_sr_1?pf_...

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

Â* Â* Â* Â* If you have negative air pressure in your attic, why don't you simply
add a few more vents? Â*There are probably eaves where a vent could be
added reducing the pressure.

Â* Â* Â* Â* As far as controlling the speed of the fan motor, I think DC motors are
better suited for such control. Â*Of course you could reduce the AC to an
AC motor, but it can present problems for the motor.

That's the problem, I think I have adequate vents. I have 2 roof
vents, and a gable vent. I'm not sure if adding another vent would fix
it.

I already asked about this, but I'll try again.
You just put in the water heater, right?
You posted about venting, but I don't know what you did.
Did you change the venting?
Did you have a problem with the old water heater pilot?
If not, you should look at your venting.
I've got no idea how you let that water heater chase you up to the
attic.

--Vic

On Aug 22, 8:35*am, Mikepier wrote:
A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...k2_dp_sr_1?pf_....

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

Don't you have any soffit vents? Reread the book on attic venting and
follow the best practices and the problem should resolve itself.

Joie

Mikepier wrote:

This is a roof mouted fan, not a whole -house fan.

I don't have issues with my furnace since in the cold weather, the
attic fan is off anyway. Its my water heater I have issues with.

I have a pull-down attic stairs in the second floor hallway. I know
it's not 100% sealed, but for the most part its pretty tight.

I really have to wonder how you know that you have a negative pressure
issue when the attic roof fan is running.

Unless you have a really small attic space, or you know that your doors
and windows and walls are really well sealed, I would think that most
homes are leaky enough so that a single roof-mounted attic fan can't
cause a negative air pressure situation inside the house.

Do you know if your kitchen (stove) or bathroom exhaust fans run
straight through to the outside? Or do they exhaust directly into the
attic? If they do (exhaust into the attic) then that's where your
connection is between the attic and household airspace is.

Do you have a whole-house (built-in) vacuum cleaner system?

What sort of HVAC system does your home have? Does it have a makeup air
intake or combustion air heat exchanger? Is it open or closed?

Gas water heater?

Fire place / wood stove?

Mikepier wrote:
On Aug 22, 9:47 am, wrote:
Mikepier wrote:
A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...k2_dp_sr_1?pf_...

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

If you have negative air pressure in your attic, why don't you simply
add a few more vents? There are probably eaves where a vent could be
added reducing the pressure.

As far as controlling the speed of the fan motor, I think DC motors are
better suited for such control. Of course you could reduce the AC to an
AC motor, but it can present problems for the motor.

That's the problem, I think I have adequate vents. I have 2 roof
vents, and a gable vent. I'm not sure if adding another vent would fix
it.
Hmmm,
You think about only output side, think about input side of the air
movement. Law of physics. Often times even vent size is not adequate.
What kind of soffit do you have? Now you are not venting the attic, you
are venting the house.

Mikepier wrote:
On Aug 22, 9:47 am, Ken wrote:
Mikepier wrote:
A few weeks ago I posted a problem with too much negative air
pressure in my house caused by my attic fan. The motor I have on
the fan is similiar to this.

http://www.amazon.com/gp/product/B00...k2_dp_sr_1?pf_...

I wanted to get somekind of speed controller to slow down the speed
of the fan. I've seen them on Broan's website, and they are rated
for 6 amps.
Any issues if I put the motor on a rheostat? Are these motors
designed to work on low voltage?

If you have negative air pressure in your attic, why don't you simply
add a few more vents? There are probably eaves where a vent could be
added reducing the pressure.

As far as controlling the speed of the fan motor, I think DC motors
are better suited for such control. Of course you could reduce the
AC to an AC motor, but it can present problems for the motor.

That's the problem, I think I have adequate vents. I have 2 roof
vents, and a gable vent. I'm not sure if adding another vent would fix
it.

Obviously, from the symptoms described, you don't have enough vents, or your fan
is way too big. IIRC, the required venting is 3 square feet / 100 sq. feet of
attic space. Half of that should be high in the space, and half should be very
low, like soffit vents. Do you have that? If all your vents are high in the
attic, that does not work well. Screen and louvers in the vents reduce the
effective area for your calculations.

You could contact Broan with your specific fan model # and ask them what would
work to control its speed.

Bob F wrote:

Obviously, from the symptoms described, you don't have enough vents,
or your fan is way too big.

You could contact Broan with your specific fan model # and ask them
what would work to control its speed.

Why are all of you (except MK) overlooking the fact that he should not
be drawing interior house air into his attic in the first place?!

Yes, most probably he needs more attic venting, probably lower down
towards the soffit (he doesn't even say that he has soffits). I'm
guessing he has no roof over-hang at all.

But a roof fan shouldn't be able to create a negative pressure in the
house. I'd like to know more about what observations or measurements
he's made that makes him think he does have a negative pressure caused
by the roof fan.

Encouraging him or giving him pointers about a fan speed controller is
stupid and is a bad tangent to follow here.

On Aug 22, 10:29*am, Vic Smith
wrote:
On Mon, 22 Aug 2011 06:54:32 -0700 (PDT), Mikepier





wrote:
On Aug 22, 9:47*am, Ken wrote:
Mikepier wrote:
A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...k2_dp_sr_1?pf_...

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

* * * * If you have negative air pressure in your attic, why don't you simply
add a few more vents? *There are probably eaves where a vent could be
added reducing the pressure.

* * * * As far as controlling the speed of the fan motor, I think DC motors are
better suited for such control. *Of course you could reduce the AC to an
AC motor, but it can present problems for the motor.

That's the problem, I think I have adequate vents. I have 2 roof
vents, and a gable vent. I'm not sure if adding another vent would fix
it.

I already asked about this, but I'll try again.
You just put in the water heater, right?
You posted about venting, but I don't know what you did.
Did you change the venting?
Did you have a problem with the old water heater pilot?
If not, you should look at your venting.
I've got no idea how you let that water heater chase you up to the
attic.

--Vic- Hide quoted text -

- Show quoted text -

I thought I answered this last time, but the water heater is vented
through an exterior brick chimney. Its not going through the attic at
all. And the water heater is right underneath the chimney vent, so
total length of ducting from the water heater to the chimney is maybe
1 - 1 1/2 feet

Mikepier wrote:
A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...TM0Q87VFEGEJM8

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?
Hmm,
I don't think I saw an attic fan under speed control. Most are on
thermostat switch which turns fan on or off depending on the temp.
inside the attic.

On Mon, 22 Aug 2011 08:18:28 -0700 (PDT), Mikepier
wrote:

On Aug 22, 10:29Â*am, Vic Smith


I already asked about this, but I'll try again.
You just put in the water heater, right?
You posted about venting, but I don't know what you did.
Did you change the venting?
Did you have a problem with the old water heater pilot?
If not, you should look at your venting.
I've got no idea how you let that water heater chase you up to the
attic.


I thought I answered this last time, but the water heater is vented
through an exterior brick chimney. Its not going through the attic at
all. And the water heater is right underneath the chimney vent, so
total length of ducting from the water heater to the chimney is maybe
1 - 1 1/2 feet

You don't say if you changed the HW vent, either location relative to
the furnace vent, or angle of entry into the chimney, or went to a
different size.
And whether you had the problem with the previous tank.
I'm no expert on venting HW tanks.
I've always left them as I found them.
But you were talking about changing the venting.
If you did, that's where I'd look, not the attic.
Besides blowing out the pilot, wrong flue draft is a safety issue.

--Vic

On Aug 22, 11:32*am, Vic Smith
wrote:
On Mon, 22 Aug 2011 08:18:28 -0700 (PDT), Mikepier





wrote:
On Aug 22, 10:29*am, Vic Smith

I already asked about this, but I'll try again.
You just put in the water heater, right?
You posted about venting, but I don't know what you did.
Did you change the venting?
Did you have a problem with the old water heater pilot?
If not, you should look at your venting.
I've got no idea how you let that water heater chase you up to the
attic.

I thought I answered this last time, but the water heater is vented
through an exterior brick chimney. Its not going through the attic at
all. And the water heater is right underneath the chimney vent, so
total length of ducting from the water heater to the chimney is maybe
1 - * 1 1/2 feet

You don't say if you changed the HW vent, either location relative to
the furnace vent, or angle of entry into the chimney, or went to a
different size.
And whether you had the problem with the previous tank.
I'm no expert on venting HW tanks.
I've always left them as I found them.
But you were talking about changing the venting.
If you did, that's where I'd look, not the attic.
Besides blowing out the pilot, wrong flue draft is a safety issue.

--Vic- Hide quoted text -

- Show quoted text -

Vic, the venting is the same, I changed nothing. It is a 3" rigid duct
(per water heater spec) that leaves the water heater on an upward
pitch and goes directly into the chimney. It is not tied into the
furnace vent, which is on a seperate duct run.
The water heater was installed in January. I first noticed problems
when I started using the attic fan in the summer. If I do a match test
by the draft hood with the attic fan on, the flame is blown out. After
I shut off the attic fan, the flame test is fine, no issues.

Hmm,
I don't think I saw an attic fan under speed control. Most are on
thermostat switch which turns fan on or off depending on the temp.
inside the attic.


This is the one on Broan's website

http://www.broan.com/display/router.asp?ProductID=2956

"Mikepier" wrote in message
...
This is a roof mouted fan, not a whole -house fan.

I don't have issues with my furnace since in the cold weather, the
attic fan is off anyway. Its my water heater I have issues with.

I have a pull-down attic stairs in the second floor hallway. I know
it's not 100% sealed, but for the most part its pretty tight.

You also may want to look into sizing of the flue, meaning the chimney is
_too_ big. It may have been ok for the previous WH, but not this one.
Here's an article, which explains it better. Around here, we are not
allowed to vent into a brick or masonry chimney.
http://www.totalhomeinspection.com/hints_chimneys.shtml

On Mon, 22 Aug 2011 09:27:04 -0700 (PDT), Mikepier
wrote:



Vic, the venting is the same, I changed nothing. It is a 3" rigid duct
(per water heater spec) that leaves the water heater on an upward
pitch and goes directly into the chimney. It is not tied into the
furnace vent, which is on a seperate duct run.
The water heater was installed in January. I first noticed problems
when I started using the attic fan in the summer. If I do a match test
by the draft hood with the attic fan on, the flame is blown out. After
I shut off the attic fan, the flame test is fine, no issues.

Okay, just checking.
Now I'm stumped too.

--Vic

Mikepier wrote:
On Aug 22, 11:32 am, Vic Smith
wrote:
On Mon, 22 Aug 2011 08:18:28 -0700 (PDT), Mikepier





wrote:
On Aug 22, 10:29 am, Vic Smith

I already asked about this, but I'll try again.
You just put in the water heater, right?
You posted about venting, but I don't know what you did.
Did you change the venting?
Did you have a problem with the old water heater pilot?
If not, you should look at your venting.
I've got no idea how you let that water heater chase you up to the
attic.

I thought I answered this last time, but the water heater is vented
through an exterior brick chimney. Its not going through the attic
at all. And the water heater is right underneath the chimney vent,
so total length of ducting from the water heater to the chimney is
maybe 1 - 1 1/2 feet

You don't say if you changed the HW vent, either location relative to
the furnace vent, or angle of entry into the chimney, or went to a
different size.
And whether you had the problem with the previous tank.
I'm no expert on venting HW tanks.
I've always left them as I found them.
But you were talking about changing the venting.
If you did, that's where I'd look, not the attic.
Besides blowing out the pilot, wrong flue draft is a safety issue.

--Vic- Hide quoted text -

- Show quoted text -

Vic, the venting is the same, I changed nothing. It is a 3" rigid duct
(per water heater spec) that leaves the water heater on an upward
pitch and goes directly into the chimney. It is not tied into the
furnace vent, which is on a seperate duct run.
The water heater was installed in January. I first noticed problems
when I started using the attic fan in the summer. If I do a match test
by the draft hood with the attic fan on, the flame is blown out. After
I shut off the attic fan, the flame test is fine, no issues.

Obviously, the attic fan is drawing air through the house, which it shouldn't.
Even adding an external intake vent near the water heater will unlikely solve
the problem as long as the leakage occurs. You need to seal all the leaks into
the attic, and add more low intake vents to the attic, or just remove the attic
fan.

If the attic fan is being used as a whole house fan, you need to open more
windows when you run it. If you are using air conditioning at the same time as
the attic fan, the leakage into the attic is just throwing cooling money away
through it.

If the attic fan is being used as a whole house fan, you need to open more
windows when you run it. If you are using air conditioning at the same time as
the attic fan, the leakage into the attic is just throwing cooling money away
through it.

In my situation however, I think the attic fan helps with the A/C on.
My house was originally installed with force hot air heat, with the
supply ducts low to the ground. Like many other people in my
neighborhood, I added on Central A/C using the existing ductwork.
Because the return vent is low on the floor along with the supply
vents, I think the attic fan "draws" that air upwards, making it feel
cooler. I could be wrong though.

On Mon, 22 Aug 2011 12:02:55 -0700 (PDT), Mikepier
wrote:

If the attic fan is being used as a whole house fan, you need to open more
windows when you run it. If you are using air conditioning at the same time as
the attic fan, the leakage into the attic is just throwing cooling money away
through it.

In my situation however, I think the attic fan helps with the A/C on.
My house was originally installed with force hot air heat, with the
supply ducts low to the ground. Like many other people in my
neighborhood, I added on Central A/C using the existing ductwork.
Because the return vent is low on the floor along with the supply
vents, I think the attic fan "draws" that air upwards, making it feel
cooler. I could be wrong though.

Mike, I read up a bit on drafts, and found your attic fan issue isn't
unique. But I didn't find any simple solutions.
Your old water heater had a horizontal diverter, which probably did a
better job of keeping downdraft from the pilot.
Dumps any downdraft away from the heater.
These were common pre-1992, if not the norm.
That explains why the flame didn't blow out before.
Besides that, newer water FVIR heaters might use a smaller pilot
flame.
I don't know if horizontal diverters meet code now, but if they do,
putting that back on solves your flame-out problem.
I see no reason they won't meet code, since the new diverters are no
better that I can see.
Shouldn't change heater operation at all since you keep the supplied
hood. Just dumps the downdraft elsewhere.
I found one place selling horizontal diverters on the net, but can't
find it now. Very little can be found about them.
I saw the one on the pic you posted and remembered I tossed a couple
of them when I put in the new style heaters, but everybody else who
knows about them must have died before the net got going.
Strange.
You should turn up the heat on the water heater to go on when the
attic fan is running to see how quickly a draft is established,
Just for kicks.
If you don't put a horizontal diverter back in, I'd check to see if a
chimney cap can improve draft. I don't know about that.
I'd do all that before messing with the attic fan.
You should have CO detectors if you don't already.

--Vic

Bob F wrote:

Obviously, the attic fan is drawing air through the house, which
it shouldn't.

I've said that about 5 times now in this thread.

Mikepier wrote:

In my situation however, I think the attic fan helps with the
A/C on.

The attic fan will help increase the life of your shingles, and it will
probably lower by a few degrees the air temp of the upper layer or
strata of air near the ceiling under the attic. You don't say if this
is a 2-story with basement, single story, etc.

Because the return vent is low on the floor along with the supply
vents, I think the attic fan "draws" that air upwards, making it
feel cooler. I could be wrong though.

You are wrong.

There is no way that you would be feeling the effects (air currents)
inside your house caused by the roof fan - unless you had a massive hole
(several square feet) somewhere in your ceiling leading to your attic
space.

Vic Smith wrote:

Mike, I read up a bit on drafts, and found your attic fan issue
isn't unique. But I didn't find any simple solutions.

There is no way his house is so well sealed such that his roof fan is
pulling interior house air into the attic, causing a negative pressure
that can only be relieved through the water heater flue pipe.

His water heater exhaust is vented directly into his chimney. Does the
chimney pass through the attic?

Why isin't anyone telling him to install a water-header draft motor?

How do we know that his furnace fan isin't causing negative pressure
around the general area of the furnace / water heater, causing reverse
air flow through the water heater flue pipe?

Is the furnace air-handler properly sealed?

Are there any return air vents/ducts near the furnace that can be
closed?

Is the furnace filter clear, or clogged?

Does the furnace have a humidifier? Is the humidifier housing sealed,
or leaky?

On Mon, 22 Aug 2011 17:29:24 -0400, Home Guy wrote:

Vic Smith wrote:

Mike, I read up a bit on drafts, and found your attic fan issue
isn't unique. But I didn't find any simple solutions.

There is no way his house is so well sealed such that his roof fan is
pulling interior house air into the attic, causing a negative pressure
that can only be relieved through the water heater flue pipe.


You can plug water heater downdraft attic fan into google and find
other cases.
Probably only happens when the chimney draft is just marginal without
an established flow.

His water heater exhaust is vented directly into his chimney. Does the
chimney pass through the attic?


What do you mean by that?

Why isin't anyone telling him to install a water-header draft motor?


I don't know if you can retrofit them. Seems you can't, but I might
be wrong. Got a link?

How do we know that his furnace fan isin't causing negative pressure
around the general area of the furnace / water heater, causing reverse
air flow through the water heater flue pipe?

Is the furnace air-handler properly sealed?

Are there any return air vents/ducts near the furnace that can be
closed?

Is the furnace filter clear, or clogged?

Does the furnace have a humidifier? Is the humidifier housing sealed,
or leaky?

He never mentioned if his A/C was running, so that might be worth
looking into.

--Vic

Vic Smith wrote:

There is no way his house is so well sealed such that his roof
fan is pulling interior house air into the attic, causing a
negative pressure that can only be relieved through the water
heater flue pipe.

You can plug water heater downdraft attic fan into google and find
other cases.

A lot of people say "attic fan" and the answers seem to indicate
"whole-house" fan.

I have to wonder if most of these situations that you're finding on
google search are really just whole-house fan and NOT roof fan.

Probably only happens when the chimney draft is just marginal without
an established flow.

I'm thinking it's the HVAC fan.

Anyone with a conventional furnace will have enough convection heat from
the furnace combustion exhaust to establish a flow up the chimney to
pull the water-heater combustion exhaust. That's why most codes don't
call for water heater draft motor when the water heater is vented into
the chimney with existing conventional furnace. When you have a high
efficiency furnace, I think most codes will call for water heater draft
motor.

In the summer when the furnace is not on, you might have more of a
problem with chimney convection.

If the furnace is near the water heater, in a small enclosed space, I
can tell you for sure that the HVAC fan will definately try to pull air
from the closest source if the air handler plenum or air filter housing
is not sealed or if there are return air intakes nearby. A clogged air
filter will make this worse.

His water heater exhaust is vented directly into his chimney.
Does the chimney pass through the attic?

What do you mean by that?

Never mind. I was thinking that a leaky chimney might be the cause of
his problem, but in fact it would actually help. If his chimney does
pass through the attic (on it's way out and above the roof) then the
roof exhaust fan would only help pull air out of the chimney if there
was a "leak" in the chimney. That would create a negative pressure at
the water heater flue intake - not a postive pressure like he's claiming
to have.

Why isin't anyone telling him to install a water-header
draft motor?

I don't know if you can retrofit them. Seems you can't,
but I might be wrong. Got a link?

I don't see why it wouldn't be easy to get ahold of a draft motor and
stick it on top of the water heater and connect it's ducting in-line
with the water heater exhaust stack and the chimney flue stack. It's
just a matter of "plumbing". Why do you think it's more complicated
than that?

Is the furnace air-handler properly sealed?

He never mentioned if his A/C was running, so that might be
worth looking into.

Not just the A/C, but is the HVAC fan running? (sometimes you just want
air circulation in the house, without the AC running)

Mikepier wrote:
A few weeks ago I posted a problem with too much negative air pressure
in my house caused by my attic fan. The motor I have on the fan is
similiar to this.

http://www.amazon.com/gp/product/B00...TM0Q87VFEGEJM8

I wanted to get somekind of speed controller to slow down the speed of
the fan. I've seen them on Broan's website, and they are rated for 6
amps.
Any issues if I put the motor on a rheostat? Are these motors designed
to work on low voltage?

I always call my whole house fan, an attic fan, because that's what it is,
in the attic.

I use a green plug to slow it down a bit.

Greg

On Mon, 22 Aug 2011 18:45:16 -0400, Home Guy wrote:


A lot of people say "attic fan" and the answers seem to indicate
"whole-house" fan.


You're probably right. I didn't look close at first.
But Mike has said his attic fan causes a downdraft, and said it's just
an attic fan.
Pretty clear from his description.


I don't know if you can retrofit them. Seems you can't,
but I might be wrong. Got a link?

I don't see why it wouldn't be easy to get ahold of a draft motor and
stick it on top of the water heater and connect it's ducting in-line
with the water heater exhaust stack and the chimney flue stack. It's
just a matter of "plumbing". Why do you think it's more complicated
than that?


You'd have to figure how to turn it on and off automatically.
Don't know if downdraft would still blow out his pilot.
Seems the horizonal diverter is the easiest path.

--Vic

Vic Smith wrote:

A lot of people say "attic fan" and the answers seem to indicate
"whole-house" fan.

You're probably right. I didn't look close at first.

But Mike has said his attic fan causes a downdraft, and said
it's just an attic fan.
Pretty clear from his description.

Actually, no.

Mike said this in his second response:

This is a roof mouted fan, not a whole -house fan.

It's just a matter of "plumbing". Why do you think it's more
complicated than that?

You'd have to figure how to turn it on and off automatically.

http://www.electricmotorwarehouse.co...ter_blower.htm

Well, they probably sell these things where-ever you can buy a gas water
heater (home despot around here at least).

I don't know how they're controlled when you've got a hot water heater
with a standing pilot. Maybe some sort of thermostatic switch that can
detect when the burners are turned on.

Don't know if downdraft would still blow out his pilot.

?

These draft motors pull air up out of the flue - they don't
"down-draft". They up-draft.

Seems the horizonal diverter is the easiest path.

He needs to put a piece of paper to cover the flue opening at the top of
the water heater and see if the paper is really being pushed down / away
from the flue opening. Or go on the roof and put a piece of paper or
cardboard over the stack opening and see if it gets sucked or pulled
down. If it is, then something in his house is pulling air down
through his chimney, and it's not his roof-mounted ventillation fan. A
kitchen or bathroom fan, or his furnace fan is doing it. Maybe he's got
a window-mounted fan (or A/C unit?) somewhere doing it.

He needs to put a piece of paper to cover the flue opening at the top of
the water heater and see if the paper is really being pushed down / away
from the flue opening. *Or go on the roof and put a piece of paper or
cardboard over the stack opening and see if it gets sucked or pulled
down. * If it is, then something in his house is pulling air down
through his chimney, and it's not his roof-mounted ventillation fan. *A
kitchen or bathroom fan, or his furnace fan is doing it. *Maybe he's got
a window-mounted fan (or A/C unit?) somewhere doing it.

I have confirmed multiple times its my attic fan.
Also my Central air has no effect on the downdraft. If the A/C is on
and the attic fan is off, the draft is fine.

My water heater has a sealed chamber for the pilot, so I don't know if
it would blow out that easily.

On Aug 23, 6:34*am, Mikepier wrote:
He needs to put a piece of paper to cover the flue opening at the top of
the water heater and see if the paper is really being pushed down / away
from the flue opening. *Or go on the roof and put a piece of paper or
cardboard over the stack opening and see if it gets sucked or pulled
down. * If it is, then something in his house is pulling air down
through his chimney, and it's not his roof-mounted ventillation fan. *A
kitchen or bathroom fan, or his furnace fan is doing it. *Maybe he's got
a window-mounted fan (or A/C unit?) somewhere doing it.

I have confirmed multiple times its my attic fan.
Also my Central air has no effect on the downdraft. If the A/C is on
and the attic fan is off, the draft is fine.

My water heater has a sealed chamber for the pilot, so I don't know if
it would blow out that easily.

You said that the water heater is on it's own chimney. What
is that flue size? If it's a large size flue, typically used with
an old furnace, it's likely that the flue is too large. That presents
a problem of another kind. If it's too large, the exhaust gas
will cool off on the way out and condense back into water.
Natural gas exhaust is acidic and over time, that condensate
eats away at the mortar joints, causing the chimney to fail.

With a furnace on the same chimney flue, that was not a
problem because the chimney could only get cold enough
in winter to cause this to happen and then the furnace is
also running. That prevents it from happening. But with
no furnace, you don't want a gas water heater venting into
a chimney that is too large, unless the entire chimney is
surrounded by heated living space.

The solution is to put in a chimney liner, which is easy
to do. Having a chimney that is too large also means that it
will not draft properly, which could also be part of the
problem here.

Mikepier wrote:

I have confirmed multiple times its my attic fan.

You've never really stated what problem you have (or you think you have)
because of this so-called negative pressure.

The one thing you've said is this:

If I do a match test by the draft hood with the attic fan on,
the flame is blown out

Does your water heater have a standing pilot, or electronic pilot?

Did you do this match test when the main burners on the water heater
were on, or off?

Also my Central air has no effect on the downdraft. If the A/C
is on and the attic fan is off, the draft is fine.

What is the condition of your home's windows and doors?

Do you think you have an ultra-sealed house? A house that's so air
tight that the only place that negative pressure can be relieved is
through your water heater flue stack?

Is your furnace near your water heater? Does it have open or closed
combustion venting (ie - is it high efficiency?).

My water heater has a sealed chamber for the pilot, so I
don't know if it would blow out that easily.

You really can't have a sealed chamber because combustion air has to be
able to enter the pilot and burner area (from somewhere) or you'll get
no burning.

Also my Central air has no effect on the downdraft. If the A/C
is on and the attic fan is off, the draft is fine.

What happens when you have the attic fan turned on, and you open a
window (a high window - second floor if you have one - you haven't said
if this is a single story or 2 story home). What happens with this
match test if the attic fan is on and you have a window open?

If you have pull-down stairs to get into the attic, then that's a large
area to seal compared to just an access hatch.

But I still wouldn't expect an attic (roof) fan to significantly
depressurize an entire house, unless you have the following MAJOR
problems:

1) you have insufficient passive soffit or gable venting (you haven't
said if you have soffits or a roof overhang)

2) you have gaps in the ceiling that connects your household airspace
with the attic airspace (perhaps where interior walls meet the attic, in
closets, etc). Generally hard to see areas.

3) Where are interior fans (kitchen, bathroom) vented? Into the attic,
or through the attic directly to the outside?

You need to tell us more about 1, 2 and 3. If you're too disinterested,
motivated or lazy to come up with an answer to those questions, then you
are not really serious about fixing your home and making it right, and
all of our efforts here are wasted on you.

" wrote:

The solution is to put in a chimney liner

What the **** is wrong with you?

If he really does have a reverse airflow through his flue caused by his
roof fan, then a chimney liner is going to do ****-all to help that
situation.

On Aug 23, 9:36*am, Home Guy wrote:
" wrote:
The solution is to put in a chimney liner

What the **** is wrong with you?

If he really does have a reverse airflow through his flue caused by his
roof fan, then a chimney liner is going to do ****-all to help that
situation.

Excuse me, ignoramus, but first, if you look at that in context,
which you did not, the problem I was specifically referring
to the chimney liner solving is the case where the chimney
is too large for the water heater. That problem can exist
regardless of any backdrafting issue and it can lead to long
term damage and failure of the chimney.

And second, having the flue correctly sized to the appliance
helps create the correct draft. If the flue is sized correctly
the hot gas stays hot and rises. If you dump a smaller
exhaust load into a chimney that is too large, the natural
draft action does not occur. So, yes the chimney liner
can help with a water heater that is having problems
with the exhaust backdrafting.

So, have another beer, maybe you'll feel better. More
likely though, it will just result in more profanity.

On Aug 23, 9:34*am, Home Guy wrote:
Mikepier wrote:
I have confirmed multiple times its my attic fan.

You've never really stated what problem you have (or you think you have)
because of this so-called negative pressure.


He did in the other thread that he referred to and I think
most of us here have read it. Let me help you out:

http://groups.google.com/group/alt.h...fb7845e?hl=en#




The one thing you've said is this:

If I do a match test by the draft hood with the attic fan on,
the flame is blown out

Does your water heater have a standing pilot, or electronic pilot?

Matters not a wit.




Did you do this match test when the main burners on the water heater
were on, or off?


Also my Central air has no effect on the downdraft. If the A/C
is on and the attic fan is off, the draft is fine.

What is the condition of your home's windows and doors?

Do you think you have an ultra-sealed house? *A house that's so air
tight that the only place that negative pressure can be relieved is
through your water heater flue stack?

Is your furnace near your water heater? *Does it have open or closed
combustion venting (ie - is it high efficiency?).

My water heater has a sealed chamber for the pilot, so I
don't know if it would blow out that easily.

You really can't have a sealed chamber because combustion air has to be
able to enter the pilot and burner area (from somewhere) or you'll get
no burning.

Also my Central air has no effect on the downdraft. If the A/C
is on and the attic fan is off, the draft is fine.

What happens when you have the attic fan turned on, and you open a
window (a high window - second floor if you have one - you haven't said
if this is a single story or 2 story home). *What happens with this
match test if the attic fan is on and you have a window open?

If you have pull-down stairs to get into the attic, then that's a large
area to seal compared to just an access hatch.

But I still wouldn't expect an attic (roof) fan to significantly
depressurize an entire house, unless you have the following MAJOR
problems:

1) you have insufficient passive soffit or gable venting (you haven't
said if you have soffits or a roof overhang)

2) you have gaps in the ceiling that connects your household airspace
with the attic airspace (perhaps where interior walls meet the attic, in
closets, etc). *Generally hard to see areas.

3) Where are interior fans (kitchen, bathroom) vented? *Into the attic,
or through the attic directly to the outside?

You need to tell us more about 1, 2 and 3. *If you're too disinterested,
motivated or lazy to come up with an answer to those questions, then you
are not really serious about fixing your home and making it right, and
all of our efforts here are wasted on you.

More attitude, eh? Why is this guy's problem of such emotional
interest
to you?

" wrote:

If he really does have a reverse airflow through his flue caused
by his roof fan, then a chimney liner is going to do ****-all to
help that situation.

Excuse me, ignoramus, but first, if you look at that in context,
which you did not, the problem I was specifically referring
to the chimney liner solving is the case where the chimney
is too large for the water heater.

You can't say that his chimney is too large unless you know if he lives
in a northern climate and if he has a high-efficiency furnace.

In a northern climate, you can have condensation inside the chimney if
there is not enough total combustion flow (furnace + water heater).
Normally for a regular furnace, it's putting out enough exhaust to keep
a good convective heat flow going and "help" the water heater flue stack
flow.

In the summer, there really isin't a problem with needed help from the
furnace (which you won't get anyways because the furnace doesn't run in
the summer). The water heater exhaust flow should have no problem
getting up and out the chimney in the summer. Now if you have a reverse
air-flow in the chimney, then nothing you can do to the chimney
(including using a liner) is going to help with that.

So unless you know what type of furnace he has, and just how cold it
gets where he lives, then you can't say that he *needs* a liner for his
water heater exhaust.

And like I said before, even in cold climates it's standard to have a
non-lined chimney and have furnace and water-heater exhaust run
passively up and out the chimney. It's only when you have a
high-efficiency furnace do you start to look at using a draft motor or a
liner to help the water-heater exhaust.

And second, having the flue correctly sized to the appliance
helps create the correct draft.

**** the draft, and the sizing. This isn't rocket science.

When you've got something creating a negative pressure in the house,
causing reverse air-flow through the water heater flue, then you put
down your books and graphs and tables and you fix the reverse air
problem.

If the flue is sized correctly the hot gas stays hot and rises.

Again, you're completely disregarding the whole point that started this
thread.

This boob thinks that he's getting a breeze flowing into his water
heater exhast flue and blowing out a match that he holds against the
draft intake vent (presumably the gap between the water heater and the
flue intake above it).

None of your correctly-sized **** is going to make that breeze go away.