Which way should air flow through a bypass Aprilaire 560 humidifier?

[Ray K.]

It's located above the evaporator, with the duct from its side
connecting it to the return duct. Flow presently is from the supply
plenum to the return duct.

I was measuring the temperature rise across the furnace and was
surprised to see the return air right into the furnace at 85F (with the
damper in the bypass duct in the summer position), and 101F in the
winter position. (No water flowing in either case.) These temperatures
are well above ambient of 70F. (Furnace output temperatures at the side
of the evaporator were 134F and 155F, giving rises of 49F and 54F,
within the label spec of 45-75F.)

Strange thing: I also measured return air temperatures almost two feet
ahead of the bypass duct. In both cases, the reading was 77F, still
surprisingly above 70F ambient.

With the damper in the summer position, it takes 54 minutes to raise the
temperature at the thermostat 4 degrees, from 65 to 69 degrees. In the
winter position, again with no water flow, it takes 80 minutes, even
though the air temperature out of the furnace is 21 degrees higher.

Measurements were made at 8:00 am. Summer measurements were made with
attic ducts in an ambient of 45F. Winter measurements were made same
time next day with attic temperature 40F. This accounts somewhat for the
longer response time. Attic ducts are 1" duct board.

Sorry for the long post, and drifting somewhat off the Subject.

Thanks for your comments. If replying more than two days after today's
date, please also email me; remove the xxx from the address.

Ray

[Bubba]

Post by Ray K.
It's located above the evaporator, with the duct from its side
connecting it to the return duct. Flow presently is from the supply
plenum to the return duct.
I was measuring the temperature rise across the furnace and was
surprised to see the return air right into the furnace at 85F (with the
damper in the bypass duct in the summer position), and 101F in the
winter position. (No water flowing in either case.) These temperatures
are well above ambient of 70F. (Furnace output temperatures at the side
of the evaporator were 134F and 155F, giving rises of 49F and 54F,
within the label spec of 45-75F.)
Strange thing: I also measured return air temperatures almost two feet
ahead of the bypass duct. In both cases, the reading was 77F, still
surprisingly above 70F ambient.
With the damper in the summer position, it takes 54 minutes to raise the
temperature at the thermostat 4 degrees, from 65 to 69 degrees. In the
winter position, again with no water flow, it takes 80 minutes, even
though the air temperature out of the furnace is 21 degrees higher.
Measurements were made at 8:00 am. Summer measurements were made with
attic ducts in an ambient of 45F. Winter measurements were made same
time next day with attic temperature 40F. This accounts somewhat for the
longer response time. Attic ducts are 1" duct board.
Sorry for the long post, and drifting somewhat off the Subject.
Thanks for your comments. If replying more than two days after today's
date, please also email me; remove the xxx from the address.
Ray

Ray, You're think way way way too much. Its a simple by-pass
humidifier. Whats with all the times temps and numbers? It doesnt
matter if you hang the humidifier on the supply or return. Either is
fine. I prefer to hang the humidifier on the return side though. That
way if it leaks (and it will at some point) it will only run down in
the return ductwork and onto the floor. If you hang it on the supply
plenum, then you run the risk of shorting out controls and rusting the
equipment when it leaks.
Bubba

[Ray K.]

Post by Bubba

Post by Ray K.
It's located above the evaporator, with the duct from its side
connecting it to the return duct. Flow presently is from the supply
plenum to the return duct.
I was measuring the temperature rise across the furnace and was
surprised to see the return air right into the furnace at 85F (with the
damper in the bypass duct in the summer position), and 101F in the
winter position. (No water flowing in either case.) These temperatures
are well above ambient of 70F. (Furnace output temperatures at the side
of the evaporator were 134F and 155F, giving rises of 49F and 54F,
within the label spec of 45-75F.)
Strange thing: I also measured return air temperatures almost two feet
ahead of the bypass duct. In both cases, the reading was 77F, still
surprisingly above 70F ambient.
With the damper in the summer position, it takes 54 minutes to raise the
temperature at the thermostat 4 degrees, from 65 to 69 degrees. In the
winter position, again with no water flow, it takes 80 minutes, even
though the air temperature out of the furnace is 21 degrees higher.
Measurements were made at 8:00 am. Summer measurements were made with
attic ducts in an ambient of 45F. Winter measurements were made same
time next day with attic temperature 40F. This accounts somewhat for the
longer response time. Attic ducts are 1" duct board.
Sorry for the long post, and drifting somewhat off the Subject.
Thanks for your comments. If replying more than two days after today's
date, please also email me; remove the xxx from the address.
Ray

Ray, You're think way way way too much.

You are right. Tha't my engineering background rearing its ugly head.

Its a simple by-pass

Post by Bubba
humidifier. Whats with all the times temps and numbers? It doesnt
matter if you hang the humidifier on the supply or return. Either is
fine. I prefer to hang the humidifier on the return side though. That
way if it leaks (and it will at some point) it will only run down in
the return ductwork and onto the floor. If you hang it on the supply
plenum, then you run the risk of shorting out controls and rusting the
equipment when it leaks.

Since the humidifier is mounted outside the supply plenum, if it leaks,
water will fall onto sheet metal on top of the furnace. There is a good
seal between the furnace top and the supply plenum, so leaks will simply
run off the sides without entering the furnace.

I mentioned the times to see if anyone other than me thinks they are too
long. With the humidifier in the supply plenum, there is a "short
circuit loop," where some of the hot air is diverted from the supply
trunk into the humidifier. The reduced cfm into the supply trunk is
offset by the higher temperatures, but I still feel that having the
furnace run for 80 minutes to raise the air from 65 to 69 is excessive,
especially when the attic temperatures (mid 40s) aren't particularly cold.

Maybe I'm expecting too much from the heating system.

Thanks for taking the time to reply.

Ray

[Bubba]

Post by Ray K.

Post by Bubba

Post by Ray K.
It's located above the evaporator, with the duct from its side
connecting it to the return duct. Flow presently is from the supply
plenum to the return duct.
I was measuring the temperature rise across the furnace and was
surprised to see the return air right into the furnace at 85F (with the
damper in the bypass duct in the summer position), and 101F in the
winter position. (No water flowing in either case.) These temperatures
are well above ambient of 70F. (Furnace output temperatures at the side
of the evaporator were 134F and 155F, giving rises of 49F and 54F,
within the label spec of 45-75F.)
Strange thing: I also measured return air temperatures almost two feet
ahead of the bypass duct. In both cases, the reading was 77F, still
surprisingly above 70F ambient.
With the damper in the summer position, it takes 54 minutes to raise the
temperature at the thermostat 4 degrees, from 65 to 69 degrees. In the
winter position, again with no water flow, it takes 80 minutes, even
though the air temperature out of the furnace is 21 degrees higher.
Measurements were made at 8:00 am. Summer measurements were made with
attic ducts in an ambient of 45F. Winter measurements were made same
time next day with attic temperature 40F. This accounts somewhat for the
longer response time. Attic ducts are 1" duct board.
Sorry for the long post, and drifting somewhat off the Subject.
Thanks for your comments. If replying more than two days after today's
date, please also email me; remove the xxx from the address.
Ray

Ray, You're think way way way too much.

You are right. Tha't my engineering background rearing its ugly head.

OH MY! Why am I not suprised.

Post by Ray K.
Its a simple by-pass

Post by Bubba
humidifier. Whats with all the times temps and numbers? It doesnt
matter if you hang the humidifier on the supply or return. Either is
fine. I prefer to hang the humidifier on the return side though. That
way if it leaks (and it will at some point) it will only run down in
the return ductwork and onto the floor. If you hang it on the supply
plenum, then you run the risk of shorting out controls and rusting the
equipment when it leaks.

Since the humidifier is mounted outside the supply plenum, if it leaks,
water will fall onto sheet metal on top of the furnace. There is a good
seal between the furnace top and the supply plenum, so leaks will simply
run off the sides without entering the furnace.

As I emailed you back (sinde you emailed me).......Water WILL find its
way into your furnace at some point. Its kind of one of those laws of
physics or gravity or whatever you want to call it. Water goes down
hill, not up.

Post by Ray K.
I mentioned the times to see if anyone other than me thinks they are too
long. With the humidifier in the supply plenum, there is a "short
circuit loop," where some of the hot air is diverted from the supply
trunk into the humidifier. The reduced cfm into the supply trunk is
offset by the higher temperatures, but I still feel that having the
furnace run for 80 minutes to raise the air from 65 to 69 is excessive,
especially when the attic temperatures (mid 40s) aren't particularly cold.
Maybe I'm expecting too much from the heating system.
Thanks for taking the time to reply.
Ray

4 degree rise in 80 mins on a 40ish degree day seems way too long.
Your himidifier has nothing to do with it. Get a competent tech out
and have him look it over.
Bubba

[Steve Scott]

Post by Ray K.

Post by Bubba

Post by Ray K.
It's located above the evaporator, with the duct from its side
connecting it to the return duct. Flow presently is from the supply
plenum to the return duct.
I was measuring the temperature rise across the furnace and was
surprised to see the return air right into the furnace at 85F (with the
damper in the bypass duct in the summer position), and 101F in the
winter position. (No water flowing in either case.) These temperatures
are well above ambient of 70F. (Furnace output temperatures at the side
of the evaporator were 134F and 155F, giving rises of 49F and 54F,
within the label spec of 45-75F.)
Strange thing: I also measured return air temperatures almost two feet
ahead of the bypass duct. In both cases, the reading was 77F, still
surprisingly above 70F ambient.
With the damper in the summer position, it takes 54 minutes to raise the
temperature at the thermostat 4 degrees, from 65 to 69 degrees. In the
winter position, again with no water flow, it takes 80 minutes, even
though the air temperature out of the furnace is 21 degrees higher.
Measurements were made at 8:00 am. Summer measurements were made with
attic ducts in an ambient of 45F. Winter measurements were made same
time next day with attic temperature 40F. This accounts somewhat for the
longer response time. Attic ducts are 1" duct board.
Sorry for the long post, and drifting somewhat off the Subject.
Thanks for your comments. If replying more than two days after today's
date, please also email me; remove the xxx from the address.
Ray

Ray, You're think way way way too much.

You are right. Tha't my engineering background rearing its ugly head.

We would never have guessed. :)

Post by Ray K.
I mentioned the times to see if anyone other than me thinks they are too
long. With the humidifier in the supply plenum, there is a "short
circuit loop," where some of the hot air is diverted from the supply
trunk into the humidifier. The reduced cfm into the supply trunk is
offset by the higher temperatures, but I still feel that having the
furnace run for 80 minutes to raise the air from 65 to 69 is excessive,
especially when the attic temperatures (mid 40s) aren't particularly cold.

What's design temp for your area? What was the outside temp when you
checked this out? The closer to design the longer the period to
recover particularly if the unit is properly sized.

[Stormin Mormon]

That's odd. My boss and I always installed Aprilaires in the return air
duct.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.org
.
.

"Ray K." <***@optonline.net> wrote in message news:l2mfb.28181$***@news4.srv.hcvlny.cv.net...
It's located above the evaporator, with the duct from its side
connecting it to the return duct. Flow presently is from the supply
plenum to the return duct.

I was measuring the temperature rise across the furnace and was
surprised to see the return air right into the furnace at 85F (with the
damper in the bypass duct in the summer position), and 101F in the
winter position. (No water flowing in either case.) These temperatures
are well above ambient of 70F. (Furnace output temperatures at the side
of the evaporator were 134F and 155F, giving rises of 49F and 54F,
within the label spec of 45-75F.)

Strange thing: I also measured return air temperatures almost two feet
ahead of the bypass duct. In both cases, the reading was 77F, still
surprisingly above 70F ambient.

With the damper in the summer position, it takes 54 minutes to raise the
temperature at the thermostat 4 degrees, from 65 to 69 degrees. In the
winter position, again with no water flow, it takes 80 minutes, even
though the air temperature out of the furnace is 21 degrees higher.

Measurements were made at 8:00 am. Summer measurements were made with
attic ducts in an ambient of 45F. Winter measurements were made same
time next day with attic temperature 40F. This accounts somewhat for the
longer response time. Attic ducts are 1" duct board.

Sorry for the long post, and drifting somewhat off the Subject.

Thanks for your comments. If replying more than two days after today's
date, please also email me; remove the xxx from the address.

Ray

[CBHvac]

Post by Stormin Mormon
That's odd. My boss and I always installed Aprilaires in the return air
duct.

Nothing odd about that....but then, you need to know what a bypass hum is
about...

Hows that hand..

Post by Stormin Mormon
--
Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.org
.
.
It's located above the evaporator, with the duct from its side
connecting it to the return duct. Flow presently is from the supply
plenum to the return duct.
I was measuring the temperature rise across the furnace and was
surprised to see the return air right into the furnace at 85F (with the
damper in the bypass duct in the summer position), and 101F in the
winter position. (No water flowing in either case.) These temperatures
are well above ambient of 70F. (Furnace output temperatures at the side
of the evaporator were 134F and 155F, giving rises of 49F and 54F,
within the label spec of 45-75F.)
Strange thing: I also measured return air temperatures almost two feet
ahead of the bypass duct. In both cases, the reading was 77F, still
surprisingly above 70F ambient.
With the damper in the summer position, it takes 54 minutes to raise the
temperature at the thermostat 4 degrees, from 65 to 69 degrees. In the
winter position, again with no water flow, it takes 80 minutes, even
though the air temperature out of the furnace is 21 degrees higher.
Measurements were made at 8:00 am. Summer measurements were made with
attic ducts in an ambient of 45F. Winter measurements were made same
time next day with attic temperature 40F. This accounts somewhat for the
longer response time. Attic ducts are 1" duct board.
Sorry for the long post, and drifting somewhat off the Subject.
Thanks for your comments. If replying more than two days after today's
date, please also email me; remove the xxx from the address.
Ray

[Greg O]

Post by Stormin Mormon
That's odd. My boss and I always installed Aprilaires in the return air
duct.
--

Nothing odd about it! Most of them you can hang where they fit. I do agree
that on a bypass that on the return is best, but either place is fine.
Greg

[jack]

replying to Ray K., jack wrote:
The answer lies in the pressure differential created by the furnace. The air
is flowing from after the fan (where the pressure is high) to before the fan.
The flow is counter intuitive.