Hi,



I have just moved into a house about 40 years old. Very nice condition and
was a good buy. There anyway to modify the fan motor so when heat or air is
required will torque up to a higher RPM.



I had this in my previous house and it was great. I admit I have not done
too much research on the motor, so this question is just for feelers and
help.



Thanks.



Jeff

"Jeff Bulach" wrote in message
...
Hi,



I have just moved into a house about 40 years old. Very nice condition and
was a good buy. There anyway to modify the fan motor so when heat or air
is
required will torque up to a higher RPM.



I had this in my previous house and it was great. I admit I have not done
too much research on the motor, so this question is just for feelers and
help.



Thanks.



Jeff



There are a couple of nice HVAC guys in this group and several who are not.

I am not one of either group.

It may be possible if you have a multi-speed motor. For anyone to help you
is going to require more information. I suggest you post again with the
brand name and model number of the furnace. A guy with the nick of Turtle is
one of the nice guys.

Colbyt

"Jeff Bulach" wrote in message
...
Hi,



I have just moved into a house about 40 years old.
Very nice condition and
was a good buy. There anyway to modify the fan motor
so when heat or air is
required will torque up to a higher RPM.



I had this in my previous house and it was great. I
admit I have not done
too much research on the motor, so this question is
just for feelers and
help.



Thanks.



Jeff


Yes, there is, but ... you have to do so with knowledge
of what you're doing. The pulley sizes can be modified
(assuming it's not a direct drive type) to increase the
speed of the fan, but the motor must be able to handle
the added load.
It's also possible that the belts, assuming there
are belts, are too worn or even the wrong width to ride
properly in the pulleys.
Some pulleys are even adjustable in size.
But, add too much load and you'll be looking for
another motor, so step carefully and listen to any
experts that may chime in here.

Regards,

Pop

Jeff Bulach wrote:
modify the fan motor so
when heat or air is required will torque up to a higher RPM.

The standard air flow rate is 400 CFM / ton for cooling and whatever the
heating (furnace or resistive heat) manufacturer recommends for heating.
Don't go messing with this unless you know what you are doing.

Jeff,

Your question is a bit confusing. Most of us are assuming that
you are asking if you can have two different fan speeds - one lower
speed for heating and a higher speed for AC. If so, then the answer
is "usually." Many fan motors have multiple taps for multiple
speeds and it is pretty easy to determine how to change those
taps IF you know what you are doing. If not, then get some advice
from somebody who has done this many times or integrate this
simple modification with a routine service call for HVAC maintenance.
The pro shouldn't charge you too much extra to "rewire" the motor
as long as he is already out to your home for the annual maintenance
call.

Also, many tract home developments built around 40 years ago
had the same furnace, AC and ductwork in most of the homes. If
you locate a neighbor with the same setup as yours, then you can
check out which taps are being used on his fan. This isn't 100%
guaranteed, but it is usually safe. Many of us could make a good
educated guess on which taps and fan speeds should be used, but
I'm not going to make that blind suggestion over a newsgroup.

Final comment: Be certain that whoever pulls out that fan/blower
assembly cleans the squirrel cage if needed and lubes the motor.
Fins on the squirrel cage can get clogged with dust, especially if
the home has every had an electronic air filter which was neglected.
Also, some motors are difficult to lube and some HVAC guys skip
one or both oil ports on the motor.

Good luck,
Gideon

Jeff Bulach wrote:
Hi,



I have just moved into a house about 40 years old. Very nice condition and
was a good buy. There anyway to modify the fan motor so when heat or air is
required will torque up to a higher RPM.



I had this in my previous house and it was great.

You can adversely affect your system's performance as well as indoor
comfort by injudiciously changing the blower speed.
Motors that have multiple speed taps are designed to allow for
maximizing performance and/or to allow the same motor to be used for
multiple applications. Increased blower speed will result in less
effective air filtration and greater air noise.

hvacrmedic

I admit I have not done
too much research on the motor, so this question is just for feelers and
help.



Thanks.



Jeff

"Colbyt" wrote in message
...

There are a couple of nice HVAC guys in this group and several who are
not.

I am not one of either group.


So Im ****ing chopped liver then, no ???


It may be possible if you have a multi-speed motor. For anyone to help
you
is going to require more information. I suggest you post again with the
brand name and model number of the furnace. A guy with the nick of Turtle
is
one of the nice guys.


You can only pull in whatever airflow your existing return ducts will
allow....ya ever wonder why it is when you stick your hand on the vaccuum
cleaner nozzle the motor actually speeds UP ????

Regardless, increase all airflow across your evaporater coils and then the
moisture that was SUPPOSED to drop out...doesent....now consider that moist
air holds a HELL of a lot more heat than does dry air.........

--

SVL

PrecisionMachinisT wrote:
"Colbyt" wrote in message
...

There are a couple of nice HVAC guys in this group and several who are

not.

I am not one of either group.



So Im ****ing chopped liver then, no ???


It may be possible if you have a multi-speed motor. For anyone to help

you

is going to require more information. I suggest you post again with the
brand name and model number of the furnace. A guy with the nick of Turtle

is

one of the nice guys.



You can only pull in whatever airflow your existing return ducts will
allow....ya ever wonder why it is when you stick your hand on the vaccuum
cleaner nozzle the motor actually speeds UP ????

Regardless, increase all airflow across your evaporater coils and then the
moisture that was SUPPOSED to drop out...doesent....now consider that moist
air holds a HELL of a lot more heat than does dry air.........

I could have let it go, but you made two incorrect points here, and
these were the only two points that you made.
Your first statement, taken at face value, says that increasing blower
rpm will not increase cfm. This is incorrect. The cfm won't increase
proportionally to blower speed, but it will increase.
Your second statement is also incorrect. Moist air, per unit volume has
a greater specific heat than dry air, and thus holds more sensible heat
energy at a given temp, OTOH, it isn't a HELL of a lot more. The
advantage of dryer air is that you can set your t-stat to a higher temp
and still be comfortable. The load on the system is reduced, not because
of the lower specific heat of the air, but because the rate of heat
infiltration into the space is proportional to the temperature
difference across the outside surfaces of the structure. With a higher
external surface TD the net load on the system will be higher,
independently of moisture content of the indoor air. In medium to low
humidity areas this isn't a big factor since indoor RH won't vary as
much with changes in blower speed as it will in high humidity areas.

In high humidity areas you can lose efficiency by reducing blower speed
or indoor coil size if there is very much air infiltration, since the
latent load will be higher, thus offsetting any gain provided by running
a higher indoor temp. Given a tight structure, the higher latent
capacity system may be more energy efficient or it may not be. There
are too many factors to establish a rule of thumb; each structure is
unique, as are the preferences and habits of its occupants. You should
target RH, and let efficiency run a close second.

Where RH isn't a factor, then increasing blower speed should be
considered, but again there are many other factors involved, one of
which is the additional energy draw of the motor at higher speeds,
another being the increase in high side pressure produced by the extra
load on the system. In most every case, what is done on the one hand to
increase efficiency is offset by some other factor to some degree, so
that small changes won't in general have a significant effect on overall
efficiency. Changing blower speed is not however a small change and
should be done only when indoor comfort is noticeably lacking, and only
after the real problem has been repaired, that is, if incorrect blower
speed wasn't the real problem.

The OP's question is essentially equivalent to asking "should I increase
the air/fuel ratio in my vehicle's carburetor?"

hvacrmedic










hvacrmedic

"RP" wrote in message
...


PrecisionMachinisT wrote:
"Colbyt" wrote in message
...

There are a couple of nice HVAC guys in this group and several who are

not.

I am not one of either group.



So Im ****ing chopped liver then, no ???


It may be possible if you have a multi-speed motor. For anyone to help

you

is going to require more information. I suggest you post again with the
brand name and model number of the furnace. A guy with the nick of
Turtle

is

one of the nice guys.



You can only pull in whatever airflow your existing return ducts will
allow....ya ever wonder why it is when you stick your hand on the
vaccuum
cleaner nozzle the motor actually speeds UP ????

Regardless, increase all airflow across your evaporater coils and then
the
moisture that was SUPPOSED to drop out...doesent....now consider that
moist
air holds a HELL of a lot more heat than does dry air.........

I could have let it go, but you made two incorrect points here, and
these were the only two points that you made.
Your first statement, taken at face value, says that increasing blower
rpm will not increase cfm. This is incorrect. The cfm won't increase
proportionally to blower speed, but it will increase.
Your second statement is also incorrect. Moist air, per unit volume has
a greater specific heat than dry air, and thus holds more sensible heat
energy at a given temp, OTOH, it isn't a HELL of a lot more. The
advantage of dryer air is that you can set your t-stat to a higher temp
and still be comfortable. The load on the system is reduced, not because
of the lower specific heat of the air, but because the rate of heat
infiltration into the space is proportional to the temperature
difference across the outside surfaces of the structure. With a higher
external surface TD the net load on the system will be higher,
independently of moisture content of the indoor air. In medium to low
humidity areas this isn't a big factor since indoor RH won't vary as
much with changes in blower speed as it will in high humidity areas.

In high humidity areas you can lose efficiency by reducing blower speed
or indoor coil size if there is very much air infiltration, since the
latent load will be higher, thus offsetting any gain provided by running
a higher indoor temp. Given a tight structure, the higher latent
capacity system may be more energy efficient or it may not be. There
are too many factors to establish a rule of thumb; each structure is
unique, as are the preferences and habits of its occupants. You should
target RH, and let efficiency run a close second.

Where RH isn't a factor, then increasing blower speed should be
considered, but again there are many other factors involved, one of
which is the additional energy draw of the motor at higher speeds,
another being the increase in high side pressure produced by the extra
load on the system. In most every case, what is done on the one hand to
increase efficiency is offset by some other factor to some degree, so
that small changes won't in general have a significant effect on overall
efficiency. Changing blower speed is not however a small change and
should be done only when indoor comfort is noticeably lacking, and only
after the real problem has been repaired, that is, if incorrect blower
speed wasn't the real problem.

The OP's question is essentially equivalent to asking "should I increase
the air/fuel ratio in my vehicle's carburetor?"


'Usenet troll' is a tough job--but SOMEBODY has to do it...

G

Once your full shaft horsepower is being consumed, any further gains to be
had in air volume lie in increasing your duct size.

As to the any specifics quantifying hell...probly best to leave that up to
speculation.

BTW, your post above was good and quite informative.

--

SVL

PrecisionMachinisT wrote:
"RP" wrote in message
...


PrecisionMachinisT wrote:

"Colbyt" wrote in message
...


There are a couple of nice HVAC guys in this group and several who are

not.


I am not one of either group.



So Im ****ing chopped liver then, no ???



It may be possible if you have a multi-speed motor. For anyone to help

you


is going to require more information. I suggest you post again with the
brand name and model number of the furnace. A guy with the nick of

Turtle

is


one of the nice guys.



You can only pull in whatever airflow your existing return ducts will
allow....ya ever wonder why it is when you stick your hand on the

vaccuum

cleaner nozzle the motor actually speeds UP ????

Regardless, increase all airflow across your evaporater coils and then

the

moisture that was SUPPOSED to drop out...doesent....now consider that

moist

air holds a HELL of a lot more heat than does dry air.........

I could have let it go, but you made two incorrect points here, and
these were the only two points that you made.
Your first statement, taken at face value, says that increasing blower
rpm will not increase cfm. This is incorrect. The cfm won't increase
proportionally to blower speed, but it will increase.
Your second statement is also incorrect. Moist air, per unit volume has
a greater specific heat than dry air, and thus holds more sensible heat
energy at a given temp, OTOH, it isn't a HELL of a lot more. The
advantage of dryer air is that you can set your t-stat to a higher temp
and still be comfortable. The load on the system is reduced, not because
of the lower specific heat of the air, but because the rate of heat
infiltration into the space is proportional to the temperature
difference across the outside surfaces of the structure. With a higher
external surface TD the net load on the system will be higher,
independently of moisture content of the indoor air. In medium to low
humidity areas this isn't a big factor since indoor RH won't vary as
much with changes in blower speed as it will in high humidity areas.

In high humidity areas you can lose efficiency by reducing blower speed
or indoor coil size if there is very much air infiltration, since the
latent load will be higher, thus offsetting any gain provided by running
a higher indoor temp. Given a tight structure, the higher latent
capacity system may be more energy efficient or it may not be. There
are too many factors to establish a rule of thumb; each structure is
unique, as are the preferences and habits of its occupants. You should
target RH, and let efficiency run a close second.

Where RH isn't a factor, then increasing blower speed should be
considered, but again there are many other factors involved, one of
which is the additional energy draw of the motor at higher speeds,
another being the increase in high side pressure produced by the extra
load on the system. In most every case, what is done on the one hand to
increase efficiency is offset by some other factor to some degree, so
that small changes won't in general have a significant effect on overall
efficiency. Changing blower speed is not however a small change and
should be done only when indoor comfort is noticeably lacking, and only
after the real problem has been repaired, that is, if incorrect blower
speed wasn't the real problem.

The OP's question is essentially equivalent to asking "should I increase
the air/fuel ratio in my vehicle's carburetor?"



'Usenet troll' is a tough job--but SOMEBODY has to do it...

G

Once your full shaft horsepower is being consumed, any further gains to be
had in air volume lie in increasing your duct size.

That's what I thought you meant


As to the any specifics quantifying hell...probly best to leave that up to
speculation.

BTW, your post above was good and quite informative.

Thanks.

hvacrmedic

Since you mention AC, I should guess that the furnace system has both heat
and AC?

In this case, typically the AC is set to the highest blower power. But not
always. You do have a local HVAC guy who services your system?

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.com


"Jeff Bulach" wrote in message
...
Hi,



I have just moved into a house about 40 years old. Very nice condition and
was a good buy. There anyway to modify the fan motor so when heat or air is
required will torque up to a higher RPM.



I had this in my previous house and it was great. I admit I have not done
too much research on the motor, so this question is just for feelers and
help.



Thanks.



Jeff