furnace blower


  #1  
Old 02-19-03, 04:01 PM
palsm23
Visiting Guest
Posts: n/a
Question furnace blower



Does anyone know if it is possible to use a rheostat (dimmer type) switch on a furnace blower?? I need to make my furnace blower speed adjustable without having to dis-connect and reconnect blower wires every time I want to adjust my speed, PLUS, I need it to run SLOWER then the slowest hard-wired speed.
I have tried a regular light dimmer switch and it does just what I want it to do. But I don't know if I should use THAT particular switch or if there is another type switch better suited for this.

Thx,

John
 
  #2  
Old 02-19-03, 08:34 PM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 10,234
Received 65 Votes on 60 Posts
John:

I'm afraid your motor will smoke if you use a light dimmer to control it's speed.
The reason is that the power output of a light dimmer is half wave direct current, not the alternating current the motor needs.
Some small shaded pole motors like those found in range hoods and ceiling fans and some power tools can run on dc power.
AC motors don't like being slowed down by voltage control.
There is such a thing for industrial use but it is not feasable for your use.

I assume you have a direct drive set-up and not belted.

I'm curious to know why you want to control the speed like this.

Tell us what you hope to accomplish and we may have some ideas for you.
 
  #3  
Old 02-20-03, 05:22 PM
hvac4u's Avatar
Member
Join Date: Aug 2001
Location: NW atlanta
Posts: 3,145
Received 0 Votes on 0 Posts
greg is right

the switch you describe increases the resistance of the circuit and drives up the amperage of the motor, burning it out much more quickly. industrial applications have frequency drives that alter the frequency (hz) and not the voltage supply
 
  #4  
Old 02-20-03, 07:21 PM
palsm23
Visiting Guest
Posts: n/a
The application is an A/C Air Handler mounterd in the ceiling of our family room. The family room is a one room addition to the original house, which was built in 1886. It is obvious to me the A/C unit is over-sized and therefore constantly cyles on and off. The blower noise is unbareable due to there being only one outlet register and one inlet register.
I have it wired to the slowest of the 4 available speeds of the motor, but this is STILL to fast....... It IS direct drive and I have considered replacing the motor with a slower RPM, thus creating the ideal result. BUT......... I am NOT sure what (if any) NEW problem might occur by slowing the blower speed down,..... such as the evaporator coil freezing up..... or whatever else could occur.
By (TRYING) the rherostat idea, at least I could remove the switch and live with the noise, if it fails.

Thx folks, any input is appreciated
 
  #5  
Old 02-20-03, 07:51 PM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 10,234
Received 65 Votes on 60 Posts
John:

You are not going to find a motor that has a slower speed than what you get with a multi-speed motor.

By slowing down the motor more than the lowest tap you will make the A/C unuseable.
You may as well just shut it off and it will be very quiet, and I can guarantee it won't freeze up.

It sounds like you should really try and correct the faulty installation.

If you give us more info maybe we can come up with a proper remedy.
We need room size, where you live, make model and capacity of a/c, duct size and length, etc, etc.
 
  #6  
Old 02-25-03, 11:23 AM
M
Member
Join Date: Feb 2003
Posts: 525
Received 0 Votes on 0 Posts
How about abandoning that unit and running a tap off of the system that controls the rest of the house?
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: