Speed control on whole house fan

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SteveM
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Speed control on whole house fan

Post by SteveM »

I have a whole house fan, and it's nice, but it is SO powerful that if you don't have enough windows and doors open, you will smell ashes from the fireplace as it sucks air thru the CLOSED chimney damper.

I also worry that it is sucking air back thru the furnace (during this weather the furnace will turn on to heat hot water).

Is there any way to change the motor and switch to provide a multi-speed capability?

I think that the power goes to the motor and then the wire running to the switch just switches the hot leg.

Steve
spro
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Re: Speed control on whole house fan

Post by spro »

The fan is fixed onto the motor? I expect it is. There is some frequency variation which could be done but outside that, extra vacuum power could be channeled by a variable damper to do something else.
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warmstrong1955
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Re: Speed control on whole house fan

Post by warmstrong1955 »

Does it have a reverse?

Guess I'm used to swamp coolers, that pressurize the house, and my shop for that matter, and you open windows here & there to direct the airflow and distribute the 'cool', so basically the opposite of what you are talkin' about. My cooler would blow the ashes up the chimney if the damper was open.

Bill
Today's solutions are tomorrow's problems.
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wsippola
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Re: Speed control on whole house fan

Post by wsippola »

For variable speed, you would have to go with a DC motor and controller or a 3ph motor and VFD (probably a fair bit cheaper). A two speed single phase motor may be an option. I have a house ventilation system, but it draws air in from the outside through a heat exchanger. It's also not very powerful at all - something like 60 watts on low speed.
SteveM
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Re: Speed control on whole house fan

Post by SteveM »

wsippola wrote:For variable speed, you would have to go with a DC motor and controller or a 3ph motor and VFD (probably a fair bit cheaper).
I suppose I could mount the VFD in the attic and use the line down to the switch for the speed control, although I'm not sure if that gives me on/off from there.
wsippola wrote: I have a house ventilation system, but it draws air in from the outside through a heat exchanger. It's also not very powerful at all - something like 60 watts on low speed.
I remember seeing something like that on This Old House. I may want to use that for the basement to get ventilation without losing heat. Can you point to some information on that type of system?

Steve
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tornitore45
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Re: Speed control on whole house fan

Post by tornitore45 »

I suppose I could mount the VFD in the attic and use the line down to the switch for the speed control, although I'm not sure if that gives me on/off from there.
If you are lucky the switch run has 2 wire and a naked ground wire. Since the VFD control is low voltage you may have two "channels" Speed and ON/OFF using the GND wire for Common.
Mauro Gaetano
in Austin TX
SteveM
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Re: Speed control on whole house fan

Post by SteveM »

tornitore45 wrote:
I suppose I could mount the VFD in the attic and use the line down to the switch for the speed control, although I'm not sure if that gives me on/off from there.
If you are lucky the switch run has 2 wire and a naked ground wire. Since the VFD control is low voltage you may have two "channels" Speed and ON/OFF using the GND wire for Common.
IIRC, there is no ground wire, except the sheathing of the BX cable.

Steve
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tornitore45
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Re: Speed control on whole house fan

Post by tornitore45 »

IIRC, there is no ground wire, except the sheathing of the BX cable.
In extreme need there are solution, if you really can not run an extra control wire pair. For example a the wire pair could be Pulse Width Modulated ( Variable TON/TOFF ratio).
A filter would extract the Average Voltage and supply the VFD lead that goes to the wiper changing the speed.
Then a simple circuit (Diode + Cap) that responds to LOW states, no matter how short they are, would drive the FVD ON/OFF control lead. Judiciously respecting the various signals polarities.

Even simpler if the VFD works like mine any Pot setting to a speed lower than the Minimum Speed Setting is practically an OFF state. However the FVD power is constantly ON, a main ON/OFF switch should be in the attic.
Mauro Gaetano
in Austin TX
reggie_obe
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Re: Speed control on whole house fan

Post by reggie_obe »

Single phase fan motor, how are you going to put a VFD on that? Might see what the motor frame # is and see if you can replace it with a two or three speed motor. Guessing, but unless you find a plug compatible motor on Fleabay or as surplus, the replacement will equal the cost of replacing (minus labor) the entire unit with one that has a multi or variable speed fan
RONALD
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Re: Speed control on whole house fan

Post by RONALD »

I have been running a whole house fan for years with a speed control.

Speed controls for those type of fans are readily available.

Below is a photo of one I found in a very quick search, there are lots more.

http://www.grainger.com/category/fan-sp ... alog/N-jtu
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SteveM
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Re: Speed control on whole house fan

Post by SteveM »

RONALD wrote:I have been running a whole house fan for years with a speed control.

Speed controls for those type of fans are readily available.

Below is a photo of one I found in a very quick search, there are lots more.

http://www.grainger.com/category/fan-sp ... alog/N-jtu
Cool, I'll have to check the data plate on the motor and see what rating I need. Thanks!

Steve
dly31
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Re: Speed control on whole house fan

Post by dly31 »

I am pretty sure those speed controls are only suitable for shaded pole motors and these are used only on direct drive fans. If your fan has a split phase or capacitor start it would likely not be usable.
Don Young
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