On Jul 14, 7:21*pm, "
wrote:
On Wed, 14 Jul 2010 12:28:36 -0700 (PDT), RickH
wrote:
On Jul 12, 11:20*pm, "
wrote:
On Mon, 12 Jul 2010 23:23:02 -0400, Tony wrote:
keith wrote:
On Jul 12, 12:03 pm, RickH wrote:
On Jul 10, 11:23 am, Lee B wrote:
Current house came with a whole house fan (not an attic fan, but the
kind in a hallway ceiling that sucks air into the attic). I was happy to
see that because I really liked the one in my old house. However the one
in the old house had a variable speed dial on it, and the new house's
fan has just one speed - high and loud with a simple off/on switch.
Is the variable speed a function of the fan itself or can that be added
at the switch? I'd definitely be having an electrician do it, but I'm
just trying to figure out if it's even doable, or if I'd end up needing
an entire new fan. And if so, would replacing an existing fan and switch
be difficult (ie cost me an arm and a leg)?
Whole house fans are great. *Yes you can put on a variable speed
controol, but I suggest you over-rate the control amperage you buy by
double. *For example if the fan draws 5 amps then get a 10 amp
control. *Also when turning it on make sure the control passes through
the higher speed, then you lower it. *This is so the motor gets enough
starting current. *I replaced the Off/High/Low switch on mine with a
variable speed. *You only use the High speed motor input wire, just
cap the low speed wire.
That depends on the motor. *If it's a universal motor it'll probably
work fine. *If it's an induction motor, probably not. *Induction
motors tend to be "constant RPM" or with a given load, "constant
power" devices. *As the voltage is reduced they'll want to maintain
RPM, which requires the same power, thus current increases.
If the fan is belt driven it's probably an induction motor.
If you use an AC motor speed controller it will work fine. *It does not
control speed with changes in voltage, it changes speed with changes in
the frequency. *This type of speed control also lets the fan run at
lower speeds without stalling. *The days of the old rheostats are long gone.
They're a tad expensive for a fan. *Have you ever seen one on a whole house
fan?- Hide quoted text -
- Show quoted text -
$39 is not too bad I dont think, I use the 10 amp one at the bottom of
this page (my fan only draws 5 amps but I wanted the controller to run
real cool so I oversized it): *I got this same model for about $25
elsewhere.
http://www.electricmotorwarehouse.com/kbwc.htm
That's a "dimmer" style controller. *Do *not* use that for an induction motor.
Induction motors need a VFD type controller, which is far more expensive.- Hide quoted text -
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Well It's been working great for 3 years now, and it runs cool, the
heat sink on the 10 amp controller barely gets warm powering a 4 amp
fan.
Here is the wording from their web site (note it says ok for fans):
"The KBWC-110K provides infinitely variable speed motor control for
Shaded Pole, Permanent Split Capacitor and Universal (AC/DC) motors.
The variable speed motor control contains the following features; an
on/off line switch, RFI filter, minimum speed trimpot and a flame-
retardant ABS enclosure. Applications include range hoods, vibrators,
humidifiers, fireplace blowers, fans, laminar flow hoods, heat tunnels
and stirrers."