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Re: GBlist: Variable speed drives

In a message dated 97-04-18 15:25:18 EDT, 
Marc.J.Rosenbaum@valley.net (Marc J. Rosenbaum) writes:

> I am trying to learn about the best way to vary substantially the
> air flow in a current project.  It is possible that the central ventilation
> system ( which includes enthalpic recovery and deep dehumidification, which

> is  why it is central and not distributed) will need to vary output from
> cfm  down to as low as 1500-2000 cfm.

The complexity depends on the size and type of AC motor.  My blower door
units have a 3/4 hp AC PSC (permanent split capacitor) motor like the kind
find on heat pump fans, and this type of motor can be controlled by an
inexpense (<$100) triac type speed control, like the ones you find in the
hardware store for   overhead fan control.  I use a 15 amp unit for my fans,
and this type control works
fine from 0 rpm to max rpm.  The manual triac controls are available from
catalogs like WW Grainger (up to 10 amps) , and I have found a way to modify
this type of control so that it can be controlled from a PC Windows program.

I notice that Dwyer has a low cost ($69) electronic fan speed control
that works with 0-10 vdc input and controls AC motors up to 10 amps. See
part number FC-1000.  I have not actually seen it.

I hope this is helpful.  Are you in VA?  The infiltec factory is in

...Dave Saum
   Infiltec Air Leakage Control

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