Converting to DC blower motor [RE-wrenches]

[R. Sparks Scott]

	Roy;

	You have probably figured out what's needed to convert to the DC motor, so
I'll concentrate on the thermostat.
	If you are concerned that the thermostat contacts are under-rated, or will
cause a sustained arc when they open, use the thermostat contacts to
control a 24 volt DC contactor which has contact ratings within the current
draw of your DC motor. My electric car uses contactors to control power to
a 24 Hp 108 VDC motor, so of course, it's possible. The higher the voltage,
the more contact opening you need. In the case of the car, they
series-connect two poles of the contactor, providing four air gaps to break
the circuit. At 24 volts, you don't really need to worry much until you
start drawing some serious current, in excess of 20-30 amps, I'd say.
	The best case design would be to use solid-state switching, or even a PWM
(pulse width modulated) speed control. While such a device is probably
expensive to purchase, constructing one is not very hard if you have
electronic skills.
	For your motor, be sure to check out C&H Sales for surplus DC motor and
blowers. The prices are reasonable, and the have a huge selection, online
at <http://www.candhsales.com>.
	Good luck

	-S

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