On Sun, 28 Mar 2010 21:00:52 -0500, "Ralph Mowery"
wrote:


"Tony Hwang" wrote in message
...
wrote:
On Sun, 28 Mar 2010 17:09:05 -0600, Tony
wrote:

Hi,
When I was replacing blower motor on our furnace
there were two replacement choices 1.0 Hp or 3/4 Hp 3 speed
motor. Between two only difference was Hp rating and full load
current draw. As sn after thought I wonder if there'd be any advantage
choosing the 1.0 Hp one. BTW, our a/c unit is 3.5ton.
TIA for any experienced comments.

You really should be consulting the installation documentation of your
system. That is not as simple as just saying bigger is better.
The air handler and the condenser have to be matched.
Hmmm,
Not knowing anyting HVAC. I put in 3/4 Hp one as the manual states.
But curious duck wannna learn. Any pointers where to look? Getting
old guy has to exercise his brain, LOL!

The HP depends on the size of the fan blades/cfm the blower has to move. If
the HP is too much it will only draw more current and cost more to run if
the relay and wiring will handle the larger current.

The current won't be significantly higher unless the fan is larger. It will
draw a little more and is a (small) waste, but it's not likely to bother the
wiring.

If the HP is too small for the blower fan, it will overload the motor, it
will slow down and burn out and not move enough air.

Yes.

This could also lead
to a burnt out firebox if gas or oil and poor cooling for the
airconditioner.

It *should* shut itself down if there is (dangerously) insufficient airflow.