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Posted by geothermaljones on November 16, 2007, 5:07 pm
HVAC Guy...
My blower doesn't have a belt, should I just blank off 1/2 the squirrel cage
w/duct tape? That's gotta change the airflow.
And when I adjust my burners, do I want that bright blue flame, or can milk
it down to that pretty orange & yellow w/ the black stream of soot?
Hope your buying life insurance on all the folks your killing.
geothermaljones
> kool wrote:
>
> > > Change the size of the pulley wheel on your motor (make it a
> > > little larger) and get a new belt if necessary. This will
> > > increase the air
> >
> > Ya, overamp your motor and burn it out...good suggestion.
>
> Oh pulleeeze.
>
> Your average 1/4 or 1/3 hp blower motor with a 1.15 sf rating can
> easily handle a pulley change from 3" to 4" or 4" to 5".
>
> Something you bone-heads forget is that the furnace blower motor is
> helped by the fact that it's always being cooled by the return air, so
> it's thermally well protected.
>
> Jorge wrote:
>
> > Does anyone have an opinion about the best option.
>
> Jorge, increasing the pulley size by 1" is a perfectly good and
> perfectly reliable solution. A year ago I did the same thing on my
> furnace to increase airflow to the second story of my house.
>
> If you're really concerned about reducing the life of your motor, then
> oil the motor and the blower bearings when you change the pulley (I
> bet they haven't been oiled for years). The motors they put in the
> old furnaces like you and I have are not very efficient (no small
> electric motor is) but they're durable.
>
> > Can anyone comment on the urgency of the situation... how soon
> > do I need to fix this problem?
> > If the high limit switch burns out, then I am probably in
> > serious trouble. How likely is that to happen?
>
> No furnace should be hitting it's high limit. It's not a situation
> you want to happen. Normally it happens because your fan belt breaks,
> or your motor dies. And no, the high-limit switch doesn't "burn out"
> because of repeated use. It's usually part of the furnace thermostat
> that starts your blower anyways and stops your motor when the furnace
> has cooled down at the end of a heating cycle.
>
> You'd only be in serious trouble if hi-limit switch failed AND your
> fan stopped turning at the same time.
>
> And in spite of what other fools here have said, it's perfectly safe
> to turn down your burners a little to compensate for insufficient
> airflow. There is nothing magical or critical about the burners that
> require a precisely controlled and specified NG input pressure. They
> can operate over a wide range of reduced NG pressure and flow rates.
>
> Turning your burners down is safer than having your furnace run and
> always be hitting the high limit. That is a fact.
>
> Do you have a humidifier attached to the furnace? Humidifiers are
> ducted to take air from the supply duct, force it through a rotating
> drum or stationary sponge, and let it re-enter the furnace through the
> cold air return. You might have too much air flowing through the
> humidifier circuit. See if there's a gate or baffle in the humidifer
> circuit and close it down and see if that helps.
>
> Something else you can do if you're really in a bind is to open a hole
> (or maybe you already have a vent) directly on the return air plenum.
> If you have insufficient cold-air return then opening a hole will
> allow the fan to "suck" more air through the furnace, thereby making
> it less likely it will hit the hi-limit.
>
> Taking the cover off your humidifier (if you have one) would suffice.
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