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hawks81 07-05-2010 10:48 PM

Forced Air Blower is too noisy, blows too much air too fast
Hey guys,

Novice HVAC guy here with some schooling in hvac but no field experience. I will provide as much information as possible.

I have a ground level ranch on a slab.
My ducts are in my concrete slab.
I have a standard efficiency down flow weatherking forced air system of an unknown model approx 10 y/o.

My issue is the blower. The blower, whether on heat or cooling, is just too much! The airflow is way too fast and the CFM is crazy! It causes the house to feel drafty and ice cold when the thermostat is set at 74 in the summer. Candles flicker and my curtains flap! Today I tried to close the vents in the "occupied rooms" and dump most of the air in the vacant rooms (to limit the drafty feeling). The closed vent, though on the same tree as the open ones..... whistled like a sailor and still forced in a lot of air!! And the open vent at the end of the tree blew my curtains like an american flag on a windy day!

I have two main trees that split like an "H" with the furnace in the middle. I have 4 vents off one side and 6 off the other airflow seems pretty even throughout the house. I know in hvac, most people want MORE airflow and cooling, not me.

Is it possible to slow down the blower motor, which will also make it quieter and less drafty?!?!
Could a DYI'er do it?
Would it be worth having a hvac tech look at it?

Thanks ahead of time guys!

beenthere 07-05-2010 11:12 PM

It can usually be slowed down.
However. If your unit is oversized. It may not be possible to slow it down, And still have it work without freezing up.

hawks81 07-05-2010 11:15 PM

Would it be a simple wiring change or something more dramatic?

I have not checked the temperature coming out of the vents, but it doesnt appear to be that cold. I should have noted that in the winter the house warms nicely but the air leaving the vents isnt that warm.

I think the blower is moving the air too fast across the plenum?

beenthere 07-05-2010 11:19 PM

On some units its just a simple wire move.
On others, its a set of jumpers/DIP switches that need changed.

Look at the instructions in your install manual. Or, on the blower door panel.

hawks81 07-06-2010 12:28 AM

Ok. The blower panel had a wiring diagram that showed the following:

Blower wiring harness:

Red - Low (Unused motor lead according to the diagram)
Blue - Med
Black - High
White - Com

The circuit board has connectors for :

This was how it was wired (which was according to the diagram):
EAC - capped with a plastic cap
MI - Red
Heat - Blue
Cool - Black
Neutral - White

If I am reading this right, the low speed is not being utilized at all. So, I swapped out the black for the red and the blower did marginally get quieter and not push as much air. My wife couldn't notice the difference. Again, I said it was marginal! The blower, however, did start smoother and didn't make that "reviving up" sound! AKA that "whirring" sound until it reaches full speed after like 2 seconds.

The vents still seems to be pushing more CFM than needed. The farthest vent from the furnace is still pouring more than enough air. Was this my only available option to change the speed? Could it simply be that my blower is overpowered for this house? I have a 1600 sq ft ranch.

beenthere 07-06-2010 05:53 AM

That it the slowest blower speed that furnace has.

Your furnace is oversized for your house. Or your duct work is undersized for your furnace.You can't put in a smaller/slower blower, because it wouldn't move enough air for the furnace to stay cool enough..

hawks81 07-06-2010 07:09 AM

Thank you very much!

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