help/suggestion for increasing flow

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help/suggestion for increasing flow

Postby newbie_owner » Thu Sep 01, 2011 11:38 pm

Hello everyone,

First off, the house is an older house, split level design. The living area and the master bedroom stay cool. The other 2 bedrooms upstairs, however, don't seem to stay cool that well. The system is an older Rheem 13 seer unit.

In the hallway upstairs, there appears to be a return vent that is approximately 16" long and 2-3" high.

On the lower level, there are 2 vents that are fed by 2 separate 4" or 6" ducts. Which imo, would be alot of unneeded air for a small area.

What I want to do is break one of those 2 ducts and install a cap as close to the air handler as possible. Is this a good idea?

The other option that I was entertaining was to upgrade the blower motor to a more stronger blowing one. The air coming out of the vents is cold, not cool, cold. I just don't think there is enough of it in those 2 bedrooms.

Suggestions and thoughts are welcomed.
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- help/suggestion for increasing flow

Postby GasFitter » Fri Sep 02, 2011 3:57 pm

I think it is more a problem of your insulation rather than air flow. But have you checked how much flow is actually coming out of the vents?
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- help/suggestion for increasing flow

Postby Freon » Sun Sep 04, 2011 9:28 am

First, be very careful about capping any duct. Since the air is already cold coming out, you may have low air flow already and capping any duct will only exacerbate the problem and could cause your evaporator coil in the air handler to freeze.

You have the classic PITA problem of hot air rising. Your first task is get the size of the condenser unit to determine the required air flow. Next you need to make a drawing of every duct including it's diameter, length and where it originates from. Based on a typically designed system having too little return air, you may need to focus on augmenting return ducting.

Once you have that information you can begin to determine your current air flow situation. Assuming you have the correct blower for the condenser's BTU/hr rating, you may need to find ways to increase the flow of air to the upstairs by increasing the diameter of the supply ducting, not capping. You can research the typical air flow for a given duct diameter and from that optimize your system.
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