Air flow problem to certain rooms


Old 03-14-12, 09:46 AM
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Air flow problem to certain rooms

I live in a one story ranch. The furnace/blower is centered on the house in the basement. From that, two main ducts come off the plenum--one to the kitchen, dining room, living room side of the house and the other to the guest bathroom, two kids rooms and the master bedroom/bathroom.

Kitchen side of the house is fine. On the bedroom side of the house we have very little air flow in the bedrooms, but the bathrooms are ok. The bedrooms are cold in the winter and the AC can not keep up in the summer even on the mild days. I have inspected the main duct and I do not see any dampers. The bedroom side of the house is over the garage which is completely insulated. I did remove the insulation from one of the duct branches that go to the master bedroom. A brief inspection didn't show anything obvious. It looks like the branch is connected to the main duct.

Winters aren't so bad, but I can't go through another summer in a hot house. Does anybody have ideas on where I should start looking?
Old 03-14-12, 10:27 AM
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The problem is insufficient airflow to the bedrooms. There may be balancing dampers in the branch ducts to the individual bedrooms but if I am correctly interpreting what you wrote the ducts are hidden by a ceiling. OR, it is entirely possible that the system was never designed with air conditioning in mind AND also designed to keep the bedrooms at a lower temperature during the heating season. This second scenario would be handled by installing smaller ducts to the bedrooms to limit the amount of warm air delivered.

You might consider hiring a plumbing (or drain cleaning) contractor to run a camera down the duct from the bedroom registers to see if there are any balancing dampers or if the ducts to the kitchen area are exposed look for balancing dampers in these ducts. Don't be surprised to not find any dampers as all too often they are not installed as a cost savings measure. Right now try to determine the size of the ducts going to the bedrooms as that will tell if they are even of sufficient size for heating alone. Cooling requires larger ducts (or more ducts and registers) and all too often the ducting system in a house is woefully inadequate for both heating and cooling. A complete re-design and re-installation of the duct system may be your only recourse.

You might be able to install dampers in the kitchen area ducts to retard their airflow and thereby increase the airflow to the bedrooms but doing so will cause other problems if the basic duct system is inadequate. These problems may be a slight as increased noise (in the bedrooms) to severe icing problems of the cooling coil or excessive temperatures on the furnace heat exchanger. Any duct changes that reduce the airflow need to be followed with careful measurements of temperature differentials and airflows.
Old 03-14-12, 07:12 PM
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What he said! Well I would of said you have duct issues. Get a heat load done first so u can see what size ducts need to go to each room
Old 05-25-12, 08:15 PM
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If the problem you have affects the entire one side of your home then I would check all 4 sides of the supply plenum to see if there is something that looks like a handle. Not all systems have these, but if yours does then vertical this handle (damper) would supply equal air to both sides of your system. Yours may have gotten partially or fully closed. Adjust it accordingly to increase air flow in one direction or the other.

Another possibility is that you have zone controls and either one or more thermostats are shut off or their respective zone control valves aren't working.
Old 05-25-12, 08:18 PM
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I would also suggest that you remove the vent covers to verify that a previous owner hasn't deliberately blocked the vents into the bedrooms. Look for towels, insulation, etc.

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