AboutHoward Livingston Expertise Can answer questions on electrical control circuits, power supply,airflow & distribution, electrical components,refrigerant problems,gas, electric & propane furnaces.No boiler or refrigerator or oil fired furnaces experience.Just HVAC questions please.
Experience 35 years experience in residential & light commercial repair & installation.
Question QUESTION: Firstly thanks for any help in advance. I have a upstairs bedroom that is partially over a garage and it is the coldest room in the winter and the hottest room in the summer. It also is the furthest room away from distribution manifold that is in the attic. The furnace / AC is in the basement. The line that runs to this room is 6" and the room has a cold air return. My question is can I simply increase this line to an 8" line to help get more air flow to that room. I already have closed most of the other upstairs room vents in the other bedrooms (total of 4 bedrooms), but still can not get this room cool enough or warm enough.. usually about 5 degrees different from other rooms that have vents closed. Thanks again.
ANSWER: A 6" duct will not supply very much air more than 10 feet length.Was that room added or is the 6" duct the original ?? Yes, an 8" will supply more air but maybe not. Depends on whether its a straight run from the supply air plenum or comes off a branch. The basement location for the furnace can be a problem too. The "air pump" blower can only pump air vertically so high, like a water pump "head" its called. So may need the duct system as a whole reevaluated.
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QUESTION: The bedroom is ~20 ft away from the supply and it is a straight run. It also comes directly from the supply manifold in the attic. The house is a newer build (2004) All of the lines that run off the supply manifold in the attic are insulated flexible lines.
Answer Got a chance to respond today. 20 ft for a 6 " ?? Does the "extended supply air plenum" it's called reduced in size as the supply lines drop off of it ?? That's critical. So if it is a rectangular supply plenum, as each duct to a room is connected to either side, it needs to be reduced to keep the same resistance throughout the entire lengthof the extended plenum. Is that clear ??
