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Discussion Starter · #1 ·
I have a cape cod that my upstairs just stays about 10 degrees warmer than my main floor. I am looking to improve flow to it but need some advice on how to go about doing it.I have a 9 year old heil 80 % 100000 btu furnace that sits in the middle of the basement ,duct work runs length wise north and south in my house 20 ft in either direction with 6 inch round running to the east and west walls to feed all wall stacks for the 2nd floor the vents and main floor vents. My supply duct is 16x8 and return is 14x8 duct with 6 inch round feeding the returns. I was wondering if reducing the supply duct down to a 12x8 to pick up some velocity on the air would help feed the last 4 six inch ducts that feed the upstairs or even increasing the 6 inch to 8 inch to feed the last 4 supply runs.Sorry about the long read guy but any help is appreciated.
 

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I'm not in the HVAC business, but this is how I was able to lower my upstairs heat. I removed it.

My problem, and I suppose yours is similar, I had no upstairs air return. Only air return was downstairs.

Hot air rises, cold air sinks. In my opinion, you can force all the cold air upstairs you want, it's just going to find a way downstairs. The warm air is staying up at the ceiling. That warm air needs to be removed.

Some may disagree with this but it did help my situation. It was a tough job finding a route from the upstairs ceiling back to the return plenum. I used 10" hard pipe, insulated with R8 duct wrap and a 14" x 20" filter grill.

Hope this helps.
 

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Your problem isn't lack of velocity in your supply duct. Its lack of return air. DO NOT reduce the size of your supply duct. Rather increase the number of returns, and the size of the return duct. Its too small.
 

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Discussion Starter · #4 ·
I'll see if I can find a route to add a couple of returns and see about increasing the return duct size.What would be a good size duct for the return ,each room has a high and low return I have closed off the low return and tried to just suck off the higher one but it doesn't seem to really make a difference.I'm just tired of having to put a a window unit in upstairs just to make it comfortable.
 

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The return duct should generally be larger then the supply duct. Best to keep both return registers open, as the registers are some what restrictive to air flow.
 
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