Quote:
Originally Posted by cabmando
I don't believe the furnace is the problem and if the tech did nothing more than Wayne said he did, that's some kind of piss poor diagnosis. One look at that installation by a good tech should tell them it's not a professional installation. Installing a new furnace with the existing duct system might result in the new furnace not operating correctly. He could have a 2 stage heat with a basic variable speed fan installed and it might work okay but I'd want that duct system assessed for proper sizing.
I'd be interesting in knowing if that pipe off the front is the only supply trunk. From the look of it, it's either a 12" or a 14" round. I'm leaning towards a 12" because the plenum on the furnace will only be 16" wide and from the video it looks like there's about 2" on either side of the pipe to each side of the plenum. I'm thinking a 12" is only good for about 500 CFM. Even if it's a 14" it's only good for about 600-650 I think. So if that's the only supply he's not moving enough air on the supply side and the return is choked at that crazy box system.
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I thought I read somewhere in this thread that the return air duct was at least 16". If not then the problem lies exactly where you say it is. For a long return air I would go as big as I could. This might involve some custom sheet metal to get around obstacles.
Also one could install 2) 12" ducts with wyes at either end to run smaller ducting through tight places. I once did a calc on a round shape and an oval with the same circumference. I was surprised at the results. Another fact is how much bigger a square is using the same hole.