Filter size for 5 ton unit

3 years ago

Hi, I have a 5 ton unit in my house, the return duct is 10" by 25" and the filter is 16" by 25". I read in the furnace manual that in case of 5 ton units there should be 2 returns (one on each side of the furnace) or one return in the bottom of the furnace. In my case there is only on return from the side of the furnace. My questions are: 1. Should I split the return duct right next to the furnace and tie it to the other side of the furnace and add another filter? 2. Will it help my AC cool down the second floor which is always a lot warmer than the main floor? Thank you in advance.

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Comments (2)

sktn77a
3 years ago
As far as filter size is concerned, the usual recommendation is 200sq in per ton. So 1000 sq in for a 5 ton unit. Your current filter/return ductwork is undersized. You need an additional return and a large filter to go with it. A return from the second floor (if possible) will help with air distribution but you may need to adjust the supply dampers also.
Shilo Bloch thanked sktn77a
klem1
3 years ago
Your return duct and filter size both should be doubled. A return on second floor will cause better cooling on second floor. Splitting present duct at air handler will do nothing positive.
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