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Phil
Phil, Mechanical Engineer
Category: HVAC
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Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a 2 ton R-22 Rheem Heat Pump with matching air

Customer Question

I have a 2 ton R-22 Rheem Heat Pump with matching air handler. It it installed in the upstairs of a 2 story 1880's Victorian house. There old "paper" insulation in the attic (around 10 feet tall) and walls. The downstairs system is a traditional gas split heat and ac system.
Every since the initial system was installed 10 years ago upstairs, it struggles to keep the upstairs around 70 degrees in the summer and sometimes to heat in the winter without auxiliary.
Just found out this week the the unit has a dead compressor so it will need to be replaced. HVAC guy said the cheapest way was just to replace the ac condenser. I questioned him about the struggling ac and he said if we upgraded tonage we would need to replace the entire unit inside as well (which is in the attic). Also, he advised that the duct work may need to be replaced if we increased the tonage. The upstairs of my house is around 1172 sq ft. There are 7 rooms including hallways and the windows are original so they are pretty drafty. There are 10 vents that are running through 6" round flex pipe. There is one single return which I can measure if needed.
Question is; first, does this 6" ducting sound adequate for a 2 ton HVAC system. also, if I replaced the 2 ton with a larger unit, any idea if the ducting would actually have to be replaced?
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello, your HVAC man is correct on all counts, You have your choice, you can either add 4 inches or more insulation in the attic, or you can replace the 2 ton system with a 3 ton system, and increase the total air flow through the ducting by 50%... that will mean leaving the 6" ducting in tact on the smaller rooms replacing the 6" with 8" duct on at least 3 of the other rooms. The return air duct will have to be enlarged as well. Your HVAC man sounds entirely capable of deciding on the duct sizes.

If I miss you tonight, I will pick your response up in the morning.

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Customer: replied 1 year ago.
From my description, does it seem as though a 2 Ton is adequate? Or perhaps the current duct size needs to be increased to accommodate even the 2 ton?
Expert:  Phil replied 1 year ago.

Hello again, if its been running for 10 years, the duct sizes is most likely OK, at 1100 square feet in a poorly insulated 1800's home you will typically need 3 tons, 2 tons for that space in a well insulated modern home would get you by in most areas except very hot and humid areas, then you would need 2.5 tons.

In an older home, especially upstairs, its going to take 3 tons unless you insulate heavily.

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