Replacing mismatched system sizes

Old 10-27-21, 11:20 AM
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Replacing mismatched system sizes

I have been in my 2100 SF, 10-11-year-old home in SC with builder grade Lennox AC, coil and furnace. The outdoor unit is very loud and makes a clunking sound when it turns on and off. Had it serviced and suggested it is close to the end of its life.

The outdoor unit is a 3 ton. The coil is 3.5 ton and the furnace is 4 ton. I've had two quotes. The lennox dealer recommends upgrading to a 3.5 outdoor unit and 3.5 coil. He stated there was likely pressure build up because of the mismatched sizes and larger furnace, and suggested adding some type of loop duct to relieve that pressure. The furnace will remain.

A trane dealer stated the three different sizes was probably what was best at install and recommended staying the same size. He didn't mention the pressure issue or the need for a loop duct. He did state the lines to the outdoor unit would need to be replaced to handle the 3.5 ton outdoor unit. Lennox dealer didn't mention that but did state they would swap out lines if needed.

Both are about 16 SEER and cost about the same to install/replace. Looking for some advice/clarity. Thank you in advance.

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