[buildingqc]

Hi, all! Back in the day, it was common practice here in the South to oversize the R-22 evap coil by a half ton for more cooling efficiency. Does this oversizing by one-half ton still apply with the newer split systems and newer refrigerants?

 

[markusolas]

Yes. It’s still good to go half ton bigger. More air flow

 

[Homer007]

Thanks, Mark. But, from what I hear from the majority of the contractors on the HVAC forums, it voids the manufacturer's warranty in most cases to mismatch the coils. I contacted Carrier to ask them directly, but they haven't gotten back to me.

 

[markusolas]

Never heard of that. Manufacturers don’t know what you doing at your home. If you don’t register new equipment then 5 years warranty if registered then 10 years warranty and they care what you install there. I go to customer and see evaporator is leaking then I check with supply house if it’s under warranty or not. If it’s under warranty then take it to supply house for to exchange for new one. Some supply houses even sell half ton bigger if don’t have same tonnage

 

[eggs]

I would not suggest over sizing the evap by 1/2 ton anymore. Back in the day we had several reasons to do so. Now a days, a lot of coils have a TXV on them, and over sizing the coil could cause high suction pressures. Since suction = temp not only could you have higher suction, but possibly over amp the compressor if not not sending cool enough gas back to the compressor. Most furnaces made now can move more than enough air across the coil, while back in the day, blower sizes were questionable. That over size was done every where, not just in the south. As for warranty, unless you had an account with the wholesaler, a contractor would handle it and it would be up to them if it would void the warranty. Carrier will not give you an answer in writing, it protects them from liability, been there, done that.

 

[markusolas]

Txv probably even better to oversized evaporator since txv can adjusts. So with txv half ton oversized it’s way to go and it’s really not oversized. Let say if go with 16 seer Ac condenser they might even give you 1 ton bigger to make it AHRImatched. So best way is to ask your system to make AHRI marched.

 

[eggs]

Seen compressors burn up because of over sized evap coils. If the TXV is sized (ported) to lets say 3 ton and a 4 ton coil (3 ton Condenser ), the super heat will be high and your compressor motor may not get enough cool gas back to keep it cool, then it over heats and is short lived. If you put a 4 ton TXV on a 4 ton coil, again on a 3 ton condenser, then suction pressure will be higher causing other issues. Although I do more refrigeration now a days than AC, but after 40 years of doing this kind of work, sizing, spec out the equipment, I also seen the results of mis-matching. Back in the old days, a 1/2 bigger coil was common, but so was low air flow. Today, in most cases that does not exist. What I have seen is some manufactures not making a 4 ton coil and going with a 5 ton for a 4 ton condenser, again, they have a TXV and the percentage is less in that size range. Going from 4 ton to 5 ton is 25%, yet going from 2 ton to 3 ton is 50%.