Thread: Condenser size larger than A-coil

The house I inspected today had a 4 year old Carrier electric forced air furnace with a 2.5 ton coil. The condenser was stolen and they replaced it with a 14 year old Goodman 3-ton unit. Is this OK??? I know you can sometimes go up on the coil but I did not think you could have a smaller coil. Any HVAC gurus out there?

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This is done quite frequently, in fact Carrier now makes a coil to fit two ton to three ton systems (same coil) You can actually get better humidity removal with a larger coil and some times a higher efficiency.

A 14yr. old unit is usually considered beyond its useful life in my opinion. Most of the condensing units average about a 10yr. life span in this area.

rick

Thanks Rick. The life line is standard verbage in my report. However, I have a past client threatening to sue me for not noticing that the coil was smaller than the condensing unit on a separate inspection because the HVAC guy said "your HI should have known that the coild being undersized would cause the system to fail." Warranty deal you know. Anyway, it is my understanding that to undersize the coil you need to change some things like orifice size etc. so the refrigerant flow is proper. This house looked like a flip so I would bet that nobody did anythng but install this old unit with the existing system.
I just wrote up that it might not be properly matched and to have an HVAC tech check it out to be sure.

No matter what the HVAC tech declared about what HI's should know, you can't know what is allowed or not without doing some research. Beyond the scope of the normal home inspection in my opinion.
I'm with Rick on the old condenser rigged on a flip house, just the age gets a flag.

I always love it when a specialty contractor tells our buyers what we are supposed to know. We had this exact same complaint once. As mentioned, it goes far beyond what your required to do at a home inspection. Particularly, considering different HVAC guys have differing opinions on sizing of units.

Originally Posted by Rick Hurst

This is done quite frequently, in fact Carrier now makes a coil to fit two ton to three ton systems (same coil) You can actually get better humidity removal with a larger coil and some times a higher efficiency.

That's when the evaporator coil is larger than the condenser coil and the system runs longer.

Frank said the condenser coil was larger. While it is only a 1/2 ton difference, I always understood that the condenser coil should be the same size as, or smaller than, the evaporator coil.

All that stuff aside ... when was the condenser stolen and when was it replaced?

That is what matters to the client, they may have looked at the house when there was a 4 year condenser there, now there is a 14 year old condenser there - *big difference*.

If the condenser was stolen before the client looked at the house, I'm not sure that installing a 14 yearn old condenser would be acceptable to code and permitting as you now have a mixed system and the SEER is unknown. That is something which should be checked out with the AHJ. Replacing the condenser unit requires a permit, and if an old condenser unit was installed, it is likely that a permit was not issued.

Bigger capacity indoor coils will generally reduce humidity removal but can increase energy efficiency and vice versa. Smaller indoor coils will aide in humidity removal to a point, then icing becomes a problem. A half ton either way likely won't create many problems on a 3 ton unit... but again that is beyond the scope of my inspections.

Jim,

Thanks, that makes sense too as the slightly larger (but not much larger) condenser unit coil will make the evaporator coil colder, removing more moisture (humidity) from the air ... until the evaporator coil freezes up, in which case it still removed more moisture from the air, it's just that the moisture is now a big block of ice with no air flow through it. Air is still flowing at it, and thus the block of ice just gets larger without really cooling anything other than itself.

And, with the evaporator coil being slightly larger, it uses all the heat transfer capacity of the condenser unit, making the evaporator coil slightly more efficient, but slightly warmer, thus removing less moisture from the air.