Thread: Is this a 3-ton System?

This will be easy for somebody out there. If the attic evap. unit of a Carrier heat pump is 5-ton and the outside unit is 3-ton, what is the system capacity?

I have a home buyer on a new construction saying that the specs. for the house call for a 5-ton system; I told him he does not have a 5-ton system, only a 5-ton attic unit.

Thanks!

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Originally Posted by David Arrington

This will be easy for somebody out there. If the attic evap. unit of a Carrier heat pump is 5-ton and the outside unit is 3-ton, what is the system capacity?

I have a home buyer on a new construction saying that the specs. for the house call for a 5-ton system; I told him he does not have a 5-ton system, only a 5-ton attic unit.

Thanks!

This is a severely mismatched system.

Scott -

I certainly agree with that!

Ok, let's change the numbers just a little. If that evap. unit is a 5-ton and the outside unit is a 4-ton, what is the system capacity? I see this a good bit.

It will be rated as a 4 ton. The outdoor condensing unit is what you base the size as the system can only put out what the condensing units is. Sometimes the coil is over sized for many reasons.

Thanks, Brian! That's the way I reported it, but just wanted to confirm since the builder in this case is questioning things.

thanks,
David

The manufacturer will be the one to contact to find out what they allow for that specific model. With the new 13+SEER units they have specific requirements. I would call or email Carrier, they are good at responding to questions.

As noted the capacity of the combined system defaults to the lower value as that is all it can handle.

I steer very clear of talking about SEER ratings with clients when they ask. Just because the condenser unit has a label with an indicated SEER number does not mean it is performaning at that level.

Even if the EVAP coil and the condenser unit are matched there can still be many things not quite up to par that will let the unit perform as labeled.

Duct work and sealing is one of the major items I look at during inspections. So many times the attic areas are "well conditioned" due to deteriorated ducts, split mastic seal on flex duct at the collar connections on the plenum chambers ... and it goes on and on.

David, good question. The outdoor unit determines the tonnage of the system with a few caveats (sp?). The indoor coil, blower has to be sized correctly to perform the desired task. In your example, even a extremely over-sized coil may be the exact match if the designer chose to oversize the duct work and slow down the air flow for a specific purpose, like the client wanted to have an extremely quiet system or wanted to use a multi speed blower in conjunction with a multi speed condenser. All coils are rated at a BTU given a specified CFM (airflow).
Bottom line is, report what you see and leave the SEER and component matching to the A/C guys.