Thread: mis matched condenser & handler

Air handler was a 3.5 ton and the condenser 4 ton - same manufacturer/ seer etc/ same year 99. What are the negatives to this and what would be a good recommendation. I have been told it will shorten the life of the unit but i do not understand the reasoning etc.
Thanks!
Jerome

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Very common match (or mis-match.)
The theory is the larger evaporator coil will boost the EER performance. No biggy in my opinion.
It will not have any appreciable negative effect to my knowledge.
If you want to get real industrious, call the manufacturer with the model numbers and ask.
Some times more than one coil was specified as an acceptable match.

Jim,

It is the other way around. The condenser is actually larger than the handler/coil.

My bad. That might still be an appropriate installation depending on the design as specified by the manufacturer.
A smaller coil will tend to lower the evaporator coil temperature and remove more moisture.
So if you are in an area with a high humidity and low sensible load, this might make sense.
Bottom line, I would not call it a bad installation if it was working properly with no obvious problems just because of an apparent mis-match.
The biggest concern I would look for is coil icing.

I have been told by HVAC guys that you can upsize the evaporator by 1/2 ton, but can not down size it at all.

Originally Posted by Jon Randolph

I have been told by HVAC guys that you can upsize the evaporator by 1/2 ton, but can not down size it at all.

That's also what I've been told, which is probably why Jim stated "The biggest concern I would look for is coil icing."

If the condenser can create more cooling capacity than the evaporator can handle, then icing up would be a distinct and very good possibility (I would think, and Jim confirmed it). Don't know what else it could cause, though.

Jim you are correct. you can do this but must be a proper match by the manufact or warranty will be voided.

Originally Posted by Jerome W. Young

Air handler was a 3.5 ton and the condenser 4 ton - same manufacturer/ seer etc/ same year 99. What are the negatives to this and what would be a good recommendation. I have been told it will shorten the life of the unit but i do not understand the reasoning etc.
Thanks!
Jerome

Call the manufacturer today and ask to speak with the technical desk and they will tell real quick what you need to know. Don't rely on hearsay, get it from the company.

Jerome,

There are evaporator coils that can be used for two different tonnage units. If you go to this web site
Evaporator Coils (Cased) and then scroll down you will see what I am talking about.

As an example, go down to CAPF3642C6 and you will see that it is rated for 3 to 3.5 tons. Now click on the model number and go to the next page. Goodman CAPF3642C6 - Buy Online This explains how the orifice is changed depending on what tonnage you need.

Part of the problem is reading the model number and trying to decide what the rating of the coil is. Every manufacturer does it differently.

I agree with what Jim has said. He knows what he is talking about. If you are in doubt about matched units, give the manufacturer a call with the model numbers from the condenser and evaporator and see what they say.

In my reports I say something like this: I do not have the ability to determine if you have matched units for capacity or SEERS. If this is an area of concern to you, please contact the manufacturer or an HVAC contractor for additional information.

Jeff Euriech
Peoria Arizona

Thanks,
I called a local dealer and the models do not match according to the manufact. recommendations, but they may have changed the coils, etc. Anyway, i explained the scenarios to the buyer and all appears to fine at this point. Hell probably replace the whole system since it is nearly 10 years old.

One other thing to remember about coil ratings, consider the airflow.
The btu or tonnage rating is "x" at "y" cubic feet per minute.
If you decrease or increase the speed of the blower or use a different air handler with the coil, the effective tonnage of the coil is affected.
One more reason sizing, seer ratings and the like is outside the realm of most inspectors, including me.
I might be able to figure it, but I don't, I just look for defects or problems in operation.
I don't calculated gas line size or drain line sizes either.

Good answer Jim. I spend too much time looking for structual defects than to trying to calculate heat loads in the house. You are right about the fact it sounds like the installer is wanting to pull more humidity out with a larger condensing unit. They make a lot of systems now which are universal so the companies do not have to stock so many different sizes in stock. Usually the equipment comes with a couple different orficies to size the output, even fan speed controllers. I have been troubleshooting problems with a rather large house that contains six geo thermal heat pumps that the owners say it never gets comfortable in. I have found that the installers have installed 3 - 2 1/2 ton cond. units to 4-1/2 air handlers, a 4 ton to a 4 ton, 3 ton to a 4 ton and 2 ton to a 2 1/2 ton. The company made several attempts to repair this system to no availe and I wonder why? got my work cut out for me.

Cobra, those geo-thermo heat pumps should be an HVAC contractor's job.
I never worked geo-thermo.

"Air handler was a 3.5 ton and the condenser 4 ton - same manufacturer/ seer etc/ same year 99." - Young

Do you mean the air handler is a 3.5-ton or the evaporator is a 3.5-ton?
They can be different tonnage ratings, or both could be 3.5-ton.

A smaller tonnage evaporator coil could possibly work using a TXV metering device in a very high humidity indoor latent heat load condition.

These higher 12-SEER condenser's use a smaller BTUH compressor, therefore a heavy latent load could possibly provide a high enough BTUH evaporator heat load to rapidly vaporize the refrigerant, resulting in a faster flow & perhaps a well enough loaded compressor & condenser.

It would all depend on the indoor, outdoor conditions & the home's air infiltration rate, plus windows & insulation.

In the old days back in the early 1970's in older units, sometimes the compressor had a higher BTUH rating than the condenser's rating.

I'd check the outdoor temp-rise off the condenser compared to the SEER Rating of the condenser.

With clean coils, - a 12-SEER with a 18-F temp-rise, & a 10-SEER with a 19 to 21-F temp rise would be an adequate 4-Ton load, due to a heavy indoor latent load condition with a 350-CFM airflow per-ton or 1400-CFM. A 4-Ton air handler for 1600-CFM would be a lot better situation!

A heavier latent indoor evaporator load will cause the higher amount of BTUH heat transfer off the outdoor condenser. - udarrell

A 1/2 ton diff is not much to worry about,,you're talking about 175 cfm,,Lose more than that with a dirty filter