Thread: 3 ton condenser 1.5 ton air handler

4500 sq ft 2 story house. 3, 3 ton condensers, 2, 3 ton air handlers and 1, 1.5 ton air handler. I knows its not uncommon to see the sizing different by a half a ton, but have never seen this before. 9 tons of A/C is way too much for this size, I wonder if it was supposed to be a 1.5 ton compressor and they just installed a 3 ton because that is what was laying around. The other strange part is that all 3 had a good TD, and they all 3 ran for 3 hours. The starting inside temp was 82 and after 3 hours it was 80. It was a mild 85 today as well. Any thoughts.

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Not really enough information to tell but seems like there is something is missing. Any chance there was another 1.5 ton air handler in another location, a unloader device (highly unusual in residential), or a dehumidifier tied in in some way?
Sorry, not much help.

I guess my first question would be where did you get the size of the equipment? Could you have misinterpreted the numbers? Probably not but that is my first thought.

No misinterpretation on the sizes.

Next thought is are the condensing units two stage?

No on the 2 stages as well. These were just your average 2008 Goodman units I really don't think there is something hidden or unconventional here. Just a uninformed or lazy installer. A few years ago i did a house with 4 units, a 5 ton a couple 3 tons and a 2 ton. The idiots had the 2 ton condenser on the 5 ton air handler etc. 3 out of the 4 were connected to the wrong equipment. The difference on that was the improperly mated units worked terrible, this one worked fine.

Oh well....I tried!

Sounds like you got it covered!

Originally Posted by Paul Kondzich

The other strange part is that all 3 had a good TD, and they all 3 ran for 3 hours. The starting inside temp was 82 and after 3 hours it was 80. It was a mild 85 today as well. Any thoughts.

Could you see the condensate discharge? If the house was vacant and the humidity was very high, it can take a lot of BTU's to remove that much water.

That's true the place was vacant. Not real sure if they were off because I was not first one there. All 3 were making a bunch of condensate. I think you nailed that part.

Originally Posted by Paul Kondzich

...The starting inside temp was 82 and after 3 hours it was 80....

All three had good TD and only lowered the temp by 2 degrees in 3 hours? I'm no AC expert, that's for sure. You said it "worked fine". Is that considered acceptable?

John the "worked fine" was probably taken out of context and was not in OP. I should have chosen words better. The report doesn't say it's fine and calls for an A/C company to check it out in addition to other issues as well. The point I was trying to make here as far as T/D, amp draw, making condensate etc it was "operating as intended."

How old is the house and how well insulated is it?

With that many tons on that size house on just a warm day and only a small temp drop in three hours it sounds like improper ducting or clogged filters.

Also could be both low refrigerant charges and restricted airflow.

Return, return, return. If the units were working 'fine'. Then it may be a distribution problem. However, in most cases I have dealt with it is a return air problem. It doesn't matter how much cold air they try to pump into a space, if at least a reasonable amount of hot air isn't being sucked out of the space, it won't cool down. That much tonnage the place should be freezing.
I'd look at duct sizes, return air ducts (if any) and amount of registers. Did each unit only have a wild return or actual return trunks to the zones?

I saw no mention of a supply air temp. 2 degrees in 3 hours is not "running fine". If there was a return air issue the evaporator coils probably would have frozen after 3 hours. Units could be over charged, TXVs not working properly( if so equipped ),blower speeds could be too low. The latter could portray the system as working correctly without providing sufficient cooling.

If you are reaching a desired temperature drop then the air distribution system is doing the best job it can. A desireable TD would be in the 18 to 20 deg F range.

Any less than the deisred temp drop and you have too high airflow. If the temp drop is higher then you have too little flow.

And I certainly don't think 9 tons is too much for that size of house.

9 tons = 4500sf (500sf per ton is common in Southern California)

Originally Posted by Marc Morin

9 tons = 4500sf (500sf per ton is common in Southern California)

And probably on the light side for Ft. Myers Fla.

Originally Posted by Marc Morin

9 tons = 4500sf (500sf per ton is common in Southern California)

That's basically right for Florida too.

Size-wise (tonnage) that is probably okay, but Paul described some other problems "3, 3 ton condensers, 2, 3 ton air handlers and 1, 1.5 ton air handler"

Oversizing the AHU to the CU is common, oversizing the CU to the AHU can, to my limited knowledge on air conditioning systems, only create problems.

As Vern said: "Could you see the condensate discharge? If the house was vacant and the humidity was very high, it can take a lot of BTU's to remove that much water." and Paul confirmed: "That's true the place was vacant. Not real sure if they were off because I was not first one there. All 3 were making a bunch of condensate. I think you nailed that part."

The first thing the air conditioning system has to do is remove the excess humidity. Sounds like it was doing that.

Marcus there were at least 2 returns per unit, I believe a total of 7, 5 first floor and 2 second which had a much smaller footprint than first floor. I am leaning toward the humidity issue of the problem with the temp drop in the house over 3 hours. So maybe the house was really supposed to have 9 tons of A/C and the smaller air handler is making it seem like 7.5 or less because of the mismatched sizes?

Originally Posted by Bruce King

How old is the house and how well insulated is it?

With that many tons on that size house on just a warm day and only a small temp drop in three hours it sounds like improper ducting or clogged filters.

Also could be both low refrigerant charges and restricted airflow.

Bruce house is 2008 with adequate insulation, but a whole bunch of single pane windows and doors.

Originally Posted by Paul Kondzich

Bruce house is 2008 with adequate insulation, but a whole bunch of single pane windows and doors.

I don't think you could install single pane windows in 2008 due to the energy code. Was the house inspected by the AHJ when it was built? AT least you couldn't in NC.

I know I'm a little late on this response. You can only have a smaller AH than CU if it's specifically approved by the manufacturer. This is usually only the case with heat pump systems. Without model and serial #'s you can't know for sure. As far as TD's go they can be deceptive. If you have low airflow and low refrigerant charge, you can have a proper looking TD. A TD is the best thing a HI can look at though. We get a lot of referral's to look at A/C systems from a few local HI. Usually there isn't any failure outside of low airflow ( which is almost always the case here in Ca. but neither buyer nor seller want to spend the money to improve performance). Hey, check it out I'm rambling on.