Why are these heat pumps so large?

2386 sq. ft. home built in 2006 in Laveen AZ. Both units model number say that they are 2.5 tons. The units are 30% bigger than my 5 ton unit. I have never seen units so big that have so little cooling capacity. I would have thought that 6 tons would be required for that size house. I know determining the adequacy of the size is beyond the scope of a home inspection. They provided plenty of cool air. Am I missing something or are these units just larger because of the new R410A freon?

I do not know why the units are so big.
The freon would not make the difference and the sizing of the unit is enough cooling.

FYI: A rule of thumb on sizing is the thermostat in the house should lose about one degree when the A/C is running on the hottest day.

Care to expand on that? Im lost.

Not many heat pumps around here, the only one I saw was similar size, only 1 needed for a similar sized house.

Efficiency…two and half tons is still two and half tons which is the “capacity” of the units. Now, I hate the installation location (poor) from a techs stand point. Hard to work in the cramped space, piss poor air flow through the outdoor units and I would pay someone else to pull or replace that unit in the back. Was this a two story house?

Just for giggles:


There have been lawsuits filed in humid areas of this country where the units was too big causing mold inside the home. The units are not efficient or do not remove humidity if they just cycle on and off.

Sometimes multiple units are used instead of one large unit because it is hard to push cold air up ductwork, and it is just more efficient.

I don’t follow your rule of thumb. Most here generaly install 1 ton per 400 sq. ft. A Manual J calculation can be done to get a more accurate size.

Here all the air handlers are installed in the attic and the registers are in the ceiling. It is easy to push cold air down. For the two months that the heat is needed it is a little bit inefficient to push the heat down.

It is two story. One unit for each level.

Loren the newer higher SEER units are physically bigger than the older units of the same tonnage.



On a regular home in my area that calculation would be cause the units to be too big and they would not cycle enough. A/C units need to run most of the time to lower humidity in the air, but I guess in Arizona humidity is not really a problem. It all depends on how energy efficient the home is, also.

Gerry correct sir. :smiley:

Doug, on the zero lot line homes here somtimes that is all you get for access or installation. Not ideal, but it is what it is…

Agreed, a 23 seer unit is the size of a Pinto.

Interesting, I just had a new 13 SEER heat pump unit installed a couple months ago. It is noticeably smaller than my previous unit. Same size, same brand. But then we don’t see many straight A/C units up here. Mostly heat pumps. And it is welcome today. 86 degrees and humid today.

We consider 86 a cold snap.:wink:

I bet your new seer 13 has double coils.

I have a 3 ton seer 14 and a 3.5 ton seer 14 , the 3 ton is physically larger that the 3.5 ton because the coils are doubled up in the 3.5 ton unit. These are 2001 model Bryant units but I would think other brands have the double coils too.

Thats a shocker Steve, the average 2.5 ton outside coil that is installed down here has grown by around 25%, they used to be about 3 x 3 x 3 (27 cuft) to a newer 13 SEER at around 3.5 x 3.5 x 4 (around 40 cuft) I started noticing how big they were when inspecting units on condo roofs where you can find 40-50 of them of all ages.



True. A lot of the older units had all the components outside the coil in a separate compartment. Lrge cabinets with relatively small coils. Now most have all the components nested inside the taller coils, very little casing, mostly high efficiency coils. Last time I upgraded a half ton, the condenser unit got a smaller footprint but grew about a foot taller. Gerry, I know what you are talking about. I was at a condo the other day, every unit there was a different brand, sizes all over the scale and mixed components from inside and outside and none marked to identify which unit it belonged to. Naturally, the sh*ttiest one there is the one you have to inspect.

A high efficiency unit is a 2 ton compressor in a 3 ton condenser.

The bigger coils get more of the heat out of the refrigerant during high ambient temps.

Size has nothing to do with “size”.

I know your not saying one “rule of thumb is better than the next”! :wink:
All rules of thumb are the same as thumb up your azz.
Also see “Head Up Your azz”!. :slight_smile:

My Ex would beg to differ :(, but anyway getting back to cases, if the 13 SEER demands bigger condensors per ton in high temp environments, does that mean that an exterior coil supplied here in Florida would be bigger than one supplied at the same rating in somewhere cooler?



Gerry, She is only your Ex because of your false advertising. When you told her about the BIG 8, she was thinking inches and didn’t understand you Brits use Centimeters… :mrgreen: