Trying to find 16+ SEER, 2.5Ton Heatpump for LEED project 2

[lgreeson]

A project I am currently working on is trying to obtain LEED certification, and the LEED consultant is requiring (or desiring) that I spec 16+ SEER, 9.0 HSPF units. These are townhouses, and the loads for half of the units fall between the capacities of a 2T and 3T, so 2.5T is a better fit. However, I have been unable to find a 2.5T that meets the SEER criteria.

Does anyone know of a manufacturer that offers a high-efficiency 2.5Ton?

Lee

 

[Wareagl487]

16 is really pushing it for air cooled equipment - easily obtained with WSHP though....

I see this one on Trane's web site - pretty close. I didn't look at the complete system rating matched with AH.

http://www.trane.com/residential/products/HeatPumps/xl19i.aspx

Or this one from Carrier...

http://www.residential.carrier.com/products/acheatpumps/heatpumps/infinity.shtml

Hope this helps.

Andy W.

 

[PatBethea]

You'll probably need to look for a unit with R-410A refrigerant. You could go with an Amana:

http://www.amana-hac.com/Home/Products/AirConditioningSystems/tabid/276/Default.aspx.

This past summer, I installed a 3-ton, 16 SEER Amana Model ASX16 in a new addition I built to my house and I've been very pleased with it. It's got a great warranty, too.

 

[lgreeson]

Andy,

Thanks for you quick reply. I forgot to mention that R-410A (or equivalent) is another requirement, which knocks out the Trane (R-22), and the Carrier model comes only in whole tonnages, no half-tons.

I am afraid I know the answer, since I have already spent a lot of time researching this on various mfrs websites and talking to sales reps, but there are more mfrs than I care to mess with. I am hoping someone with knowledge of a specific make/model can point me in the right direction.

I may have to choose between jeopardizing the LEED certification and selecting properly sized equipment, versus keeping with the LEED prescription and grossly oversizing the equipment.

Thanks again,

Lee

 

[gepman]

Although the unit that PatBethea mentions is an A/C unit only it looks like Amana makes a heat pump unit that may meet your requirements.

http://www.amana-hac.com/Portals/1/pdf/SS-ASZ16.pdf

 

[lgreeson]

Thanks to everyone for your help. I am open to other mfrs if anyone else cares to post, but it looks like there is at least one model that meets the strict requirements.

Lee

 

[Wareagl487]

The Carrier 25HNA9 has a 2-stage compressor. This may be cheating, but have you considered specifying a 3-ton with variable speed air handler knowing full well that it will operate at part load 99% of the time? You get the ratings you desire and won't over cool the space......

Andy W.

 

[gepman]

I don't like the term "2-stage" even though it has gotten a foothold in the small package unit HVAC world. If you look at how ASHRAE defines "stages" in refrigeration it is two compression stages NOT two capacity steps. But that is just nitpicking.

The Amana unit uses a Copeland UltraTech which has two "stages" also. I am not sure which compressor the Carrier uses, probably the same one. You would need to know at what capacity the steps are to see if you would get good efficiency. I believe the Copeland is at 66% and 100%. I believe that it would be cheating to oversize the unit and run only at the low capacity because the whole idea of LEED is to be the most environmentally conscious and energy efficient. Part of the efficiency is operating at the right capacity point more often which a properly sized two "stage" compressor will do more often than an oversized compressor.

If anyone is interested in reading a little more on two "stage" compressors and real two stage heat pumps see the thread

http://www.eng-tips.com/viewthread.cfm?qid=201282&page=1

which is also titled "Heat Pump Defrost Cycle Design" in which both of these are discussed.

 

[EmeraldCoastHVACR]

With a VSD HP, it is better to size for 3 ton.

The 3 ton VSD HP will not only draw the same current as the 2.5 ton HP at lower capacities but also offer higer heat load capacity at lower temperatures.

 

[gepman]

EmeraldCoastHVACR
Do you have an example of a VSD Heat Pump in the 3 ton range with the 16 SEER rating and the 9 HSPF?

Copeland doesn't recommend running their scroll compressors on VSD's however they have made a modulating scroll compressor using their "Digital" Scroll. Basically it is a duty cycle machine similar to unloading and loading cylinders on a recip except that they are loading and unloading the scroll. I have seen it and it does a good job of maintaining a constant suction pressure which is how a compressor ought to be controlled (the suction pressure setpoint can be changed depending on the how the room temperature is meeting the room temperature setpoint, i.e. "floating suction pressure control").

 

[EmeraldCoastHVACR]

gepman,

No I can't without researching.

But I would suggest Igresson verify & persue the possibilities -- I'm confident a 3 ton 2 stage comp with VSD fans will offer this gentleman what he's looking for for certification.

He just has to be diligent in his verification & reasoning,

 

[gepman]

EmeraldCoastHVACR
I thought you meant a VSD compressor not VSD fans. VSD condenser fans are relatively common. Most of the energy is in the compressor not the condenser fan. The Amana unit above has a two speed condenser fan which helps a lot more than one might think.