Carrier HAP program and heating calculations

[jistre]

I'm trying to model a system with an air source heat pump as the heating source, and am getting some results I can't make sense of. The program runs through the simulation and calculates heating coil loads, but then insists that there are no heating equipment loads. Hence, the heating equipment energy usage comes out to be zero.

I've gone back and checked, and have defined the central heating portion of the system's system components tab and entered equipment data in the system's equipment tab. I'm at my wit's end as to why the program refuses to put any load on the equipment.

Any help would be greatly appreciated.

 

[doopedeng]

If you haven't already figured out your problem, you should contact the HAP helpers. They are extremely knowledgeable because they are (or at least used to be) the people who developed the software. Call the number below, leave a message and they usually respond within a day or two. I have had to do this on a number of occasions and have always been pleased.

1-800-253-1794

Dooped

 

[EnergyProfessional]

He might not have the subscription since he asks here. I assume they only help when you subscribe (that's how it works for Trane TRACE).
Jistre: I don't know HAP so well, but TRACE. Did you try out a boiler or something to see if you heating load for the spaces exists?
Does it say heating load zero, or heating energy use zero? If it shows a load, it might be an error that you have a heat pump with infinite COP or something else not properly specified. (not sure if HAP has that, but TRACE has the unload curves and ambient relief curves for heat pumps and chillers etc.). If you create your own equipment you could have screwed something up. Try using a standard heat pump that is default in HAP.
(now you see, I'm not sure if HAP lets you create your own equipment at all). but trying everything in default and then one one by changing things may get you to find the error.

Obviously, if you have subscription, call them. I know Trane has good support, and heard Carrier has too. You can send them your file too if they let you.

Good luck!

 

[jistre]

Nah, we have a subscription. I talked to them and I think we figured out the problem. I need dehumidification, even in the winter (S. Louisiana), and reheat ends up being the largest part of the heating coil load. However, because of ASHRAE 90.1 appendix G, I have to model this building with packaged DX RTU cooling and air source heat pump heating. I suspect that when the program encounters this while modeling a single zone CAV system, it assumes that the heat pump and DX are the same equipment and cannot run at the same time. Hence, no subcool for dehumidification, and only straight sensible load on the heat pump because if there is no subcool, then there is no reheat needed.

So, when you look at this system modeled for our climate, there's almost no heating load, even though there really is because of dehumidification.

This is my theory because if I turn dehumidification off, the heating equipment load equals the heating coil load equals the sensible heat loads, but if I turn it back on, it goes all pear shaped. Also, if I switch the system type from single zone CAV to a dual duct CAV, then it correctly shows the loads since there are then two separate equipment trains to provide air to the hot and cold decks.

At least that's what I'm telling people.

 

[jistre]

Thanks for the input, by the way.