ASHRAE 90.1. Appendix G says that, even if a zone is heating only in the
actual building, a cooling system identical to that in the baseline system
should be modeled in the as-built model with intermittent fan operation to
meet the loads. I have seen projects with zones that have only unit heaters
with no cooling air supply. eQuest does not allow for modeling of any
cooling system in a zone with a unit heater. What would be your approach to
solving this problem?
I would appreciate it very much if you could help me with this question.
Thank you very much in advance for your suggestions,
Best Regards,
Simge Andolsun, PhD.
You could always model them as Packaged Terminal Air-Conditioners. Define the heat source to match your unit heaters (gas/electric). Then you get DX cooling.
On jobs I've worked on with electric resistance heat and no cooling, I've used the PTAC system type, zeroed out the fan-power, selected electric heat, and it was accepted by the reviewers. In that case I DID NOT separate out fan power from the cooling EER, since otherwise I would not account for the artificial fan energy in addition to the artificial cooling energy mandated by having to model a cooling system.
Nathan Miller - PE, LEED(r)AP BD+C, CEM
Dear Nathan Miller,
Thank you very much for your response. Would you explain what you meant by
not separating out fan power from the cooling EER?
The solution I was thinking was creating a dummy zone which is exactly the
same as the zone with the unit heater and connecting the baseline cooling
system to this new zone. This doubles the lights and equipment though, but
this could easily be fixed by simply dividing these energy consumption
items by two. What do you think about this solution? Can you think of any
drawback of this solution?
I'd appreciate it very much if you could help me with these questions,
Thanks,
Best Regards,
Simge Andolsun, PhD
Simge,
In the past, I've just altered the cooling schedule for the space, so it never goes into cooling mode. Then I model the space per ASHRAE 90.1 Appendix G.
Thanks,
David W. Griffin II
I know this has been addressed previously, but for heating only spaces you can treat them as heating only spaces as long as you cite addendum "DN" in your documentation. Check the ASHRAE website for specifics but in short this allows for heating only spaces that are served by unit heaters or unit ventilators (system 10 and 11). I think it makes more sense to treat the spaces in this manner than in adding cooling to both proposed and baseline where it does not exist otherwise.
Brendan Hall, PE, LEED AP BD+C