Forum discussion
NC-2009 EAp2: Minimum Energy Performance
I have to model electric unit heaters in HAP for spaces like Stairs, Trash rooms, Vestibules etc. The issue is that the Stairs are already served by heat pumps and electric unit heaters will turn on only to maintain the space setpoint when the heat pump is not sufficient. How should I model a schedule for this type of system in HAP? Also how do I model a system like this without double counting the stairs in baseline and proposed cases?
Nishank
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5867 thumbs up
May 11, 2018 - 9:34 am
Not sure about HAP but most software allow you to model supplemental heating in a space. The electric unit heater should come on in response to the heat pump's ability to meet the load in the space. I would not schedule it but select some other means to control its operation like a thermostat.
If you can't model both systems in the space then you should create a different zone for those spaces, proportion the load, and model a heat pump with electric back up. It should be thermodynamically similar.
Nishank Shah
LEED Green AssociatePeter Basso Associates
May 11, 2018 - 9:59 am
Thanks Marcus,
So to make sure I understand it correctly, I need to divide the load proportionally between the water source heat pump and electric unit heater, create a separate zone (therefore a separate system) for the electric unit heater which will serve the proportionally divided load and proportionally divided area (since I don't want to double count the space) and then create a baseline using the same approach?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5867 thumbs up
May 11, 2018 - 10:40 am
So you can't model a supplemental heating source in HAP? That is by far the best way to do this.
You should not proportion the load between the two systems. You should create a separate zone of those areas and proportion the load between the two zones. The zone with the electric unit heater would include a separate heat pump with the same efficiency using electric heat as the back up.
Nishank Shah
LEED Green AssociatePeter Basso Associates
May 11, 2018 - 11:11 am
Unfortunately not. The way HAP models WSHP is only with its set of equipment, meaning cooling tower and auxiliary HW boiler. It cannot model supplemental heating in the form of electric heat in the same system..
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5867 thumbs up
May 11, 2018 - 11:31 am
So model an air heat pump with a similar efficiency as the WSHP. This should get you close. You could downgrade the efficiency a little to account for the impact on the water loop. You might also call HAP and ask them for a work around. It would help to document what you are doing for the reviewer.
Nishank Shah
LEED Green AssociatePeter Basso Associates
May 11, 2018 - 11:49 am
I'll do that. Thanks for your help.