Hi Markus,
There is an issue with the project we're modelling, where your opinin would be highle appreciated.
The main HVAC system of our project (small retail building) consists of rooftop units and baseboard heating units (zone level). This Rooftop equipment is a variable volume air flow (without VAV boxes), DCV controlled from the main retail zone . Additionally, upon the insistence of the owner, AC split units for some of the rooms are installed with the presumption to cover an additional cooling if needed. These AC split units are controlled individually only by the room occupants upon their wish (not by room thermostat). This does not include the server room, which is modelled as a separate system.
As the main HVAC system (Rooftop equipment) covers all the cooling loads alone (there is no unmet load hours), these AC split units will be switched on probably only during the hottest summer days for no more than one to two hours daily. So based on the fact that the Rooftop system covers the cooling loads, we have included the additional split systems' el. loads as miscellaneous equipment loads with a respective operating schedule.
The energy modelling software (HAP 4.70) however, doesn't have the option to include an additional room level equipment (regardless if it is needed or not). Since there is already one room level equipment - baseboard heaters, if we would've need these AC units we should've model them via an exceptional calculation method, which practically happen that it is not needed.
The comments we've received from the reviewers are:
- Either to explain why we've modelled those split units as misc. load or
- To modelled them directly within the energy modelling software so that to provide heating and cooling for the conditioned spaces.
Our request are for an advice how to proceed with our reply to the reviewers.
Do you think that a narrative explanation of the above regarding the assignment of the split units as misc. loads is acceptable, or we should find a way to to modelled them directly within the energy modelling software.
Your opinion is realy valuable for us.
Thanks.
Vassil Vassilev
ManagerTermoservice
13 thumbs up
July 14, 2015 - 3:33 am
Hi Marcus,
Sorry of misspelling your name on my initial query.
Is it likely to get your opinion on the above issue or I should rephrase it.
Thanks
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
July 14, 2015 - 8:46 am
I did answer it last week. Did you post it in more than one forum? If not it appears that my answer did not save and I will try again.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
July 14, 2015 - 9:23 am
Trying again.
You should not model these units as a miscellaneous load in the space. Contact HAP to see if there is a way to model them within the software. If not, I think the best way to include this energy use is to calculate it outside the software while also attempting to account for the interactive effects. Perhaps a separate model or maybe engineering calculations. Be conservative in your calculations (energy use is higher than you think it will be). Explain the limitation of the software. Submit it as an exceptional calculation with a negative value.
Vassil Vassilev
ManagerTermoservice
13 thumbs up
July 14, 2015 - 11:33 am
Marcus, Thanks a lot.
The idea with a negative value is really a good one.