Dear Everyone
I have a question regarding to use additional systems in Baseline case. I use Carrier HAP for modelling purpose. Usually in our office buildings we have CAV system with falcoils/VRV in office spaces and water heaters in toilets, corridors and some technical spaces. Usually corridors and toilet vestibules are supplied by precooled air with no terminal cooling. There is no thermostat cooling control in those spaces. In proposed I model them with precool air only. Terminal cooling is switched off the same as thermostat cooling control so I do not get any unmethours. Toilets transfer this precooled air from vestibules so they are indirectly cooled. Some toilets does not include any conditioning unit so they are indirectly conditioned. I have a question regarding to correct modelling methodology of Baseline systems of that case. These are my ideas.
- For precooled spaces (toilet vestibules) use predicted temperature of these spaces in cooling time and system 3. For spaces without CAV air supply and indirectly heated (toilets without conditioning units) use system 9. That is our methodology that we use for our previous LEED projects and it was accepted. The problem is that it causes enormous numbers of System 3 and System 9 in addition to main system 5 or 7, because they need to be modelled as per thermal zone. In our previous projects we had about 100 of systems. Energy use of that systems is not really significant in my opinion and it is time consuming to model them.
- If spaces are precooled connect them into main system (System 5 or 7) with predicted temperature that may occur in cooling time. For spaces indirectly cooled and heated I hear that some modelers add them to adjacent spaces and create thermal block. So in that case they also can be served with main system. In that case for every semi-cooled and indirectly cooled space we can use main system. It reduces significantly number of additional systems.
- Add precooled to main system and indirectly cooled into system 9. That is intermediate solution between those two.
Many thanks for Your help.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
March 8, 2018 - 10:17 am
1. We don't think this approach can be justified as it does not appear that you are applying any G3.1.1 exceptions to use a secondary HVAC system. The use of a system 9 for indirectly cooled systems is also not appropriate.
2. This is how we would model these spaces. The thermal blocks should be the same in both models.
3. A system 9 would not apply to an indirectly cooled space.
Jerzy Wójcik
Director / OwnerJW+A | Green Building Experts
March 8, 2018 - 11:23 am
Thanks Marcus
So procedure with pre cooled and indirectly cooled spaces is clear.
Would it be appropirate if instead of creating thermal blocks which includes indirectly conditioned space we will create a separate thermal zone ( with thermostat control set for predicted temperature ) for that space served by mail systems. For example if toilet is indirectly cooled and heated by adjacent hall space served by VRV can we just set this toilet as one of the separate thermal zone in system?
This approach would be convenient in Carrier HAP.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
March 12, 2018 - 3:06 pm
I suppose that could work. You should provide an explanation to the reviewers about how you developed the temperature settings based on the predicted temperatures in the space.