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Should the ASHRAE system 8 chiller be connected to the system 7 condenser in OpenStudio?

asked 2020-03-25 07:38:31 -0500

Nathalia gravatar image

updated 2020-03-26 09:17:08 -0500

Hi, I am modeling a baseline in OpenStudio with two ASHRAE systems: system 7 (kitchen) and system 8 (other rooms). When you get the ready model of system 7 in OpenStudio it comes with Condenser Water Loop and system 8 does not. I would like to know if I connect the Chiller from system 8 to the system 7 condenser.

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answered 2020-03-26 14:52:36 -0500

Anthony Hardman gravatar image

Not sure why you'd be mixing those two systems for an appendix G model? As of 90.1-2013 your baseline system type depends on your climate zone. Prior to that, it generally depended on the buildings heat source. If gas heat was available, system 7 would be your baseline for the entire building (with some rare exceptions that I don't want to get into). If this is just an academic exercise, the chilled/condensing water rules for systems 7 & 8 are identical so you could share the condenser loop if you wanted.

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It's not really an academic exercise, I'm doing LEED V4 certification for a restaurant inside the mall. LEED V4 uses ASHRAE 90.1-2010, for this reason I am using two systems

Nathalia gravatar image Nathalia  ( 2020-03-27 06:17:31 -0500 )edit

v4 CI for the restaurant or NC for the whole mall? In either case, if the mall is more than 150,000 sf and uses a gas heat source, then system 7 should be the baseline. Within the restaurant, you should check to see which zones are subject to G3.1.1 system exceptions. One or more zones (e.g. the part of the kitchen served by a MAU) are likely subject to exceptions b or d.

Anthony Hardman gravatar image Anthony Hardman  ( 2020-03-27 11:56:03 -0500 )edit

Both system 7 and 8 should have both CHW and CW loops. I'd first question why the OS System 8 does not have CHW/CW loop. Check this. If the kitchen is subject to G3.1.1 Exception d. the last sentence indicates that for all electric building the heating source shall be electric resistance (for the kitchen). If the rest of the building is System 8 (CHW + Elec Resistance) then the kitchen effectively becomes a psuedo System 8 as well (terminal unit typ is different for System 7 vs 8). Both System 7 and 8 can and should be on the same CHW loop. The CW loop serves the chillers on that CHW loop.

dradair gravatar image dradair  ( 2020-03-30 08:42:35 -0500 )edit

If the kitchen is subject to G3.1.1 Exception b. the System 3 or 4 should not have CHW / HW. Stand-alone System 3 or 4.

dradair gravatar image dradair  ( 2020-03-30 08:43:45 -0500 )edit

System 8 in OpenStudio has a CHW loop, but it doesn't have a CW loop, so my question is whether I should connect to the system 7 CW loop. Thanks for the answers.

Nathalia gravatar image Nathalia  ( 2020-04-01 07:33:39 -0500 )edit

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Asked: 2020-03-25 07:38:31 -0500

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Last updated: Mar 26 '20