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How to Model 'No Cooling' in CBECC-Com

asked 2015-12-21 10:59:40 -0500

agerman's avatar

updated 2015-12-21 15:10:24 -0500

I have a high-rise apartment building with a central boiler serving in-unit fan coils for heating and no cooling system. Previously, buildings with no cooling systems had to be modeled with a right-sized cooling coil, if there were more than 150 unmet cooling load hours. But CBECC-Com now let's you model HVAC systems without cooling, even when unmet cooling load hours are greater than 150. However, in this case the proposed building has 0 cooling energy use. My understanding is that this doesn't meet the intent of the ACM which specifies a cooling system must be modeled. What is the guidance on how to deal with these scenarios? Thanks.

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answered 2015-12-21 15:15:31 -0500

pflaumingo's avatar

@agerman, previous direction I have received from the development team was to model a baseline cooling system so that you aren't claiming any efficiency in cooling. This obviously isn't very simple to do in CBECC-Com without a true autosizing function for the proposed model because this brings in so many theoretical unknowns - sizing chiller may affect where it operates on it's part load curve, how many unmet hours is reasonable because often you'll see the baseline also has some unmet hours, envelope performance, etc. It seems what you're supposed to do is make an "honest" attempt to not claim efficiency for cooling.

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Thanks pflaumingo. That's what I recall as the previous guidance as well. And agreed it's not straightforward and an autosizing function is really necessary. What is curious is that with the latest update, when you try to model any zonal system without a cooling coil CBECC-Com gives you an error and the following guidance (for a FPFC): "Set to 1 Btu/hr if the system has no ChW cooling capacity." I'm still waiting to hear back from the technical team if there's been any changes in their guidance on this. I'll update this forum when I do.

agerman's avatar agerman  ( 2015-12-22 10:52:58 -0500 )edit

@agerman, I believe the reason it says that is for instances where you have supply air coming from an air handler, but locally you have a heating coil (or some system that uses hot water that you can't model and you've approximated as two-pipe heating). If their position is different that'd be very interesting because just about any building will pass if cooling is not included.

pflaumingo's avatar pflaumingo  ( 2015-12-22 11:03:15 -0500 )edit

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Last updated: Dec 21 '15