Rooftop Control

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Dear All,

If a constant volume rooftop is controlled with a thermostat located in
a zone, then we have to use either PSZ or PVVT systems to define its
control zone.

How would one model a control where the rooftop supply air temperature
setpoint is set according to the return air temperature (ie. average of
zone temperatures)?

Thank you in advance,

?mer Moltay, LEED AP BD+C, ASHRAE BEMP, ASHRAE CPMP
Mimta EcoYapi, LEED Proven Provider
Hekimsuyu Cad. 559. Sk.
No:39 34255 Kucukkoy Istanbul Turkey
Tel: 90-212-617-2296
Fax: 90-212-617-2297
Mobile: 90-533-957-1394
www.eco-yapi.com
www.buildingenergymodels.com

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Hi ?mer,

One way to do this would be to merge all of the zones/spaces into one. There may be a way to do what you want without merging zones, but nothing is coming to mind. Good luck

Alex Chapin PE, BEMP, LEED AP BD+C, O+M
Energy Engineer | Mason & Hanger
A Day & Zimmermann Company
O 804.521.7072
4880 Sadler Road, Suite 300 | Glen Allen, VA 23060
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I cannot recall dabbling with this in recent memory, but I think you might want to read up on the staged-capacity/staged-volume PVVT system options in the doe2 reference.

Volume 2: Dictionary > HVAC Components > SYSTEM > Staged Flow/Capacity DX Cooling/Heating Systems

Reviewing the help files, it looks like there are a few options for sequencing that are actually constant volume with 2+ stages of cooling, engaged in response to discharge temperature. This would appear to be one step removed from return air monitoring as posed, but in line with the concept of varying your mechanical cooling energies in response to aggregate load conditions.

~Nick

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Nick Caton, P.E. (US), BEMP
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