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Constant Volume Multizone HVAC System Setpoint Manager

asked 2015-07-17 08:09:17 -0500

dpud12's avatar

updated 2017-08-05 13:12:47 -0500

I am working on writing a measure for creating a Multizone Constant Volume HVAC system with reheat and wondering what the most appropriate supply air setpoint manager to use is. I see that there is a Single Zone Reheat setpoint manager, however, there is no equivalent for Multizone systems. Also, when I attempt to use the Multizone Humidity setpoint managers, they throw an error when running the simulation.

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For multi-zone air loops you can use the SetpointManagerScheduled object. I'll let @Kyle Benne address humidity control. You can only add humidity control to specific types of equipment.

David Goldwasser's avatar David Goldwasser  ( 2015-07-17 09:33:16 -0500 )edit

But since I want to model a Constant Volume system, isn't a scheduled setpoint manager not applicable? I thought that to satisfy the zone load given a constant air input, the temperature would need to vary free of a schedule

dpud12's avatar dpud12  ( 2015-07-17 09:56:04 -0500 )edit

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answered 2015-07-17 10:34:29 -0500

Use a SetpointManager:Scheduled set to ~55F on the supply outlet node if you want constant supply air temp, or a SetpointManager:Warmest:TempAndFlow if you want to have supply air temp reset based on the worst-case zone. In either case, the supply air temp will be cold, and any necessary reheat will be done by the zone terminals, not the central heating coil. The SetpointManager:SingleZone:Reheat is only used for single zone systems, where the reheat is done at the central heating coil (instead of at a terminal).

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Thank you both @David Goldwasser and @aparker So how common are single duct Multizone CV systems that have a fixed supply air temp set at 55? This produces a huge amount of simultaneous heating and cooling in my model and doubles the consumption for both these end uses.

dpud12's avatar dpud12  ( 2015-07-17 12:04:09 -0500 )edit

They are pretty common, especially in old buildings. According to the Energy Star Building Upgrade Manual "Retrofits involving conversion from CV to VAV are perhaps the most widely employed energy-saving retrofit to commercial HVAC systems, because typical airflow requirements for VAV systems are only about 60 percent that of CV systems."

aparker's avatar aparker  ( 2015-07-19 09:46:07 -0500 )edit

@aparker Thanks for the informative link!

dpud12's avatar dpud12  ( 2015-07-20 08:47:37 -0500 )edit

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Asked: 2015-07-17 08:09:17 -0500

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Last updated: Jul 17 '15