Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
There are several configurations possible for conditioning a single zone. A single zone system (ZoneHVAC:) or an air loop (AirloopHVAC:) can be used. Although they would be set up differently, with an air loop connected to a splitter and mixer, a main branch, and zone connections, while zone equipment would be connected directly to a zone, the work essentially the same.
Zone equipment would be used to meet a load, so controlling the equipment to a set point temperature is not an option. Airloop equipment can serve a single zone and certain configurations can be controlled using a temperature set point. The CoilSystem:Cooling:DX or place directly on the main branch a Coil:Cooling:Water object. Both of these can be used to control the coil using a set point manager. See example file 5ZoneAutoDXVAV for a DX cooling coil configuration and example file 5ZoneAirCooled for use of water coils.
If your coil set point temperatures at set at 95F heating, and 55F cooling, then yes, both coils will turn on to maintain their individual temperature set points. If you set both set point temperatures to the same value, only one coil should run. If you want to control both coils to different temperatures, then the only way to avoid both coils operating at the same time would be to use the availability schedules to turn the cooling coil off during the heating season, and the heating coil off during the cooling season.
Fan cycling is another issue. The set point based control is typically accomplished using a constant volume fan and this fan will not shut of unless the fan availability schedule turns the fan off, for example at night. If the system is needed to operate during the night, then a night cycle availability manager could be used to turn the system on to maintain a (setback) temperature.
There is also a new equipment model, namely AirloopHVAC:UnitarySystem, that can model any coil type and provide both load based and set point based control.
| | 2 | No.2 Revision |
There are several configurations possible for conditioning a single zone. A single zone system (ZoneHVAC:) or an air loop (AirloopHVAC:) can be used. Although they would be set up differently, with an air loop connected to a splitter and mixer, a main branch, and zone connections, while zone equipment would be connected directly to a zone, the they work essentially the same.
Zone equipment would be used to meet a load, so controlling the equipment to a set point temperature is not an option. Airloop equipment can serve a single zone and certain configurations can be controlled using a temperature set point. The CoilSystem:Cooling:DX or place directly on the main branch a Coil:Cooling:Water object. Both of these can be used to control the coil using a set point manager. See example file 5ZoneAutoDXVAV for a DX cooling coil configuration and example file 5ZoneAirCooled for use of water coils.
If your coil set point temperatures at set at 95F heating, and 55F cooling, then yes, both coils will turn on to maintain their individual temperature set points. If you set both set point temperatures to the same value, only one coil should run. If you want to control both coils to different temperatures, then the only way to avoid both coils operating at the same time would be to use the availability schedules to turn the cooling coil off during the heating season, and the heating coil off during the cooling season.
Fan cycling is another issue. The set point based control is typically accomplished using a constant volume fan and this fan will not shut of unless the fan availability schedule turns the fan off, for example at night. If the system is needed to operate during the night, then a night cycle availability manager could be used to turn the system on to maintain a (setback) temperature.
There is also a new equipment model, namely AirloopHVAC:UnitarySystem, that can model any coil type and provide both load based and set point based control.
