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RE: [EnergyPlus_Support] Cooling follows heating setpoint

I do not think this is always true.  The reheat heater has two functions.  For cooling it is a reheat heater, which follows the cooling setpoint schedule.  For heating, it is the zone main heater which follows the heat set point schedule.
If a user do not modify the template expansion, and use the zone thermostat to control the zone cooling and heating, the type 4 DB  thermostat schedule is followed.  There may be cooling in Winter, because of the high internal load, or solar radiaton load through windows
In Summer, or when the building is warmer than the zone, and at light demand, the VAV damper will close.  If the zone temperature is still too load (over cooling) the reheat heater will be turned on to heat the zone to the cooling setpoint schedule value.
In Winter, or when the building is cooler than the zone. the VAV damper will open first.  When the supply air cannot meet the zone heating demand, the reheat heater will be turned on to meet the zone temperature to the heating set point schedule value.  If the supply air is sufficient to heat the  zone to or above the heating set point value, the reheat heater should  not be turned on.
If the VAV system supply air temperature is set at the middle of the dead band, (which is not the ASHRAE guide line value of 14°C) the reheat heater may not be required at all.
If the zone thermostat operation is over written by using setpoint managers, the operating condition will follow what the user has defined.  This is one reason why I discourage users to add their own set point managers without fully mastered the application rules.  Whenever a setpoint manager is used, one must have the sensor reference point, control elements, controlled nodes, and control schedules..
I am not sure whether the HVACtemplate:zone:VAV is now using the setpoint method or not.  Last time (version 6), the theremostat setpoint  schedules were used.  This is why I prefer a user to post the template IDF, rather the modified IDF, when trying to solve problems. Modified setpoint manager set is very difficult to trace.

 Dr. Li  


To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx
Date: Tue, 21 Aug 2012 08:24:14 -0500I do no
Subject: RE: [EnergyPlus_Support] Cooling follows heating setpoint


EnergyPlus maintains the heating setpoint during cooling season for reheat systems


James V Dirkes II, PE, BEMP, LEED AP

Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653


From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of bhensii
Sent: Monday, August 20, 2012 11:15 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Cooling follows heating setpoint



I have a VAV system in a building.
But for some reason my cooling seems to follow my heating setpoint!
any idea why this could be happening?


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