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Re: [EnergyPlus_Support] Time heating setpoint not met





 in my design i dont use EMS , because i think ems is after deisgn , ems related to simulation , i set  heating setpoint in my plant :HW outler temperature : 78  C , and i set zone heating setpoint : 30 C , and also in sizing plant : design loop exit temperature : 78  ( for hot water plant ) , but in my result i see the zone air temprature for winter design day is nearly 25-24 
 
 
From: YuanLu Li <yli006@xxxxxxxxxxx>
To: EnergyPlus_Support <energyplus_support@xxxxxxxxxxxxxxx>
Sent: Saturday, March 3, 2012 10:47 PM
Subject: RE: [EnergyPlus_Support] Time heating setpoint not met

 
Toorn's question was:
 
"if i set heating setpoint =30C then i see in the winter design day the zone mean air temperaure is nearly 24-25C ."
could you help me and describe it why this happens?
 
The above is for Linda, because the color background in the mail was not visible.

I think her heating setpoint is the HW outlet temperature, or the temperature where the HW pump is stopped using EMS
 
The zone temperature should be below the HW temperature at the inlet of the radiator, when the outdoor environment is at -10°C.

 
For Tooran:
 
I have mentioned many times.  If your radiator flow rate is fixed, and the boiler temperature is fixed, there is no way that the zone mean air temperature should meet the set point value, at any other conditions, other than the sizing condition.
i set radiator flow rate autosize , to determine in which flow rate of radiator , zone mean air temperature in winter design day is nearly my setpoitn temperature.
 
With your present settings, the range of temperature is from 18°C to 32°C depending on the outdoor condition and the internal loading, for the three month period.  You did not plot the outdoor temperature, so you do not know when the limiting condition occured.
 
You have removed most of the Output variable display I set in the IDF that I returned to you. 
You have already got all the data required by your professor, i.e., the total building heating load requirement, (from the IdealLoadsAirSystem simulation)  the  zone temperatire variation with boiler temperature (using HW setpoint schedule), and the gas fire capacity (Burner PLR).
 
If he wanted to control the building temperature by using a fixed  boiler temperature and on/off control on the HW pump based on the boiler temperature, you hae done that as well.
i never want do it , i never want to control building temperature
However, you still do not understand the reason for simulation and how to debug the building surface warnings and to select the relevant variables for viewing.
 
You still do not know the deadband, the setback, and the operating range of a thermostat in EPlus.  The zone thermostat is a setpoint register and can be scheduled, and it is not a thermometer measuring the zone temperature. 
 
If you wanted each zone to reach the set zone thermostat value, you must have individual zone control elements, i.e., a valve at each zone radiator activated by the zone thermostat.
 
ok you r right Dr.Li i dont know all of this .
 
 
  Dr. Li  

 
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: t.t111ir@xxxxxxxxx
Date: Sat, 3 Mar 2012 12:00:38 +0000
Subject: Re: [EnergyPlus_Support] Time heating setpoint not met

 
i wrote wrong in the   yellow highlighted line ,  the red line in correct
 

From: Tooran <t.t111ir@xxxxxxxxx>
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Saturday, March 3, 2012 3:26 PM
Subject: [EnergyPlus_Support] Time heating setpoint not met

 
dear members ,

i want to design the hot water plant loop and i wnat to know what size pump and boiler must have to that their capacity is engough for keeping the zone mean air temperature = 25 C ( i set heating setpoint =25C) for winter design day , but when i run it i see in the winter design day i have time heating setpoint not met and the zone mean air temperature is nearly 20-21-19 C.
if i set heating setpoint =25C then i see in the winter design day the zone mean air temperaure is nearly 24-25C .
if i set heating setpoint =30C then i see in the winter design day the zone mean air temperaure is nearly 24-25C .
could you help me and describe it why this happens?
thanks








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