HJ
On 10/26/2012 7:08 PM, Griffith, Brent wrote:
This air handler has a setpoint manager for the supply air deck temperature that is totally separate from the thermostats in the zone. Whenever the air handler is running it will run the cooling coil to target a deck temperature of 12.8C and thereby load the chiller.
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of HJ
Sent: Friday, October 26, 2012 4:39 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Chiller won't shut off for cool seasons
I just changed the setpoint to 27 C and still the chiller is running when air temperature is 19 C. I also noticed the idf file in the email is wrong. I attached the new idf file and the output file here. The output file contains the room air temperature, setpoint temperature and chiller energy consumption
On 10/26/2012 6:24 PM, HJ wrote:
Thanks Jeremiah. It seems to be the case. Since the difference between room air temperature and setpoint for chiller is less than 2 C.
HJ
On 10/26/2012 6:02 PM, Jeremiah Crossett wrote:
You could use an availability schedule that turns off during days/hours you do not want cooling and call it from the thermostat object. The concern with this approach is that your zone may actually be above your 23c. You might want to try it with your availability schedule to turn off the chiller during cold seasons, and then plot the output variable for well mixed zone air temperature to see if the temperatures are above 23C.. If they are above 23, than that would explain why the chiller was on..
If you are not using the thermostat type "dual setpoint with deadband" than you may have an issue where your heating and cooling are in a battle. You may wish to use this type of thermostat for all models, and have a deadband of at least 3c..
If you are using "dual setpoint with deadband" and still have chiller turning on you might then plot internal gains to see if you can find the source of the thermal energy before you go and use an availability schedule to turn off the chiller. The cooling energy use during in expected times is really an indicator that your control strategy should be adjusted, so in theory if you did nothing but turn off the chiller with an availability schedule than you would still have the temperatures above 23c.
Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions
120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951
On Fri, Oct 26, 2012 at 2:29 PM, HJ <wanghaojie630@xxxxxxxxx> wrote:
Hi all,
I use openstudio to export idf file for energyplus. I use packaged
rooftop VAV with reheat and a thermostat to control it.
For working hours, the setpoint for cooling is 23 C (I want to use
hybrid ventilation in the future, so i set this a little higher). I
expect it to turn off the cooling system when indoor air temperature
below 23 C. However, I can see the chiller electricity consumption is
not zero and may be very high even when indoor temperature is around 18C.
I attached the idf file here and wonder if there is any other default
control schedule that override the thermostat control?
Many thanks,
HJ
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