Re: [EnergyPlus_Support] cooling load peak when HVAC starts working

[Yan Xue <yxue2011@xxxxxxxxx>]

Hi

I have start up the HVAC at 5:00am and attached the new idf file, however, there is still the peak at around 6:00am when the internal heat load increase. Can't figure out the reason.

Best wishes

Yan



----- Original Message -----
From: "Jeremiah Crossett" <jcrossett@xxxxxxxxxxxxxxx>
To: "EnergyPlus Support" <EnergyPlus_Support@xxxxxxxxxxxxxxx>
Sent: Monday, January 28, 2013 10:48:22 AM
Subject: Re: [EnergyPlus_Support] cooling load peak when HVAC starts working






This may be because of the thermal mass & surface temperatures-- it takes a bit more to start up than it does to run and it is not optimum to have startup coincide with occupancy. This can also cause comfort issues and load hours not met. You may want to use an optimum start time of 5 am or even 4, the key is to have your HVAC system start before your loads arrive so that your space is fully conditioned when the people and sun arrive. 


Best- 







Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions 
120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951 
www.phasechange.com 









On Mon, Jan 28, 2013 at 7:32 AM, Yan Xue < yxue2011@xxxxxxxxx > wrote: 








Dear all 

I conducted simulation for a building including HVAC system. HVAC operation schedule is from 6:00am - 10:00pm and timestep is 10 per hour (6min). When I check the sensible cooling load for timestep report, there is a peak around 6:00am. It is reasonable that cooling load rate increase suddenly at 6:00am since internal heat load increase but the increase value for cooling load rate is too high which is much more than internal heat load increase. Besides, the cooling load decreases suddenly just after a few timestep which is not reasonable as well. 

Is this problem related with timestep? I attached idf file and appreciate it very much if somebody can help me. 

Yan 






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Attachment not found:
d:\eudora\attach\Mixed_cooling load1.idf