[Equest-users] PSZ Very High Unmet Hours

[John Aulbach]

Adam:

How do you vary flow for a VFD is you aren't varying flow?

And how do you get the air to 110°F if you are leaving the "hot deck" at 80°F?

What did you change in the proposed model over the base model?

An .INP and .PD2 file of each would be helpful.



John R. Aulbach, PE, CEM
Senior Energy Engineer

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www.ptrenergy.com| jaulbach at ptrenergy.com



________________________________
From: Adam Gonthier <agonthier at Horizon-Engineering.com>
To: equest-users at lists.onebuilding.org; bldg-sim at lists.onebuilding.org; Vidya 
Gowda <vgowda at Horizon-Engineering.com>
Sent: Thu, July 29, 2010 1:21:44 PM
Subject: [Equest-users] PSZ Very High Unmet Hours


Dear eQuest users, 
 
I am having some difficulty with a project I am working on, and I was hoping I 
could receive some help or any information on a building a with packaged single 
zone units with DX cooling and hot water coils for heating, with a VFD to vary 
the supply flow (there are no VAV boxes in the system, and the supply reacts to 
overall building pressure rather than specific zonal needs determined by 
pressure sensors in the ductwork).   There is no reheat in the system either.  

 
It is a LEED for schools project where the simulation of the proposed model 
shows very high unmet loads for heating and the total energy consumption for 
space heating is 199 MBTU which is unrealistically low as compared to the 
baseline model space heating which is 6369 MBTU.  We do not see many unmet hours 
in the control zone, but since the unit supplies many zones, we are getting very 
high unmet heating hours in non-control zone spaces.  We are seeing on the order 
of 4000-5000 hours unmet in many zones.
 
I have modeled the heating for all zones by specifying the 
Heat Source as hot water loop, 
The Zone Heat Source is not installed, as the design has no reheat. 
Zone entering maximum supply temperature is at 110 degrees. 
Hot deck max leaving temp is 80 degrees
Reheat delta T: n/a
 
Many thanks in advance, 
Adam A. Gonthier
Energy Engineer
Horizon Engineering Associates, LLP
347.297.9005
www.horizon-engineering.com

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