PVAVS System In Equest - 15, 000 hours out side of throttle range

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I am an Architect doing the energy model for a number of two story schools
over 85,000 SF, and using eQuest for LEED energy design and documentation.

I am doing the energy model for LEED compliance and I am modeling the base
case with a Packaged Rooftop Variable Air Volume System to compare with my
VAV system for the design case. I reverse engineered my design case to
modify the mechanical system, but all of the simulations indicate I have
15,000 hours outside of the throttle range. My hotwater loop has two
boilers and my heating coils are assigned to the loop, but there does not
seem to be any output from the system. The system report summary indicates
that it is not serving any square footage, so I think there is a bug
somewhere. I have fiddled with the THROTTLE RANGE, HEAT-CONTROL,
COOL-CONTROL, HEAT-SET-T, and MIN-SUPPLY-T after reading various posts but
nothing changes the lack of heat. I've also fiddled with baseboard heat and
pre-heat but nothing seems to affect the hours outside of throttle range.
Does anyone have any suggestions?


James Geers's picture
Joined: 2011-09-30
Reputation: 0

Did you try looking at the hourly reports for the equipment that should be
generating the loads? If the AHUs and zone coils are calling for heat but
it isn't being supplied, then it could be a problem with the hydronic system
inputs. If there is not a load on the coils, then the problem may lie in
the airside system inputs. This is typically where I start when I have this
problem. I have had this happen when I have unconditioned zones being
served by a system intended to serve conditioned zones. If I have any
unconditioned zones, I put them under a ghost single-zone system that only
serves unconditioned zones (uses no fan power, cooling, etc).

I hope this helps!


Eric Studer's picture
Joined: 2011-09-30
Reputation: 200

Do you have a value entered at the system level for Reheat Delta T?
This is a pretty easy one to miss that will prevent your system from
having any reheat and can result in very high hours out of range.

Please note my new e-mail address: andrewc at interfaceeng.com

Andrew Craig, EIT,LEED AP

Andrew Craig2's picture
Joined: 2011-10-02
Reputation: 0

I believe that was the problem, I had left it blank assuming it would go to
a default value. Thank you, I wish I would have figured that out a few days


James Geers's picture
Joined: 2011-09-30
Reputation: 0