[Equest-users] PREHEAT/HEATING-CAPACITY in SYSTEM is too low toprovide the requested supply temperature

Umesh Atre umesh at innovativedesign.net
Wed Oct 7 07:54:26 PDT 2009


Have you tried using the UVT instead of the HVSYS ? 
 
 


________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of
Matutinovic, Luka
Sent: Tuesday, October 06, 2009 6:24 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] PREHEAT/HEATING-CAPACITY in SYSTEM is too low
toprovide the requested supply temperature


Fellow eQuesters,
 
I'm having trouble de-bugging unmet heating hours for two systems in the
attached building stemming from the following warning message:
 
PREHEAT/HEATING-CAPACITY in SYSTEM AHU-16 
is too low to provide the requested supply temperature for
the calculated mixed air temperature using total ZONE loads
(on LS-A/B) and SYSTEM design parameters, plus outside air
conditions (on LS-C), and specified capacities & air flows.
Requested temperature is 95.00 calculated is 64.00
Check HEATING-CAPACITY, HEAT-SET-T, PRE-HEAT-T, MAX-SUPPLY-T,
DESIGN-HEAT-T, and ZONE loads for consistency.
 
I'm trying to model an air-side system for the below-grade parking
garage of the building that has a gas-fired furnace, no cooling and
provides ventilation (with the ability to provide 100% OA when
appropriate).  The system type descriptions in the help file led me to
select a HVSYS (heating and ventilation) system.  Each system serves two
zones and I've specified a zone entering max of 95F (MAX-SUPPLY-T) and
set the zone heating design temperature to 64F (DESIGN-HEAT-T).  I've
also let eQuest auto-size the furnace capacity using a heat sizing ratio
of 1.2.  
 
I'm getting the above error, but I don't understand what is causing it.
I think it may have something to do with my heating schedules or the
outdoor air flows although I cannot trace the problem.
 
Any help would be much appreciated.
 
Thanks,
 

Luka Matutinovic, B.A.Sc., LEED(r) AP

Green Building Consultant
 
T. 416.644.0649

F. 416.487.9766  
Toll Free 1.888.425.7255
www.halsall.com 

HALSALL ASSOCIATES LTD. 
Toronto  Richmond Hill  Ottawa  Sudbury 
Burlington  Calgary  Vancouver  Dubai 

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2009 Globe and Mail
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