[Equest-users] Hot water loop demand and boiler sizing

Rich Tesoriero RTesoriero at swinter.com
Wed May 6 11:30:22 PDT 2009

I had a similar error recently and adjusted LOOP-SIZE-RATIO on the Basic 
Specifications tab for the loop

The safety factor for loop sizing. (Note that safety factors could have 
already been specified within the secondary HVAC systems attached to this 
loop). This keyword is used only when SIZING-OPTION = SECONDARY-EQUIP; it is 
ignored for the PRIMARY-EQUIP sizing method. When primary equipment is to be 
auto-sized by the program, this keyword modifies the default capacity 
assigned. Note that this keyword affects only the auto-sizing of the primary 
equipment based on secondary loop loads. It has no effect on the design loop 
flow;  the loop flow is based on the sum of the coil flows or other loads 
attached to the loop. However, the design pump flow can be modified via 
keywords in the PUMP command.


-----Original Message-----
From: "James Hansen" <JHANSEN at ghtltd.com>
To: "Josh Doherty" <jdoherty at dcengineering.net>
Cc: equest-users at lists.onebuilding.org
Date: Wed, 6 May 2009 14:15:04 -0400
Subject: Re: [Equest-users] Hot water loop demand and boiler sizing

I constantly struggle with the same issue (loop sizing) and whether or not 
it is actually having an impact on energy consumption.
In a recent project I did, I had the same results as you.  However, I went 
to the hour-by-hour report page for the plant, and using your example below: 
 I would get something like -2992234 buth at 8am, -1000000 at 9am, -2900000 
buth at 10am, etc..  The heating load was bouncing high and low, meaning the 
loop had to be sized for -2992234 but the actual maximum heating load that 
your system would see in actual operation was closer to the average of these 
two “bouncing” numbers (ie -2000000 in your case).
Never figured out why, and posted a question here and received no answers.  
Stepped utility block was 15 mins, didn’t have any weird temperature 
setpoints, etc.
Ultimately I don’t think these warning messages are too concerning, but I 
also know NEVER to use eQuest to do my load calcs for maximum 
heating/cooling equipment sizing.
GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA 22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
703-276-1376 (Fax)
From: equest-users-bounces at lists.onebuilding.org 
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Josh 
Sent: Wednesday, May 06, 2009 2:07 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Hot water loop demand and boiler sizing
Energy Modelers,
I am getting the following warning message when I type in the actual boiler 
“Hot Water Loop:  the heating capacity is smaller than the secondary 
demand.  Primary = -2000000 and Secondary = -2992234.”
If I let eQuest size the boilers, everything is fine…so I know it has to 
do with me putting in the actual boiler capacity for the proposed design.  
However, the issue here is there is no way the max heating demand is almost 
-3.0 MBh as it states in the warning message.  I can not figure out where 
eQuest is getting this number; especially since the SS-D report (which 
should tell me the absolute max load demand on the building HVAC system – 
including outside air) says the maximum heating load is -1035.026 MBh.  Can 
anyone please help me determine why I am getting this error, where the 
-2992234 number is coming from, and if the SS-D report really is the actual 
maximum HVAC load demand?  Thanks everyone for their help. Your time is very 
much appreciated.
Josh Doherty
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