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

[James Hansen]

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)

www.ghtltd.com <http://www.ghtltd.com/> 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Josh
Doherty
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 capacity:

 

"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

 

 

 

 

 


The information contained in this communication is confidential, may be privileged, and is intended only for the use of the addressee.  It is the property of GHT Limited.  Unauthorized use, disclosure or copying of this communication or any part thereof is strictly prohibited and may be unlawful.  If you have received this communication in error, please notify me immediately by return e-mail or by e-mail to ght at ghtltd.com, and destroy this communication and all copies thereof, including all attachments.  Thank you.



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