[Bldg-sim] Condensing Boilers for DHW

[Robby Oylear]

The only challenge I found in modeling DHW with a hot water loop was the
incoming water temperature being based on return water temperature,
however by adjusting the DT and supply temperature on the process load I
think I've approximated it properly.  

 

I ran two loops, one a DHW loop and one a HW loop and found them to be
within 1% of each other.  Then when I switched the HW boiler over to a
condensing boiler I found a 14% savings.  Finally, to verify that the
condensing boiler was operating correctly, I increased the supply T so
that the return water temp would be around 110.  After doing this the
results came within 1% of each other again. 

 

Sounds like this is the way to go for modeling a condensing boiler for
DHW. 

 

Robby Oylear, LEEDR AP

Mechanical Engineer

direct: 206.788.4571

cell: 206.354.2721

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

 

From: Robby Oylear [mailto:robbyo at rushingco.com] 
Sent: Tuesday, July 14, 2009 1:37 PM
To: 'bldg-sim at lists.onebuilding.org'
Subject: Condensing Boilers for DHW

 

With the release of eQUEST 3.63b we are given the option to model
Condensing Gas-Fired Boilers for hot water heating.  However, domestic hot
water can still only be modeled by simplistic DW Heaters which have
options only for Electric, Gas, & Steam.

 

Would it make sense to just model the DHW loop as a HW loop with a process
load equal to the service hot water demand or is there some fundamental
reason why a hot water loop shouldn't be used as a domestic loop in
eQUEST?

 

Any input is appreciated.  Thanks.

 

Robby Oylear, LEEDR AP

Mechanical Engineer

direct: 206.788.4571

cell: 206.354.2721

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

Logo_B&W_1

 

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