[Equest-users] Loop flow control in WLHP

[Steven Gates]

Doug/Karen,

 

Check out CIRCULATION-LOOP:LOOP-OPERATION = SUBHOUR-DEMAND

 

For a loop of type WLHP or CW only, this control strategy will cause the
loop pump to cycle subhourly in accordance with the cycling demands of the
attached WLHP/DX units.  However, it will not affect the operation of a
boiler/fluid-cooler that may also be attached to the loop; those components
are assumed to run for the entire hour.

 

Steve Gates

 

  _____  

From: Doug Maddox [mailto:DougM at TWGI.com] 
Sent: Tuesday, November 24, 2009 9:45 AM
To: steve.gates at doe2.com
Subject: Loop flow control in WLHP

 

Steve,

 

I saw the email below posted on the eQuest email list.  I checked it out in
a test run and found the same problem.  My guess as to the cause is that if
a heat pump runs for a fraction of an hour, water valve is modeled as fully
open for that entire hour, resulting in excessive flow.  Could that be the
cause?  If so, is there a simple solution?

 

Thanks, 

Doug Maddox

The Weidt Group

802-262-1033

 

  _____  

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Karen
Walkerman
Sent: Friday, November 20, 2009 2:12 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Loop Operation

 

Hi All,

I'm having some issues with loop and pump operation in eQuest.

I have tested this issue with water loop heat pump loops.  Basically, I set
my loop design DT, but for many hours, the loop operates at very low
temperature differentials.  With the given load on the loop, this requires a
high flow, and results in high pump energy!

Specifically, for a heat pump loop, I'm expecting a 7-10 F difference in
supply and return temperatures at all times.  I just ran a test model with a
loop design DT specified at 10 F.  For hours when there is a heating only
load on the loop, I have an average difference in supply and return
temperatures of about 3 degrees.  This requires the pump to move about 3
times more water than necessary.  My system is modeled with variable speed
pumps, and isolation valves at each heat pump.

Any suggestions are greatly appreciated!

Thanks,

--
Karen

    
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