[Equest-users] Loop flow control in WLHP

[Karen Walkerman]

I have further found that the low differential temperatures between supply
and return happens when the loop is in heating mode only.  When the loop has
a cooling only load, the temperature differentials are as expected (I can
send a test file directly if anyone is interested).

If the pump is cycling, then this should help maintain a higher difference
in supply and return temperatures.

--
Karen

On Tue, Nov 24, 2009 at 1:51 PM, Steven Gates <stvgates at pacbell.net> wrote:

>  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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