[Bldg-sim] 2 Pipe System Heating/Cooling Change Over

[Demba Ndiaye]

Justin,

"Demand" is not adapted to 2-pipe loops. You should use either "Snap" or "Scheduled".

Note that as James pointed out, it is very difficult to figure out the correct changeover period (if it exists!) when using a schedule.

Regards,



[cid:image005.jpg at 01CE2407.2CA11BD0]Demba Ndiaye, Ph.D., P.E., LEED AP BD+C, BEMP
Senior Energy Analyst/Mechanical Engineer

Setty & Associates, Ltd.

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From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Justin Chin
Sent: Monday, March 18, 2013 5:22 PM
To: James Hansen; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] 2 Pipe System Heating/Cooling Change Over

I could model it as snap, but I would still get some unmet hours for certain days.  So far modeling as demand operation seems to be satisfying the thermostat settings in the summer, but I just can't figure out why heating isn't turned on.  And the model does have to meet LEED requirements.
On Mon, Mar 18, 2013 at 5:12 PM, James Hansen <JHANSEN at ghtltd.com<mailto:JHANSEN at ghtltd.com>> wrote:
I usually use a snap function to specify when the loop is in heating / cooling:

[cid:image001.png at 01CE2406.9392FAD0]

By the way, I've modeled a few 2-pipe systems (in the DC area) before, and it is nearly impossible to get the unmet load hours below 300 for the average building (without significantly relaxing the thermostat setpoints, or having supplemental heating/cooling systems).  Hopefully you are not modeling this for LEED purposes!

GHT Limited
James Hansen, P.E., LEED AP
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703-338-5754<tel:703-338-5754> (cell)
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www.ghtltd.com<http://www.ghtltd.com/>

From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org>] On Behalf Of Justin Chin
Sent: Monday, March 18, 2013 5:06 PM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] 2 Pipe System Heating/Cooling Change Over

Hello eQuesters,

  I am trying to model a two pipe system with a demand operation loop for a residential building in Maryland.  Currently, my two pipe system turns on cooling when the zones are calling for cooling as expected, however it never changes over to heating during the winter.  It is always either off, or on very rare occasions cooling, resulting in high unmet heating hours.  Can some one explain how the two pipe system determines when to change from heating to cooling mode?

I've looked at the zones they are definitely below the heating throttling range.  Does eQuest take a sum of the room loads on the loop to determine to heat or to cool?

Your help is greatly appreciated.

Thanks!
Justin

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