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

[Justin Chin]

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> wrote:

> I usually use a snap function to specify when the loop is in heating /
> cooling:****
>
> ** **
>
> ****
>
> ** **
>
> 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*
> Senior Associate
> 1010 N. Glebe Road, Suite 200
> Arlington, VA  22201-4749
> 703-243-1200 (office)****
>
> 703-338-5754 (cell)
> 703-276-1376 (fax)****
>
> www.ghtltd.com****
>
> ** **
>
> *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 5:06 PM
> *To:* 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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