[Equest-users] Baseline Fan power calculation

[Nick Caton]

Both models should indeed match with respect to thermostat setpoints.

With respect to model documentation, it would be totally appropriate to clearly state the design setpoint (71.6), 20 degree SAT difference mandate, and supply CHW temperature, together result in a conflict with the energy modeling software.  Raising both models' set points uniformly to 75 would be a very appropriate fix given the circumstances.

That said, I would not discount the potential effects of fan heat however, as Steve suggested to investigate.  The temperature flagged by this particular error (cooling coil leaving) can be directly affected by the presence and location of a fan in the airstream.  If you are currently specifying draw through, the coil leaving temperature will be pushed downward from your specified LAT by the degrees the fan raises... whereas if the fan is blow through it doesn't affect the required leaving coil temperature to meet the specified LAT... This is admittedly hard to put to words, but it makes more sense if you sketch it out.   If I'm not mistaken, I don't believe 90.1 cares where the baseline fans are located with respect to the coils, so long as the other specified parameters are met, and this distinction has made the difference for me in the past to avoid this particular error in the most simple fashion.

~Nick

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Hala Jaber
Sent: Wednesday, January 22, 2014 3:44 PM
To: James Hansen; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Baseline Fan power calculation

James,
Do you think that i can set the thermostat set point to 75 for baseline only, i think the baseline and proposed design should have the same indoor temp, if i can do that this will help since i dont have problem in this small amount of saving that may differ.
thank you james.

On Thu, Jan 23, 2014 at 12:38 AM, James Hansen <JHANSEN at ghtltd.com<mailto:JHANSEN at ghtltd.com>> wrote:
If it was me, I'd just set the space temperature to 75 degrees, knowing that the difference between that and 71.6 degrees probably won't make a huge difference in the savings between baseline and proposed.

I thought I remember seeing something from Jeff Hirsch a while back that showed how to de-activate this particular alarm so that the model would run??

GHT Limited
James Hansen, PE, LEED AP, BEMP
Senior Associate
1110 N. Glebe Road, Suite 300
Arlington, VA 22201
703.243.1200 (main)
703.338.5754 (direct/cell)
www.ghtltd.com<http://www.ghtltd.com>

From: Hala Jaber [mailto:halajaber82 at gmail.com<mailto:halajaber82 at gmail.com>]
Sent: Wednesday, January 22, 2014 4:30 PM
To: James Hansen; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Baseline Fan power calculation

Dear James, thank you, but i have already set the warmest rest temp as required by section G3.1.3.12 supply air temerature reset, but still  i have the problem in the 20 degree difference between the 71.6 and the cooling coil supply temp.
I hope if this clarify more my question.


Hala Jaber.

Sustainable Design Engineer.; LEED AP BD +C .

+962-79-7570197

email: halajaber82 at gmail.com<mailto:halajaber82 at gmail.com>
On Wed, Jan 22, 2014 at 11:57 PM, James Hansen <JHANSEN at ghtltd.com<mailto:JHANSEN at ghtltd.com>> wrote:
System 8 has a main AHU that feeds parallel fan powered VAV boxes.  For your main AHU, you need to make sure your cooling reset temperature for supply air (LAT) is set to "warmest".

GHT Limited
James Hansen, PE, LEED AP, BEMP
Senior Associate
1110 N. Glebe Road, Suite 300
Arlington, VA 22201
703.243.1200 (main)
703.338.5754 (direct/cell)
www.ghtltd.com<http://www.ghtltd.com>

From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Hala Jaber
Sent: Wednesday, January 22, 2014 3:56 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] Baseline Fan power calculation

Thanks James,but what do you mean by LAT, in addition to the fact that i
have modeled the chilled water supply temperature reset as per the
requirement the rest based on outdoor dry bulb temp using :44 F at 80 f and
above,  54 f at 60 f and below, so how can i compromise this since the
actual thermostat cooling set point is 71.6, and i don't have AHU in
baseline,  its system 8.
Thanks alot

--

Hala Jaber.

Sustainable Design Engineer.; LEED AP BD +C .

+962-79-7570197

email: halajaber82 at gmail.com<mailto:halajaber82 at gmail.com>

On Jan 22, 2014 8:24 PM, "James Hansen" <JHANSEN at ghtltd.com<mailto:JHANSEN at ghtltd.com>> wrote:

> If your CHW supply temp is 44F, and your LAT setpoint for the AHU is 51.6,
> then you are 6F higher.  Check your reset schedules - if you allow reset
> for CHW without also allowing reset for the AHU (both per ASHRAE), you may
> have a condition where the CHW supply is within 6 degrees of your LAT.
>
>
>
> GHT Limited
>
> *James Hansen, PE, LEED AP, BEMP*
>
> *Senior Associate*
>
> *1110 N. Glebe Road, Suite 300*
>
> *Arlington, VA 22201*
>
> * 703.243.1200 (main)*
>
> * 703.338.5754 (direct/cell)*
>
> *www.ghtltd.com<http://www.ghtltd.com/>* <http://www.ghtltd.com<http://www.ghtltd.com/>>

> Hey eQuest users,
> I have a new challanging  requirement in the appendix G section G3.1.2.8,
> its required the supply air-to room air cooling temperature difference is
> 20 degrees for each HVAC system. Now my question is how can i achieve this
> if my baseline is system 8 and the chilled water leaving temperature is
> specified 44 F with return delta t=12,at the same time that in my design
> the indoor thermostat temp=71.6 F , and the supply cooling temp should be
> 51.6F,  here when i set this value i got an error in eQuest stating that"
> the cooling coil leaving temperatures must be at least 6 F higher than
> entering water temp" and when i set the cooling supply air temp





--

Hala Jaber.

Sustainable Design Engineer.; LEED AP BD +C .

+962-79-7570197

email: halajaber82 at gmail.com<mailto:halajaber82 at gmail.com>



--

Hala Jaber.

Sustainable Design Engineer.; LEED AP BD +C .

+962-79-7570197

email: halajaber82 at gmail.com<mailto:halajaber82 at gmail.com>
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