[Equest-users] RV: excessive underheating

Keith Swartz kswartz at ecw.org
Thu Nov 13 07:16:24 PST 2014
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Dante,

Keep in mind that the reheat deltaT in Screen 6 of 7 of the Airside System part of the DD Wizard is the change in the supply air temperature, not the change in the coil water temperature. See the Help screen.

Keith Swartz, PE, BEMP, LEED AP
Senior Energy Engineer | Energy Center of Wisconsin | Madison.Chicago.Minneapolis
608.210.7123 | www.ecw.org<http://www.ecw.org/>

From: Dante Garcia [mailto:dgarcia at sumacinc.com]
Sent: Wednesday, November 12, 2014 11:46 AM
To: John Aulbach (jra_sac at yahoo.com<mailto:jra_sac at yahoo.com>); equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] RV: excessive underheating

John,

The report that I sent to you was considering dT= 20 F in the reaheat option (Air-side System), in that case underheating issues is solved, but cooling demand in increased tremendously and I do not how to solve that issue, here the reports:
The SS-R report shows that there are no unmet load hours :
[cid:image005.jpg at 01CFFF22.7F1C3640]


The problem is that the cooling capacity is too high (625 ton). The proposed design has a 75 ton chiller, but the autosize baseline design has a 625 tons (7501 kBtu/h) DX cooling capacity.

[cid:image006.jpg at 01CFFF22.7F1C3640]

I also had a lot of trouble trying to meet heating load hours, and could only satisfy them by putting dT=20F in the reaheat option. If I put less dT or more dT the unmet load hours increase.
[cid:image007.jpg at 01CFFF22.7F1C3640]

The warning still appears for most of the zones though (even if with no unmet load hours):
[cid:image008.jpg at 01CFFF22.7F1C3640]


When fulfilling the heating hours (with reheat dT= 20F), the cooling capacity raised dramatically. Thus, heating and cooling seem to be correlated, but I can't find why the cooling capacity is so high for a 37230 gross sq ft building.

Thanks for your help!

Dante

De: John Aulbach [mailto:jra_sac at yahoo.com]
Enviado el: lunes, 10 de noviembre de 2014 03:52 p.m.
Para: Dante Garcia
Asunto: Re: [Equest-users] excessive underheating

Dante:

I ran your model and do not see where you are underheating at all !! I checked SS-R and it indicates all zones are neither undercooled or under heated.

Can you send me a screenshot of your SS-R reports?

John

On Monday, November 10, 2014 10:59 AM, Dante Garcia <dgarcia at sumacinc.com<mailto:dgarcia at sumacinc.com>> wrote:

Hi John,

Here in Attached INP and PD2 files,

I have tried your recommendations before without success, eQuest version is 3-65.

Thank you!

SUMAC
Dante Garcia, LEED AP BD+C | Analista LEED Energía
Tel: +511.253.5355 Anexo 16 (Lima, Perú)
Cel: +51.989.685.769 (Lima, Perú)
Tel: +593.4.600.0613 (Guayaquil, Ecuador)
Tel: + 571.3151985 (Bogotá, Colombia)
Tel: +1.773.857.7906 (Chicago, USA)
dgarcia at sumacinc.com<mailto:dgarcia at sumacinc.com>
www.sumacinc.com<http://www.sumacinc.com/>



De: John Aulbach [mailto:jra_sac at yahoo.com]
Enviado el: viernes, 07 de noviembre de 2014 06:31 p.m.
Para: Dante Garcia; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Asunto: Re: [Equest-users] excessive underheating

Hi Dante:

It always helps to include your .INP and .PD2 files on your email to this forum, so experts can help you.

Without seeing anything more, I would increase the deadband in your deadband thermostat from 2 to 4 06 6 DegF. I would also set the the COOL-CONTROL to WARMEST.

Otherwise, please attach your files. And let us know which version of eQuest you are using.

John R. Aulbach, PE
Los Angeles CA USA

On Friday, November 7, 2014 2:14 PM, Dante Garcia <dgarcia at sumacinc.com<mailto:dgarcia at sumacinc.com>> wrote:

Good Day eQuest-users,

I apologize if anyone can help me in the following use, there is a VAV with reheat system, DX cooling and Hot Water Reheat. The Hot Water reheat is supplied by a boiler. The building is one floor with perimeter and core zones.

The following issue cause excessive unmet load hours in heating, I figure out that changing Heat/Rehat: Hot Water delta F from 30 F to 20 F reduce unmet load hours but cooling capacity is increased tremendously, also the following warning is maintained.

Please, any of you have go ahead with the following warning?

**WARNING**********************************************************************
             ZONE EL1 WSW Zone (fG.z1)
             might have insufficient heating capability.
             Check that the SYSTEM or ZONE HEATING-CAPACITY plus this
             ZONEs BASEBOARD-RATING is adequate to maintain the ZONE
             specified DESIGN-HEAT-T for the calculated peak ZONE load
             (see LS-A or LS-B for the ZONE peak load.)

             SYSTEM S1 Sys (PVAVS)
             which supplies the above listed ZONE, has a design heating
             coil exit temperature, HEAT-SET-T,(plus any zone reheat)
             below its MAX-SUPPLY-T or the ZONE DESIGN-HEAT-T, which
             might account for the insufficient heating capability.

             ZONE EL1 WSW Zone (fG.z1)             has a THERMOSTAT-TYPE
             of REVERSE-ACTION, which, when added to the issues listed
             in the messages above, will cause excessive underheating.

Thank you!

SUMAC
Dante Garcia, LEED AP BD+C
Tel: +511.253.5355 Anexo 16 (Lima, Perú)
Cel: +51.989.685.769 (Lima, Perú)


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