[Equest-users] electric heating issues

Carol Gardner cmg750 at gmail.com
Thu Mar 24 11:40:41 PDT 2011


Hi Will,

Sorry to say but I agree with Rob and Bill. If you are providing heated hot
water to the baseboards then you are using a hybrid system. Maybe I am
missing something, but it seems pretty clear.

Carol

On Thu, Mar 24, 2011 at 11:10 AM, Will Mak <wmak at epsteinglobal.com> wrote:

> I thought the heating system only referred to the heating source itself?
> (not including preheat fuel source??)
>
>
>
> *William Mak, LEED Green Associate*
> Mechanical Design Engineer
>
> *EPSTEIN*
> Architecture
> Interiors
> Engineering
> Construction
>
> 600 West Fulton Street
> Chicago, Illinois 60661-1259
>
> D: (312) 429-8116
> F: (312) 429-8800
>
> E: wmak at epsteinglobal.com
> W: www.epsteinglobal.com
>
> þ Epstein is a firm believer in sustainability. We ask that you please
> consider the environment before printing this e-mail.
>
>
>
> *From:* Rob Hudson [mailto:rdh4176 at gmail.com]
> *Sent:* Thursday, March 24, 2011 12:23 PM
> *To:* Will Mak
> *Cc:* Bishop, Bill; equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] electric heating issues
>
>
>
> as per the baseline system discussion, i would use System 5.  If you read
> the 90.1 manual, it says if you use a fossil/electric hybrid heating system
> to implement System 5 in the baseline.
>
>
>
>
>
> Rob
>
>
>
>
>
> On Thu, Mar 24, 2011 at 12:14 PM, Will Mak <wmak at epsteinglobal.com> wrote:
>
> See comments below, thanks!
>
>
>
> *William Mak, LEED Green Associate*
> Mechanical Design Engineer
>
> *EPSTEIN*
> Architecture
> Interiors
> Engineering
> Construction
>
> 600 West Fulton Street
> Chicago, Illinois 60661-1259
>
> D: (312) 429-8116
> F: (312) 429-8800
>
> E: wmak at epsteinglobal.com
> W: www.epsteinglobal.com
>
> þ Epstein is a firm believer in sustainability. We ask that you please
> consider the environment before printing this e-mail.
>
>
>
> *From:* Bishop, Bill [mailto:wbishop at pathfinder-ea.com]
> *Sent:* Thursday, March 24, 2011 10:21 AM
> *To:* Will Mak; equest-users at lists.onebuilding.org
> *Subject:* RE: [Equest-users] electric heating issues
>
>
>
> Will,
>
>
>
> The first thing I would do is reconsider your selection of System 6 for the
> Baseline. Since you have gas boilers for preheat, I would choose System 5.
> System 6 is all electric, but you say your baseline gas consumption is high,
> so you are currently modeling gas boiler(s) in the baseline. Unfortunately,
> if you go with System 5, your baseline reheat will be hot water which will
> save cost versus your proposed design.
>
>
>
> *Yes, I am modeling the gas boilers in the baseline purely for preheating.
> So you are saying that because I am modeling gas boilers (even though they
> are just for preheat), I technically can run with System #5 for my baseline
> model?*
>
>
>
> Since both your baseboards and your reheat are electric in the proposed
> design, your high electric use is probably not a baseboard control issue
> (provided you are not showing many unmet load hours). One thing to consider
> is your preheat leaving temperature – making it higher will favor the gas
> boilers and reduce the zone electric heating. I’m guessing that the
> requirement for identical preheat coil control in G3.1.2.3 means that you
> use the same preheat leaving temperature in the baseline and proposed
> models.
>
>
>
> *I currently have both models at minimum leaving temperatures for preheat
> of 60F (which is the design preheat leaving air temp). You would think that
> because the preheat is pumping out 60F air to the VAV boxes, you would see
> similar zone heating requirements. However, the proposed design’s zone
> heating is much higher. Could it possibly be the parallel fan powered boxes
> that help the baseline model that much?*
>
>
>
> Make sure you are modeling your ventilation identically between the
> baseline and proposed models, unless you have DCV.
>
>
>
> *Yup, I have the same OA cfms for both models*
>
>
>
> Check your reports to make sure you don’t have a lot of simultaneous
> heating and cooling going on. Maybe you can increase the cooling supply
> temperature (and convince the HVAC designer to do it) to the highest
> allowable temperature that meets cooling and dehumidification loads.
>
>
>
> *Currently, I have the cooling supply temp at 52.5 F. This was because the
> design engineer wanted to take advantage of the efficiency of the chillers
> on the project for cooling energy savings. Perhaps this could be the issue?
> The cooling temperature is too low that it triggers the reheat/baseboard to
> kick on all the time??*
>
>
>
> Your baseline may have similar, or even less, heating load depending on the
> proposed envelope, due to the reduced lighting load in the proposed design.
> With electric baseboard and electric reheat, it will be difficult to show
> much heating savings unless you have a much better envelope or ventilation
> heat recovery. We should all be red-flagging electric reheat and baseboards
> whenever we see them on projects.
>
>
>
> *So you are saying that electric heat/reheat is bad for 90.1 PRM??*
>
> * *
>
> *Thanks for the response!*
>
>
>
> Regards,
>
> Bill
>
>
>
> *William Bishop, PE, BEMP, LEED® AP **|** Pathfinder Engineers &
> Architects LLP*
>
> Mechanical Engineer
>
>
>
> *Error! Filename not specified.*134 South Fitzhugh Street
> Rochester, NY 14608
> T: (585) 325-6004 Ext. 114                F: (585) 325-6005
>
> wbishop at pathfinder-ea.com           www.pathfinder-ea.com
>
> P   Sustainability – the forest AND the trees. P
> ------------------------------
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Will Mak
> *Sent:* Thursday, March 24, 2011 10:31 AM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] electric heating issues
>
>
>
> Hello all,
>
>
>
> I currently modeling a project for LEED NC v2009 submission for a corporate
> office building that’s roughly 125,000 SF. The proposed design’s primary
> HVAC system are AHUs + VAVs w/Electric Reheat supplemented with electric
> baseboard along hot water preheat generated from gas boilers. This system
> also uses chilled water with very efficient chillers from a DES. The
> baseboard is suppose to take care of the envelope loads and the VAV electric
> reheat coils will take care of the rest. Based on the size of the building,
> the baseline HVAC system shall be System #6: Packaged VAV with PFP Boxes.
>
>
>
> I’m pretty down the road on the models and for some reason cannot get
> savings between the 2 models. The heating energy use on electrical
> consumption overrides any savings attributed from lighting, site lighting,
> cooling energy use, etc. Also, I know that in 90.1-2007, preheat must be
> model identical on the proposed and baseline models. I am having a hard time
> modeling both to be the same (inputs for preheat capacity are the same but
> the energy use is different). The gas consumption is significantly higher on
> the baseline model.
>
>
>
> I double checked the loads from both models and the heating/cooling
> requirements are roughly the same so there’s nothing wrong with the building
> shell/internal load inputs. Any guidance on how to reduce the consumption on
> the heating use for electrical consumption would be great! I am confused why
> the baseline model wouldn’t require similar, if not more, heating
> requirements and isn’t using more heating use for electrical consumption.
> Also, guidance to ensure that the preheat is model identical would help too!
>
>
>
> Thanks!
>
>
>
> Cliffnotes:
>
> Proposed System: AHUs w/VAV Electric Reheat + Electric Baseboard//Chilled
> Water from DES//Hot Water Preheat
>
> Baseline System: Packaged VAV with PFP Boxes
>
> Issue #1: Heating electrical consumption is super high on proposed model
> despite similar loads for both models.
>
> Issue #2: Preheat is not being model identical as required from 90.1-2007.
> Capacity and design inputs are same for building but baseline building is
> using significantly more gas.
>
>
>
> *William Mak, LEED Green Associate*
> Mechanical Design Engineer
>
> *EPSTEIN*
> Architecture
> Interiors
> Engineering
> Construction
>
> 600 West Fulton Street
> Chicago, Illinois 60661-1259
>
> D: (312) 429-8116
> F: (312) 429-8800
>
> E: wmak at epsteinglobal.com
> W: www.epsteinglobal.com
>
> þ Epstein is a firm believer in sustainability. We ask that you please
> consider the environment before printing this e-mail.
>
>
>
>
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>
>
> --
> Rob Hudson
>
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-- 
Carol Gardner PE
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