[Equest-users] Excessive summer heating

Daniel Knapp danielk at arborus.ca
Fri Mar 6 11:28:36 PST 2015


Hi Amy,

If the system is a constant volume system providing 100% OA at a relatively low temperature the model may be behaving as expected, i.e. the system may be designed such that it causes significant reheat with air that is too cold for comfort (with the supply temperature limited by the needs of the warmest zone, say to 55-60ºF) being delivered to the rooms. If this is the case, then I would suggest you reply to the comment with a description of the system being modelled and explain why there is excess reheat. Given that the reheat is penalizing the proposed model (i.e. costing LEED points), it probably won’t be a sticking point for the review. 

That said, I’m wondering what the rationale is for modelling a 4-pipe fan coil system with 100% OA as a VAV system with a constant supply air flow rate. Is the VAV system meant to be a make-up air system supplying fresh air to the corridors? I’m thinking that in a 4-pipe fan coil system the make-up air system would typically be designed to deliver tempered air at 65-75ºF with the fan coils in each zone providing additional cooling or heating as needed, in which case there should be no need for reheat. Can you try changing the cooling setpoint for the VAV systems to a maximum reset temperature of 65-70ºF? Would this be in accordance with the design? 

All the best,
Dan

—
Daniel Knapp, PhD, PPhys, LEED® AP O+M
danielk at arborus.ca

Arborus Consulting
Energy Strategies for the Built Environment
www.arborus.ca
76 Chamberlain Avenue 
Ottawa, ON, K1S 1V9 
Phone: (613) 234-7178 ext. 113
Fax: (613) 234-0740




> On Mar 6, 2015, at 1:07 PM, Coles Jennings <C.Jennings at ha-inc.com> wrote:
> 
> Amy,
>  
> Even though it is 100% OA, is it constant volume? The min-flow-ratio applies to total supply air for each zone, not just outside air. If min-flow-ratio is set to 1.0, then the VAV unit will never reduce its supply flow and you will certainly  have a lot of summer reheat.
>  
> Thanks,
> 
> Coles Jennings, PE, BEMP, LEED AP BD+C 
> Senior Associate 
> Sr. Energy Engineer, Building Sciences Studio Manager 
> 
> H&A | Hankins & Anderson | www.ha-inc.com 
> d: (804) 521-7045 p: (804) 285-4171 f: (804) 217-8520 
> 
> From: Harmon, Amy [mailto:aharmon at sbmce.com] 
> Sent: Friday, March 06, 2015 12:51 PM
> To: Coles Jennings; Singhal, Harshul; equest-users at lists.onebuilding.org
> Subject: RE: Excessive summer heating
>  
> Hi Coles!
> I have a 100% OA unit.  I had to increase the reheat to decrease unmet heating hours.
>  
> Amy Harmon 
> Mechanical Engineer
> Scheeser Buckley Mayfield LLC                                   
> 1540 Corporate Woods Parkway
> Uniontown, OH 44685
> Phone: (330) 896-4664 ext. 107
> Direct: (330) 526-2707
> Fax: (330) 896-9180
>  
> From: Coles Jennings [mailto:C.Jennings at ha-inc.com] 
> Sent: Friday, March 06, 2015 11:41 AM
> To: Harmon, Amy; Singhal, Harshul; equest-users at lists.onebuilding.org
> Subject: RE: Excessive summer heating
>  
> Amy,
>  
> The min-flow-ratios for your VAV zones are 1.00, meaning airflow is never reduced to those spaces. Check the “Air Flow” drop-down in the air-side zone spreadsheet, and check the Min Flow Ratio column. This explains the high amount of summer reheat. 
>  
> Also, your VAV reheat coils are set to 50°F reheat delta T, which is very high.
>  
> Thanks,
> 
> Coles Jennings, PE, BEMP, LEED AP BD+C 
> Senior Associate 
> Sr. Energy Engineer, Building Sciences Studio Manager 
> 
> H&A | Hankins & Anderson | www.ha-inc.com 
> d: (804) 521-7045 p: (804) 285-4171 f: (804) 217-8520 
> 
> 
> From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Harmon, Amy
> Sent: Friday, March 06, 2015 11:29 AM
> To: Singhal, Harshul; equest-users at lists.onebuilding.org
> Subject: Re: [Equest-users] Excessive summer heating
>  
> Hi Harshul!
> Thanks for the response, it’s not the unmet heating hours I’m too concerned about it unless something I did previously has caused the summer excessive heating. 
> The LEED reviewers commented that report PS-A & PS-B showed an excessive amount of heating during the summer months…in the month of July the heating load of 269 MBTUs of heating roughly 20.9% of the total heating and cooling load (269 MBTU + 1018.7 MBTU).
>  
> Amy Harmon 
> Mechanical Engineer
> Scheeser Buckley Mayfield LLC                                   
> 1540 Corporate Woods Parkway
> Uniontown, OH 44685
> Phone: (330) 896-4664 ext. 107
> Direct: (330) 526-2707
> Fax: (330) 896-9180
>  
> From: Singhal, Harshul [mailto:HSinghal at ThorntonTomasetti.com] 
> Sent: Friday, March 06, 2015 10:32 AM
> To: Harmon, Amy; equest-users at lists.onebuilding.org
> Subject: RE: Excessive summer heating
>  
> Hi Amy,
>  
> The current model (you sent) has 172 unmet load hours coming from zone: “EL5 SSW Perim Zn (G.SSW2)”
>  
> I gave a real quick look at model and as per LEED it looks fine to me. DO you mean to decrease these unmet load hours or you already made changes and sent the model here at eQuest group?
>  
> I would say check SS-R report and see what zones have unmet load hours & you can increase supply CFM in those particular zones.
>  
> Best,
> Harshul Singhal, LEED AP BD+C 
> Project Consultant 
> Thornton Tomasetti 
> 386 Fore Street, Suite 401 
> Portland, ME  04101 
> T +1.207.245.6060  F +1.207.245.6061   
> D +1.207.245.6074   
> HSinghal at ThorntonTomasetti.com 
> www.ThorntonTomasetti.com
>  
> From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Harmon, Amy
> Sent: Friday, March 06, 2015 9:58 AM
> To: equest-users at lists.onebuilding.org
> Subject: [Equest-users] Excessive summer heating
>  
> I received comments back from the LEED reviewers; they comment that I have excessive summer heating.  Prior to submitting to USGBC, I had already fooled with the throttling range and system cooling control to warmest.  Tweaking those helped with the unmet heating hours I had previously.  Could messing with those 2 items before have caused the excessive summer heating?  Any suggestions to lower the excessive summer heating?  I’ve attached the inp and pd2 file.  I’m running version 3.64.
> Any help is appreciated.  Thanks!
>  
> Amy Harmon 
> Mechanical Engineer
> Scheeser Buckley Mayfield LLC                                   
> 1540 Corporate Woods Parkway
> Uniontown, OH 44685
> Phone: (330) 896-4664 ext. 107
> Direct: (330) 526-2707
> Fax: (330) 896-9180
> aharmon at sbmce.com
> www.sbmce.com
>   
> Please consider the environment before printing this email. This e-mail (including any attachments) is confidential and may be legally privileged. If you are not an intended recipient or an authorized representative of an intended recipient, you are prohibited from using, copying or distributing the information in this e-mail or its attachments. If you have received this e-mail in error, please notify the sender immediately by return e-mail and delete all copies of this message and any attachments. 
>  
> Thank you 
>  
>  
> <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><> 
>  
> The information in this email and any attachments may contain
>  
> confidential information that is intended solely for the
>  
> attention and use of the named addressee(s). This message or
>  
> any part thereof must not be disclosed, copied, distributed
>  
> or retained by any person without authorization from the
>  
> addressee. If you are not the intended addressee, please
>  
> notify the sender immediately, and delete this message.
>  
> <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><> 
>  
>  
> _______________________________________________
> Equest-users mailing list
> http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
> To unsubscribe from this mailing list send  a blank message to EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG



More information about the Equest-users mailing list