[Bldg-sim] sizing for baseline case acc to App. G

[Chris Yates]

So does that mean, for an all air system, off-coil temperature is 
actually lower in cooling and higher in heating for the startup period?
Chris

On 24/06/2010 12:16, Seth P. Spangler wrote:
>
> Vinay,
>
> You are to increase the cooling/heating coil capacities as required by 
> ASHRAE Appendix G. However, the over sizing is for coil capacity only 
> -- the airflow rate should be sized at 100% of what your energy 
> modeling program calculates as being required to meet the space load.
>
> Thanks
>
> Seth Spangler, LEED® AP
>
> RMF Engineering, Inc
>
> Ph: (843) 971-9639 ext:1497
>
> Fax: (843) 971-9641
>
> sspangle at rmf.com
>
> *From:* bldg-sim-bounces at lists.onebuilding.org 
> [mailto:bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *James V 
> Dirkes II, PE
> *Sent:* Wednesday, June 23, 2010 7:16 PM
> *To:* 'Vinay Devanathan'; bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] sizing for baseline case acc to App. G
>
> Dear Vinay,
>
> I'm not sure of the rationale for the ASHRAE 90.1 oversizing 
> requirements, however here are my thoughts:
>
> · I think the principal engineering rationale for oversizing is to 
> allow a building to reach its setpoint temperature quickly after a 
> period of inactivity.  As an example, if a building is inactive during 
> a holiday and the temperature is allowed to float several degrees 
> lower (in winter), the additional 25% heating capacity will enable 
> faster return to the normal setpoint temperature.  Steam heating 
> systems can need even more capacity for proper warmup capacity.
>
> · Oversizing is also a common practice as a "safety factor".  Most 
> load calculation software even has a separate input for adding this 
> "safety factor".
>
> *The Building Performance Team
> James V. Dirkes II, P.E., LEED AP
> *1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
>
> *From:* bldg-sim-bounces at lists.onebuilding.org 
> [mailto:bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Vinay 
> Devanathan
> *Sent:* Wednesday, June 23, 2010 10:00 AM
> *To:* bldg-sim at lists.onebuilding.org
> *Subject:* [Bldg-sim] sizing for baseline case acc to App. G
>
> Hello All,
>
> Just to clarify a point -
>
> What does the oversizing of capacities by 15% for cooling and 25% for 
> heating exactly mean? Do we only size the cooling and heating capacity 
> or also increase the airflow rate corresponding to the oversizing?
>
> Thank you.
>
>
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