[Bldg-sim] ASHRAE systems exception B interpretation

[Jim Dirkes]

Veronica,
I'm not sure if I understand your problem, but the exceptions for
non-predominant HVAC sytems are based on
"Peak thermal loads that *differ *by xx W/m2 or more from the average of
other spaces..."

Thus, if all zones are 30 W/m2, they should be modeled with the normal
Baseline HVAC.  If, however, one or more zones is 15W/m2 or 50 W/m2, you
have justification for using Systems #3 or #4.

On Tue, Oct 13, 2015 at 11:37 AM, Veronica Ochoa <
veronica.ochoa at hurleypalmerflatt.com> wrote:

> Hi,
>
>
>
> I’m modelling a data center with 50 thermal zones for LEED EAp2/c1
> purposes. The baseline system determined based on area and building type is
> system 8. However when doing the load deviation average to determine
> suitability for System 4 (under exception B), all but 6 zones are greater
> than the 31 W/m2 of the averaged cooling load per system/floor. This means
> that I will have 6 zones (2.5% of total area) as system 8 and 44 zones as
> system 4. Do I need to follow the exception that says that each zone served
> by System 4 should be modelled as one zone per system?? I find this a bit
> too much… I was wondering if you can simplify this by grouping similar
> spacetypes by setpoints or floors and reduce the number of systems.
>
>
>
> Also, in the preliminary submission 100% of the zones were submitted as
> system 4, but this was noted by the USGBC reviewer as an error (as it was
> based on the average of the entire building not per system). As it has been
> now corrected and only 2.5% of the zones will be system 8, we are
> estimating the difference will be negligible. Would a narrative explaining
> this suffice? Has anyone been in this situation and how did you approach
> it?
>
>
>
> Many thanks in advance for your help,
>
> Veronica Ochoa
>
> Consultant
>
> *hurleypalmerflatt*
>
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> veronica.ochoa at hurleypalmerflatt.com
>
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-- 

James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
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