[Bldg-sim] Conservative design cooling load calculations vs baseline sizing

[Patrick Bivona]

Hi Mike,

I can't say I'm frustrated yet. Just going through the learning curve. I'm
sure frustration will come in time!

I was musing about the potential imbalance in sizing approach between the
proposed design and the baseline design. If we assume for a second that
engineers also use ASHRAE design days when sizing equipment for the
proposed design, there is still a potentially significant difference
between schedules used for sizing and normal operation schedules. Is the
1.15 sizing factor for baseline cooling enough to cover such imbalance? I
don't know enough to say so yet.

Patrick




On 5 December 2013 20:19, Michael tillou <michael.tillou at gmail.com> wrote:

> Hi Patrick,
>
> I just wanted to clarify for you that Appendix G (G3.1.2.2.1) requires the
> simulation of sizing runs for equipment selection based on either the peak
> from the weather file or ASHRAE 99.6% heating and 1% cooling design
> temperatures.  As far as I know this is not something USGBC or GBCI has
> written a clarifying rule on for LEED.
>
> As far as being frustrated over engineers doing overly conservative load
> calculations, welcome to life as an energy analyst.  The best you can hope
> for is to use simulation to show them and the building owner that they are
> over engineering the system and try to get some concession.  Ultimately at
> the end of the day it's the engineer who is stamping the work and taking on
> the liability that has the final say.
>
> Mike.
>
> Sent from my iPad
>
> On Dec 4, 2013, at 11:17 PM, Patrick Bivona <patrick.bivona at gmail.com>
> wrote:
>
> > Hi,
> >
> > When sizing cooling equipment for apartments, the design team on my
> project used a worst case scenario approach of maxing out all internal
> loads. For instance, lighting would be on during the day, with full
> occupancy and all plug equipment running, while the sun is hitting the
> windows. Adjacent rooms would be considered without cooling.
> > For LEED, the sizing for the baseline is based on schedules representing
> typical operations for occupancy, lighting, plug, etc. That leads the
> baseline to size equipment that has smaller capacity than what considered
> for the proposed design.
> > There's an extra dimension, in the fact the design team sized equipment
> for each individual room, reaching their peak load at different times of
> the day. So the total cooling capacity is the sum of the worst possible
> scenarios. The model currently uses a single zone per apartment, with a not
> so worst case scenario.
> > How do I solve this conundrum? Am I missing something?
> > Thanks,Patrick
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