[Bldg-sim] FW: Residential or Nonresidental? And sizing for PTAC units.

[Loren Appin]

Thank you both Andrew and Keith,

Understanding the exceptions, and also correct calculations for the EER
(didn't realize there was a limit of 15,000 BTU for the calculation until I
read the small print!) are very helpful.  It brings up another question,
now, though:

When modeling a PTAC unit, and taking this EER value, would you use this to
include the supply fan energy?  G.3.1.2.1 states that you should separate it
into various components, which confuses me a bit.  I know this is getting
down to minutia, however, just trying to make sure I'm doing this
correctly.  If this is something that is common practice to look over, and
just make sure to include the supply fan efficiencies within the EER for
entire unit (something that would make sense to me as it is a packaged
unit), also let me know.

Thanks again,

Loren

On Mon, Mar 10, 2008 at 6:35 PM, Keith Swartz <kswartz at ecw.org> wrote:

>  Loren,
>
>
>
> One of the notes under Table G3.1.1A of ASHRAE 90.1-2004 states,
> "Residential building types include dormitory, hotel, motel, and
> multifamily. Residential space types include guest rooms, living quarters,
> private living space, and sleeping quarters. Other building and space types
> are considered nonresidential." The User's Manual also says, "If a building
> has both residential and nonresidential spaces, for instance a residential
> tower with retail and restaurants at the base, then the HVAC system type is
> determined separately for the residential and nonresidential portions."
>
>
>
> I recently did an energy model for a motel that had first floor retail
> spaces, a swimming pool, an indoor parking garage, and a fairly large lobby.
> I used realistic systems for these spaces instead of PTACs or PTHPs. For a
> different motel I modeled, the nonresidential spaces were rather
> insignificant, so I used PTHPs throughout.
>
>
>
> Regarding which capacity to use for the EER calculation, I would use
> realistic capacities. For example, for the space that needs 40 kBTU/h, I
> would assume that there would be two 20 kBTU/h units and use 20 kBTU/h for
> the capacity in the EER equation.
>
>
>
> I think the decision to use an average EER for all the units is a judgment
> call depending on how complex you want your model to be. It's the usual
> trade-off between making assumptions to simplify the model or adding
> complexity to get more accuracy (presumably).
>
>
>
> Sincerely,
>
> Keith Swartz, PE, LEED(R) AP
>
> Energy Center of Wisconsin
>
> 455 Science Drive
>
> Suite 200
>
> Madison, WI 53711
>
>
>
> Phone: 608-238-8276 ext. 123
>
> Fax:     608-238-0523
>
> www.ecw.org
>
> The Energy Center of Wisconsin is an independent, nonprofit organization
> that seeks solutions to energy challenges.
>   ------------------------------
>
> *From:* Loren Appin [mailto:lorenappin at gmail.com]
> *Sent:* Sunday, March 09, 2008 3:31 AM
> *To:* bldg-sim at lists.onebuilding.org
> *Subject:* [Bldg-sim] Residential or Nonresidental? And sizing for PTAC
> units.
>
>
>
> Hi All,
>
> I'm modeling a 6 story hotel, and am confused with how I should classify
> the building.  The hotel is all guest rooms, and is not really mixed use.
> So according to ASHRAE this seems that it would fall under the residential
> category, and I would be using PTAC or PTHP systems.  Under table G3.1.1Ait specifically says hotels are considered residential building types, not
> just space types... so I assume I'm correct?   However, would I use a VAV or
> PSZ system for areas that are not technically guest rooms, or does this not
> matter as a hotel is considered a residential "building type"?
>
>
> Also, when modeling a PTAC system it appears to me that you would get the
> EER information from 6.8.1D using the equation, however, sometimes it my
> system summary gives me a peak/capacity of a unit as 30KBtu or even 40 for
> one room and I know that PTAC units usually don't go much about 20.  So
> would the equation in this table still hold?  Finally, if I am getting
> varying capacities for each unit as would be expected, would you suggest
> taking an average of all the systems, and then use this capacity as the one
> to enter into the equation to get the EER and then apply this EER to all
> systems across the board?
>
> Thanks so much for the help!
>
> *Loren Appin*
>
> Energy Engineer
>
> *Silpa Inc.*
> s i m p l e  .  s c i e n t i f i c   .   s u s t a i n a b l e
>
> AMERICAS | MIDDLE EAST | INDIA
>
> www.silpa.com | Mob: +971.50.9250895
>
>
>
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-- 
Loren Appin
loren.appin at gmail.com | +971.50.9250895
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