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

[Keith Swartz]

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 <http://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 G3.1.1A it 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 <http://www.silpa.com/>  | Mob: +971.50.9250895

 

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