[Bldg-sim] fossil hybrid or electric

[Maria Karpman]

I think that in Morgan's case using PTHP baseline is also justified. From
what I understand, the project is a residential buildings with electrically
heated living units and gas-heated common spaces. Applying G3.1.1 to the
project, predominant conditions are residential with electricity as heat
source; non-predominant conditions are non-residential with fossil fuel
heat. Based on G3.1.1 exception (a), non-predominant conditions accounting
for less than 20,000 SF may be ignored when selecting the baseline system
from Table G3.1.1A, thus the baseline for the project is PTHP. If
residential units were served by WSHP, then predominant conditions would be
residential with Fossil/Electric Hybrid heating source, and the baseline
system would by PTAC.  

 

Maria

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Robby Oylear
Sent: Wednesday, August 29, 2012 11:14 AM
To: Morgan Heater
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] fossil hybrid or electric

 

Morgan,

 

I agree with Bill.  I find this LEED CIR (see below) to be helpful in
determining how fossil/electric hybrid systems should be handled.  Your
scenario sounds similar to item 5 under the examples of systems that would
be modeled with fossil fuel heating.

 


LEED Interpretations


11/1/2011 ID#10132

.         MPR/Prerequisite/Credit: EAp2: Minimum Energy Performance

.         Primary Rating System: Core & Shell v2.0

Email


Ruling


Clarification is requested regarding when a building heat source in Table
G3.1.1A should be identified as "Fossil/Electric Hybrid" versus "Electric". 

The ASHRAE 90.1-2007 User's Manual states that a fossil/electric hybrid
source "refers to a system with any combination of fossil and electric heat,
and the baseline system for this is a fossil fuel system". Therefore, the
heating source for the proposed building would be considered "Fossil Fuel"
or "Fossil/Electric Hybrid" if the building uses any fossil fuel source for
space heating (including backup heating or preheating), and the baseline
building heat source would be fossil fuel.

Exception: ASHRAE 90.1 Section G3.1.1 Exception (a) stipulates additional
system type(s) for non-predominant conditions (i.e.
residential/non-residential or heating source) if those conditions apply to
more than 20,000 square feet of conditioned floor area. 

EXAMPLES OF BASELINE HEATING SOURCE DETERMINATION: 

The Baseline heat source from Table G3.1.1A for the following Proposed Case
system types would be fossil fuel since the proposed system design includes
a combination of fossil and electric heat:

1. Variable air volume system with gas furnace preheat and electric reheat
2. Packaged terminal heat pumps with outside air tempered by fossil fuel
furnace
3. Water source heat pumps with fossil fuel boiler
4. Ground source heat pumps with backup fossil fuel boiler
5. 90,000 square feet is conditioned by a variable air volume system with
electric reheat, and 10,000 square feet is conditioned with fossil fuel
furnaces

The following buildings would be modeled with an additional system type with
a different Baseline heating source in accordance with Section G3.1.1
Exception (a):

1. 90,000 square feet is conditioned by a variable air volume system with
electric reheat, and 20,000 square feet is conditioned with Packaged DX
systems with fossil fuel furnaces. In this case, the 90,000 square feet of
area would be modeled with an electric heat source in the Baseline Case
(System Type #6 - Packaged VAV with Electric PFP Boxes), and the 20,000
square feet of area would be modeled with a fossil fuel heat source in the
Baseline Case (System Type #3 - Packaged Single Zone AC with fossil fuel
furnace).
2. 50,000 square feet is conditioned by water source heat pumps with a
fossil fuel boiler, and 25,000 square feet is conditioned by electric heat
pumps. In this case, the 50,000 square feet of area would be modeled with a
fossil fuel heat source in the Baseline Case (System Type #5 - Packaged VAV
with hot water reheat), and the 25,000 square feet of area would be modeled
with an electric heat source in the Baseline Case (System Type #4 - Packaged
Single Zone Heat Pump).

Applicable Internationally.


Formal Inquiry


Table G3.1.1A lists two possible categories for the building heating source:

(1) Fossil fuel, fossil/electric hybrid, & purchased heat; 
(2) Electric and other. 

In cases where the proposed building design includes both a natural gas
heating source and an electric heating source, when should the heat source
in Table G3.1.1A be identified as "Fossil/Electric Hybrid" versus
"Electric"?

Robby Oylear, PE, LEED AP

Mechanical Engineer

Senior Energy Analyst

 

D 206-788-4571

 <http://www.rushingco.com/> www.rushingco.com

 

On Tue, Aug 28, 2012 at 5:41 PM, Bishop, Bill <bbishop at pathfinder-ea.com>
wrote:

Morgan,

 

My vote is for PTAC with hot-water boiler.

 

Regards,

Bill

 

 <mailto:wbishop at pathfinder-ea.com>  

 <mailto:wbishop at pathfinder-ea.com> From:
bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Morgan Heater
Sent: Tuesday, August 28, 2012 8:12 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] fossil hybrid or electric

 <mailto:wbishop at pathfinder-ea.com>  

 <mailto:wbishop at pathfinder-ea.com> Hi - I've got an appendix G baseline
system question.  Here's the scenario, let me know what you think.  

 <mailto:wbishop at pathfinder-ea.com>  

 <mailto:wbishop at pathfinder-ea.com> Proposed Building:

 <mailto:wbishop at pathfinder-ea.com>  

 <mailto:wbishop at pathfinder-ea.com> 1.       Multi-family residential,
amenity/common space < 20,000 square feet

 <mailto:wbishop at pathfinder-ea.com> 2.       Electric baseboard heat in the
units

 <mailto:wbishop at pathfinder-ea.com> 3.       Condensing gas furnaces in the
corridors and back of house spaces

 <mailto:wbishop at pathfinder-ea.com> 4.       VRF in amenity common spaces

 <mailto:wbishop at pathfinder-ea.com>  

 <mailto:wbishop at pathfinder-ea.com> My understanding is that because my
non-predominant condition (common/amenity space) is less than 20,000 square
feet, I use a single system for the whole baseline building (G3.1.1a).  I've
got a mix of gas and electric heat in the baseline building,  does this mean
that my base system is PTAC with a hot water boiler?

 <mailto:wbishop at pathfinder-ea.com>  

 <mailto:wbishop at pathfinder-ea.com> Thanks!  

 <mailto:wbishop at pathfinder-ea.com>  

 <mailto:wbishop at pathfinder-ea.com>  

 <mailto:wbishop at pathfinder-ea.com> Morgan Heater, P.E.

 <mailto:wbishop at pathfinder-ea.com> BEMP, LEED AP

 <mailto:wbishop at pathfinder-ea.com> morgan at ecotope.com

 <mailto:wbishop at pathfinder-ea.com> 206-322-3753 ext 209

 <mailto:wbishop at pathfinder-ea.com>  

 <mailto:wbishop at pathfinder-ea.com> 
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