[Equest-users] Excessive Heating Savings
Robert Stephenson
rstephenson at southface.org
Mon Nov 8 13:18:28 PST 2010
Thanks Eddie,
As a trial, I ran my proposed design again with the system type set to Packaged Single Zone. This increased my heating usage and decreased the savings to ~75%. Out of curiosity I started a new project again and set my parameters in the wizard to a split system single zone heat pump (residential) and ended up with packaged variable volume variable temperature for my system type in detailed mode. Any advice on what system type I should be specifying and why the difference are there? I looked to the help file and found very little except the table outlining the different system types. Is there a layer I am missing?
Also, how would I go about backing the fan power out of my efficiencies as was suggested in another response?
I have attached my .inp and .pd2 files if anyone has some time to take a quick look.
Thanks again,
Robert Stephenson, LEED AP
Project Manager, Residential Green Building Services
Tel: 404-604-3589
Fax: 404-872-5009
Email: rstephenson at southface.org <mailto:username at southface.org>
Web: www.southface.org <http://www.southface.org/>
241 Pine Street NE, Atlanta, GA 30308
<http://www.southface.org/>
Building know-how for a sustainable future
Get involved with Southface <http://www.southface.org/get-involved/become-a-member/> today!
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From: Eddie Corwin [mailto:ecorwin at altanova-energy.com]
Sent: Monday, November 08, 2010 3:03 PM
To: Robert Stephenson; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Excessive Heating Savings
My first guess would be to look into the residential systems further. Read the topic on this particular system in the help file. As far as I can remember, this system will automatically, reduce the set point temperatures, and flow rates (or something similar) based on the occupancy. This can provide significant savings, especially if you have a low occupancy rate. So I would start from there. If you attach you input file, we (the online community) can take a look at it hopefully find the true issue.
-Eddie
________________________________
From: Robert Stephenson <rstephenson at southface.org>
To: equest-users at lists.onebuilding.org
Sent: Mon, November 8, 2010 2:25:18 PM
Subject: [Equest-users] Excessive Heating Savings
Hello All,
I am having some issues with modeling the heating and cooling systems in mid-rise multifamily buildings. I have a number of these projects and they all use similar and fairly simple systems, a single split system heat pump serving each dwelling unit. When modeling these projects I have followed the guidelines from Appendix G with additional guidance from the ENERGY STAR High Rise program’s simulation guidelines. No matter the project location, I am getting heating savings that seem very out of whack with the upgrades made in the proposed design (higher efficiency HVAC, better windows, upgraded insulation, etc.), the particular model I am looking at now has heating savings over 90%.
An outline of my system inputs follows. I developed this approach based on the guidelines discussed above, past listserv discussions, and the input of other local energy modelers.
Proposed Model
· System type set to Residential System 2
· System capacities based on actual design
· Electric Input Ratios
o Cooling
EIR=((1/(SEER*0.778+1.4)-0.012167)/((1/3.413)+0.012167)
SEER 14 yields 0.227 CEIR
o Heating
EIR= (1/((HSPF*0.28+1.13)*3.412)-0.012167)/((1/3.412)-0.012167)
HSPF 7.7 yields 0.274 HEIR
· Fan Power set to zero given that fan power is accounted for in SEER and HSPF efficiency ratings
Baseline Model
· System type set to PTHP, Packaged Terminal AC with heat pump heating, per Appendix G and ENERGY STAR simulation guidelines.
· System capacities set by equest, 15% oversized for cooling and 25% for heating
· Electric Input Ratios
o Cooling
EER per 90.1: EER = 12.3-(0.213*Cap/1000)
Capacity set to 15,000 Btu/hr yields 9.1 EER
EIR= (1/EER-0.012167)/((1/3.413)+ 0.012167)
Yields 0.32 CEIR
o Heating
EIR= 3.2-(0.026*Cap/1000)
Capacity set to 15,000 Btu/hr yields 2.81 COP
EIR=1/COP
Yields 0.356 HEIR
· Fan Power set to zero given that these are packaged units
Outside air rates, infiltration levels, and supplemental heating are set identically in both models. The only other issue of note is that the proposed design has unit heaters (electric resistance heat) in the stairwells, which I have modeled as PTHPs in the baseline design with heating only. I would assume this would be a loss for the proposed design, though negligible, given the increased efficiency of the PTHPs versus electric resistance, but I’m not seeing that reflected in the results.
If anyone has advice on what I might be missing I would appreciate it. Tips on places to check myself in the .sim file would also be great.
Thanks in advance,
Robert Stephenson, LEED AP
Project Manager, Residential Green Building Services
Tel: 404-604-3589
Fax: 404-872-5009
Email: rstephenson at southface.org <mailto:username at southface.org>
Web: www.southface.org <http://www.southface.org/>
241 Pine Street NE, Atlanta, GA 30308
<http://www.southface.org/>
Building know-how for a sustainable future
Get involved with Southface <http://www.southface.org/get-involved/become-a-member/> today!
<http://www.twitter.com/southfaceenergy> <http://www.linkedin.com/companies/southface> <http://www.facebook.com/pages/Southface/92291631957>
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