[Equest-users] Efficiency conversions revisited

Thu Jul 9 12:10:14 PDT 2015

I am hoping for some insight for modeling the efficiencies of split system heat pumps and other such stand alone systems.

In this case, the shop drawing provides the ARI rated efficiencies which include the fan power.  But this shop drawing does not provide the fan motor power.

In the past I would convert the rated EER to COP using COP = EER/3.4121 and I would assume no fan power as the rating includes the fan power.  But this project is being submitted to the USGBC and I am worried that the GBCI may have an issue with this.

As Maria pointed out, 90.1-2013 now provides the formula to convert EER to COP, removing the fan power.  The baseline fan power would be calculated using the formulas in G3.1.2.10.  Would it be best to use the same method to calculate the proposed case fan power and COP?

[cid:image003.png at 01D09C46.E75BA0D0]
Christopher Jones, P.Eng.
Senior Engineer

WSP Canada Inc.
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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Maria Karpman
Sent: Tuesday, May 26, 2015 10:18 AM
To: 'Nicholas Caton'; 'Equest-users'
Subject:: Reply： The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007

As far as SEER to EER and HSPF to COP conversions, 90.1 2013 finally provided these in G3.1.2.1, along with the formulas for extracting fan power from efficiency ratings:

G3.1.2.1 Equipment Efficiencies. All HVAC equipment
in the baseline building design shall be modeled at the mini-
mum efficiency levels, both part load and full load, in accordance
with Section 6.4. Chillers shall use Path A efficiencies
as shown in Table 6.8.1-3 where efficiency ratings include
supply fan energy, the efficiency rating shall be adjusted to
remove the supply fan energy. For Baseline HVAC Systems 1,
2, 3, 4, 5, and 6, calculate the minimum COPnfcooling and
COPnfheating using the equation for the applicable performance
rating as indicated in Tables 6.8.1-1 through 6.8.1-4.
Where a full- and part-load efficiency rating is provided in
Tables 6.8.1-1 through 6.8.1-4, the full-load equation below
shall be used:

COPnfcooling = 7.84E-8 × EER × Q + 0.338 × EER
COPnfcooling = –0.0076 × SEER2 + 0.3796 × SEER
COPnfheating = 1.48E-7 × COP47 × Q + 1.062 × COP47
(applies to heat-pump heating efficiency only)
COPnfheating = –0.0296 × HSPF2 + 0.7134 × HSPF

where COPnfcooling and COPnfheating are the packaged HVAC
equipment cooling and heating energy efficiency, respectively,
to be used in the baseline building, which excludes
supply fan power, and Q is the AHRI-rated cooling capacity
in Btu/h.

EER, SEER, COP, and HSPF shall be at AHRI test conditions.
Fan energy shall be modeled separately according to
Section G3.1.2.10.

Hope this helps,

Maria

--
Maria Karpman LEED AP, BEMP, CEM
________________
Karpman Consulting
www.karpmanconsulting.net<http://www.karpmanconsulting.net/>
Phone 860.430.1909
41C New London Turnpike
Glastonbury, CT 06033

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nicholas Caton
Sent: Friday, May 29, 2015 11:17 AM
To: 赵永青; Equest-users
Subject: Re: [Equest-users] RE: Reply： The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007

Yeah same for my case (not AFUE), though that’s good thinking!

When I do have an AFUE boiler requirement, I have found it easier to stick with the default library curves / standby inputs & to determine the full load HIR with the following equations:

HIR = f(AFUE):   [Reference: California Energy Commission's 2005 "Nonresidential Alternative Calculation Method (ACM) Approval Manual"]
                For single packaged central furnace (baseline system #3):                            HIR = (.005163*AFUE+0.4033)^-1
                For Boilers where 75 ≤ AFUE < 80 (Baseline systems #1, #5 &#7):               HIR = (0.1*AFUE+72.5)^-1*100
                For Boilers where 80 ≤ AFUE < 100 (Baseline systems #1, #5 &#7):            HIR = (0.875*AFUE+10.5)^-1*100

For completeness, here are the other equations I keep handy for converting other seasonal efficiencies to steady-state inputs:

EER=f(SEER):      [Reference: NREL Building America House Simulation Protocol (Revised), citing Wassmer, M. (2003). A Component-Based Model for Residential Air Conditioner and Heat Pump Energy Calculations.]
(AC) (Baseline Systems #1, #3, #5 & #6):               EERNET= -0.0182*SEER^2 + 1.1088*SEER
(HP-cooling) (Baseline Systems #2 & #4):              EERNET = -0.02*SEER^2 + 1.1268*SEER

COP=f(HSPF):    [Reference: Wassmer, M. (2003). A Component-Based Model for Residential Air Conditioner and Heat Pump Energy Calculations. Masters Thesis, University of Colorado at Boulder.]
(HP-heating) (Baseline Systems #2 & #4):             COPNET = -0.0255*HSPF^2 + 0.6239*HSPF

IIRC, each of the above cited references determines these equations based on a survey of real-world equipment from various manufacturers in order to plot a quadratic trendline.  That trendline establishes the relationship between steady state full load efficiency and the associated seasonal efficiency rating.  In time (or until such equations are added to Appendix G to regulate how modelers approach seasonal efficiency requirements), it may be appropriate to seek out similar research to update these equations every so often, but for the present and past couple of years I have had zero problems using this family of equations for my LEED reviews.

~Nick

NICK CATON, P.E.
Owner

Caton Energy Consulting
  1150 N. 192nd St., #4-202
  Shoreline, WA 98133
  office:  785.410.3317
www.catonenergy.com

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