[Equest-users] Efficiency conversions revisited

Fri Jul 10 09:07:38 PDT 2015

It might be challenging to get fan info for small units. If the unit in question accounts for a small fraction of the total HVAC system capacity, I would use some rule of thumb (e.g. assume 365 W/CFM). If reviewers complain about it, you would then try to get data from design team or manufacturer, but the change would have negligible impact on performance rating so you are not risking much by simplifying. On the other hand, if your proposed HVAC is an aggregation of small units (e.g. project involves a multifamily building with split system units serving each apartment), then I would establish fan power more accurately up-front, as it may have significant impact on project’s performance.

Maria

-- 

Maria Karpman LEED AP, BEMP, CEM

________________

Karpman Consulting

 <http://www.karpmanconsulting.net/> www.karpmanconsulting.net 

Phone 860.430.1909 

41C New London Turnpike

Glastonbury, CT 06033

From: Jones, Christopher [mailto:Christopher.r.Jones at wspgroup.com] 
Sent: Friday, July 10, 2015 11:17 AM
To: Maria Karpman; 'Nicholas Caton'; 'Equest-users'
Subject: RE: [Equest-users] Efficiency conversions revisited

Thanks Maria,

This question is for small, split system AC units, no duct work.  The shop drawing doesn’t provide an external static pressure drop, not total.  The shop drawing does not include the rated fan motor power.    

I will check with the design team to see if they can get the supplier to provide the answer.

cid:image003.png at 01D09C46.E75BA0D0

Christopher Jones, P.Eng. 
Senior Engineer

WSP Canada Inc.

2300 Yonge Street, Suite 2300

Toronto, ON M4P 1E4
T +1 416-644-4226

F +1 416-487-9766

C +1 416-697-0065

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

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Maria Karpman
Sent: Friday, July 10, 2015 11:06 AM
To: 'Nicholas Caton'; Jones, Christopher; 'Equest-users'
Subject: Re: [Equest-users] Efficiency conversions revisited

I believe example below from 90.1 2007 User’s Manual answers the COP part of your question. (Note that all of the parameters in the Q portion of the example are for ARI conditions, which are usually identified in manufacturer’s catalogs).

Fan power modeled in the proposed design must come from project drawings. If it is not shown, I would ask design team to add it as this is required for documenting code compliance: 

6.5.3.1.2 Motor Nameplate Horsepower. 

….The fan bhp must

be indicated on the design documents to allow for compliance

verification by the code official.  

Alternatively, you can calculate fan power as BHP=PD × CFM/4131, where PD is the total pressure drop (not just external pressure drop). PD should again come from design team. BHP can then be converted to Watts (fan input power) as bhp × 746 / Fan Motor Efficiency. 

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: Nicholas Caton [mailto:ncaton at catonenergy.com] 
Sent: Thursday, July 09, 2015 5:41 PM
To: Jones, Christopher; Maria Karpman; Equest-users
Subject: RE: Efficiency conversions revisited

I haven’t heard any rumors of GBCI enforcing/requesting 90.1-2013 be utilized… yet.  

Based on the pace of LEED’s 90.1 adoption, it seems to me by the time LEED gets around to 90.1-2013 ASHRAE may well have revised/fleshed out further those passages (I’m expecting the Ec/Et issue for large boilers to eventually be formally addressed eventually).  Until that time comes I’m pretty sure it’s up to the modeler’s discretion to use any method that is considerate of the requirements in play and applied consistently between projects.

I noted you’re talking about “actual” equipment with a cutsheet to reference:  GBCI shouldn’t have a problem with you keeping fan energy in your cooling/heating EIR inputs if the actual system fan does not operate independently of the remote unit.  Any effort to pull the fan energy out of your cooling/heating EIR inputs by such curves/equations would net the same results and wouldn’t be meaningful.

My copy of 90.1-07 is boxed up right now so I can’t directly cite, but the same passage mandating continuous fan operation during occupied hours for baseline systems says not to pull fan energies out for cycling systems… all that passage is specific to baseline systems but the framework should carry over to allowing you to simulate the proposed systems in the same fashion.  Keep in mind that passage and the new stuff Maria copied us on below is all specific to BASELINE systems and isn’t directing how to simulate the proposed/actual counterparts ;).

Regards,

~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

From: Jones, Christopher [mailto:Christopher.r.Jones at wspgroup.com] 
Sent: Thursday, July 09, 2015 12:10 PM
To: Maria Karpman; 'Nicholas Caton'; 'Equest-users'
Subject: Efficiency conversions revisited

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.

2300 Yonge Street, Suite 2300

Toronto, ON M4P 1E4
T +1 416-644-4226

F +1 416-487-9766

C +1 416-697-0065

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

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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