Indoor fan separation at ARI

13 posts / 0 new
Last post

*Dear all,*

* I've got the following reply for a psz system in the
baseline case during preliminary LEED design submittal:*

*"N*ote that section G3.1.2.1 requires that where efficiency ratings, such
as EER and COP, include fan energy, the descriptor shall be broken down
into its components so that supply fan energy can be modeled separately.
Because the efficiency ratings are calculated at ARI-rated conditions, the
fans should also be broken out at ARI-rated conditions. Most simulation
software programs have the capability to perform this step automatically.
Provide documentation showing that this calculation has been performed by
the software automatically or provide calculations consistent with the
ASHRAE 90.1-2007 User?s Manual showing that the calculation has been
performed at ARI-rated conditions."

What I did is that I referred to eQuest library, and documented the
following paragraph to the reviewer:

"COOLING-EIR:
The Electric Input Ratio (EIR), or 1/(Coefficient of Performance), for the
cooling unit at ARI rated conditions..... This EIR is at ARI rated
conditions, i.e., without correction for different temperature or part
load. Note: If you include fan electric energy consumption in your value of
COOLING-EIR, then you should set SUPPLY-KW/FLOW to zero. Otherwise, the
supply fan electrical energy will be double counted........ Imbedding the
fan energy into the COOLING-EIR is valid only if the fan is constant volume
and INDOOR-FAN-MODE = INTERMITTENT; i.e. the fan cycles on/off with the
compressor. If the fan runs continuously during occupied hours, or the fan
is variable volume, then the fan energy cannot be included in the
COOLING-EIR (or HEATING-EIR)."

And I did set fan kw/cfm to zero, intermittent, and constant volume, but
I've got the SV-A report reporting zero kw power demand, and zero fan (kw)
for the system and its zones.

*Then I got an advice stating that:*

"You should do what the reviewer mentions, divide the indoor fan from the
efficiency rating at ARI-rated conditions and model it separately; this way
you will be able to report the appropriate fan power"

My question is:* where do I separately input the indoor fan power (kw), and
what value should it be?, knowing that this is a baseline case that do not
refer to an actual design.*

Thanks,

*Omar ElRawy, LEED AP BD+C*
LEED Project Manager
EA Sustainable Building Consultants
http://www.ea-buildingconsultants.com

Omar ElRawy's picture
Offline
Joined: 2015-06-10
Reputation: 0

Omar,

I wrote the following fan power email previously so it is not specific to your case, but it may be helpful and includes an important caution on defaults. To your specific question, fan power is calculated per G3.1.2.9. There are static pressure allowances for baseline PSZ if applicable to your case, listed in 6.5.3.1.1. There are a few tools available to help calculate the fan power for Appendix G if you don?t create your own, such as EMIT from Rocky Mount Institute.

There are two ways to enter system fan power ? using either SUPPLY-STATIC and SUPPLY-EFF, or using SUPPLY-DELTA-T and SUPPLY-KW/FLOW. These inputs are shown here:

[http://ARCHIVER.PATHFINDER-EA.COM:8080/cgi-mod/getstubbedattachment.cgi/image004.jpg?charset=utf-8&cid=image004.jpg%4001CDEA94.E3CF3780&delivery=1357351320&len=35534&md5=6075eb6dd225742240674662c0eec1c0&mid=45c6611a05a825b62347e012aae8664ad408abdbe8db2cb944d695b0c4aa42ef2ade843d]

I have found that it generally makes sense to enter SUPPLY-KW/FLOW (in kW/cfm), because it can be easily calculated if you have the fan BHP, and because baseline ASHRAE 90.1-Appendix G system fan power is calculated the same way.
The eQUEST wizard generates values for static and efficiency. You can see in the screen shot above that I have created and applied a user-defined default value of 0.0003 kW/cfm. However, I have not ?restored default? to the static and efficiency values assigned by the wizard. Since the static and efficiency values are red, these are considered user inputs, which override user-defined defaults. In the example above, my user-defined default value has not been used, resulting in lower-than-intended fan power. To remove the unwanted values in red above, you can right-click and ?restore default?, which in this case will leave an empty box for static and ?n/a? for efficiency. The quicker way to do this for a model with many systems is to do a find-and-replace in the input file and delete all the lines with ?SUPPLY-STATIC? and ?SUPPLY-EFF?.

This concludes this episode of D?oh! How could I miss that?!

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

[cid:image007.jpg at 01D0A295.FDE1B9C0] [cid:image008.jpg at 01D0A295.FDE1B9C0]

134 South Fitzhugh Street Rochester, NY 14608

T: (585) 698-1956 F: (585) 325-6005

bbishop at pathfinder-ea.com www.pathfinder-ea.com

[http://png-5.findicons.com/files/icons/977/rrze/720/globe.png]Carbon Fee and Dividend - simple, effective, and market-based.

Bill Bishop's picture
Offline
Joined: 2012-02-25
Reputation: 7

I seem to get this comment frequently so I have it all typed out as a stock
LEED comment response. The advice you received is correct. You can use the
following formulas for fan power and EIR:

kW/cfm = BHP / 0.746 * Fan Motor Efficiency (<----from Appendix G)

BHP = CFM * 0.0013 + Pressure Drop Adjustment

The baseline EIR is then calculated with fan energy modeled separately,
using the following formula (same as what eQuest uses in Wizard mode):

[image: Inline image 1]

Where ARI Fan Power = fan power at rated ARI conditions (W/Btuh), and CAP =
total cooling capacity (Btuh). At rated ARI conditions, the supply fan is
rated at 0.365 kW/cfm and 400 cfm/ton, such that:

[image: Inline image 2]

When normalizing the cooling capacity, the formula is:

[image: Inline image 3]

When applied to a baseline EER=9.5, the resulting EIR=0.3051. The eQuest
wizard will also do this for you correctly, but usually at LEED submittal
time we are all well past the wizard phase, so the formulas above are handy
to have.

Good luck!

Elizabeth

*Elizabeth Gillmor PE, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
Anonymous

Chris you are right, the unit labels should have been W/cfm not kW. Thanks
for the catch!
[image: Inline image 2]

*Elizabeth Gillmor PE, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
Anonymous

Note that 90.1 2013 finally supplied the ?official? formulas for extracting fan power from EER, SEER, COP47, and HSPF ratings. The resulting EIR is slighting different compared to the eQUEST formulas discussed below that many of us have been using ? for example, the ASHRAE equations account for system capacity, resulting in varying EIR depending on system size.

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.

--

Maria Karpman LEED AP, BEMP, CEM

________________

Karpman Consulting

www.karpmanconsulting.net

Phone 860.430.1909

41C New London Turnpike

Glastonbury, CT 06033

Maria Karpman's picture
Offline
Joined: 2011-09-30
Reputation: 0

Dear all,
Thanks William Bishop, Elizabeth Gillmor, Yongqingzhao, and Maria
Karpman, this is a lot of helpful data.

I think *Maria* did brief the whole subject, but I just need to ask few
questions that will help in well documenting this point to the LEED
reviewer:

*1. Where can I find these official formulas so that I can refer to and
attach to my reply please? *
*2. What is the difference between SEER and SEER2, and HSPF and HSPF2?*

*Concerning fan power*, I'am referring to ASHRAE 90.1 2007 section 3.1.2.9*
to find the following:*

bhp = CFMs x 0.00094 + A ----- (where I'am considering
my auto-sized eQuest CFM for this value)

Pfan (Watts) = bhp ? 746 / Fan Motor Efficiency (For systems 3 through 8)

So I'am stopping at both equations to find myself confused with *Elizabeth*'s
equations (KW/cfm = bhp/0.746*Fan Motor Efficiency, and bhp=CFM x 0.0013+A)

For example, my system is 248 CFM, as per section 3.1.2.9, my calculations
will be as follows:

- bhp=248x0.00094+0 = 0.23312
- Pfan = (0.23312x746)/0.825 = 210.79 W
- W/CFM = 210.79/248 = 0.8499 W/CFM

*I wonder if Elizabeth is using a different 90.1 version, or I'am just
confused at the 3.1.2.9 interpretation?*

Thanks for consideration,

*Omar ElRawy, LEED AP BD+C*
LEED Project Manager
EA Sustainable Building Consultants
http://www.ea-buildingconsultants.com

Omar ElRawy's picture
Offline
Joined: 2015-06-10
Reputation: 0

Sorry for any confusion, I was just copying/pasting my LEED response for a
system Type 5. Yes, you would follow G3.1.2.9 with the appropriate numbers
for system types 3-4.

LEED refers you to the EMIT user guide for these formulas, you can
reference that:
http://www.rmi.org/Content/Files/EMITUsersGuide.pdf

*Elizabeth Gillmor PE, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
Anonymous

Hi Elizabeth,
I am looking at the EMITUsersGuide. The input dialog shown on page 12 asks for the Main Supply Fan Power and the Return Fan Power. I assume it is asking for the fan power at design conditions ? bhp/motor efficiency from the fan curve?

[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

Jones, Christopher's picture
Joined: 2015-06-11
Reputation: 0

Thanks so much Elizabeth, Now my fan power calculations results comply with
EMIT results, so I will be documenting both.

Best Regards,

*Omar ElRawy, LEED AP BD+C*
LEED Project Manager
EA Sustainable Building Consultants
http://www.ea-buildingconsultants.com

Omar ElRawy's picture
Offline
Joined: 2015-06-10
Reputation: 0

Omar,

?2? after SEER and HSPF means squared ? I did not notice that formatting got messed up when I copied from 90.1. Here it is again:

On a separate note, 248 CFM design flow rate for the baseline HVAC system seems unrealistically low. I would double check that you are applying G3.1.1 correctly (For systems 1, 2, 3, and 4, each thermal block shall be modeled with its own HVAC system. For systems 5, 6, 7, and 8, each floor shall be modeled with a separate HVAC system.)

Good luck,

Maria

--

Maria Karpman LEED AP, BEMP, CEM

________________

Karpman Consulting

www.karpmanconsulting.net

Phone 860.430.1909

41C New London Turnpike

Glastonbury, CT 06033

Maria Karpman's picture
Offline
Joined: 2011-09-30
Reputation: 0

Yes I believe that is the case. (I use the baseline App G values if design
numbers are unknown or TBD)

*Elizabeth Gillmor PE, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
Anonymous

Thanks Maria,
Which 90.1 version are you referring to, as I can't
find this part in my 2007 version.
Concerning the 248 CFM, it is an auto-sized value by eQuest for a 342 ft2
lift lobby space.

Thanks for consideration,

*Omar ElRawy, LEED AP BD+C*
LEED Project Manager
EA Sustainable Building Consultants
http://www.ea-buildingconsultants.com

Omar ElRawy's picture
Offline
Joined: 2015-06-10
Reputation: 0

Omar, the fan power equations are from G3.1.2.1 of 90.1 2013.

Maria

--

Maria Karpman LEED AP, BEMP, CEM

________________

Karpman Consulting

www.karpmanconsulting.net

Phone 860.430.1909

41C New London Turnpike

Glastonbury, CT 06033

Maria Karpman's picture
Offline
Joined: 2011-09-30
Reputation: 0