[Equest-users] Appendix G Fan Simulation

Amanda Bogner amanda at bvm-engineering.com
Fri Dec 4 11:39:08 PST 2009


Jason,

 

You do not need to use the Allowable Nameplate Motor HP (Table 6.5.3.1.1a)
equation to determine the system fan power for an Appendix G baseline.  

 

For System 1, I can confirm that you've calculated the allowable fan system
BHP correctly as 173.02.  Using the fan CFM reported in the SV-A report is
also correct.

 

>From here, you'll determine the fan motor efficiency.  G3.1.2.9 indicates
the following:

Fan Motor Efficiency = the efficiency from Table 10.8 for the next motor
size greater than the bhp using the enclosed motor at 1800 rpm.  

 

>From Table 10.8, the fan motor efficiency = 95%

 

Then, use the equation provided in G3.1.2.9 for system types 3-8, as
follows:

Pfan = bhp x 746 / fan motor efficiency = 173.02 x 746 / 0.95 = 135866 W =
135.87 kW

 

I find it easiest to leave the wizard as a default value, simulate the model
after all other parameters are defined, then calculate the fan power based
on the CFM reported in the SV-A report.  Then, input a kW/cfm in the
detailed mode.  Re-simulate and cross check the fan power reported in the
SV-A report.  The fan power reported here should be equal to 135.87 kW.
Additionally, the peak demand for ventilation fans should also correspond to
this value (or a sum of the fan power for multiple air systems).  FYI, you
may need to make some small adjustment to the kW/CFM to get to the correct
total fan power.  I typically do this using a ratio of input vs. output to
come up with an adjusted kW/CFM.

 

On another note, in the table below System 2 and 4 are described as a
packaged multizone with HW reheat and split system single zone DX with
electric heat, respectively.  These system types do not correspond with any
of the Appendix G Baseline HVAC Systems, as described in Table G3.1.1A.  You
may want to have another look at this.  Also, be careful with modeling a
unit heater in the baseline case.  Be sure that the space can be considered
semi-heated, otherwise this system will need to be modeled with both heating
and cooling.  For more information about this see the definitions provided
in Section 3, Table 3.1, and Table G3.1 Item 10.

 

Good Luck.

 

Amanda Bogner, PE LEED AP

Manager of Simulations



BVM Engineering, Inc.

834 Inman Village Parkway

Suite 230

Atlanta, Georgia 30307

404.806.2018 x 103

404.806.2019 FAX

 

 

 

From: Jason Wendel [mailto:jwendel at heatheng.com] 
Sent: Friday, December 04, 2009 12:48 PM
To: 'Amanda Bogner'; 'Equest-users at lists.onebuilding.org'
Subject: RE: [Equest-users] Appendix G Fan Simulation

 

Ok, so here's the spreadsheet I set up to calculate the bhp with the
pressure drop allowances 

		
>From eQuest

>From Table 6.5.3.1.1B Fan Power Limitation Pressure Drop Adjustment

>From Table 6.5.3.1.1A Fan Power Limitation


System #

 

Calculated CFM

Ducted Return (0.5)

Particulate Filtration Credit: MERV 13 thru 15 (0.9)

Sound Attenuation Section (0.15)

"A"      (Table 6.5.3.1.1b)

Allowable Fan System BHP (Table G3.1.2.9 also)

Allowable Nameplate Motor hp (Table 6.5.3.1.1a)


1

Packaged VAV System with HW Reheat

111,328

 

24.25

4.04

28.30

173.02

166.99


2

Packaged Multizone with HW reheat

91,857

11.12

20.01

3.34

34.47

153.88

137.79


3

Unit Heaters

8,573

 

 

 

0.00

8.06

9.43


4

Split System Single Zone DX with Electric Heat

25,258

 

5.50

0.92

6.42

30.16

27.78

 

.  From what you're saying, do I not even bother with the bhp input in the
wizard mode, just set up the system and run the simulation, then calculate
the kW/cfm and put that in from the detailed mode?  Do I use the total fan
KW from the SV-A output and the cfm from that output (shown below)?



-Jason

 

From: Amanda Bogner [mailto:amanda at bvm-engineering.com] 
Sent: Friday, December 04, 2009 11:40 AM
To: Jason Wendel
Subject: RE: [Equest-users] Appendix G Fan Simulation

 

You've indicated that you're using the BHP directly in eQuest.  But, I think
you need to take this value and use the equations in G3.1.2.9 which will
account for the fan motor efficiency.  It doesn't appear from the
information below that you're doing this step.

 

>From here, you'll end up with a fan power wattage.  I usually divide this by
the total supply air and input it in the detailed mode as a kW/CFM value.   

 

If you would like to send me your detailed calculations, I can have a more
thorough look at it.  Specifically:

 

-          what pressure drop allowances are you able to take

-          what are you calculating your 'A' value to be

-          can the pressure drop allowance be applied to 100% of the air

 

 

Amanda Bogner, PE LEED AP

Manager of Simulations



BVM Engineering, Inc.

834 Inman Village Parkway

Suite 230

Atlanta, Georgia 30307

404.806.2018 x 103

404.806.2019 FAX

 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Jason
Wendel
Sent: Friday, December 04, 2009 11:19 AM
To: 'Equest-users at lists.onebuilding.org'
Subject: Re: [Equest-users] Appendix G Fan Simulation

 

Sorry to rehash this but I've been going through the baseline fan power, and
still don't have the answers I need.

 

I've got a 113,000 cfm (from the SV-A System Design Parameters report) VAVR
system on my baseline that when I go through all the calculations for ASHRAE
90.1-2007 (from Table G3.1.2.9, Table 6.5.3.1.1a and b) I get 176.13 bhp.
I put that in the wizard entry for BHP for the VAVR system and don't get any
errors, BUT when I put in the bhp that I solved for the packaged multi-zone
AHU's that will be used in the building also (92,000 cfm, 153.88 bhp), using
the same calculations, it gives me an error that the static is at 56 in
w.c., and it needs to be below 15.  

 

What's going on?  Also, if you use the equations from Table 6.5.3.1.1a and
b, then the break horsepower is higher than the allowable nameplate hp.
Isn't that backwards?

 

-Jason

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul
Erickson
Sent: Sunday, September 20, 2009 10:39 AM
To: ron lamarre; Matthew Higgins
Cc: Equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Appendix G Fan Simulation

 

Ron, to comment on your statement, "I believe that the kW/CFM is based on
the Baseline BHP and Baseline Fan Power formula in ASHRAE 90.1-2004
G3.2.1.9.  The CFM is the total building CFM", 90.1-2007 makes it the most
clear that the CFM is actually ONLY the Baseline's peak SUPPLY CFM.  The
same is true for 90.1-2004, it's just not very clear.  However the reviewers
do know that this is true and have most recently been asking for a
demonstration of calculation methodology.

 

Regards,

Paul

 

Paul Erickson LEED AP 

Sustainable 

 <http://www.aeieng.com/> Affiliated Engineers, Inc.   

5802 Research Park Blvd. | Madison, WI  53719 | P 608.236.1112 | F
608.238.2614  

 <mailto:perickson at aeieng.com> perickson at aeieng.com | www.aeieng.com 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of ron lamarre
Sent: Friday, September 18, 2009 11:49 PM
To: Matthew Higgins
Cc: Equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Appendix G Fan Simulation

 

Hi to all:

 

I believe that the kW/CFM is based on the Baseline BHP and Baseline Fan
Power formula in ASHRAE 90.1-2004 G3.2.1.9.  The CFM is the total building
CFM; see the air-side summary report for the total bulding CFM.  

 

To get the correct total building CFM, set the Baseline
supply-air-to-room-air at a 20-degree F differential.  For instance, if your
summer (cooling) set-point temp = 75 degreesF, then the cooling supply air
temp from the unit is 55-degree F.  If your winter (heating) set-point temp
is 70-degree F, then your heating supply air temp from the unit is 90-degree
F.  Run a simulation and eQUEST will determine the CFM for each system based
on this differential; then balance the systems to be under the 300 unmet
hours limit.  Then open the air-side summary report to see the total CFM of
all your systems.  Use that total CFM in the BHP and Baseline Fan Power
calculations under G3.2.1.9.  To use the formulas, you need to use a
calculator with a "natural log" button and an "e" button for the energy
constant (e=1.28....just like "pie" = 3.14).

For a Baseline Type 3 PSZ System, the fan power should be in the
neighborhood of 0.0007; this may be why GBCI questioned your result.  Then
assign this fan power to each baseline PSZ system in your building and
re-run the simulation.  Include the formula in the LEED submittal template
or narrative to demonstrate how its calculated; as well as including the
Air-side Summary Report.  GBCI will see both the total baseline CFM and the
baseline fan power calculations.

 

The Proposed conditions are the proposed set-points, proposed supply air
temps, and proposed kW/CFM for each system as designed.  If the RTU fans run
continuously during occupancy periods, separate the supply air fan power,
which is the kW to use, from the RTU power.  This allows design teams to
take credit for using high efficient HVAC systems (low kW/CFM).

 

Hope this helps.

 

Ron Lamarre, AIA, NCARB

Architect - LEED AP


 

 

  _____  

From: Matthew Higgins <higgins at edi-arch.com>
To: "Equest-users at lists.onebuilding.org"
<Equest-users at lists.onebuilding.org>; BLDG SIM <bldg-sim at gard.com>
Sent: Thursday, September 17, 2009 5:12:10 PM
Subject: [Equest-users] Appendix G Fan Simulation

I've seen multiple posts regarding 2004 Appendix G Fan Power and one post
from Ming Zeng suggested the following:
"Baseline model fan usually gives 0.00078KW/cfm.  For proposed fans,
typically it is 0.00016-0.00018 KW/cfm/in static*"*

I have two problems related to this because my Baseline KW/cfm is closer to
0.001 KW/cfm for a bunch of unitary Type-3 systems, which is indefinitely
way too high.

FIRST
Many people have referred to the calculated fan power as an allowance, which
to me, would appear to be a threshold not to exceed based on the 20deg-F
delta for Appendix G Fan Sizing. I figure this is not the case because
others refer to the fan power as something that is simulated in the model as
a KW/cfm.
I've also seen posts where numbers are expressed as KW/kcfm, which would
indicate fan power KW per thousand cfm; which again is not an applicable
figure for simulation using eQuest.

SECOND
I'm struggling with these items because a recent GBCI reviewer has asked me
to re-calculate my fan power because my BHPs are a bit higher than they
should be. When I "re-calculate" these values I do not come up with the
numbers they do (BHP ASHRAE - attached).

I'm trying to reconcile my response and eQuest inputs before we re-submit,
but I'm not sure what to do.

Much thanks.

-- Matthew Higgins, LEED AP + ASHRAE-HBDP
Environmental Dynamics, Inc.
Architecture and Sustainability Consulting Services
505.242.2851 x.103

Any data provided by the Consultant, verbal or written, are to be considered
opinions of building energy and/or daylight performance. The Client
understands that the Consultant has no control of occupant habits, equipment
or material performance or characteristics, site or climate conditions or
the Contractor's method of assembly, and that the Consultant's opinions
regarding building energy/daylight performance are made on the basis of the
Consultant's professional judgment and experience. The Consultant makes no
warranty, express or implied, that the energy/daylight performance of the
building will not vary from the Consultant's opinion of building
energy/daylight performance.

 

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