[Equest-users] Supply Fan Power

Kathryn Kerns kathryn.kerns at bceengineers.com
Fri May 20 09:13:10 PDT 2011


I may have missed something earlier, but I think apartment buildings
according to ASHRAE 62.1 require a whole building exhaust to ensure
ventilation. This is usually taken care of by intermittent use of the
toilet exhaust fan system. I think 62.1 says something like you can
achieve adequate ventilation by running the exhaust fan intermittently
at something like 70 cfm for a period of time (which I can't remember)
or running it continuously at 30 cfm. So, if the toilet exhaust is being
used for this purpose, it becomes part of the HVAC system and is not
separate. The laundry and kitchen exhaust fan systems are process
oriented and are part of the process loads.  The apartment minimum OSA
requirement is usually provided by a bunch of little holes in a panel
connected to some of the windows.

 

 

 

Kathryn Kerns

Systems Specialist

BCE Engineers, Inc.

| Ph: 253.922.0446 | Fx: 253.922.0896 | 

 

 

________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Cam
Fitzgerald
Sent: Friday, May 20, 2011 8:36 AM
To: Bishop, Bill; Paul Diglio; M. Shields;
equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

Good morning, all,

 

Try looking at it this way. Exhaust fans (separate fans or components of
the proposed HVAC unit) that operate continuously during occupied
periods in conjunction with the HVAC systems serving the adjacent areas
should be included in the Baseline system fan power calculated using
Section G3.1.2.9. Exhaust fans that operate intermittently during
occupied periods should be considered process loads and modeled with the
same airflow, power, and schedule as the proposed case fan. If the fan
motor efficiency is regulated in Section 10 (1 HP and larger) and the
proposed design used higher efficiency motors, savings for the improved
efficiency may be claimed.

 

Hope this helps!

 

Cam S. Fitzgerald, PE, LEED AP

 

Energy Opportunities, LLC

a 7group company

phone:  (717) 292-2636 x11

fax:  (717) 292-0585

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop,
Bill
Sent: Friday, May 20, 2011 11:29 AM
To: Paul Diglio; M. Shields; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

Paul,

True, makeup air can come from windows or infiltration, but it still
constitutes a load that is met by heating and cooling coils if there is
a thermostat. Are you going to model the baseline toilet-exhaust-only
system and zone with those coils to handle the loads? If yes, use the
same G3.2.1.9 system type as the rest of the project and be done with
it. If no, you are either going to have a problem with unmet
heating/cooling hours, or you're considering the zone unconditioned and
the toilet fan is a process load that should be modeled identically
between the baseline and proposed models.

Bill

 

From: Paul Diglio [mailto:paul.diglio at sbcglobal.net] 
Sent: Friday, May 20, 2011 11:12 AM
To: Bishop, Bill; M. Shields; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

The makeup air can come from operable windows or infiltration and does
not necessarily need to be conditioned.


Paul Diglio

 

________________________________

From: "Bishop, Bill" <wbishop at pathfinder-ea.com>
To: M. Shields <mshields at fstrategies.com>; Paul Diglio
<paul.diglio at sbcglobal.net>; equest-users at lists.onebuilding.org
Sent: Fri, May 20, 2011 11:03:05 AM
Subject: RE: [Equest-users] Supply Fan Power

Maybe this is the source of the confusion. I disagree that toilet
exhaust fans constitute independent HVAC systems that have to modeled
separately in the baseline. To me, toilet exhaust, kitchen exhaust and
clothes dryer exhaust are all components of the system that heats, cools
and ventilates the zone(s). The air handlers, heating and cooling coils
that serve these zones are designed to supply and condition the
ventilation air that is exhausted, regardless of whether or not the
exhaust is at the air handler or through a zonal exhaust fan. Yes, a
toilet exhaust fan can operate with the HVAC system off, but the makeup
air has to come from somewhere, and it needs to be heated/cooled (even
if indirectly by mixing with the room air). I mentioned previously that
I usually omit exhaust fans in baseline systems. Another reason I do
this is because eQUEST zonal exhaust fans cannot operate when the system
fan is off.

 

My personal interpretation of G3.2.1.9 is that if you choose to model
separate supply and exhaust fans in the baseline system, the calculated
baseline fan power is split up into supply and exhaust components so
that their total power equals the calculated value. I do not think
G3.2.1.9 requires you to model separate fans for any reason. It only
adds complexity and modeling effort, not baseline fan energy.

 

Regards,

Bill

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of M.
Shields
Sent: Friday, May 20, 2011 10:48 AM
To: 'Paul Diglio'; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

I agree the toilet exhaust system would be independent, but I guess I am
having trouble coming up with an example of an exhaust system which is
not independent other than an ERV which seems to be covered under
G3.1.2.10.  Thus if everything other than ERVs are independent, why does
G3.1.2.9 specify exhaust as one of the systems to be included in that
calculation?

 

From: Paul Diglio [mailto:paul.diglio at sbcglobal.net] 
Sent: Friday, May 20, 2011 10:37 AM
To: M. Shields; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

Michael:

Would not the toilet exhaust be an independent system?  It does not
return air to the HVAC system and can operate with the HVAC system off.

I am modeling a residential high rise and am modeling the kitchen
exhaust hoods as an independent system.  In my case the toilet exhaust
fans have been eliminated and the toilet/apartment exhaust air is
returned to an ERV.  Each apartment is being supplied with ventilation
air from a DOAS.  In my case, I will model the toilet exhaust as part of
the HVAC system.

 

Paul Diglio

________________________________

From: M. Shields <mshields at fstrategies.com>
To: equest-users at lists.onebuilding.org
Sent: Fri, May 20, 2011 10:25:43 AM
Subject: Re: [Equest-users] Supply Fan Power

Thanks for all of the comments.  I think I may have figured out how the
reviewer got confused.

 

As part of my documentation I provided a table which showed the supply
and exhaust cfm, bhp, and kw as calculated from G3.2.1.9 for the
baseline building.  I then showed the same for the proposed building
using the actual equipment specified.  The building has stacks of
apartment units, each stack has an exhaust riser which has a
continuously running fan on the roof.  I am interpreting everything
correctly now, the baseline building should only list the supply cfm,
bhp, and kw as calculated from G3.2.1.9 which includes the fan power
from this exhaust riser.  The proposed building would then use the
actual supply fan and exhaust fans specified.

 

Does this seem like the correct path?  Alternatively the exhaust riser
could be modeled separately in both buildings using the proposed
equipment as a process load.

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop,
Bill
Sent: Friday, May 20, 2011 9:51 AM
To: Nick Caton; Patrick J. O'Leary, Jr.;
equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

Michael,

 

I'm confused by your LEED reviewer's comments. As Patrick mentioned, it
would help to know what the reviewer means by "independent fan systems".
I can think of only two situations where you would need to model
identical fan power in the baseline and proposed models. One is if you
have no heating and/or cooling system in the proposed design, in which
case the proposed system "shall be identical to the system modeled in
the baseline building design" per Table G3.1(10.). Since you mention
that you used the actual fan power in the proposed building, I'm
assuming that heating and cooling systems have been specified for your
proposed design.

The other situation is for process loads. If you have fan power
associated with non-HVAC systems, it should be treated as a process load
and modeled identically between the baseline and proposed designs. An
example of this that has been discussed on this forum previously is
parking garage exhaust.

 

I rarely model anything but supply fans in the baseline model unless
there are process loads. I see no point in modeling return, exhaust or
relief fans. The fan power calculated in G3.1.2.9 is for the sum of
supply, return, exhaust and relief fans. The baseline systems have to
move the same amount of air regardless of the combination of fan types,
and the fan power is based on, and entered as, kW/cfm, so you will end
up with the same fan energy in the baseline model regardless of how many
fans you model for each baseline system.

 

I don't know what the reviewer is trying to say with their comment about
system types 1 through 8 and Table G3.1.1A.

 

Regards,

Bill

 

 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick
Caton
Sent: Friday, May 20, 2011 9:50 AM
To: Patrick J. O'Leary, Jr.; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

Color me concerned... This reviewer may have an argument but I can't
reason it.  I think he/she may be leading us off the path regarding what
the baseline fan power calculations apply to...

 

You've got exhaust fans in a proposed model matching the construction
documents.  Sounds okay so far...  Going through this line by line:

 

*         I would start with directing the reviewer to the glossary.
The entry for "HVAC system" reads: the equipment, distribution systems,
and terminals that provide, either collectively or individually, the
processes of heating, ventilation, or air conditioning to a building or
portion of a building."

o   Clearly, an exhaust fan providing ventilation to a building
independent of other systems is an HVAC system.  The reviewer's phrasing
of "..independent fan systems of the HVAC systems" is a
misinterpretation.

o   Building on the understanding that an independent exhaust system is
a complete HVAC system, Table G3.1.10.a is as far as you need to go for
support of following the construction documents.

*         I'd again reject the reviewers' choice of words:  Exhaust fans
are not "independent fans of the HVAC systems."

*         Sections G3.1.2.8 and G3.1.2.9 agreeably apply only to
baseline systems.  They have no bearing on the topic at hand (what goes
in the proposed model), unless your baseline fan capacities/efficiency
calcs didn't follow the instructions.

*         The request to document the independent fan systems' energies
separately is not new.  May as well do that after all's said and done.

 

That's my initial take.  Thoughts, anyone?

 

~Nick

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Patrick
J. O'Leary, Jr.
Sent: Friday, May 20, 2011 8:35 AM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

it reads to me that your initial interpretation is what the reviewer is
asking for.  on the other hand the question is what is constituting an
"independent" exhaust fan here.  if the exhaust fan is part of the
balance of the supply/return/exhaust system it probably should be
modeled as such as it is not really different than having a return fan
installed in the ductwork somewhere and not in a unit itself.  per hte
90.1 user's manual (page g-28 in 2004), "System fan electrical power for
supply, return, exhaust and relief fans is calculated based on the
following formula.  The power from this formula includes supply, return,
relief, and exhaust fans ..."   if the exhaust fan is not part of the
designed system supply/return/exhaust then i would think your initial
interpretation of what the reviewer is asking is correct.  whichever
situation applies make sure the response documents the purpose of the
exhaust fans and how 90.1 applies (including section/user manual
references).

On 5/20/11 6:15 AM, M. Shields wrote: 

The exact comment is this:

 

"The fan power spreadsheet for the Baseline and Proposed models indicate
that the fan power of the exhaust fans have not been modeled identically
in each model. All independent fan systems of the HVAC systems in the
actual design must be modeled identically between the Proposed and
Baseline models at actual equipment capacities (fan volume and fan
power) as required by Table G3.1.10 in the Proposed building column,
since the fan design air flow rates and fan power per Sections G3.1.2.8
and G3.1.2.9, respectively, only applies to system types 1 through 8 in
Table G3.1.1A. If appealing this credit, revise the Proposed and
Baseline models so all independent fan systems of the HVAC systems are
modeled identically between the Proposed and Baseline models. In
addition, separate the energy consumption and peak demand energy for
independent fans in Table 1.8.1 and Table 1.8.2 of the template and
provide revised SV-A reports for each model reflecting the changes."

 

I initially interpreted this to be that for exhaust systems the bhp/kw
needs to be identical in both buildings and based on the specified
equipment from the mechanical designer, however, my supply fan energy
was Ok.  After reading the comment and Appendix G I am not unsure if I
also need to specify the fan power to be the same for both models, ie
use table G3.1.2.9 to calculate fan power for both instead of just the
baseline.

 

From: equest-users-bounces at lists.onebuilding.org [
mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Patrick
J. O'Leary, Jr.
Sent: Friday, May 20, 2011 8:57 AM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

from your wording of "independent" it sounds like you may have an
application where you have a unit in the proposed building that is
required but not provided in the design?  or something similar.  is this
the case?  if a unit is required in the proposed per the requirement all
spaces be heated/cooled (per the definitions) they are required to be
the same as the units in the baseline building.  if this is not the case
if you post the exact comment it may shed some light on the subject.
otherwise i would argue the comment is in error - if all of your zones
are served by units in the proposed and you have matching units in the
baseline (regardless of system types) then your approach would be
correct.  

On 5/20/11 5:31 AM, M. Shields wrote: 

Good Morning All,

 

I recently received comments back from LEED and one of them was about my
fan power.  In the submission I calculated all of my fan power using
G3.1.2.9 for the baseline building, and I used the actual fan power in
the proposed building.  The reviewer has commented that all independent
fan systems have to be modeled identically in both the baseline and the
proposed building.  The supply fans use very high efficiency motors, and
as such are substantially more efficient than the calculation that
G3.1.2.9 provides.  Is there no way to take credit for using high
efficiency supply fans?

 

Thanks,

 

____________________________
Michael Shields

Email: mshields at fstrategies.com

 

 
 
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