[Equest-users] Supply Fan Power

Paul Diglio paul.diglio at sbcglobal.net
Fri May 20 09:37:31 PDT 2011


Bill:
For an apartment building with PTHP, the system cycles on temperature so there 
is not necessarily a load on the system for the infiltration load due to open 
windows or trickle vents.

Per the eQuest Help menu, the zone exhaust fans are modeled with the exhaust air 
source as infiltration to simulate residential kitchen or bathroom exhaust and 
the exhaust fan will operate independently of the space conditioning system.

Without stirring up the controversy of Thermal Zones again, for an apartment, I 
have two zones in each zone group.  One is the main area including the bathroom 
and one is the kitchen.  This way I can add another exhaust fan in the kitchen 
with a separate fractional schedule.

The BEPS indicates a significant difference in energy use when adding the 
exhaust fans to the model.

How do you account for this energy if you do not model the fans?

Paul Diglio




________________________________
From: "Bishop, Bill" <wbishop at pathfinder-ea.com>
To: Paul Diglio <paul.diglio at sbcglobal.net>; M. Shields 
<mshields at fstrategies.com>; equest-users at lists.onebuilding.org
Sent: Fri, May 20, 2011 11:28:37 AM
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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