[Equest-users] ASHRAE 62.1 Unoccupied Vnetilation
Jeremy Poling
Jeremy.Poling at transwestern.net
Mon Mar 14 11:36:10 PDT 2011
Michael,
You brought up a good point - I have not yet had to apply the 2010
version of the standard so I was only looking into the issue in the 2007
version.
There is a revision in ASHRAE 62.1-2010 that actually agrees with my
interpretation as it functions for DCV (not necessarily for the
building's unoccupied hours). ASHRAE 62.1-2010 Section 6.2.7 still
covers dynamic reset of OA and Section 6.2.7.1.2 says: "The breathing
zone airflow (Vbz) shall be reset in response to current occupancy and
shall be no less than the building component (Ra*Az) of the DCV zone."
So during occupied hours at a minimum, your OA can go no less than Ra*Az
(under ASHRAE 62.1-2010).
I could not find an official interpretation on the issue of ventilation
during unoccupied hours but there are quite a few interpretations that
regularly unoccupied spaces (even if occupiable) are not required to be
ventilated.
So that is the place where I think I could use more input, since the
first part seems true: under the current version of the standard DCV
cannot reduce OA to 0, only to the minimum amount determined by Ra*Az.
Jeremy R. Poling, PE, LEED AP+BDC
Manager | Sustainability Services
TRANSWESTERN
234 W. Florida St.
Milwaukee, WI 53204
Phone 414.255.3322 | Fax 414.224.7780 | Mobile 414.426.7273
Jeremy.Poling at Transwestern.net
http://www.transwestern.net/Energy-Sustainability.asp
From: Michael.Hupel at jci.com [mailto:Michael.Hupel at jci.com]
Sent: Monday, March 14, 2011 12:57 PM
To: Nick Caton
Cc: Charles Welch; equest-users at lists.onebuilding.org;
equest-users-bounces at lists.onebuilding.org; Jeremy Poling; Paul Diglio
Subject: Re: [Equest-users] ASHRAE 62.1 Unoccupied Vnetilation
ASHRAE 62.1 - 2010, Sec. 6.2.6.1 (Variable Load Conditions) wording on
Occupied concurs with previous versions of 62.1. However, a space may
temporarily be unoccupied for whatever period of time does not negate
the responsibility to maintain Indoor Air Quality as Per Section 6.3.
Michael Hupel
Project & Business Development
Johnson Controls L. P.
3070 Mainway Drive
Burlington, ON L7N 3X1
(905) 335-3325 ext. 237
(905) 730-9642 cell
From:
"Nick Caton" <ncaton at smithboucher.com>
To:
"Paul Diglio" <paul.diglio at sbcglobal.net>, "Jeremy Poling"
<Jeremy.Poling at transwestern.net>, "Charles Welch"
<cwelch at capitalreviewgroup.com>, <equest-users at lists.onebuilding.org>
Date:
03/14/2011 01:19 PM
Subject:
Re: [Equest-users] ASHRAE 62.1 Unoccupied Vnetilation
________________________________
In agreement and in extension of Jeremy/Paul's thoughts:
62.1-2007 and 2004 define a "breathing zone" as "the region in an
occupied space..." in the glossary.
Once a space is unoccupied, it ceases to have a breathing zone. When
there's no breathing zone, per 6.2.6.1, there's little to discuss ;).
Do provide ventilation for off-gassing. Another good example from my
short experience has been tire storage.
~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
<mailto:equest-users-bounces at lists.onebuilding.org> ] On Behalf Of Paul
Diglio
Sent: Monday, March 14, 2011 8:19 AM
To: Jeremy Poling; Charles Welch; equest-users at lists.onebuilding.org
Subject: [Equest-users] ASHRAE 62.1 Unoccupied Vnetilation
Jeremy:
I don't see anything in 62.1 that implies ventilation is required during
the unoccupied mode.
I agree that there are off-gassing considerations to be taken into
account. 62.1-2004 had a section that stated, in so many words, that if
there was an accumulation of contaminants during the unoccupied period,
the fans shall be started before occupancy to purge the contaminants. I
did not see this in 62.1-2007, but I do not have a searchable copy, just
a cut & paste from Real-Read.
Some designers specify a night purge mode to clear the air after the
cleaning crew has left the building in order to purge the air of the
cleaning solution odors.
62.1-2007, section 6.2.6.1 states that the "Ventilation systems shall be
designed to be capable of providing the required ventilation rates in
the breathing zone whenever the zones served by the system are
occupied". I take the "required ventilation rates" to mean those
defined in Table 6.1 which is where the CFM per person and the CFM/Ft2
is defined.
I would be interested if anyone else on the forum shares your
interpretation.
Paul Diglio
________________________________
From: Jeremy Poling <Jeremy.Poling at transwestern.net>
To: Paul Diglio <paul.diglio at sbcglobal.net>; Charles Welch
<cwelch at capitalreviewgroup.com>; equest-users at lists.onebuilding.org
Sent: Mon, March 14, 2011 12:40:06 AM
Subject: RE: [Equest-users] EMS Control System Modeling
Paul,
I just have a literal viewpoint - I think it is more me identifying a
problem with equivalence in the codes: 90.1 allows cycling of fans
during unoccupied hours but I haven't seen anything in 62.1 that says
you can turn off the area-based component of the ventilation
calculation. I'm in the position most of the time of either modeling
someone else's design or reviewing a model built by someone else so this
usually becomes a discussion I have if the model is attempting to take
credit for DCV strategies. I mean, it is very literal, but the basic
VRP equation is Ra*Az + Rp*Pz=Vbz and the only thing that changes over
the short-term is Pz, right? The 62.1-2007 User's Manual on page A-6
points to Section 5.4 and Section 6.2.6.1 that state that ventilation is
required whenever zones are occupied. That said, on page 6-2 the User's
Manual describes the two components of the VRP the way I mentioned
earlier: one for the "occupant-related component" and the other for the
"building area-based component" that is described as "The building
area-based component is intended to dilute sensory contaminants emitting
from materials and furnishings within the space, and from non-occupant
activities and processes taking place within the space." From my
reading, this agrees that there are sources of IAQ contamination that
originate from the building itself that have nothing to do with the
occupancy of the building. Since the building is present 24/7 it would
make sense that it is generating IAQ contaminants 24/7 and therefore,
those contaminants need dilution over that time. So the math says the
answer to the equation cannot be 0, but in reality this will represent
an energy penalty in most climate zones for a large portion of the year.
Thoughts? I'm definitely okay being proven wrong here, but I haven't
found anything in the text of the standard that overtly confirms that no
outdoor airflow should be provided during unoccupied times.
Jeremy R. Poling, PE, LEED AP+BDC
From: Paul Diglio [mailto:paul.diglio at sbcglobal.net
<mailto:paul.diglio at sbcglobal.net> ]
Sent: Friday, March 11, 2011 7:13 PM
To: Jeremy Poling; Charles Welch; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] EMS Control System Modeling
Jeremy:
Are you saying that one needs to provide the Az amount of ventilation
air during unoccupied hours? So you model the fans to run 24 X 7 to
provide ventilation?
Paul Diglio
________________________________
From: Jeremy Poling <Jeremy.Poling at transwestern.net>
To: Charles Welch <cwelch at capitalreviewgroup.com>;
equest-users at lists.onebuilding.org
Sent: Fri, March 11, 2011 3:03:34 PM
Subject: Re: [Equest-users] EMS Control System Modeling
Charles,
One more thought for your consideration: since the DCV is based on
occupancy, the occupancy schedule is also going to drive it in reality
and in the model (as you're aware - just stating for the record).
Because of that, the hourly people-schedule is going to drive the
results given by the model. It may make sense to go through and look at
that schedule in detail to be certain it reflects your best
understanding of how the spaces will be occupied. Following on that
thought, a very real example of where DCV can save energy is going to be
after hours or during non-peak occupancy times (for the large conference
room spaces, etc.). ASHRAE 62.1-2007 Section 6.2.6 and Section 6.2.7
both will tell you how low your minimum ventilation rate can go during
the unoccupied period.
A note for everyone who reads this: I've been told I take a very literal
read of the code so this may not agree with your understanding of it,
but in my literal view I see Section 6.2.7 allowing you to reduce the
value of Pz in your VRP calculations to 0 during unoccupied times but
since Az remains fixed you are not allowed to reduce the outdoor air
down to 0 during unoccupied times. Explanatory material behind the
development of the current procedures in the standard explains that the
VRP calculation has two components: one to deal with IAQ associated with
people-generated contaminants and one for building-generated
contaminants. Regardless of your view on that, you should be able to
arrive at a minimum OA number that is LESS than the amount specified
using peak occupancy or time-averaged occupancy (per 6.2.6).
So - in summary: I would double check your occupancy schedule to make
sure it reflects what you are expecting to see in the building and then
double check your minimum OA setting to make sure it will allow the
system to reduce OA when occupancy drops. Also, one possible
"exaggeration" may be viewing it from a system energy perspective or a
whole building perspective: if I leave one zone and go to another and
both zones have DCV, then the one I left will reduce OA and the one I
entered will increase OA but the net effect should be to balance each
other out (oversimplified, but the concept is what I was going for not
the math). So when you look at building-level energy consumption for
the ventilation system the individual unit savings will wash out. The
only savings you'll see are when people leave the building altogether.
Jeremy R. Poling, PE, LEED AP+BDC
Manager | Sustainability Services
TRANSWESTERN
234 W. Florida St.
Milwaukee, WI 53204
Phone 414.255.3322 | Fax 414.224.7780 | Mobile 414.426.7273
Jeremy.Poling at Transwestern.net <mailto:Jeremy.Poling at Transwestern.net>
http://www.transwestern.net/Energy-Sustainability.asp
<http://www.transwestern.net/Energy-Sustainability.asp>
From: equest-users-bounces at lists.onebuilding.org [
mailto:equest-users-bounces at lists.onebuilding.org
<mailto:equest-users-bounces at lists.onebuilding.org> ] On Behalf Of
Charles Welch
Sent: Friday, March 11, 2011 1:14 PM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] EMS Control System Modeling
Thank you very much to those who helped me out with this... Finally made
some good headway.
Quick question....
Modeling the DCV for my location (AZ) I shows only a very small
improvement in energy consumption for my HVAC, does this sound correct?
I have always been "led to believe" by the local control companies that
DCV is a huge improvement?
Myth, sales "exaggeration", or have some of them found a way to control
the DCV in a manner that I am not modeling correctly?
Opinions or pointers appreciated.
----- Original Message -----
From: Karen Walkerman <mailto:kwalkerman at gmail.com>
To: MatthewRLarson at eaton.com <mailto:MatthewRLarson at eaton.com>
Cc: GCollins at glumac.com <mailto:GCollins at glumac.com> ;
cwelch at capitalreviewgroup.com <mailto:cwelch at capitalreviewgroup.com> ;
equest-users at lists.onebuilding.org
<mailto:equest-users at lists.onebuilding.org>
Sent: Wednesday, March 09, 2011 2:48 PM
Subject: Re: [Equest-users] EMS Control System Modeling
Regarding DCV there are a few things to know:
1. demand is based on the number of people in the space and the outdoor
air per person specified at the zone level. If your outdoor air rate is
not entered as a per person air rate, then DCV will not work properly
2. If your fans are not constant volume, ie they can cycle or they are
variable speed, then you need to make sure that the proper ventilation
air is supplied in your base case. Usually, I set the fan flow to
'variable'. If, in reality, the fans cycle on and off, I change the fan
curve to linear. Then, i set the minimum flow to be equal to the
outdoor air rate fraction. Otherwise, implementing DCV can actually
RAISE energy.
On Wed, Mar 9, 2011 at 10:59 AM, <MatthewRLarson at eaton.com> wrote:
Charles,
Regarding the DCV, you need to specify the "Minimum OA Control Method"
under the Outdoor Air tab for the system to state whether the CO2 sensor
is in the return or in the space. Then at the zone level, specify the
"Minimum Flow Control" under the Air Flow tab to state if the minimum OA
resets up or down depending on occupancy level. To ensure the amount of
OA going into a space doesn't go below the ASHRAE 62.1 minimum, I always
input the OA Flow per Person and/or Flow per Area at the zone level as
well. DCV has always been something I've been a little dicey about so
any additional suggestions/comments would be great.
Thanks,
Matthew Larson, LEED AP BD+C
Project Engineer
Energy Solutions Group
E M C Engineers, Inc.
Eaton's Electrical Services & Systems
143 Union Blvd, Suite 350
Lakewood, CO 80228
tel: +1 303 328-3419
mobile: +1 303 668-2511
fax: +1 303 974-1239
MatthewRLarson at Eaton.com <mailto:MatthewRLarson at Eaton.com>
www.eaton.com/energysolutions <http://www.eaton.com/energysolutions>
Error! Filename not specified.
From: equest-users-bounces at lists.onebuilding.org
<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:
equest-users-bounces at lists.onebuilding.org
<mailto:equest-users-bounces at lists.onebuilding.org> ] On Behalf Of Greg
Collins
Sent: Tuesday, March 08, 2011 5:53 PM
To: Charles Welch; equest-users at lists.onebuilding.org
<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] EMS Control System Modeling
Charles - A quick suggestion for the setback is to try setting your
system fans to "cycle on any." Otherwise, your system might not kick on
to maintain setback temperatures.
Greg Collins
GLUMAC | (949) 833-8190
From: Charles Welch [mailto:cwelch at capitalreviewgroup.com
<mailto:cwelch at capitalreviewgroup.com> ]
Sent: Tuesday, March 08, 2011 4:24 PM
To: equest-users at lists.onebuilding.org
<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] EMS Control System Modeling
I am doing an quick estimate for adding EMS control to an existing HVAC
system (schools) which incorporate the following measures
1) Automatic thermostat setbacks for building occupation
2) Demand controlled ventilation
3) Economizers
Here are my "challenges"
1) Simulation with setback temperatures shows no reduction in energy
2) I am unsure how to handle DCV
3) Simulation with economizers show very little reduction
I would appreciate any pointers, suggestions, etc. on what to do here.
I would especially appreciate any example files to see how you input the
data to get proper results.
Thanks in advance for any help.
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