[Equest-users] ASHRAE 62.1 Unoccupied Vnetilation
Paul Diglio
paul.diglio at sbcglobal.net
Mon Mar 14 06:19:13 PDT 2011
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]
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
http://www.transwestern.net/Energy-Sustainability.asp
From: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
>To:MatthewRLarson at eaton.com
>Cc:GCollins at glumac.com ; cwelch at capitalreviewgroup.com ;
>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
>www.eaton.com/energysolutions
>Error! Filename not specified.
>
>From: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
>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]
>Sent: Tuesday, March 08, 2011 4:24 PM
>To: 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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