[Equest-users] EMS Control System Modeling

[Paul Diglio]

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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