[Equest-users] Modeling Reverse Acting TStat EF

Wed Oct 19 11:17:46 PDT 2016

Hi everyone,

Thanks again for all your input.

I've run into a snag.  I cannot seem to get the fan to turn on when the
temp > 80 degF.  When I look at some of the reports I see that there is no
reported unmet clg hours for this zone which is a red flag - not sure why
this is.  There is a sizable clg load in this zone: 65 MBH.  I do see on
the SS-F that the max zone temp hits 86.1 degF.  Any thoughts?

On Tue, Oct 18, 2016 at 4:00 PM, Nicholas Caton <
Nicholas.Caton at schneider-electric.com> wrote:

> Hey Darryl,
>
>
>
> This turned into a big response, but it seems the problem we’re trying to
> help solve is a moving target!
>
>
>
> 1.       The advice to enter something nominal but tiny for cooling
> capacity, to avoid autosizing & prevent airstream cooling, is based on the
> earlier statement that you do not intend to cool the airstream making up
> the exhaust.  Going the other route of just making it “free cooling”
> (EIR=0) goes against your goal of modeling reality as now the exhaust
> “makeup” airstream is being conditioned on its way in, resulting in milder
> interior temperatures for determining hourly zonal heat transfers.  An
> equally viable alternative I generally prefer to “lock out” cooling
> operations by the way is an airside system COOLING-SCHEDULE with hourly
> values of zero.  An expected side effect of of crippling/breaking your
> PSZ’s cooling capacity with a tiny number is that you will end up with a
> justifiable quantity of unmet cooling hours – so expect & make note of that
> swing in unmet hours so you can quantify &  parse it out later for your own
> QC/documentation.
>
> 2.       Based on the reference help entries, I’m concerned the
> night-cycle-ctrl inputs are intended specifically for the inverse case only
> (reacting only to provide heating when the system is off.  I think the
> effect you’re looking for (turning on only when thermostat calls request
> it) can be achieved for PSZ by simply not defining a fan schedule
> (right-click, default that dropdown field).  *Either way*, you can &
> should check/verify intended system operation via custom hourly reports for
> the associated system & control zone – include hourly zone temperatures,
> associated tstat setpoints, and something like fan operation/cfm to verify
> if the system is only operating when intended.
>
> 3.       I’m not certain zonal exhaust inputs are necessary at all if you
> are modeling a 100% OA PSZ, but be cautious you aren’t ending up
> unintentionally “double-counting” fan energies between your PSZ fan power
> inputs and your zonal exhaust power inputs (or lack thereof).  I think you
> can “zero out” the zonal kW/cfm or else make it a very tiny number if you
> do decide zonal exhaust inputs are needed.
>
>
>
> Ah… The fact you intend to model hot water unit heaters probably throws a
> wrench into the advice/discussion so far…
>
>
>
> “Furnace” generally implies gas combustion heating in doe2/eQUEST.  That’s
> not what you want for hot water heating.
>
>
>
> If it’s fair to assume the space is well-mixed during heating scenarios
> (i.e. not much stratification), then you can probably get by with
> accounting for the associated unit heater by specifying hot water
> baseboards with appropriate heating capacity in the zone.  Have them
> controlled by a heating temperature schedule (sounds like you want this set
> to 60F all the time).  You might want to specify the associated loop and
> boilers/meters first so that you can assign those in the same step.
> Downside to layering in baseboards as an approach is the unit heater fan
> energies won’t get picked up explicitly – the heat those contribute will
> instead be supplied by the HHW loop, and the energies associated with their
> fan operations for air circulation will not be picked up automatically.
> You could layer that in however (if it’s pertinent) by doing an hourly
> report to identify when baseboards are in operation (delivering heat), then
> assigning that to the space as an equipment load, capturing the heat
> contributions and electricity consumption.
>
>
>
> If accounting for exhaust and unit heater fan energies operations
> separately/distinctly is a major priority… you’ll probably need to re-think
> the broader approach & system type selection.  UHT is an attractive option
> for picking up unit heater operations explicitly and clearly on its own,
> but that system type affords no capacity to handle OA/exhaust.  You’d
> either need to accomplish the exhaust/damper operations at the zonal level
> (spoon-feeding expected operations as a fractional or ON/OFF schedule since
> we’ve established thermostat schedules are not presently an option).  You
> could alternatively pair UHT’s with an airside-system-based approach to the
> exhaust/damper operations (like the PSZ we’ve been discussing) if you split
> your zone/spaces geometrically to afford separations to assign different
> systems to, thermally connected with airwalls.  Advantage to this approach
> is the flexibility to separate the conditioned volume if air mixing is not
> going to be stellar (stratification expected) during heating.
>
>
>
> Hope this helps steer the ship!
>
>
>
> ~Nick
>
>
>
> *Nick Caton, P.E., BEMP*
>
>   Senior Energy Engineer
>   Energy and Sustainability Services
>   Schneider Electric
>
> D  913.564.6361
> M  785.410.3317
> E  nicholas.caton at schneider-electric.com
> F  913.564.6380
>
> 15200 Santa Fe Trail Drive
> Suite 204
> Lenexa, KS 66219
> United States
>
> [image: cid:image001.png at 01D189AB.58634A10]
>
>
>
>
>
> *From:* Darryl Kasun [mailto:darryl.kasun at gmail.com]
> *Sent:* Monday, October 17, 2016 1:26 PM
> *To:* Nicholas Caton <Nicholas.Caton at schneider-electric.com>
> *Cc:* Brian Fountain <bfountain at greensim.com>; Julien MARREC <
> julien.marrec at gmail.com>; equest-users <equest-users at lists.onebuilding.org
> >
>
> *Subject:* Re: [Equest-users] Modeling Reverse Acting TStat EF
>
>
>
> Hi everyone - thank you so much for the replies.  Just wanted to provide
> as a summary as to what I've modeled thus far - pls comment if you have any:
>
>
>
> *SYSTEM LEVEL:*
>
>
>
> - Modeled the reverse acting t-stat system as a PSZ with the following
> inputs at the system level:
>
> - Control zone is the zone the supply fan serves
>
> - Supply fan kW/CFM equals that of the EF
>
> - Delta T across supply fan = 0
>
> - Supply fan schedule is on/off type with default off for all hours
>
> - Night Cycle Control: On Any
>
> - min outside air ratio = 1.0
>
> - CLG Cap left blank
>
> - EIR = 0
>
>
>
> *ZONE LEVEL:*
>
>
>
> - HTG/CLG design temps are 60/80 degF;
>
> - E/A control is "No Airflow Tracking"
>
> - E/A flow matching the flow of the EF (11,000 CFM)
>
> - E/A source: infiltration
>
> - Max clg rate left blank
>
>
>
> *QUESTIONS REMAINING:*
>
>
>
> - Can I simply leave the CLG capacity to be auto-sized?  Brian you had
> mentioned to put in a minimal value for this input but I do not understand
> why.
>
> - This zone also has HW UHs serving it - how to I implement them?  I see
> at the system level there's an option for the Zone Heat Source to be
> furnace which provides the opportunity to account for a UH's fan energy but
> looks like a furnace cannot be connected to a HW loop.
>
>  - Any advice of thermostat type?
>
>
>
> Thanks again
>
> Darryl Kasun
>
>
>
> On Mon, Oct 17, 2016 at 11:04 AM, Nicholas Caton <
> Nicholas.Caton at schneider-electric.com> wrote:
>
> Hey Brian,
>
>
>
> You’re absolutely right – I should have double-checked before posting.  In
> my mind’s eye, I recalled assigning a temperature schedule to zonal exhaust
> inputs, but it does appear I misremembered and that isn’t a direct option.
>
>
>
> Tricking an airside system as you’re describing into the intended behavior
> must be how I’ve managed this in the past.  A thermostat schedule is
> minimally needed at the system to define the intended “trigger
> temperatures,” and one could optionally also specify a fan schedule to go
> beyond intermittent and enforce off/on hours as might happen in the real
> world via tstat + relays.
>
> ~Nick
>
>
>
> *Nick Caton, P.E., BEMP*
>
>   Senior Energy Engineer
>   Energy and Sustainability Services
>   Schneider Electric
>
> D  913.564.6361
> M  785.410.3317
> E  nicholas.caton at schneider-electric.com
> F  913.564.6380
>
> 15200 Santa Fe Trail Drive
> Suite 204
> Lenexa, KS 66219
> United States
>
> [image: cid:image001.png at 01D189AB.58634A10]
>
>
>
> -----Original Message-----
> From: Brian Fountain [mailto:bfountain at greensim.com]
> Sent: Monday, October 17, 2016 9:55 AM
> To: Nicholas Caton <Nicholas.Caton at schneider-electric.com>; Julien MARREC
> <julien.marrec at gmail.com>; Darryl Kasun <darryl.kasun at gmail.com>
> Cc: equest-users <equest-users at lists.onebuilding.org>
> Subject: Re: [Equest-users] Modeling Reverse Acting TStat EF
>
>
>
> Does this mean the exhaust fan can cycle based on zone temperature?   I
> had thought that the exhaust fan schedule was just on/off, on/off/flag and
> fraction. That means you have to pre-define the expected schedule rather
> than having the EF respond to the hourly space timestep temperature.
>
>
>
> What we have done in the past is to model the EF as a PSZ with the fan
> power as the supply fan power and the "indoor fan mode" as intermittent.
> Cooling capacity set to a small non-zero value (as zero invokes
> auto-sizing).
>
>
>
>
>
>
>
>   Original Message
>
> From: Nicholas Caton via Equest-users
>
> Sent: Monday, October 17, 2016 10:39 AM
>
> To: Julien MARREC; Darryl Kasun
>
> Reply To: Nicholas Caton
>
> Cc: equest-users
>
> Subject: Re: [Equest-users] Modeling Reverse Acting TStat EF
>
>
>
> From: Nicholas Caton
>
> Sent: Monday, October 17, 2016 9:38 AM
>
> To: 'Julien MARREC' <julien.marrec at gmail.com>; Darryl Kasun <
> darryl.kasun at gmail.com>
>
> Subject: RE: [Equest-users] Modeling Reverse Acting TStat EF
>
>
>
> Yep - Julien has the right idea!
>
>
>
> The other input of interest for your case is that at the same input
> screen, you can select the exhaust source as "infiltration," which means
> the associated makeup airstream = outside conditions.
>
>
>
> ~Nick
>
>
>
> Nick Caton, P.E., BEMP
>
> Senior Energy Engineer
>
> Energy and Sustainability Services
>
> Schneider Electric
>
> D 913.564.6361
>
> M 785.410.3317
>
> E nicholas.caton at schneider-electric.com
>
> F 913.564.6380
>
> 15200 Santa Fe Trail Drive
>
> Suite 204
>
> Lenexa, KS 66219
>
> United States
>
>
>
>
>
>
>
> -----Original Message-----
>
> From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org
> <equest-users-bounces at lists.onebuilding.org>] On Behalf Of Julien MARREC
> via Equest-users
>
> Sent: Saturday, October 15, 2016 3:41 PM
>
> To: Darryl Kasun <darryl.kasun at gmail.com>
>
> Cc: equest <equest-users at lists.onebuilding.org>
>
> Subject: Re: [Equest-users] Modeling Reverse Acting TStat EF
>
>
>
> Zonal exhaust fan has an option to control that on a temp schedule if I
> recall correctly.
>
>
>
> Open the zone, tab "outside air" then at the right you can specify a zonal
> exhaust fan. (All this from memory so might differ slightly)
>
>
>
> Cheers,
>
> Julien
>
>
>
> Envoyé de mon iPhone
>
>
>
> > Le 15 oct. 2016 à 20:57, Darryl Kasun via Equest-users <
> equest-users at lists.onebuilding.org> a écrit :
>
> >
>
> > Hi eQUESTers,
>
> >
>
> > First off, you probably will not likely appreciate this and I'll preface
> this with saying that I'm a total bandwagon jumper but I am okay with that.
>
> >
>
> > GO JAYS!!!
>
> >
>
> > Now that that's out of the way I am trying to model a very simple system
> that I'm sure many of you have modeled before.
>
> >
>
> > I have a zone that has an exhaust fan in it. When the temp. reaches
> above 80 degF, an exhaust fan turns on and a damper opens to draw OA into
> the zone.
>
> >
>
> > I've been fooling around with a few systems trying to figure out a good
> way to model this but haven't come up with one yet.
>
> >
>
> > Let me know if have any recommendations.
>
> >
>
> > Thanks!
>
> > Darryl
>
> >
>
> > _______________________________________________
>
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>
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>
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