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[EnergyPlus_Support] Re: DOAS Outdoor Air Rate
Well the original work around was determining the max (assuming I used the same people schedule for each zone which is what I did since it was a decent enough representation) then determine what the FA requirement I would be looking for each zone then used the Controller:OutdoorAir to set my Minimum Outdoor Air Flow Rate to just under (95%) the peak value I'd be looking for then set the Maximum Outdoor Air Flow Rate to just over (105%)the peak value I was looking for. This worked like a charm but then after doing some more investigating I found the answer I was looking for in the Controller:MechanicalVentilation object.
The Controller:MechanicalVentilation object allows for demand control ventilation, which is what I am looking to model, and added in the DesignSpecification:OutdoorAir and ZoneAirDistribution objects to the MechanicalVentilation object. Then I added the MechanicalVentilation object into the OutdoorAir and put in minimum/maximum outdoor air flow rates that were "safe" as in 0 to like 150% of max and the thing worked like a charm.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jean marais" <jeannieboef@...> wrote:
>
> Sounds good. Bear in mind that zone A might have it's maximum ODA requirement of 1000 at another time than zone B has its maximum of 900...or the demand times may co-inside. As this is a DOAS with only air tempering function as the zone loads are caught 100% by zone equipment, the ODA requirement of the ODAmixer should be 100% all of the time. This should confer the ODA control onto the VAV dampers. Could you put the zone's ODArequirement into the terminal damper's fields somehow?Else, an EMS to dynamically change the minimum damper setting as per people load. I'm not sure the ODA controller is designed to handle DOAS situations per say. What I mean is that as soon as the minimum ODA in the ODAcontroler is anything less than 100%, it will start mixing and then it is no longer a 100% ODA system.
>
> This may have changed since v7.1 so don't quote me. Didn't the newer versions come with new DCV objects? As Jim said the CO2 monitoring DCV may be an alternitive option.
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Jim Dirkes <jim@> wrote:
> >
> > It will be interesting to try it out :).
> > If, however, your peak OA is 1000, I think you want to specify that as the Maximum, and the People schedule also as Maximum.
> > I'm assuming that the VAV system's only purpose is ventilation, so it's flow is determined solely by ventilation needs.....
> >
> > James V Dirkes II, PE, BEMP, LEED AP
> > www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
> > Energy Analysis, Commissioning & Training Services
> > 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> > 616 450 8653
> >
> > From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of ntraughpee
> > Sent: Tuesday, November 06, 2012 5:06 PM
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > Subject: [EnergyPlus_Support] Re: DOAS Outdoor Air Rate
> >
> >
> >
> > Yeah I actually did this right after I posted the message
> >
> > What would be a good way to ensure I meet the FA requirements for a VAV?
> >
> > Put in a value for Minimum Outdoor Air (as in 1000 CFM which is my peak FA requirement load) then put in my People Schedule into the Minimum?
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support%40yahoogroups.com>, Jim Dirkes <jim@<mailto:jim@>> wrote:
> > >
> > > Matthew,
> > > Apart from using a ZoneControl:ContaminantController, I think what you want to do is either:
> > >
> > > 1. Use Controller:OutdoorAir to force specific OA flow, something like:
> > >
> > >
> > > Controller:OutdoorAir
> > >
> > > Name
> > >
> > > OAController_FitnessDOAS
> > >
> > > Relief Air Outlet Node Name
> > >
> > > NodeOut_EA_FitnessDOAS
> > >
> > > Return Air Node Name
> > >
> > > NodeIn_RA_FitnessDOAS
> > >
> > > Mixed Air Node Name
> > >
> > > NodeOut_MA_FitnessDOAS
> > >
> > > Actuator Node Name
> > >
> > > NodeIn_OA_FitnessDOAS
> > >
> > > Minimum Outdoor Air Flow Rate
> > >
> > > 0 (or whatever you wish)
> > >
> > > Maximum Outdoor Air Flow Rate
> > >
> > > (your maximum value)
> > >
> > > Economizer Control Type
> > >
> > > FixedDryBulb
> > >
> > > Economizer Control Action Type
> > >
> > > ModulateFlow
> > >
> > > Economizer Maximum Limit Dry-Bulb Temp (C)
> > >
> > > 50
> > >
> > > Economizer Maximum Limit Enthalpy (J/kg)
> > >
> > > Economizer Maximum Limit Dewpoint Temp (C)
> > >
> > > Electronic Enthalpy Limit Curve Name
> > >
> > > Economizer Minimum Limit Dry-Bulb Temp (C)
> > >
> > > -40
> > >
> > > Lockout Type
> > >
> > > NoLockout
> > >
> > > Minimum Limit Type
> > >
> > > FixedMinimum
> > >
> > > Minimum Outdoor Air Schedule Name
> > >
> > > Minimum Fraction of Outdoor Air Schedule Name
> > >
> > > SchCpct_AlwaysOn
> > >
> > > Maximum Fraction of Outdoor Air Schedule Name
> > >
> > > (Something here that parallels your people schedule)
> > >
> > > Mechanical Ventilation Controller Name
> > >
> > > Time of Day Economizer Control Schedule Name
> > >
> > > High Humidity Control
> > >
> > > Humidistat Control Zone Name
> > >
> > > High Humidity Outdoor Air Flow Ratio
> > >
> > > Control High Indoor Humidity Based on Outdoor Humidity Ratio
> > >
> > > Heat Recovery Bypass Control Type
> > >
> > >
> > > 2. Or use the Controller:MechanicalVentilation and let E+ calculate the OA flow per your criteria.
> > >
> > >
> > > James V Dirkes II, PE, BEMP, LEED AP
> > > www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
> > > Energy Analysis, Commissioning & Training Services
> > > 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> > > 616 450 8653
> > >
> > > From: EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support%40yahoogroups.com> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support%40yahoogroups.com>] On Behalf Of Jean marais
> > > Sent: Tuesday, November 06, 2012 3:50 PM
> > > To: EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support%40yahoogroups.com>
> > > Subject: [EnergyPlus_Support] Re: DOAS Outdoor Air Rate
> > >
> > >
> > >
> > > The sizing:zone object is for sizing. How the system then operates...is the job of the controling equipment. I'm not sure what the "Outdoor Air Flow Rate Fraction Schedule" in the DesignSpecification:OutdoorAir object does (without looking at the ioref). A similar sounding field in the ODAController, for example, may override other minimums, i.e. it takes the worst of the minimums...so double check that. Then concentrate on the ODAController as this will be doing the controlling during simulation.
> > >
> > > Goodluck,
> > >
> > > Jean
> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx<mailto:EnergyPlus_Support%40yahoogroups.com><mailto:EnergyPlus_Support%40yahoogroups.com>, "ntraughpee" <matthew.sverre.anderson@<mailto:matthew.sverre.anderson@<mailto:matthew.sverre.anderson@%3cmailto:matthew.sverre.anderson@>>> wrote:
> > > >
> > > > Hey Everybody,
> > > >
> > > > So I am attempting to model a DOAS with zone fan coil system and I am having some troubles getting the outdoor air rate to come out how I want it. Basically I am looking to model a demand control ventilation system where we are bringing in outdoor air based upon occupancy rates. The fan coils themselves have no economizers or outdoor air besides what the DOAS system brings in. Currently in "cooling" months it brings in 100% OA where I want it to only bring in the amount of fresh air needed to meet the FA requirements and then temper that air and supply it to the zones and since it is supposed to be a school where occupancy is minimized during the summer months we should be bringing in a very small amount of outdoor air where during those months.
> > > >
> > > > The DOAS system is a VAV with no reheat. There are 4 separate AHU's with 3 zones per AHU. I have a People load with a "people" schedule. Then I have done this:
> > > >
> > > > In the DesignSpecification:OutdoorAir object I have OutdoorAirMethod = Flow/Person with the Flow/Person = 10 CFM. Then in the Outdoor Air Flow Rate Fraction Schedule Name I have a schedule with a value for AllDays = 1.
> > > > - Am I correct in thinking that this draws from the "People" object in InternalGains to determine what the OA CFM needs to be? -
> > > >
> > > > Then in the AirTerminal:SingleDuct:VAV:NoReheat object I have the Design Specification Outdoor Air Object Name as the related DesignSpecification:OutdoorAir object. I also have the max airflow rate set to what it should be and the minimum set to zero.
> > > >
> > > > Then in the Controller:OutdoorAir I have the minimum/maximum outdoor air flow set and it put to NoEconomizer.
> > > >
> > > > Is my thinking correct? What am I missing?
> > > >
> > >
> >
>
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