RE: [EnergyPlus_Support] Re: Min ODA rate is not being met?

Autosizing is finicky; you may get errors if you turn one off without manually sizing all of the items it was autosizing. I think neither adversely affects the other; they work together.

Sorry if that’s somewhat incoherent. I try to use “all or nothing” (i.e., all autosized or all manually sized.)

The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of jeannieboef
Sent: Tuesday, September 07, 2010 9:50 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: Min ODA rate is not being met?

I just thought of something. I have:
SimulationControl,
Yes, !- Do the zone sizing calculation
Yes, !- Do the system sizing calculation
No, !- Do the plant sizing calculation
Yes, !- Do the design day calculation
No; !- Do the weather file calculation

I could turn off the "!-Do the zone sizing calculation" which may be overiding the system sizing calculation. It has other values. This could be the problem, but what usually needs the zone sizing calculation? Zone equipment?

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "jeannieboef" <jeannieboef@...> wrote:
>
> Well spotted. The fan is not on, but that does not effect the sizing calculations that still nicely calculate the size the fan must be to bring the air flow to meet the loads and ODA requirements.
>
> Theoretically, I shouldn't need to specify the minimum air flow for the zone at zone level if I do it here in the Air Loop Sizing, but I can give it a try.
>
> My method for the fan powers has worked by the way...thanks to your input (not directed at me, but I tend to read most of your comments).
>
> 1) I will try specifying it at zone level as well.
> 2) I will then try with the fans on.
>
> Thanks again.
>
> Jean.
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "James V Dirkes II, PE" <jvd2pe@> wrote:
> >
> > It seems that the 0.175 value should be met. Is the fan on? (If not, there
> > will be no flow)
> >
> >
> >
> > You might try setting the outdoor air fields in Sizing:Zone
> >
> >
> >
> > The Building Performance Team
> > James V. Dirkes II, P.E., LEED AP
> > 1631 Acacia Drive NW
> > Grand Rapids, MI 49504
> > 616 450 8653
> >
> >
> >
> > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of jeannieboef
> > Sent: Tuesday, September 07, 2010 3:43 AM
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > Subject: [EnergyPlus_Support] Min ODA rate is not being met?
> >
> >
> >
> >
> >
> > Min ODA rate is not being met. Resulting airflow is 0.03 m3/s which is
> > smaller than the 0.175 Min ODA rate input in the sizing object.
> >
> > Any idea why?
> >
> > !JMM VENTILATION 118204
> > Sizing:System,
> > 118204 AHU, !- AirLoop Name
> > Sensible, !- Type of Load to Size On
> > 0.175000, !- Design (minimum) outside air volumetric flow rate {m3/s} !630
> > m3/hr
> > 1, !- Minimum System Air Flow Ratio
> > 7, !- Preheat design set temperature {C}
> > 0.008, !- Preheat design humidity ratio {kg-H2O/kg-air}
> > 11, !- Precool design temperature {C}
> > 0.008, !- Precool design humidity ratio {kg-H2O/kg-air}
> > 13, !- Central cooling design supply air temperature {C} ! For cooling room
> > setpoint 24°C as per G3.1.2.8 deltaT = 11°C
> > 32, !- Central heating design supply air temperature {C} ! For heating room
> > setpoint 21°C as per G3.1.2.8 deltaT = 11°C
> > NonCoincident, !- Sizing Option
> > No, !- 100% Outdoor Air in Cooling
> > No, !- 100% Outdoor Air in Heating
> > 0.008, !- Central cooling design supply air humidity ratio {kg-H2O/kg-air}
> > 0.008, !- Central heating design supply air humidity ratio {kg-H2O/kg-air}
> > DesignDay, !- Cooling Design Air Flow Method
> > 0, !- cooling design air flow rate {m3/s}
> > DesignDay, !- Heating Design Air Flow Method
> > 0; !- heating design air flow rate {m3/s}
> >
>

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