Re: [EnergyPlus_Support] VAV with 100% OA

I think you want to leave the minimum and maximum flow rate fields blank (or give a large range) and use the fraction outdoor air fields. Then at the zone dampers, you can specify flow rate schedules or operation.

On 9 Oct 2015 23:31, "Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

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Francesco,
Your schedule affects only outdoor airflow. Apparently you want to make a change in the total airflow, however.

I have never done this, but I think you may be able to do it with an EMS program.

On Fri, Oct 9, 2015 at 4:55 AM, fpasserini.tn@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

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I have created a very simple model, because I want to understand how I can model a VAV system where the ventilation rates are lower during the weekends and the air system operates always with 100% outdoor air (I don't want any recirculation).
During the occupation hours I want to have 1,00m3/s during week days and 0,10m3/s during the weekends, therefore I have imposed the following control:

Controller:OutdoorAir,
Air Loop AHU Outdoor Air Controller, !- Name
Air Loop AHU Relief Air Outlet, !- Relief Air Outlet Node Name
Air Loop AHU Extract Fan Air Outlet Node, !- Return Air Node Name
Air Loop AHU Mixed Air Outlet, !- Mixed Air Node Name
Air Loop AHU Outdoor Air Inlet, !- Actuator Node Name
1, !- Minimum Outdoor Air Flow Rate {m3/s}
1, !- Maximum Outdoor Air Flow Rate {m3/s}
NoEconomizer, !- Economizer Control Type
ModulateFlow, !- Economizer Control Action Type
, !- Economizer Maximum Limit Dry-Bulb Temperature {C}
, !- Economizer Maximum Limit Enthalpy {J/kg}
, !- Economizer Maximum Limit Dewpoint Temperature {C}
, !- Electronic Enthalpy Limit Curve Name
, !- Economizer Minimum Limit Dry-Bulb Temperature {C}
NoLockout, !- Lockout Type
FixedMinimum, !- Minimum Limit Type
mechvent pterra, !- Minimum Outdoor Air Schedule Name
On, !- Minimum Fraction of Outdoor Air Schedule Name
mechvent pterra, !- Maximum Fraction of Outdoor Air Schedule Name
, !- Mechanical Ventilation Controller Name
, !- Time of Day Economizer Control Schedule Name
No, !- High Humidity Control
, !- Humidistat Control Zone Name
1, !- High Humidity Outdoor Air Flow Ratio
Yes, !- Control High Indoor Humidity Based on Outdoor Humidity Ratio
BypassWhenWithinEconomizerLimits; !- Heat Recovery Bypass Control Type

where the schedule is

Schedule:Compact,
mechvent pterra, !- Name
Fraction, !- Schedule Type Limits Name
Through: 12/31, !- Field 1
For: Weekdays SummerDesignDay WinterDesignDay, !- Field 2
Until: 08:30, !- Field 3
0, !- Field 4
Until: 18:00, !- Field 5
1, !- Field 6
Until: 24:00, !- Field 7
0, !- Field 8
For: AllOtherDays, !- Field 9
Until: 08:30, !- Field 10
0, !- Field 11
Until: 18:00, !- Field 12
.1, !- Field 13
Until: 24:00, !- Field 14
0; !- Field 15

Since the air flow shall be independent from the cooling load and from the heating load, I have forced the air flow rates in Sizing:System.
As fan I'm using Fan:VariableVolume and as terminal AirTerminal:SingleDuct:Uncontrolled

If I consider the output, the outdoor air flow rate is modulated properly, but there is recirculation (the supplied air flow rate, i.e. OA + recirculated air, is constantly equal to 1m3/s).
I attach the model.
What is wrong?
Best Regards

Francesco

--
James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct: 616.450.8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx

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