Re: [EnergyPlus_Support] VAV with 100% OA

On Fri, Oct 9, 2015 at 5:31 PM, 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

Website l Â LinkedIn

â???happiness is the joy produced in us by truth. To be truly happy means coming to know how things really are, experiencing ?reality in its ultimate rootâ??¦
What matters more to oneâ??s happiness than getting more freedom and power is the end toward which we order whatever freedom and power we have. Unless we order ourselves to the truth, more freedom and more power will bring only more unhappiness, examples of which abound.

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

Website l Â LinkedIn

â???happiness is the joy produced in us by truth. To be truly happy means coming to know how things really are, experiencing ?reality in its ultimate rootâ??¦
What matters more to oneâ??s happiness than getting more freedom and power is the end toward which we order whatever freedom and power we have. Unless we order ourselves to the truth, more freedom and more power will bring only more unhappiness, examples of which abound.