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Re: [EnergyPlus_Support] Economizer for zone 3C





Looks good to me.
I normally use the same schedule for "Minimum Outdoor Air Schedule Name" as is used for the fan so that outdoor air is not used during unoccupied periods.

On Wed, Mar 16, 2016 at 10:18 AM, fpasserini.tn@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
 

I have to model an economizer for a baseline model (according to ASHRAE 90.1-2010, LEED v.4) of a building located in climate zone 3C.

According to Table G3.1.2.6B the High-Limit shutoff shall be equal to 24°C.

I think that I have to impose the following fields in the objects Controller:OutdoorAir :


Controller:OutdoorAir,

    Air Loop A p01 AHU 1  Outdoor Air Controller,  !- Name

    Air Loop A p01 AHU 1 Relief Air Outlet,  !- Relief Air Outlet Node Name

    Air Loop A p01 AHU 1 Extract Fan Air Outlet Node,  !- Return Air Node Name

    Air Loop A p01 AHU 1 Mixed Air Outlet,  !- Mixed Air Node Name

    Air Loop A p01 AHU 1 Outdoor Air Inlet,  !- Actuator Node Name

    4.21,                    !- Minimum Outdoor Air Flow Rate {m3/s}

    autosize,                    !- Maximum Outdoor Air Flow Rate {m3/s}

    FixedDryBulb,            !- Economizer Control Type

    ModulateFlow,            !- Economizer Control Action Type

    24,                      !- 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

    ventilation,             !- Minimum Outdoor Air Schedule Name

    ,                        !- Minimum Fraction of Outdoor Air Schedule Name

    ,                        !- 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 4.21 m3/s is the design ventilation rate.

"ventilation" is a schedule relative to the hours when there is OA ventilation in the proposed model. Shall I consider that schedule also for the baseline model?


When the outdoor air temperature is lower than 24°C, the air flow rate will be increased if it is useful to achieve the setpoint temperature that I imposed according to G3.1.3.12 (reset higher by 2.3°C under the minimum cooling load conditions) with the following objects:


SetpointManager:MixedAir,

    Air Loop A p01 AHU 1  Outside air system Mixed Air Manager,  !- Name

    Temperature,             !- Control Variable

    Air Loop A p01 Supply Side Outlet 1,  !- Reference Setpoint Node Name

    Air Loop A p01 AHU 1 Heating Coil Air Outlet Node,  !- Fan Inlet Node Name

    Air Loop A p01 Supply Side Outlet 1,  !- Fan Outlet Node Name

    Air Loop A p01 AHU 1 Mixed Air Outlet;  !- Setpoint Node or NodeList Name


NodeList,

    Air Loop Setpoint Manager Node List,  !- Name

    Air Loop A p01 Supply Side Outlet 1;  !- Node 1 Name


SetpointManager:OutdoorAirReset,

    Air Loop Setpoint Manager,  !- Name

    Temperature,             !- Control Variable

    17.3,                   !- Setpoint at Outdoor Low Temperature {C}

    16,                   !- Outdoor Low Temperature {C}

    15,                   !- Setpoint at Outdoor High Temperature {C}

    26,                   !- Outdoor High Temperature {C}

    Air Loop Setpoint Manager Node List;  !- Setpoint Node or NodeList Name


Do you think that this approach is correct?

Will the economizer cool the supplied air (through increased ventilation rate) also in winter, when it isn't advantageous?

Best Regards


 




--

James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
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Posted by: Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>


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