Just be careful. Increasing flowrate (total) is not the same as increasing outdoor air flowrate. The fan has its limits. What you want is to make sure your minimum outdoor air requirement at system level is equal to the design outdoor air flow rate in the controller, and that the autosized "Maximum Outdoor Air Flow Rate {m3/s}" is not more than what the fan can bring.
So you have your
- design oda
tempered by your
- oda schedule ("ventilation")
that sets the minimum.
And the max is currently autosized and hopefully pulls its value from the sizing:system object. This is right for the baseline. The sizing method should be sensible and not "ventilation requirement" for baseline.
Setback managers also look good, however you are placing two set points on the same node. The second will override the first. You should get a warning.
I can't figure out what temperature setpoint the SetpointManager:MixedAir is going to try and place. I guess they come from the controller.
On 16 Mar 2016 11:59 pm, "Jim Dirkes jim@... [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote: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@... [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.
1631 Acacia Dr, GR, Mi 49504
Direct: 616.450.8653
jim@...
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