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Re: [EnergyPlus_Support] CompactVAV system Heating Coil not sizing
The main problem here is that the zone min flow rates are set to zero, and the
system min flow rate is set to autosize, which then becomes zero. For a single
duct system, the heating coil sizing routine assumes that the heating coil will
be active at the min flow rate, so it sees no flow and sizes to zero capacity.
A couple of issues:
1. I am guessing that during heating operation you want the VAV dampers in
each zone to modulate to control the zone temperature. The VAV terminal units
will only do this is the zone dampe heating action is set to REVERSE ACTION.
And, due to limitations in the current model, reverse action only works for VAV
terminal units with a hot water reheat coil. You may be able to get the
operation you desire by specifying hot water reheat, reverse action, and then
setting the reheat coil availability schedule to zero at all times.
2. The Compact HVAC sizing inputs are not set up for this type of system (I
will add some suggestions to the list of possible enhancements). You will need
to take the expidf file and modify the SYSTEM SIZING object to specify the
"Central heating design supply air temperature" as 43.333 and the "minimum
system air flow ratio" as 1.0. I think this will produce the desired result.
Mike
On 7 Jun 2005, at 19:44, octavius1st wrote:
> I am trying to use a compact system desciption to define a basic VAV
> system for a residential type building. After running this file the
> designed heating capacity is zero. Cooling seems fine. Does any one
> have any suggestions to what might be wrong?
> (schedules, zones, etc. should be fine)
>
> Thanks,
> Neal
>
> ===============================================================
>
> COMPACT HVAC:ZONE:VAV,
> FamilyRoom, !- Zone Name
> VAV, !- Air Handling System Name
> BC1, !- Thermostat Name
> autosize, !- Zone Supply Air Max Flow Rate {m3/s}
> 0, !- Zone Supply Air Min Flow Fraction
> flow/person, !- Zone Outside Air Flow Type
> 0, !- Zone Outside Air Flow Rate {m3/s}
> None, !- Reheat Coil Type
> , !- Reheat Coil Availability Schedule
> Normal; !- Zone Damper Heating Action
>
> !- More zones that I have omitted for this post
>
> COMPACT HVAC:ZONE:VAV,
> Kitchen, !- Zone Name
> VAV, !- Air Handling System Name
> BC1, !- Thermostat Name
> autosize, !- Zone Supply Air Max Flow Rate {m3/s}
> 0, !- Zone Supply Air Min Flow Fraction
> flow/person, !- Zone Outside Air Flow Type
> 0, !- Zone Outside Air Flow Rate {m3/s}
> None, !- Reheat Coil Type
> , !- Reheat Coil Availability Schedule
> Normal; !- Zone Damper Heating Action
>
> !- =========== ALL OBJECTS IN CLASS: COMPACT HVAC:SYSTEM:VAV
> ===========
>
> COMPACT HVAC:SYSTEM:VAV,
> VAV, !- Air Handling System Name
> On, !- System Availability Schedule
> autosize, !- Supply Fan Max Flow Rate {m3/s}
> autosize, !- Supply Fan Min Flow Rate {m3/s}
> 0.7, !- Supply Fan Total Efficiency
> 1000, !- Supply Fan Delta Pressure {Pa}
> 0.9, !- Supply Fan Motor Efficiency
> 1, !- Supply Fan Motor in Air Stream
> Fraction
> Chilled Water, !- Cooling Coil Type
> BCCa, !- Cooling Coil Availability Schedule
> , !- Cooling Coil Setpoint Schedule
> 12.778, !- Cooling Coil Constant Setpoint {C}
> Gas, !- Heating Coil Type
> BCHa, !- Heating Coil Availability Schedule
> , !- Heating Coil Setpoint Schedule
> 43.333, !- Heating Coil Constant Setpoint {C}
> 0.8, !- Gas Heating Coil Efficiency
> 0, !- Gas Heating Coil Parasitic Electric
> Load {W}
> None, !- Preheat Coil Type
> , !- Preheat Coil Availability Schedule
> , !- Preheat Coil Setpoint Schedule
> , !- Preheat Coil Constant Setpoint {C}
> 0.8, !- Gas Preheat Coil Efficiency
> , !- Gas Preheat Coil Parasitic Electric
> Load {W}
> 0, !- Maximum Outside Air Flow Rate {m3/s}
> 0, !- Minimum Outside Air Flow Rate {m3/s}
> FIXED MINIMUM, !- Minimum Outside Air Control Type
> Off, !- Minimum Outside Air Schedule Name
> None, !- Economizer Type
> NO LOCKOUT, !- Economizer Lockout
> , !- Economizer Upper Temperature Limit {C}
> , !- Economizer Lower Temperature Limit {C}
> , !- Economizer Upper Enthalpy Limit {J/kg}
> , !- Supply Plenum Name
> ; !- Return Plenum Name
>
>
> !- =========== ALL OBJECTS IN CLASS: COMPACT HVAC:PLANT:CHILLED
> WATER LOOP ===========
>
> COMPACT HVAC:PLANT:CHILLED WATER LOOP,
> CWL, !- Plant Loop Name
> , !- Pump Schedule
> INTERMITTENT, !- Pump Control Type
> Default, !- Chiller Plant Operation Scheme Type
> , !- Chiller Plant Operation Scheme Name
> , !- Chilled Water Setpoint Schedule
> 7.2222, !- Chilled Water Constant Setpoint {C}
> Constant Flow, !- Chilled Water Pump Configuration
> 179352, !- Primary Chilled Water Pump Rated Head
> {Pa}
> 179352, !- Secondary Chilled Water Pump Rated
> Head {Pa}
> , !- Condenser Plant Operation Scheme Type
> , !- Condenser Plant Operation Scheme List
> Name
> , !- Condenser Water Temperature Control
> Type
> , !- Condenser Water Setpoint Schedule
> , !- Condenser Water Constant Setpoint {C}
> 179352; !- Condenser Water Pump Rated Head {Pa}
>
>
> !- =========== ALL OBJECTS IN CLASS: COMPACT HVAC:PLANT:CHILLER
> ===========
>
> COMPACT HVAC:PLANT:CHILLER,
> Chiller1, !- Chiller Name
> Electric Centrifugal Chiller, !- Chiller Type
> autosize, !- Capacity {W}
> 2.696, !- COP {W/W}
> AIR COOLED, !- Condenser Type
> 1; !- Priority
>
>
> !- =========== ALL OBJECTS IN CLASS: COMPACT HVAC:PLANT:HOT WATER
> LOOP ===========
>
> COMPACT HVAC:PLANT:HOT WATER LOOP,
> HWL, !- Plant Loop Name
> On, !- Pump Schedule
> INTERMITTENT, !- Pump Control Type
> Default, !- Hot Water Plant Operation Scheme Type
> , !- Hot Water Plant Operation Scheme List
> Name
> , !- Hot Water Setpoint Schedule
> 71.111, !- Hot Water Constant Setpoint {C}
> Constant Flow, !- Hot Water Pump Configuration
> 179352; !- Hot Water Pump Rated Head {Pa}
>
>
> !- =========== ALL OBJECTS IN CLASS: COMPACT HVAC:PLANT:BOILER
> ===========
>
> COMPACT HVAC:PLANT:BOILER,
> Boiler1, !- Boiler Name
> Hot Water Boiler, !- Boiler Type
> autosize, !- Capacity {W}
> 0.8, !- Efficiency
> NaturalGas, !- Fuel Type
> 1; !- Priority
>
>
>
>
>
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>
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>
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>
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>
========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
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