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Re: [EnergyPlus_Support] Autosizing air and water circuits for zone heating
EnergyPlus is not able to autosize multiple systems. In your case, the
autosizing will attempt to size both the direct air flow rate and the baseboard
capacity to meet the full zone heating load. You should be able to limit the
flow rate of the direct air units at the zone level by specifying "flow/zone"
in the ZONE SIZING objects. The baseboard units will still size to the full
heating load. To downsize the baseboards, you will have to do some runs and
then use hard sizes in the baseboards. I am not sure why the baseboard units
are not coming on when you limit the flow of the forced air system. Is it
possible that the air is being supplied at a temperature higher than 20C?
Check the controls.
Mike
On 9 May 2006 at 14:14, Elmer Morrissey wrote:
> Hello all,
>
> I have another autoszing problem. I have 3 zones that are fed with
> heated auxiliary air at 20C supply air. Any additional heat required
> to maintain zone temps should be picked up by convector units.
>
> ZONE EQUIPMENT LIST,
> Equip:1, !- Name
> DIRECT AIR, !- KEY--Zone Equipment Type 1
> RB:1, !- Type Name 1
> 1, !- Cooling Priority 1
> 1, !- Heating Priority 1
> BASEBOARD HEATER:WATER:CONVECTIVE, !- KEY--Zone Equipment Type 2
> HB:1, !- Type Name 2
> 2, !- Cooling Priority 2
> 2; !- Heating Priority 2
>
> A boiler system supplies hot water to the heating coil in the AHU
> and to the convector units.
>
> (from my interpretation of the EIO file?)
> If I fully autosize the system, E+ thinks that it should force:
> Calculated heating design air flow rate [m3/s], 4762.2.
>
> However, the actual flow rate is constrained by my input in the
> Direct Air objects to no greater than 0.2 m3/s. E+ seems to be think
> the AHU needs to supply all the hot air in the zone. This forces
> mass oversizing of the flowrate in the boiler circuit.
>
> Therefore, I tried to force E+ strain of thought by using this?
>
> SYSTEM SIZING,
> A1:Loop, !- name of an AIR PRIMARY LOOP object
> sensible, !- type of load to size on
> 0.05144145, !- Design (minimum) outside air
> volumetric flow rate {m3/s}
> 1, !- minimum system air flow ratio
> 5, !- Preheat design set temperature {C}
> 12, !- Central cooling design supply air
> temperature {C}
> 20, !- Central heating design supply air
> temperature {C}
> noncoincident, !- Sizing Option
> Yes, !- Cooling 100% Outside Air
> Yes, !- Heating 100% Outside Air
> , !- Central cooling design supply air
> humidity ratio {kg-H2O/kg-air}
> , !- Central heating design supply air
> humidity ratio {kg-H2O/kg-air}
> Design day, !- cooling design air flow method
> , !- cooling design air flow rate {m3/s}
> flow/system, !- heating design air flow method
> 0.05144145; !- heating design air flow rate {m3/s}
>
> This corrects the boiler flowrates sizing problems however it means
> that the convector units never turns on.
>
> Can anyone shed any light on how I might fix things? (or I do I need
> to post some additional information)
>
> Kind regards
>
> -Elmer
>
>
>
>
>
>
>
>
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
>
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
>
> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
>
> EnergyPlus Documentation is searchable. Open EPlusMainMenu.idf and press the
> "search" button.
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
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