[EnergyPlus_Support] Re: Autosizing air and water circuits for zone heating

["Elmer Morrissey" <elmofuddly@xxxxxxxxx>]

Can anyone help?


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Elmer Morrissey" 
<elmofuddly@...> 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
>






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