Re: [EnergyPlus_Support] Re: "strange" autosize of Coil:Cooling:DX:SingleSpeed

So you want the cooling to be sized assuming no ventilation air and the heating to be sized with ventilation air? That will be difficult. EnergyPlus sizing expects the same outdoor air requirement for both heating and cooling. You could try to make an adjustment to the Sizing:System Central Cooling Design Supply Air Temperature (raise it by some amount to produce and equivalent delta-T across the coil ad design conditions). Or it may be easiest in this case to do a simulation with zero outdoor air in the desired zones and use the cooling coil sizing results to set hard capacity values for the coils.

Mike

---In EnergyPlus_Support@xxxxxxxxxxxxxxx, <fpasserini.tn@...> wrote :

During summer season in some systems there is no outdoor air (those spaces are unoccupied since June until September and the SummerDesignDay is 7/21). Nevertheless, as â??User Design Air Flow [m3/s]â?? the value that is imposed in DesignSpecification:OutdoorAir is considered also in â??zone coolingâ??, although I imposed a schedule that is zero during the summer season. I asked to the helpdesk and it seems that the calculations for minimum outdoor air do not look at the schedules in the DesignSpecification:OutdoorAir object.

Here an example:

DesignSpecification:OutdoorAir,

0serviziopalestra:Spogliatoio1 Design Specification Outdoor Air Object, !- Name

Flow/Zone, !- Outdoor Air Method

0.009440, !- Outdoor Air Flow per Person {m3/s-person}

0.000000, !- Outdoor Air Flow per Zone Floor Area {m3/s-m2}

0.110000, !- Outdoor Air Flow per Zone {m3/s}

0.000000, !- Outdoor Air Flow Air Changes per Hour {1/hr}

occupazione aule; !- Outdoor Air Flow Rate Fraction Schedule Name

The schedule is the following one:

Schedule:Compact,

occupazione aule, !- Name

Fraction, !- Schedule Type Limits Name

Through: 1/15, !- Field 1

For: AllDays, !- Field 2

Until: 24:00, !- Field 3

0, !- Field 4

Through: 6/10, !- Field 5

For: Weekdays SummerDesignDay WinterDesignDay, !- Field 6

Until: 07:50, !- Field 7

0, !- Field 8

Until: 16:10, !- Field 9

1, !- Field 10

Until: 24:00, !- Field 11

0, !- Field 12

For: Saturday, !- Field 13

Until: 07:50, !- Field 14

0, !- Field 15

Until: 12:20, !- Field 16

1, !- Field 17

Until: 24:00, !- Field 18

0, !- Field 19

For: AllOtherDays, !- Field 20

Until: 24:00, !- Field 21

0, !- Field 22

Through: 9/10, !- Field 23

For: AllDays, !- Field 24

Until: 24:00, !- Field 25

0, !- Field 26

Through: 12/20, !- Field 27

For: Weekdays SummerDesignDay WinterDesignDay, !- Field 28

Until: 07:50, !- Field 29

0, !- Field 30

Until: 16:10, !- Field 31

1, !- Field 32

Until: 24:00, !- Field 33

0, !- Field 34

For: Saturday, !- Field 35

Until: 07:50, !- Field 36

0, !- Field 37

Until: 12:20, !- Field 38

1, !- Field 39

Until: 24:00, !- Field 40

0, !- Field 41

For: AllOtherDays, !- Field 42

Until: 24:00, !- Field 43

0, !- Field 44

Through: 12/31, !- Field 45

For: AllDays, !- Field 46

Until: 24:00, !- Field 47

0; !- Field 48

The cooling design day (SummerDesignDay) is 7/21. As you can see, on 7/21 the value of the schedule is 0.

Nevertheless, the â??User Design Air Flow [m3/s] â?? in â??Zone coolingâ?? for that zone is calculated equal to 0.110 m3/s (=Outdoor Air Flow per Zone in DesignSpecification:OutdoorAir, without considering the schedule).

Here an image from the html report: http://oi58.tinypic.com/rtg85f.jpg


			http://oi58.tinypic.com/rtg85f.jpg
			View on oi58.tinypic.com	Preview by Yahoo

Iâ??ll let you know if Iâ??ll find a solution with the help of the helpdesk.

Best Regards

---In EnergyPlus_Support@xxxxxxxxxxxxxxx, <jeannieboef@...> wrote :

That is strange. If the sizing objects have correctly deturmined that the design flowrate for cooling is zero, then why would the coil capacity be non-zero.

And to achieve your off coil outlet air setpoint with the minimum outdoor air?Does it need non-zero capacity to achieve that? You probably have that at Setpoint-11C.

Mit freundlichen GrÃ¼Ã?en- Sent from my iPhone (excuse the brevity)

i. A.

Jean Marais

b.i.g. bechtold

Tel. +49 30 6706662-23

On 07.12.2014, at 16:33, "fpasserini.tn@... [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

In Sizing:System the field "Type of Load to Size On" is "Sensible".
Regards