Re: [EnergyPlus_Support] Re: Why Autosize does not consider System Outdoor Air Loads

German,

If you set the ventilation rate in the ZoneHVAC:FanCoil Object it will account for the ventilation in the zone level sizing (only in expanded file)

You can then use differing OA schedules to say that the zone ventilation is available only during the sizing period, and the system level ventilation is available during the run period

I think you must be speaking of when using the HVAC Templates, as when the templates expand, if theres a DOAS, Energyplus writes the OA in the FCU to 0 per this note and sets the ventilation in the DOAS

! Setting fan coil outdoor air to zero, because zone is served by dedicated outdoor air system (DOAS)

-Jason

On Thu, Jul 3, 2014 at 10:06 PM, 'jeannieboef@xxxxxxxxx' jeannieboef@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

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Hi Karen, as soon as you posted this, I went to test it, because it messes up my current understanding of the autosizing in e+. For GermÃ n's case, it does not work and fits my current mental model. For HJ's case, it would work as long as the zone setpoint is able to be corrected by the system's air supply. So if he has a zone heating setpoint of 20 and is trying to heat with 13 C system supply air, it will not size the equipment properly and the issue is the same as GermÃ n's. Â

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

i. A.
Jean Marais
b.i.g. bechtold
Tel. Â +49 30 6706662-23

On 03.07.2014, at 23:53, "Karen Walkerman kwalkerman@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

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I think that you might not be setting the design heating and cooling supply air temperatures correctly in the Sizing:System object. If you have an air handler providing unconditional ventilation air to zones, set the design heating temperature equal to the outdoor temperature of your heating design day at the system level. Same with cooling. Then your ZoneHVAC equipment should size correctly.

Karen

On Jul 3, 2014 12:30 PM, "HJ wanghaojie630@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

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Thanks. I misspoke, actually s1 provide 13 air temperature all time. So in summer it provide some cooling, and winter it preheat air to 13 C. In this case, will s2 be oversized for summer and undersized for winter?

HJ

On 7/3/2014 12:16 PM, ecoeficiente@xxxxxxxxx [EnergyPlus_Support] wrote:

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In your case, s2 will only be sized for zone loads without accounting for s1 ventilation load. But, as you say, your s1 system provides neutral air temperature, that is, no load. In that case you do not have the problem I mentioned.

Regards.