[EnergyPlus_Support] RE: RE: maximum design supply fan air flow

UPDATE 2 (I'm sorry...): In the field â??Zone Heating Design Supply Air Temperatureâ?? of the object Sizing:zone I imposed 39Â°C (the heating setpoint of the zone is equal to 28Â°C) but the supply air temperature in the design day is different. Here the graph: https://imageshack.com/i/nm2fyvj Why?
Does the html report present the conditions that I imposed in the object Sizing:zone while the graphs of the .eso file present other conditions?!
I'm using also SetpointManager:SingleZone:Heating
The Max Air Flow Rate [m3/s] of the supply fan and of the return fan is equal to 0,12 m3/s, i.e. it is equal to the â??User heating [m3/s]â?? but it is less than the â??Calculated heating [m3/s]â?? of the â??System Design Air Flow Ratesâ?? table.

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

UPDATE: The "User Design Air Flow [m3/s]" of the zone 00INTERRATO:28CENTRALE, which is the zone that is supplied by the AHU â??UTA 28centraleâ??, is also equal to 0.49 m3/s. The "Calculated Design Air Flow [m3/s]" is equal to 0.39 m3/s (0.49/0.39 = 1.25). Now the problem is: I don't see 0.39 m3/s in the graphs. Why? Shall I use 0.39 m3/s or 0.49 m3/s to calculate the "system fan power" according to G3.1.2.9?

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

In the report â??HVAC Sizing Summaryâ?? the â??User Design Air Flow [m3/s]â?? is greater than the â??Calculated Design Air Flow [m3/s]â?? and the ratio between them is what I imposed in the field â??Zone heating sizing factorâ?? of the object Sizing:Zone (i.e. 1.25). That is clear.

My problem is understanding the â??System Design Air Flow Ratesâ??. Among the â??System Design Air Flow Ratesâ?? there are â??calculated heating [m3/s]â?? and â??user heating [m3/s]â??. For the AHU â??UTA 28centraleâ?? (System 3) I get the following table:

https://imageshack.com/i/npbyh7j

Is â??calculated heatingâ?? greater than â??user heating [m3/s]â?? because â??calculated heating [m3/s]â?? is what is neccessary to meet the heating gain while the â??user heatingâ?? is relative to the outdoor air need?

The calculated heating is equal to 0.49 m^3/s but in the graphs I don't see such a value. The following graph regards the winter design day and maximum value is equal to 0.12m^3/s, i.e. what I imposed as outdoor air flow rate in the object Controller:OutdoorAir (during the afternoon there is occupation and therefore there is outdoor air flow, while during the night and the morning there is â??night cycleâ??):

https://imageshack.com/i/neyr1qp

How can the value 0.49 m^3/s be explained, please?

In the calculation of the system fan power according to G3.1.2.9 shall I consider 0.49 m^3/s?

Regards

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

Sounds right. But even if the fan is undersized, "design" implies that which happens on the design sizing day, so in my opinion, the design capacity air flows are the ones of interest.

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 22.10.2013, at 18:24, <fpasserini.tn@...> wrote:

The equations of the paragraph G3.1.2.9 of ASHRAE 90.1-2007 need the "baseline system maximum design supply fan air flow rate". I consider the html report. Is the "baseline system maximum design supply fan air flow rate" the maximum between "System Design Air Flow Rates" in HVACSizingSummary and "Max Air Flow Rate" in "Fans" in Equipment Summary?
I think that the "System Design Air Flow Rates" is evaluated in the SizingPeriod:DesignDays conditions while the "Max Air Flow Rate" is evaluated in the RunPeriod, right?
Regards