Re: [EnergyPlus_Support] static pressure setpoint

[fred buhl <wfbuhl@xxxxxxx>]

Cliff,

You can't set the supply duct static pressure setpoint in EnergyPlus. 
The delta pressure is
static pressure. It is used to calculate the fan design energy 
consumption. The actual performance
is calculated by fractional power versus fractional flow curves. This is 
explained in the
Engineering Reference document. The fan power calculations are done in 
the same manner as
in DOE-2. The curves are the same. EnergyPlus does not normally compute 
duct pressures. The AirFlowNetwork
capability can do so, but this is not coupled to the fan model. You can 
not use a Controller object to
control duct static pressure.

To calculate "real" fan performance it would be necessary to calculate 
EnergyPlus fan curve coefficients
outside of EnergyPlus, using at least a simple pressure-dependent duct 
model and a more sophisticated
fan model, perhaps the one developed by Jeff Stein and Mark Hydeman. We 
are working on providing such a
calculation, but it is not available yet.

Fred Buhl

Clifford Federspiel wrote:

>The "Delta Pressure" variable is not the same as the supply duct static 
>pressure or the static pressure setpoint. According to the documentation, 
>Delta Pressure is "The pressure rise in Pascals at full flow and standard 
>(sea level) conditions (20o C and 101325 Pa)."
>
>Is Delta Pressure the static pressure or the total pressure? From an 
>offline conversation about this subject, my understanding now is that 
>EnergyPlus doesn't compute duct pressures. If that is true, then what does 
>EnergyPlus do with Delta Pressure? If it is false, then can duct pressure 
>be the control variable of a Controller object?
>
>At 08:57 AM 5/12/2006, you wrote:
>  
>
>>the static pressure is set in the fan object.  Note that it is a constant.
>>
>>
>>
>>-----Original Message-----
>>From: EnergyPlus_Support@xxxxxxxxxxxxxxx 
>>[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]On Behalf Of Clifford Federspiel
>>Sent: Friday, May 12, 2006 9:31 AM
>>To: EnergyPlus_Support@xxxxxxxxxxxxxxx
>>Subject: [EnergyPlus_Support] static pressure setpoint
>>
>>
>>How do I set the supply duct static pressure setpoint of a VAV system?
>>
>>
>>Clifford Federspiel, PhD, PE
>>Principal, Federspiel Controls, LLC
>>828 San Pablo Avenue, Suite 115E, Albany, CA  94706-1693
>>v: 510-418-3392 | f: 510-526-4309 | cf@xxxxxxxxxxxxxxxxxxxxxx
>>www.federspielcontrols.com
>>
>>
>>
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>
>
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