[EnergyPlus_Support] Re: Fans

["don_shirey <shirey@xxxxxxxxxxxxxxxxxx>" <shirey@xxxxxxxxxxxxxxxxxx>]

> Yes, these two fan objects are quite similar.
> 
> Fan:Simple:Const Volume models a constant air volume fan that runs 
> continuously when it is scheduled "ON".
> 
> FAN:SIMPLE:OnOff models a constant air volume fan that is available 
to 
> operate when it is scheduled "ON". However, it only operates when 
the 
> cooling or heating system comes on to meet a cooling or heating
load 
for 
> that simulation time step.  The fan cycles on and off with the 
cooling or 
> heating system (i.e., AUTO fan mode). If you look at objects 
"UNITARY 
> SYSTEM:..", "FURNACE:..." and "AIR CONDITIONER:WINDOW:CYCLING", you 
see the 
> input field "Operating Mode" or "Operation Mode".  If you choose 
> "CycFanCycComp" or "CycFanCycCoil", then the FAN:SIMPLE:OnOff
object 
needs 
> to be specified to get the fan power and fan heat correctly 
calculated.  If 
> you choose "ContFanCycComp" or "ContFanCycCoil", then you should 
specify 
> Fan:Simple:Const Volume (although the on/off fan object would 
probably work 
> in this case too).


I need to clarify my earlier response. The description about when to 
use Fan:Simple:Const Volume and when to use Fan:Simple:OnOff for the 
object "AIR CONDITIONER:WINDOW:CYCLING" is correct. 

Currently, Fan:Simple:OnOff is the only valid supply air fan for use 
with the objects "UNITARY SYSTEM:..." and "FURNACE:...".  Just make 
sure that the part-load fraction correlation (function of part load 
ratio) for the heating and/or cooling coils is input correctly as 
described in the IO Reference Manual (i.e., the curve should be 
normalized to 1.0 when the part-load ratio equals 1.0). If you've 
input the part-load fraction correlation correctly, then 
Fan:Simple:OnOff will work for both continuous fan operation 
(ContFanCycCoil) as well as OnOff operation (CycFanCycCoil).


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