[EnergyPlus_Support] Re: AHU & FCU

["Alan Jackson" <alanjackson7@xxxxxxxxx>]

i am not sure how far along you have gotten with this issue, and i
will not be of help but i am curious from others if it is possible to
model a system similar to yours with a CV AHU serving the zone and
have a secondary FCU also in the same zone? Does energyplus allow this?

-
aj


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "beyangj" <beyangj@...> wrote:
>
> Dear all,
> 
> I¡¯m modeling a system of FCU with fresh air handling unit. I defined
> an AIR PRIMARY LOOP which treats the fresh air and use DIRECT AIR to
> feed the zone, and the fan coil unit serve the net remaining load. In
> the ZONE EQUIPMENT LIST, I set the heating and cooling priorities to 1
> for the DIRECT AIR and 2 for the fan coils. 
> 
> There are some problems for this model,
> 
> 1. There are two inlet nodes for each zone, one inlet node is for
> outside air processed from the Primary Air Unit, and the other inlet
> node is for FCU. But I found that INLET NODE 1:System Node
> MassFlowRate and INLET NODE 2:System Node MassFlowRate are the same
> for the same zone. I set INLET NODE 1 for Direct Air and INLET NODE 2
> for FCU. The mass flow rate of these two nodes shouldn¡¯t be the same. 
> 
> 2. For my model, the AHU processes all the outside air, and no outside
> air for FCU. But I have 2 times the required fresh air for some
> working hours, half is from the AHU, half comes from the fan coil unit
> even when I set the maximum outside airflow rate of the fan coil unit
> as 0. For some hours, the flow rate of the outside air are smaller
> than the sum of the zones needed fresh air, even sometime it is less
> than that of one zone. Why they are not the same all the time? I
> wonder how I can set the flow rate of fresh air for FCU as 0, and just
> let the AHU have the desired amount of fresh air.   
> 
> 3. I found that the air flow rate of the AHU AIR LOOP INLET:System
> Node MassFlowRate is constant, much greater than the flow rate of the
> AHU outside air. I thought there must be return air recirculating. I
> also found the System Node MassFlowRate are constant for different
> nodes in a year, respectively. How can I set the flow rate of the
> return air as 0 for the AHU? The System Node MassFlowRate should be
> variable for specific node at different hour?
>  
> 4. I also found something strange. The AHU COOLING COIL CHW
> OUTLET:System Node Temp[C] is about 21[C] in the summer, but CHILLER
> CHW INLET:System Node Temp[C] is about 7.6[C], and the CHILLER CHW
> INLET:System Node Setpoint Temp[C](Hourly) is 6.67[C]. Why the AHU
> COOLING COIL CHW OUTLET temperature can be such a high temperature?
> 
> 5. There are 5 zones in this model, and there is a FCU for each zone.
> I set the 5 FCUs as the same pattern, but the air loop in the SVG file
> are different, 2 FCU air loop have return air loop, but 3 FCU loops
> seem not have return air loop. What may make the difference?
> 
> Thanks a lot in advance!
> 
> Young
>




------------------------------------

The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/join
    (Yahoo! ID required)

<*> To change settings via email:
    mailto:EnergyPlus_Support-digest@xxxxxxxxxxxxxxx 
    mailto:EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx

<*> To unsubscribe from this group, send an email to:
    EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/