[Bldg-sim] FCU with outside air fan
Yuvaraj Saravanan
Yuvaraj.Saravanan at arup.com
Tue Sep 23 09:11:26 PDT 2008
Hi All,
I am trying to model a residential unit served by a Fan coil unit (FCU). It has a separate outside air fan and exhaust fan operating 24/7. The fan coil unit is available to operate for all hours but should operate intermittently depending on the room load.
I tried modeling this by selecting a 4-pipe FCU and specified the exhaust and outside air at the thermal zone level. I made the FCU to operate intermittently by making the Fan on mode to be intermittent. By doing this, what I observed in the hourly report was:
1. FCU unit cycles intermittently as intended.
2. Exhaust fan operates continuously (24/7) (with the specified cfm) as intended.
3. However, the outside air cycles per the FCU.
If the FCU is off, then OA cfm is zero
If FCU supply air cfm < the OSA cfm specified at the zone level, then hourly OSA cfm matches the FCU supply air cfm If FCU supply air cfm > the OSA cfm specified at the zone level, then hourly OSA cfm matches the cfm specified at the zone level.
As mentioned before, I want my outside air to operate continuously with constant flow-rate. Can anyone suggest me a way to model this system?
Thanks in advance for your help!
Regards,
Yuvaraj
> ______________________________________________
Yuvaraj Saravanan, PE
Engineer
> Arup
12777 West Jefferson Boulevard Suite 200
Los Angeles CA 90066
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yuvaraj.saravanan at arup.com
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