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 Saravanan, PE