Re-cooling zone air after mixing with return air

I am modeling a mechanical VAC system in Energyplus similar to the image below where the system mixes fixed amount of conditioned and return air and cools it down again. image description

But I am facing difficulties with the zone equipment side. So I was wondering if I am building the system correctly or not.

Is it possible to build the system in Energyplus as depicted in the figure above?
If yes, any specific components that I should use? (I have tried the AirTerminal:SingleDuct:InletSideMixer combined with ZoneHVAC:FourPipeFanCoil but I'm getting a node error at the inlet side mixing box)
Any other suggestion/tips in implementing this example system in energyplus are also very welcome.

Thank you

It depends if your are using constant flow or variable flow with fixed proportions.

For constant flow:

I believe your application actually warrants using an AirTerminal:SingleDuct:ConstantVolume:FourPipeInduction, for which you'll set the Induction Ratio to $\frac{80\%}{20\%} = 4$. If you don't have a heating coil in your terminal unit, you might have to include one anyway and zero it out, as I believe it's required.

For help and examples:

This object is available in the OpenStudio Application as of 1.9.0 (release candidate right now) if you need help setting it up.
The example file 5ZoneFPIU.idf uses one of these.

For variable flow

Probably try to debug your error, using a VAV terminal and a ZoneHVAC unit is likely the way to go.