Precool coil and AHU coil


I googled so much but failed to find anything about how to add a precool coil in the AHU/VAV system.
I tried to use Ironbug to add a water coil and variable fan and setpoint in the OA stream, but the sizing doesn’t run correctly and the off-coil temperature of the precool coil doesn’t seem to work.
Is it because EnergyPlus doesn’t support PAU+AHU at all? If so, how do you model this system?


Is your “precool coil” meaning cooling coil with hot gas reheat?
any diagram will be helpful for me to understand.

Hi @MingboPeng, diagram attached.

Hi @XavierZhouLadybug This is how you add components in OA stream:

Yes, that’s how I did it. I’ll tidy up my script and upload soon.

Hi @MingboPeng

Script attached.
20200308_test ironbug_to (667.2 KB)

Thank you!

@XavierZhouLadybug so what’s your problem? It doesn’t run?

It can run. But the off-coil temperature of the PAU is not controlled.

@XavierZhouLadybug oh, ok, try this:

1 Like

It works! And I moved the fan before the coil, it works too!

However, I still encounter the following error. Can it be ignored?

  1. The simulation has not run correctly because of this severe error:
    ** Severe ** Calculation of cooling coil design UA failed for coil COIL COOLING WATER 1

Try to check the air/water temperature settings in this coil, the default value might be not working with your setpoint. And also check this coil’s sizing as well.