Fan Control

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We have a bit of an in-office argument going on and I was wondering if
people could share some insight on the subject.


A user has a VAV system with dampers at the VAV boxes and a VFD on the
supply fan. To properly model this, would the user make sure that the Fan
EIR is 'Variable Speed Drive FPLR' and then change Fan Control to
'Discharge' or leave it as 'Fan EIR FPLR'?

If you are supposed to leave the fan control dialogue as 'Fan EIR FPLR' then
what is the purpose of being able to change the fan control if you have
already selected the appropriate Fan EIR curve?

Thanks for helping solve the in-office dispute,

Tony Kriel, LEED AP

Tony Kriel's picture
Joined: 2011-09-30
Reputation: 0


As I understand it, the fan control settings offered such as "Discharge"
just set an assumption for the fan part load performance curve (EIR
FPLR) used in the simulation.
You can either use one of the predefined fan performance assumptions, or
define your own using "Fan EIR FPLR"

When you set FAN-CONTROL to "Discharge", then right click on the Fan EIR
FPLR and 'restore default' it will revert to n/a. It will not do this
when you have FAN-CONTROL set to "Fan EIR FPLR"

I'm not sure which takes priority if you have both FAN-CONTROL set to
"Discharge" and a custom Fan EIR FPLR input. You could easily run some
tests and see.

Kind Regards,

Molly Curtz, P.E.

Molly Curtz's picture
Joined: 2011-09-30
Reputation: 0