Viconics VZ7656E Installation Guide - Manual (Page 27)

27 | VZ7656E1000W Installation Guide
F
RESH
A
IR
D
AMPER
C
ONTROL
S
EQUENCES
The fresh air damper can be controlled through more than one sequence to achieve
different control strategies such as free cooling (economizer mode), minimum fresh air
control and CO
2
level control. Here are the control sequences available:
Note: For the sequences mentioned below, the following conditions must be met in
order for the sequences to be performed as stated:
-
Max Pos parameter value must be greater than Min Pos Parameter value.
- Mac CO
2
parameter value must be greater than Min CO
2
Parameter value.
- Max FA parameter value must be greater than Min FA Parameter value.
Economizer Control Mode Only
If the fresh air damper is to be used only for free cooling purposes (economizer mode,
without fresh air measurement station or CO
2
control), only the Min Pos parameter and
the free cooling sequence will be active.
- The FA Range parameter should be set to 0 CFM. (Default Value = 0 CFM)
- Set the Chngstpt parameter to desired value which free cooling is enabled.
(Default Value = 55°F)
If the outside air temperature is greater than the changeover setpoint, then normal
mechanical cooling will be used. If the outside air temperature is less than or equal to the
changeover setpoint, then free cooling will be enabled and mechanical cooling stages will
be locked out.