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Figure 14 shows typical wiring of a fan-powered reheat box which uses the 24VAC transformer in the VAV box
controls to power the VAV / VVR board. This is a typical view, and the box manufacturer instructions should be
referenced for exact wiring details.
Figure 14: Typical Fan-Powered Box Output Wiring
INSTALLING THE VARISTORS
Each VAV or VVR is shipped with four (4) varistors for installation on existing fan or electric heat contactors. The
devices clamp on electrical noise typically associated with drop-out of contactor coil voltage, which may cause the
VAV controller to malfunction. To install the varistors, connect in parallel with contactor coil wiring as shown in
Figure 15.
Figure 15: Varistor Installation Details
L
1
L
2
N
O
C
N
O
C
N
O
C
N
O
C
+
4
3
2
1
2
4
V
A
C
H
E
A
T
IN
G
R
E
L
A
Y
O
U
T
P
U
T
S
BOX TERMINAL STRIP
H
O
T
C
O
M
M
O
N
F
A
N
/H
E
A
T
1
H
E
A
T
2
H
E
A
T
3
H
E
A
T
4
V
A
V
/V
V
R
C
O
N
T
R
O
L
L
E
R
B
O
A
R
D
VARISTOR
L1
L3
L2
L1
L2
L3
LOAD
EXISTING CONTROL
CIRCUIT
EXISTING CONTACTOR
