7
T-Product · BCU 465 · 2006 April
System Design Informa-
tion
Cable Selection and Wiring
Use maximum AWG 14 (2,5 mm
2
)
wire for signal and control leads.
Use maximum AWG 12 (4 mm
2
) wire
for ground lead. Adequate ground
connection must be provided be-
tween burner and BCU.
The BCU is suitable only for perma-
nent wiring. Do not reverse L1 phase
and L2 neutral conductor.
Do not route BCU wires in the same
conduit as frequency converter wir-
ing or wires emitting strong fields.
Different phases of the three-phase
power system may not be applied
to the inputs. Do not apply voltage
to the outputs for valves and ignition.
Do not connect the gas valve to the
air valve output (terminal #26).
Wiring to the burner:
Use high-voltage cable (non-shield-
ed) for the two following cable types
A
and
B
:
FZLSi 1/7 up to 356 °F (180 °C),
Order No. 04250410 or
FZLK 1/7 up to 176 °F (80 °C),
Order No. 04250409
When using one electrode for igni-
tion and flame monitoring, a direct
connection from burner ground to
BCU must be provided.
A = Ionization line
I
9
A
Length of ionization line: maximum
16 ft (5 m).
Note: If transformer is externally
mounted the sensor lead can be
up to 160 ft (50 m).
Do not lie in parallel with ignition
cable.
B = Ignition lead
Z
B
Length of ignition lead: Recommend-
ed: < 3 ft (1 m); max: 16 ft (5 m).
The longer the lead, the more the
ignition power is reduced.
Use unshielded high voltage cable
and RFI suppressed plug 1 k
Ω
.
Do not place into metal conduit or
metal cable duct. Place far away
from main supply power cables
and interference sources.
Keep the ignition cable short inside
the BCU housing.
C = UV cell leads
1
2
3
UV
9
11
10
C
Length of UV cell leads: maximum
16 ft (5 m).
Note: If transformer is externally
mounted the UV cell leads can be
up to 160 ft (50 m)
Do not lie in parallel with ignition,
control or high voltage wiring.
Use main power supply leads suit-
able for operation - in accordance
with local regulations.
