BCU 370 · Edition 01.19
17
Function
3 .1 .5 Assignment of connection terminals
Terminal
Type
Designation
Function
1, 2
V AC input
Supply voltage
Voltage to operate the BCU,
1 = phase (L1), 2 = neutral conductor (N)
3
V AC output
Fan
Connection for fan control
4
Safety circuit
output
Gas valve V1
Connection of phase for gas valve V1
5
Gas valve V2
Connection of phase for gas valve V2
6
Gas valve V3
Connection of phase for gas valve V3
7
Inputs for
pressure switches
Minimum air pressure
Connection for pressure switch to monitor the minimum air pressure
9
Minimum gas pressure
Connection for pressure switch to monitor the minimum gas pressure
11
Maximum gas pressure
Connection for pressure switch to monitor the maximum gas pressure
8, 10 and
12
V AC outputs
Mains supply
Phase for pressure switch mains supply
13
Flame control
Flame amplifier input
Input for flame amplifier
14
Supply voltage to UV sensor
Output for supply voltage to UV sensor
15
Burner ground
Burner ground input for UV sensor
16
Ignition transformer output
Output for (external) ignition transformer
17, 18
1) 2)
Floating contact
Signalling contact for operating
signals
Contact between terminals 17 and 18 closes once the operating signal has been
received from the burner
19, 20
1) 2)
Signalling contact for faults
Contact between terminals 19 and 20 closes in the event of a BCU fault signal
21
1) 2)
V AC input
Start-up signal
Signal applied: BCU start; no signal: BCU stop
22
1) 2)
Controlled air flow
Signal applied: fan is started to supply air to the combustion chamber for cooling, for
example. Only functional in standby. The function is deactivated as soon as a signal is
received at terminal 1 (BCU start).
23
1) 2)
Remote reset
Input for external signal (button) to reset the unit after a fault lock-out
24
Controller enable/emergency stop Connection for higher-level safety devices and interlocks (e.g. emergency stop)
25
2)
Connection for
external three-
point step
controller
Controller enable
Output signal for controller enable for the three-point step controller. The actuator can
be set to various positions.
26
2)
Y- (to ignition position)
Connection for the signal to activate the ignition position
27
2)
Y- (to min. position)
Connection for the signal to activate the position for minimum capacity
28
2)
Y+ (to max. position)
Connection for the signal to activate the position for maximum capacity
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