Baxi LUNA DUO-TEC 1.70 User Manual page 31

10.7.3 CONNECTION POSSIBILITIES FOR THE PCB (SCU-S02)
If the boiler is fitted with the control PCB (SCUS02), then this is automatically
recognized by the automatic control unit of the boiler.
CAUTION
On removing this PCB, the boiler will show fault code E38. To prevent this
fault, an auto-detect must becarried out after removing this PCB (See chapter:
"Carrying out an auto-detect").
The LED status indicator D3 at the top right of the control PCB indicates the status:
• Continuous signal: PCB working normally.
• Flashing signal: No connection.
• No signal: No voltage or faulty PCB (Check the wiring).
HEATING SYSTEM EXTERNAL PUMP CONTROL
An external pump for the heating system can be connected to the Pump terminals of the control board. The maximum input power
is 300 VA/ 0.4 FHP. An auxiliary relay must be used for a pump with a larger input.
EXTERNAL THREE-WAY VALVE (3WV) CONTROL
The external three-way valve (120 VAC) can be used when connecting an DHW indirectly water heater. The neutral position of the
three-way valve can be set using parameter P34.
The three-way valve is connected as follows:
• N = neutral.
• C = heating system.
• D = indirect tank.
CAUTION
If the neutral position of the three-way valve is adjusted with parameter P34, the pump should be connected as follows:
• N = N pump.
• C = L pump.
• = Ground.
EXTERNAL GAS VALVE CONTROL
If there is a call for heat, an alternating voltage of 120 VAC, 1 A (maximum) becomes available on the EgV terminals of the control
board to control an external gas valve.
OPERATION SIGNAL AND FAILURE SIGNAL (EgV)
The alarm or operation signal is selected using parameter P40.
• If the boiler is operating, the operation signal can be switched using a dry set of contacts (maximum 120 VAC, 1 A) on the NO
and C terminals of the connection.
• If the boiler locks out, the alarm can be transmitted using a dry set of contacts (maximum 120 VAC, 1 A) on the No and C
terminals of the connection.
PRESSURE SWITCH MINIMUM GPS
The minimum gas pressure switch shuts the boiler down if the inlet gas pressure becomes too low. Connect the minimum gas
pressure switch to the Gps terminals. The presence of the gas pressure switch must be set using parameter P41.
X1
Pump
NL
Pump
N L
31
F 4AT
SCU-SO2
X3 X4
3wV EgV
NC D NL
Status
3wV EgV
Nc C No Tsol Gps
NC D NL
Nc C No Tsol
7703477.01 (1-03/18)
D3
X2
X5
Hru
Gps Hru