17.0 Electrical Measurements
29
© Baxi Heating UK Ltd 2012
Useful Electrical Measurements
All voltages for mains A.C. are taken from earth and the stated pin.
Function
PCB Conn.
Voltage
CH Demand
X3
Pin 1 (Blue)
230v
Pump ON
X13
Pin 2 (Brown) 230v
X11
Pin 5 (Black)
225v Lo 260v Hi
(Pump runs at ‘Hi’ speed only in DHW, both speeds in CH)
Pressure Sensor
X22
Between Pins 11 and 12 (red and white) 1 bar = 3v (approx)
Diverter Valve (CH)
X13
Pin 4 (Black) 240v
Pin 5 (Brown) 0v
Diverter Valve (DHW) X13
Pin 4 (Black) 0v
Pin 5 (Brown) 240v
Fan ON
X11
240v @ Pin 2
X23
Full Power: Circa 8v DC between Black and Blue
DHW Hall Sensor
X22
ON between Pins 11 and 12 (Red + White) 1v
OFF between Pins 11 and 12 (Red + White) 0v
Between Pins 11 and 13 (Red + Blue)
5v constant
It is not advisable to measure at the smaller P.C.B. connections such as the Electronic Gas Valve as the voltages need to be
taken from the actual edge connector on the board and damage could easily occur.
Water Temperature Sensors
All the sensors use the same resistance/ temperature measurements.
The graph below can be used to establish an approximate measurement, but the important point is to ensure the resistance
reduces as temperature increases.
0
2
4
6
8
10
12
14
16
18
20
20
40
60
80
Temperatur
e (°C)
0
100
120
Resistance (Ohms)
Temperature Sensors & Resistance
Heat Exchanger
Sensor
Water
Sensors
Both C.H. & D.H.W. sensors have the same resistance. The Heat Exchanger sensor has a different curve, but the
temperature/resistance curve is the same.
A further check can be made using the Information Menu as described on page 16. Even if the boiler is not operating the
temperatures can still be read in the Information Menu making it possible to check if a sensor is reading correctly.
