16
9.
TEMPERATURE CONTROL P.C.B.
The temperature control PCB provides three types of functions for the boiler as follows.
1. on /off selection for domestic hot water / central heating /reset boiler after lock out
2. Temperature selection for either domestic hot water/central heating.
3. LED displays for standby / burner on / lockout display.
Maximum resistance value for P1 D.H.W is 5.20k
Ω
.
Maximum resistance value for P2 C.H. is 5.20k
Ω
.
Voltage is supplied to the PCB from J1 black at 5V dc.
Voltage readings between black/ blue (P1), range from 0V dc in off position to 4.20V dc in
the max position.
Voltage readings between black/ brown (P2), range from 0V dc in the off position to 4.20V
dc in the max position.
10. HYDRAULIC UNIT THREE-WAY VALVE MICRO SWITCH
This is located on the 3 way valve to the left hand side of the brass diaphragm housing. In
the central heating (C.H.) mode the switch is kept closed, as the tip of the switch rests on
the diaphragm push rod. When hot water is demanded the disc and push rod both move.
This releases the micro switch. Once this occurs the boiler is operating in the D.H.W.
mode.
In standby mode the supply voltage to the switch is 22V dc from J4 (blue)
In operation the voltage is 12.2V dc returning to the P.C.B. to J4 (brown)
11. AIR PRESSURE SWITCH
The air pressure switch proves that the fan is running and creating enough air flow through
the boiler for combustion. The correct operation of the switch is dependant on the plastic
venturi which is located at the top of the fan housing outlet.
In normal operation the fan creates an air flow though the venturi causing a pressure drop
inside the venturi. This is transmitted to the air pressure switch via the connecting tubes.
This causes the contacts within the switch to make, and the ignition process begins.
Voltage is supplied to the switch from J4 (21V dc) 3rd black from left
Voltage returns to PCB from the switch. J4 (21V dc) 4
th
black from left. This occurs when
switch contacts are closed.
If the contacts in the switch jam and remain in the closed position after the fan has stopped
running. Then the boiler will fail on the next ignition sequence and fault 1 will be displayed
after 15 seconds.
Connections of the air tubes to the switch are as follows.
Top tube from venturi to P2 on air pressure switch (left hand side) provides negative
pressure to switch from venturi
Summary of Contents for FEB-24E UK
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Page 11: ...11 2 Electrical Components Electrical Circuit Diagram ...
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Page 26: ...26 Central Heating Logic Programme Figure 1 Figure 2 ...
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