901
30
General Notes - For use on the
901
fitted with VMF7 Printed Circuit Board
*The pilot light can only be ignited after the Fan (16) has run for at least 20 seconds on full speed.
*The central heating pump (32) will run to disperse heat if the temperature at the heat exchanger limit thermostat (50) is too high
*The frost thermostat (51) will switch on the boiler for central heating if the temperature is too low.
*Fuse on P.C.B.: 2 Amp.
LED n
°
signification:
1
Mains on/low voltage on
2
Flowmeter (136) on
3
Central heating room thermostat (72) / clock (62) calling
4
Sensor (34) or (42) calling for heat
5
Central Heating waiting time, max. 3 minutes delay following shut off
Boilerstat (63), Clock (62), Roomstat (72) or use of Hot Water
6
Demand for heat - relay (RY2) will be energised
7
Air pressure switch (43) on, air flow checked
Jumpers JP1 - JP4
Fitted
Not fitted
JP1
No waiting time
Waiting time on
JP4
Fan control
Fan control
High & Low speed
High speed only/off
RY not energised
RELAY RY
RY1
central heating pump
RY2
on/off relay
RY3
-
RY4
fan
temp.
Ohm
10
°
C
890 ohm
25
°
C
1000 ohm
60
°
C
1300 ohm
80
°
C
1490 ohm
Temp.
sensor
RY energised
Note
If RY1 is not energised
the Central Heating pump
will run
Check operation using LED's as a fault finding guide. First check section A, then B, then C, then D.
0 = LED off
1 = LED on
x = LED either on/off is not important
Domestic Hot water tap open
(Flow rate greater than 2,5 l/min)
LED
OK
FAULT
POSSIBLE CAUSE OF FAULT
1
1
0
No mains electricity/switches off/fuse blown.
2
1
0
D.H.W. flowmeter (136) not operating.
3
X
X
Not required for D.H.W.
4
1
0
- D.H.W. sensor (42) not connected or D.H.W. temperature too high
5
0
1
- Waiting time operating: replace P.C.B.
6
1
0
Short circuit on D.H.W. sensor (42) or resistance lower than 500 Ohm
- C.H. limit thermostat (50) open circuit (pump run)
- C.H. water pressure low (114 open circuit)
A
GENERAL TEST FOR D.H.W. AND CENTRAL HEATING (First check A and B above)
LED/REL.
OK
FAULT
POSSIBLE CAUSE OF FAULT
RY2
energised
not energised
Check first A and B above
RY4
energised
not energised
Air pressure switch (43) not in NC position or miswired:
- check wiring
- fan (16) at low speed remove jumper JP4
7
1
0
- fan (16) not running at full speed or
- air flow too low:
- air pressure switch (43) faulty
B
CENTRAL HEATING ON Room stat (72) at Max, HW tap closed
LED
OK
FAULT
POSSIBLE CAUSE OF FAULT
1
1
0
No main electricity/switches off, fuse blown.
2
0
1
Hot water tap open - D.H.W. flowmeter (136) contact closed
3
1
0
Roomstat (72) or clock (62) not calling for heat
4
1
0
- Central heating sensor (34) not connected or
- boiler temperature too high or
- boiler thermostat (61) below CH temperature
5
0
1
Waiting time still operating (max. 3 minutes)
6
1
0
- C.H. sensor (34) short circuit or resistance lower than 500 ohm
- C.H. limit thermostat (50) open circuit (pump will run)
- C.H. water pressure low (114 open circuit)
C
IGNITION OF PILOT
1
Fan (16) should run at full speed for at least 20 seconds
(open hot tap or set controls so boiler is callingfor heat).
2
Check first A, B and C above
3
Push ignition button (60) fully in
4
Microwitch (66) will close
5
Ignition transformer (67) will energise
6
Check spark and position of spark electrode (24)
D
