Keston Thermomatic RSM20/FB, Installation & Servicing Instructions Manual, Page: 24 / 46

Page 24
SECTION 7 Fault finding algorithm Thermomatic combination boiler model RSM 20/FB
Carry out initial fault finding checks i.e. check gas, water, electrical system check i.e. earth continuity, resistance
to, short circuit, polarity.
Repeat checks after any servicing / fault finding.
Fig. 7.1.
CONDITION 1.
Does the fan motor
start?
Is the red light on the
instrument panel on (shut
dow n signal)?
Press slightly the red button
(restart). Red light off?
Faulty control box.
Replace it.
Is there voltage to the
boiler (240V)
Check the main supply 3 A.
fuse for continuity.
Is there Voltage to the fan
motor?
Is the safety thermostat (ST)
open?
Has the reload
button tripped
Unscrew the black cap of safety
Thermostat and push the button to
restore the contact
Faulty safety
Thermostat (ST)
Replace it.
Is the motor stuck?
Release the motor or
replace it.
Replace the fan
assembly
Sw itch on. If f aulty,
replace MS.
Does the programming clock
(PC)(if fitted) call for heat?
Adjust the time of consent
for boiler operation
Is the main sw itch (MS) on?
Is the boiler htg. regulatory thermostat (HT)
calling for heat?
Does the differential pressure sw itch
(DPS) give conent (closed circuit
betw een betw een terminal C and
NC)?
Are the w iring connections
of the DPS controls correct?
Is the control box faulty?
No Yes No
No
No
No
No
No
Yes
Yes
Yes Yes
Yes
No
Replace HT
Replace DPS
Reset the electrical connections
according to the w iring diagram
Replace control
box.
Yes
Yes
Yes
No
No
No
No
No
Yes
No