-14-
OSO FAULT FINDING GUIDE
Hot water from taps is cold
Excessive Hot water from taps
If in doubt at any stage you must consult a qualified electrician
If problem still persists
contact a competent
engineer / plumber
Insufficient hot water
when boiler is used
Remove hot water dip pipe and
fit seperate expansion vessel.
(see page 15)
Is the
programmer set to
central heating or
not switched on?
Check and
set to hot
water
programme.
Is the
motorised
valve
operating
correctly?
Check wiring
or plumbing
connections
Check and
reset
button
Has
cylinder
thermal
cut-out
operated?
Is the boiler
working?
NO
NO
YES
YES
YES
YES
NO
Thermostat/Solar
controller set too high
Reduce
Temperature setting
Faulty
Thermostat
replace
Is Thermostat wired
as per layouts for
“S” or “Y” plan
installation
Is 2-port motorised
valve closing when
cylinder reaches
temperature?
Connect wiring as
per instructions
Check cylinder
Thermostat is switching
on & off with
programmer & hot water
on
Wiring Fault
Seek advice
from
electrician
Check wiring
on cylinder
Thermostat
NO
YES
NO
YES
NO
YES
NO
YES
Activate boiler
Low solar gain