- 9 -
OSO FAULT FINDING GUIDE
Note: Disconnect electrical supply before removing any electrical equipment covers
FAULT
POSSIBLE CAUSE
REMEDY
No water flow from hot
taps
Poor pressure and flow
from taps
Water from hot taps is
cold
Excessive hot water from
taps
-check which heat source
is operating - boiler or
immersion heater
Intermittent water dis-
charge through tundish
when water is being
heated
Continous water discharge
(slow dribble)
Continous water discharge
(fast flow steaming hot
water)
Continous water discharge
(fast flow)
1. Mains supply off
2. Strainer blocked
3. Cold water inlet Pressure
Reducing Valve incorrectly
fitted
1. Strainer blocked
2. Poor incoming supply
1. Programmer set to central
heating or not switched on
2. Boiler not working
3. Cylinder thermal cut-out has
operated (indirect units only)
4. Motorised valve not
operating correctly
5. Immersion heaters not
switched on
6. Immersion heater thermal
cut-out has operated
1. Check temperature with
thermometer. Reading
should be 60-65°C
2. Check wiring is correct
3. Thermostat set too high
4. Faulty thermostat
1. Faulty expansion vessel
2. Thermal control failure
(Note: Water will be hot)
1. Expansion relief valve faulty
2. Temperature and Pressure
relief valve is faulty
1. Temperature and Pressure
Relief Valve operated due to
excess temperature
1. Cold water inlet pressure
Reducing Valve not working
1. Check and open stop cock
2. Turn off water supply. Remove strainer
and clean (see Pressure Reducing Valve
page 8)
3. Check and refit as required (see item 3
page 5 of this manual).
1. Turn off water supply. Open cold tap.
Remove strainer and clean (see Press-
ure Reducing Valve page 8 in this
manual)
2. Fit OSO SuperStream system to boost
mains supply
1. Check and set to hot water
2. Check boiler operation. If fault suspected
consult installer or boiler manufacturer
3. Check and swich on
4. Check wiring and/or plumbing connecti-
ons to motorised valve (see pages 8 or 10)
5. Check and switch on
6. Check and reset button (see thermostat
diagram page 9 and safety cut-out on p. 4)
1. If lower temperature is required at taps,
fit thermostatic mixing valve
2. Seek advice from electrician
3. Lower temperature at thermostat to 55°C
4. Replace thermostat
1. Repressurize expansion vessel. Follow
recommissioning instructions on page 8.
2. Switch off power to immersion heater(s)
and boiler supply to the unit. When
discharge has stopped, check thermal
controls, replace if faulty. Contact a
competent person
Identify which valve is discharging and
replace
1. Switch off power to immersion heater
and contact competent person
2. If immersion was not switched on,
isolate power to boiler and contact
competent boiler engineer
1. Check pressure from valve, if greater
than 3 bar replace (see page 8)
