10
8. OSO Fault Finding Guide
Alternative Discharge
Discharge pipes should be in metal and
dedicated to the unvented cylinder. The pipe
should have a continuous fall and should terminate
in a safe and visible place.
Downward discharges at low level, i.e. up to 100 mm above
external surfaces such as car parks, hard standings, grassed
areas etc. are acceptable providing that where children may
play or otherwise come into contact with discharges,
a wire cage or similar guard is positioned to prevent contact,
whilst maintaining visibility.
Discharge at high level, i.e. into a metal hopper and metal
down pipe with the end of the discharge pipe clearly visible (tundish visible or not)
or onto a roof capable of withstanding high temperature discharges of water and 3
m from any plastics guttering system that would collect such discharges
(tundish visible).
Important - note:
Disconnect electrical supply before removing any electrical equipment covers.
FAULT
POSSIBLE CAUSE
SOLUTION
No water flow from hot taps.
1. Mains supply off.
2. Strainer blocked.
1.
Check and open stopcock.
2.
Turn off water supply. Remove strainer and
clean (see Servicing Procedure page
9
).
Water from hot taps is cold.
1.
Immersion heaters not switched on
9 (if in use)
2.
Immersion heater thermal cut-out has operated
(if in use)
3.
Programmer set to central heating or not switched on.
4.
Boiler not working.
5.
Cylinder thermal cut-out has operated .
6.
Motorised valve not operating correctly.
1.
Check and switch on.
2.
Check and reset button (
under thermostat control knob)
3.
Check and set to hot water.
4.
Check
Heat Pump
operation. If fault suspected consult
installer
or
Heat Pump
manufacturer.
5.
See 6.3 on page
7.
6.
Check wiring and/or plumbing connections to motorised
valve (see
3.6
on page 5 and
wiring
diagrams on page
7
and
8
.
Intermittent water discharge.
1. Reduced expansion vessel charge.
1. Follow instruction page
9
“Intermittent or slow water
discharge from tundish”.
Continous water discharge.
1. Thermal control failure (Note: Water will be hot).
2. Cold water inlet Pressure Reducing Valve not working.
3. Temperature and pressure relief valve faulty.
4. Expansion relief valve not working properly.
1.
Switch off power to immersion heater and
Heat Pump
supply to the unit. When discharge has stopped, check
thermal controls, replace if faulty. Contact a competent
person.
2.
Check pressure from valve, if greater than 3 bar
replace (see page
9
)
.
3.
R
eplace valve
(see page 9).
4.
Check and replace if faulty (see page
9
).
manual).
Minimum size of
Maximum resistance allowed,
Minimum size of
discharge pipe D2* expressed as a lenght of straight Resistance created by
Valve outlet size discharge pipe D1* from tundish
pipe (i.e. no elbows or bends)
each elbow or bend
22 mm
up to 9 m
0.8 m
G1/2
15 mm
28 mm
up to 18 m
1.0 m
35 mm
up to 27 m
1.4 m
28 mm
up to 9 m
1.0 m
G3/4
22 mm
35 mm
up to 18 m
1.4 m
42 mm
up to 27 m
1.7 m
35 mm
up to 9 m
1.4 m
G1
28 mm
42 mm
up to 18 m
1.7 m
54 mm
up to 27 m
2.3 m
Where a single pipe serves a number of discharges, such as in blocks of flats,
the number served should be limited to not
more than 6 systems so that any installation discharging can be traced reasonably easily. The single common dis-charge
pipe should be at least one pipe size larger than the largest individual discharge pipe to be connected. For further
information contact your Building Control Office
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