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20 RD
20 RI

IM/5a

Installation details

The OSO unvented unit is designed for use with supply pressure up to 16 bar. For pressures over
16 bar an additional pressure reducing valve must be fitted in the supply pipe to the unit.
Wall mounting brackets are available for OSO unvented units 100-170 litres capacity.

Components supplied with the unit for site fitting

(See also page 2 for component list)

*

Multibloc valve, includes pressure reducing valve, line strainer, balanced cold water take off, 

(for shower or bidet only)

check and expansion valve.

*

Tundish

*

1/2''F x 15 x 15 tee piece.

*

Flexible hose.

*

3/4'' x 22mm Elbow / Drain Cock.

*

Commissioning valve, 1/2'' BSP male.

*

Motorised valve (indirect only).

Components factory fitted

*

Immersion heater(s).

*

Thermostats / thermal cut-out.

*

Temperature and pressure relief valve.

This manual gives detailed advice for installation and should be read carefully
prior to fitting any unvented unit. Where components are supplied only for
indirect units, this is clearly shown.
This OSO cylinder must be installed by a competent person and be installed in
compliance with the OSO Installation and Maintenance Instructions, all current
legislation, codes of practice and regulations governing the installation of
unvented hot water cylinders in force at the date of installation.

-1-

PLEASE LEAVE THIS MANUAL WITH THE 

OSO

UNIT AFTER INSTALLATION

INSTALLATION MANUAL

PRODUCT REF.

HEIGHT

DIAMETER

WEIGHT EMPTY

MAX WEIGHT FULL

100

720

580

34

132

900

580

40

163

1150

580

48

215

125

170

1400

580

60

261

210

1600

580

64

303

250

2090

580

82

397

330

DIMENSION AND WEIGHTS TABLE 1

00142040-06 IM/5

Health and Safety

Manual Handling Operations Regulations 1992 defines manual
handling as: “any transporting or supporting of a load (including the
lifting, putting down, pushing, pulling, carrying or moving thereof) by
hand or bodily force”. The Regulations set no specific requirements
such as weight limits. However common sense still has to be used
based on an ergonomic approach for each individual.

20S (IM) 16pp ISSUE 8

Summary of Contents for 20 RD

Page 1: ...d unit Where components are supplied only for indirect units this is clearly shown This OSO cylinder must be installed by a competent person and be installed in compliance with the OSO Installation and Maintenance Instructions all current legislation codes of practice and regulations governing the installation of unvented hot water cylinders in force at the date of installation 1 PLEASE LEAVE THIS...

Page 2: ...Cold Feed Tube Not Supplied See Table 2 Hot Water Outlet 22mm 510511 510505 550803 219002 71259 80020 80030 10 11 12 13 14 15 16 17 18 Flexible Hose Secondary Return 1 2 BSPF Fit 1 2 Fx1 2 Mx15mm Tee piece Not supplied Commissioning Valve Fitting 1 2 MI Drain Cock Elbow Drain Cock Cable Entry Electrical Box Tee Piece Discharge Pipe Not supplied Motorised Valve Not Factory Fitted Indirect Only 2021...

Page 3: ...the blanking cap from the pressure reducing valve 3 and connect to the shower or bidet cold supply Major shower manufacturers advise fitting a mini expansion vessel in the balanced cold supply pipework to accommodate thermal expansion and prevent tightening of shower controls Using the balanced cold connection to feed outlets that do not require a balanced cold supply can reduce the flow available...

Page 4: ...rmostat fails c Thermostat is set too high 2 Remember before resetting the safety cut out or altering the thermostat setting isolate electrical supply to the unit prior to removal of the electrical box lid 3 Reduce thermostat setting and press the reset button After adjustments are completed ensure the lid to the electrical box is replaced correctly and the retaining screw is fitted 4 If still out...

Page 5: ...black plastic plugs in the body are pressure gauge connections to enable pressure monitoring to be carried out should the system develop a fault It is recommended that these be accessible the pressure reducing valve has two only one need be accessible 6 Expansion relief drain pipework must be connected to a safe visible discharge point via a tundish and the pipework must have a continuous fall 7 T...

Page 6: ...mplete Benchmark logbook Pressure Reducing Valve 1 Isolate cold water supply 2 Unscrew the retaing nut of the valve The complete operating mechanism including the strainer can be removed 3 Clean the filter mesh and the cartridge under running water 4 Replace cartridge ensuring that strainer is correctly located and reassemble the unit Pressure Reducing Valve cartridge and strainer Part No 510 501 ...

Page 7: ... water heater controller Contact your local electricity company if in doubt Indirect Units Motorised valve To comply with regulations governing the installation of indirect unvented cylinders a motorised valve must be fitted in the primary flow Your OSO unit has been supplied with a two port motorised valve which will act as a positive energy cut out should the safety cut out operate The motorised...

Page 8: ...For Other Boilers Refer To Boiler Manufacturer S Plan Wiring Layout 8 ...

Page 9: ...n either circuit the white wire is not needed and must be made electrically safe L N 4 3 1 2 4 6 L N 4 3 1 2 4 6 1 2 3 4 2 5 L N E 1 2 3 Br Bl Gr Or 5 2 1 10 3 Br Bl Gr Or 8 2 1 10 3 1 2 3 4 5 6 7 8 9 10 9 Honeywell ST 6400 Programmer 7 day Honeywell ST 6300 Programmer 24 Hr ST 6300 Room stat Mains HTG Valve V4043H DHW Valve V4043H Direct units Indirect units Adjustment screw Automatic by pass ...

Page 10: ...For Other Boilers Refer To Boiler Manufacturer Y Plan Wiring Layout 10 ...

Page 11: ... made electrically safe 11 Mid position Valve not supplied L N 4 1 3 1 2 4 7 6 Honeywell ST 6400 Programmer 7 day L N 4 1 3 1 2 4 7 6 Honeywell ST 6300 Programmer 24Hr 1 2 3 4 2 5 L N E 1 2 3 W G O Bl 5 7 8 2 3 Br Bl Gr Or 9 2 1 8 3 ST 6300 Room stat Mains V4073A1039 DHW Valve V4043H 1 2 3 4 5 6 7 8 9 10 Automatic by pass ...

Page 12: ...ermostat diagram page 9 and safety cut out on page 4 of installation manual 3 Check and set to hot water 4 Check boiler operation If fault suspected consult installer or boiler manufacturer 5 As at No 2 6 Check wiring and or plumbing connections to motorised valve See pages 8 or 10 of the installation manual Intermittent water discharge 1 Reduced internal expansion 2 Thermal control failure Note W...

Page 13: ... boiler supply to the unit When discharge has stopped check thermal controls and replace as necessary If problem still persists contact a competent engineer plumber Intermittent water discharge If problem still persists contact a competent engineer Mains supply off Line strainer blocked Cold water PRV incorrectly fitted Open supply valve Clear line strainer Check and refit as required YES YES NO N...

Page 14: ...d valve operating correctly Check wiring or plumbing connections Check and reset button Has cylinder thermal cut out operated Is the boiler working YES NO NO YES NO YES YES YES YES NO D DI IR RE EC CT T I IN ND DI IR RE EC CT T Cylinder Thermostat set to high Connect wiring as per instructions Faulty thermostat replace Check wiring on cylinder thermostat Wiring Fault Seek advice from electrician I...

Page 15: ...ge is adjustable between 0 5 5 0 bar It is advisable to remove the hot supply connection and fit a suitable expansion vessel see 1 above see fig 3 3 Table 3 gives details of cylinder and expansion vessel capacities for a range of pressure settings 4 The expansion vessel must be suitable for potable water and charged to the same pressure as the pressure reducing valve Standard Capacity 100 125 170 ...

Page 16: ...SECONDARY RETURN Downward discharges at low level i e up to 100mm 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 5 6 4 3 2 1 HOT TAPS HOT OUTLET COLD INLET FIGURE 4 FIGURE 5 1 Sec...

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