Ariston STI 125 INDIRECT, STD 125 DIRECT, STD 150 DIRECT, STD 210 DIRECT, STI 150 INDIRECT User Manual

UNVENTED CYLINDER

RANGE

UNVENTED WATER STORAGE CYLINDER

No longer than every 12 months, the magnesium anti-corrosion

anodes should be checked by your service engineer/installer.

Installation and Users Guide

IMPORTANT

Please read these instructions carefully

before installing the cylinder.

Failure to do so may invalidate the Warranty

WATER BYELAWS

These bye-laws ensure a good supply of wholesome water, and that only approved materials, pipes and fittings are used to
convey water.

BUILDING REGULATIONS

These are a statutory document and take priority over all other regulations and recommendations. The installation of an
unvented hot water storage cylinder is classified as a "Controlled Service" and Regulation G3 applies. To meet the
requirements of the Regulation, installation of an unvented system should be undertaken by a "competent installer".

All installations of unvented hot water storage systems having a capacity of more than 15 litres should be notified to the
relevant Local Authority by means of building notice or by the submission of full plans. It is important to note that it is a
criminal offense to install an unvented hot water storage system without notifying the Local Authority.

DELIVERY

The range is available with the following options;

The wall-hung range (50, 75, 100 litre models), which are supplied as the following;

One large box containing;

1) The unit with factory fitted Temperature & Pressure Relief Valve and Immersion Heater.

One small box containing;

1) Unvented control pack (Expansion vessel, 2 piece Cold Water Combination Valve, Tun Dish).

The Ariston Contract and the Ariston Comfort (Indirect only) floor-standing range (125, 150, 200 litre models).

The Contract is supplied with the following;

One large box containing;

1) The unit with factory fitted Temperature & Pressure Relief Valve.

2) Immersion Heater(s) (not fitted).

3) Cylinder Thermostat (Indirect only, not fitted).

4) Feet x 3.

One small box containing;

1) Unvented control pack (Expansion vessel, 2 piece Cold Water Combination Valve, Tun Dish, Drain Cock and Motorised
Valve (Indirect only).

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Hot and cold water are both drawn off the same source of supply. Remember, there will not be a storage tank to help
compensate for variations in the demand on the system.

A minimum pressure of approximately 1.5 bar and 20 litres per minute is required for satisfactory operation. 85% of UK
dwellings have a mains pressure above 2.0 bar.

THE MAINS WATER SUPPLY MUST NOT EXCEED 12 BAR

SITING AND FIXING

The cylinder may be installed at any convenient position, as it is connected to the mains cold water supply, it is equally
effective on any floor.

However, do not install the unit in premises which may be subject to freezing. Ensure that the floor load bearing strength is
adequate to take the weight of the cylinder when full of water (see table 1).

The ST50, ST80 and ST100 models are wall mounted. All other models are free standing. These are supplied with feet
which are attached to the heater via self tapping screws which are also supplied. All units must be installed in the
VERTICAL POSITION.

For maintenance purposes leave at least 500 mm free space in front of the unit, for access to electrical components,
immersion heater(s) and magnesium anodes.

CONNECTION OF MAINS WATER SUPPLY
For Contract & Comfort models:
On the front of the unit there is a label to identify the connection ports. Please check this before making any connection
to the unit.

For units up to 300 litres it is recommended that all mains cold water supply pipe work is a minimum of 22mm, with the
exception of model ST50 where 15mm can be used. For 500 litre models the supply should be 28mm. An Isolating Valve
should be installed between the cold water supply and the cylinder for servicing. ALL PIPEWORK MUST BE FLUSHED TO

AVOID DAMAGE TO THE CONTROL VALVES.

Please refer to figs. 1, 2 , 3, 3, 3, 3, 3 for a suggested installation layout.

COLD WATER COMBINATION VALVE

The Cold Water Combination Valve can be connected either close by the unit or alternatively it may be installed in a remote
position from the unit as there is no requirement to site it in close proximity to the cylinder. This allows a flexible and
convenient installation. However, it is important to note allowances for the discharge pipe work from the Expansion Relief
Valve must be accounted for.

A Balancing Port is supplied on the 22mm (for units above 50 litres) valve allowing balanced cold water supply to the rest of
the building giving excellent results with mixer and shower valves. If the facility is not needed a plug is supplied. Refer to fig.
4

Although this facility is not built into the 15mm valve (supplied with Contract ST50), a Tee Piece may be inserted between
the two components giving the same results. Refer to fig. 5

CONNECTION TO SERVICES

Again it is recommended that a 22mm pipe run should supply the outlets throughout the building, especially to baths and
showers. Short runs of 15mm pipe may be used to connect basins and sinks.

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The Comfort is supplied with the following;

One large box containing;

1) The unit with factory fitted Temperature & Pressure Relief Valve.

2) Factory fitted Immersion Heater (Dry pocket).

3) Factory fitted Cylinder Thermostat.

4) Feet x 3.

One small box containing;

1) Unvented control pack (Expansion vessel, 2 piece Cold Water Combination Valve, Tun Dish, Drain Cock and Motorised
Valve).

The high capacity floor-standing range (300, 500 litre models), which are supplied as the following;

One large box containing;

1) The unit

2) Factory fitted Temperature & Pressure Relief Valve (300 litre models only).

3) Factory fitted Immersion Heater(s)

4) Factory fitted Cylinder Thermostat.

5) Feet x 3.

One small box containing;

1) Unvented control pack (Expansion vessel, 2 piece Cold Water Combination Valve, Tun Dish, Drain Cock and Motorised
Valve) (500 litre model 1" Temperature & Pressure Relief Valve).

HOW THE HEATER WORKS

The Immersion Heater(s) are connected through a thermostat which senses the water temperature. The operating
temperature can be pre-set by adjusting the spindle in the head of the thermostat. In addition to the thermostat there is a
Thermal Cut-out incorporated if the thermostat fails and the water temperature rises too high. Once the cut-out operates it
can only be re-set manually after the fault has been rectified.

Indirect models have dual thermal controls. In addition to the above there is a separate Cylinder Thermostat and Thermal
Cut-out for controlling the indirect circuit. Again the Thermal Cut-out operates if the Cylinder Thermostat fails, by
disconnecting the live feed (call for hot water) from the programmer.

Floor-standing models have Magnesium Anodes provided to prevent corrosion of the water cylinder tank. Wall-hung units
have a single Magnesium Anode.

The factory fitted Temperature & Pressure Relief Valve at the top of the cylinder is a safety device to back-up the
Thermostat(s) and Thermal Cut-out(s). It works by sensing an excess in water temperature or pressure and releasing the
hot water into a Discharge Tundish and drain.

The cylinder will only work in the vertical position. The inlet pipe needs to deliver cold water to the bottom of the tank. When
water is heated it expands. To accommodate this increase in volume an Expansion Vessel is provided. A Cold Water
Combination Valve is also provided in two pieces, loose jointed for ease of installation. These comprise a Combined Line
Strainer/Pressure Reducing Valve and Core Non Return Valve/Expansion Relief Valve.

The Strainer prevents any debris entering the other controls. The Pressure Reducer ensures the correct operation of the
Expansion Vessel, and prevents any damage to the control valves through too great a pressure.

The Non-Return Valve ensures the water expansion is forced into the Expansion Vessel and prevents contamination of the
mains cold water supply. The Expansion Relief Valve will discharge expanded water to the Discharge Tundish if the
Expansion Vessel fails.

COLD WATER SUPPLY

It is important to ensure that the cold water main is capable of supplying the increased demand which will be imposed on it.

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AB

CD

ELECTRICAL

The electrical installation must be in accordance with the current I.E.E. wiring regulations.

FITTING IMMERSION HEATER(S) (CONTRACT RANGE ONLY)

These are supplied but not fitted with the Ariston Contract range. A Sealing Gasket is supplied with each element and must
be used to ensure a correct seal. Care must be taken not to cross thread the Immersion Heater(s) when fitting. Each
Immersion Heater is supplied with a Regulation Thermostat and manual reset Thermal Cut-out. This will activate if the
Regulation Thermostat fails. Under no circumstances should this be bypassed.

Although the Immersion Heaters are a standard 21/4” thread, they must not be substituted with anything but an
original Ariston spare part.

DIRECT SYSTEMS

A mains supply of 240V, 3kW (13 amps) is required. Heat resistant cable, round 3 or 4 core 2.5mm2 (to BS6141 table 8)
must be used to connect the electrical supply through the Economy 7 time control switch using either system ‘A’ or ‘B’ as
illustrated in fig. 8.

Should the Economy 7 system not to be used, a separate 13 amp supply to each element will be required. Through a
double pole fused isolating switch having a contact gap of at least 3mm on each pole. Make the connection(s) to the
Immersion Heater(s) as per figs. 9, 10. For 500 litre models consult the wiring diagram on the reverse of the inspection
panel.

The Thermostat(s) on the Immersion Heater(s) should be adjusted to trip at 60°C. This is the ideal temperature to prolong
element life in hard water areas. Scale on the sheath builds up more rapidly at temperatures above this causing the element
to overheat and premature failure can occur. Higher temperatures without additional controls would result in scalding.

In addition to the thermostat the Thermal Cut-out will switch power off to the element should the thermostat malfunction,
causing an excessive rise in water temperature. The Thermal Cut-out can be reset manually after the fault has been
corrected.

INDIRECT SYSTEMS

Again for models up to 300 litres a mains supply of 240v, 3kW (13 amps) will be required for the direct Immersion Heater.
Heat resistant cable, round 3 core 2.5mm² (to BS) must be used. For 500 litre models consult the wiring diagram on the
reverse of the inspection panel.
For indirect controls a 240V, 3amp supply is required.
On Comfort models the Indirect thermostat is factory fitted, for Contract models it is necessary to fit the thermostat using
P.T.F.E Tape (Please consult the label on the face of the unit for the correct location in both cases).

The cables must be clamped in position (as previously stated) and the control thermostat should be set at 60°C for the
reasons above. In addition to the thermostat there is a Thermal High Temperature Cut Out should the thermostat fail. Refer
to figs. 11 & 12 for full wiring instructions.

WARNING : THIS APPLIANCE MUST BE EARTHED.

The earth continuity conductor of the electrical installation must be effectively connected to all exposed parts of other
appliances and services in the room in which the water heater is to be installed, conformity with the I.E.E. wiring regulations.

NOTE : Do not switch on the Immersion Heater or fire the boiler until the water heater is full of water.

COMMISSIONING

Check for obvious signs of damage to the cylinder and controls and also that the controls fitted correspond with the
reference quoted in these instructions.

Ensure that the Drain Cock at the base of the water heater is closed before commencing.

1) Open all outlet taps.

2) Turn on mains water supply and allow the water heater to fill.

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SECONDARY RETURN

On Floor-standing models a Secondary Return may be fitted. On Contract and Comfort models via the special port on the
side of the cylinder (consult the label on the face of the unit for the correct location), for 300 and 500 litre models refer to fig.

6. A Non Return Valve (not supplied) must be fitted to prevent back flow and a Bronze Pump will be needed in conjunction
with a Pipe Thermostat to circulate the hot water (both not supplied).

DISCHARGE PIPEWORK

1) The Tundish must be vertical and fitted within 500mm of the Temperature & Pressure Relief Valve and must be located
with the cylinder. The Tundish must also be in a position visible to the occupants, and positioned away from any electrical
devices. The discharge pipe from the tundish should terminate in a safe place where there is no risk to persons in the
vicinity of the discharge and to be of metal.

2) Discharge pipes from the Temperature & Pressure Relief and Expansion relief valve may be joined together.

3) The pipe diameter must be at least one pipe size larger than the nominal outlet size of the safety device unless it's total
equivalent hydraulic resistance exceeds that of a straight pipe 9m long.

I.e. Discharge pipes between 9m and 18m equivalent resistance length should be at least 2 sizes larger than the nominal
outlet size of the safety device. Between 18m and 27m at least 3 larger, and so on.
Bends must be taken into account in calculating the flow resistance.
See fig. 7 and Table 2.

4) The discharge pipe must have a vertical section of pipe at least 300m in length, below the Tundish before any elbows or
bends in the pipework.

5) The discharge pipe must be installed with a continuous fall.

6) The discharge must be visible at both the Tundish and the final point of discharge, but where this is not possible or
practically difficult; there should be clear visibility at one or other of these locations. Examples of acceptance are:

i) Ideally below a fixed grating and above the water seal in a trapped gully.
ii) Downward discharges at a low level; i.e. up to 100mm above external surfaces such as car parks,

hard standings, grassed areas etc. These 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.

iii) Discharges 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 3m from any plastic guttering systems that would such a discharge (Tundish
visible).

iv) 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 can be traced reasonably easily.
The single common discharge pipe should be at least one pipe size large than the largest individual
discharge pipe to be connected. If unvented hot water storage systems are installed where
discharges from safety devices may not be apparent I.e. in dwellings occupied by the blind, infirm or
disabled people, consideration should be given to the installation of an electronically operated device
to warn when discharge takes place. Note: The discharge will consist of scalding water and steam.
Asphalt, roofing felt and non-metallic rainwater goods may be damaged by such discharges.

WARNINGS

The outlet from the Temperature & Pressure Relief Valve must not be used for any other purpose. This also applies to the
Expansion Relief Valve. No other valve is to be fitted between the Cold Water Combination Valve and the cylinder.

The Temperature & Pressure Relief Valve must not be removed in any circumstances. Any of the above will totally
invalidate the warranty.

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FAULT POSSIBLE CAUSES REMEDY

1) Mains Cold Water Check and open Isolating
supply shut off and/or Stop Valve. Check

water, Local Water Authority

NO HOT WATER 2) Line Strainer Turn off mains water supply,
FLOW blocked remove Line Strainer and

clean

3) Cold Water Check direction of flow
Combination valve arrows on valve, refit in
fitted incorrectly correct position if necessary

1) Low Mains Water Check pressure, consult
Pressure Local Water Authority if

necessary

REDUCED FLOW 2) Line Strainer Turn off mains water supply,
RATE partially blocked remove Line Strainer and

clean

3) Size of Service Increase to size stated on
Pipe too small page 4

1) Direct Immersion Check Immersion Heater,
Heater is not switch on if necessary
switched on

2) Direct Thermal Test Thermostat operation
Cut-Out has and wiring, if faulty,
operated correct/replace. Reset Cut-Out

WATER FROM 3) Boiler Programmer Check switch on Domestic
HOT TAPS set to Central Hot Water if necessary
IS COLD Heating only

(Indirect models)

4) Boiler is not Check boiler operation, if
functioning fault suspected consult
(Indirect models) Manufacturer's Instructions

5) Indirect Thermal Test Thermostat operation
Cut-Out has and wiring, if faulty,
operated correct/replace. Reset

Cut-Out

6) Motorised valve Check wiring and operation of
jammed or not Motorised Valve correct/
wired correctly replace as necessary
(Indirect models)

DISCHARGE FROM 1) Pressure above 7 Shut down boiler or immersion
PRESSURE/ bar, failure of heater. Check pressure
TEMPERATURE Pressure Reducing Reducing Valve and Thermal
RELIEF VALVE Valve. Temperature Controls. Replace if

above 90 C failure necessary
of thermal control

DISCHARGE FROM 1) Continually. Check pressure from valve.
EXPANSION Pressure Reducing Replace if over 3.5 bar
VALVE Valve faulty

When heater is heating Check charge of vessel. Re­Faulty Expansion charge vessel to 3.5 bar or
Vessel or lost charge replace if necessary

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FAULT FINDING

3) Close taps in turn after having purged the system of air.

4) Check for leaks around the controls and Immersion Heaters and again after the unit has heated up.

5) Check that no water is passing to waste through the relief valves.

6) Test the operation of the Temperature & Pressure Relief and Expansion Valves by lifting/turning the manually operated
test lever/cap and observing that water flows through freely and safely to waste.

7) Check that the discharge pipe is plumbed so that it falls continuously and that no taps, valves or other shut off devices
are installed in the pipe.

8) Check that all thermostats are set at 60°C.

9) DIRECT UNITS. Switch on Immersion Heater(s) and allow unit to heat up. Check operation of Thermostat(s).

10) INDIRECT UNITS. Fill the indirect (primary) circuit following the boiler instructions. Switch on the boiler, ensure that the
programmer is to Domestic Hot Water. Allow unit to heat up and check operation of indirect thermostat on motorised
valve(s).

11) Demonstrate operation to user, including operation of Temperature & Pressure Relief Valve and what to do if it
operates.

12) Give this book to the user to retain for future reference and make the customer aware that periodic checks of the
equipment are essential for safety.

MAINTENANCE

No longer than every 12 months, the installer should check the Magnesium Anti-corrosion Anodes (consult the label on the
face of the unit for the correct location). Assessment of the condition of the bottom anode can be made by judging the
condition of the top anode.
If the heating element is heavily coated with scale we recommend descaling at the time of this inspection. The Expansion
Vessel may need to be recharged periodically by your installer.

WARNING :

SWITCH OFF THE POWER SUPPLY BEFORE WORKING ON THE APPLIANCE.

If the Thermal Cut-Out has operated the cause must be found before resetting.

Removal of top & bottom Anodes;

1) Close the mains supply service valve.

2) Open hot water taps.

3) Attach a hose and open the drain cock and allow the cylinder to empty.

4) The anodes are removed by unscrewed using an Allen key.

EXAMINE THE ANODES AND REPLACE IF THE DIAMETER IS LESS THAN 10mm.

The use of P.T.F.E. sealing tape is recommended to ensure watertight connection for Anodes.
Descale the Immersion Heater(s) and remove any lime deposit from the cylinder. Replace in reverse order. THIS DOES
NOT APPLY TO COMFORT MODELS.

Check controls as per the following:-

1) Check and clean the Line Strainer before refilling the system.

2) Check pressure in Expansion Vessel and top up as necessary.

3) Check manually by lifting the test lever, the Temperature & Pressure Relief Valve.

4) Check manually by turning the test knob the Expansion Relief Valve.

5) Check discharge pipes from both Temperature & Pressure Relief and Expansion Relief Valve for obstructions.

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