iSteel
INSTALLATION MANUAL
ISSUE 2015 – V1
FOR MORE INFORMATION GO TO:
www.atagheating.co.uk
INTRODUCTION
Cold Wa
ter Inlet Set
LOOSE
15 x 22mm Tundish
LOOSE
Temperature & Pressure Relief Valve
FITTED
Expansion Vessel
LOOSE
Expansion Vessel Bracket
LOOSE
Compression Nut Connection For Expansion Vessel
LOOSE
Immersion Heater(s)
- dependant on size and configurati
on LOOSE
Instruction Manual
LOOSE
Benchmark Log Book
– at the rear of this manual
LOOSE
The corrosion resistant iSteel Unvented cylinder is made from Duplex Stainless Steel. It is highly insulated with
environmentally friendly foam enclosed in a rust resistant white steel case.
It is available in Direct, and Indirect versions in a family of 7 sizes from 90 - 300 litres. Twin Coil Indirect units are available
in 5 sizes from 150 - 300 litres. There is also a range of slim-style units from 60 - 210 litres again in Direct and Indirect
versions, please contact ATAG Heating Technology about slim-style units.
To help ensure compliance with the relevant Water and Building Regulations all iSteel units are supplied complete with
the necessary safety and control devices needed to connect to the cold water mains. In order to ensure high flow-rate
performance with minimum pressure drop even in lower pressure areas, pre-set high quality controls have been selected.
iSteel is approved to demonstrate compliance with Water Regulations and Building Regulations G3 & Part L.
STORAGE PRIOR TO INSTALLATION
iSteel should be stored upright in a dry area and kept in its original packaging until immediately prior to installation.
INSTALLATION PREREQUISITES
This Cylinder should only be installed by a competent installer holding their G3 unvented qualification. The installation of
this product is also notifiable under the national Building Regulations.
ONCE COMPLETED THIS INSTRUCTION MANUAL IN ITS ENTIRETY SHOULD BE LEFT WITH THE HOME OWNER.
WHAT IS BENCHMARK?
Benchmark places responsibilities on both manufacturers and installers. The purpose is to ensure that customers are
provided with the correct equipment for their needs, that it is installed, commissioned and serviced in accordance with
the manufacturer’s instructions by competent persons and that it meets the requirements of the appropriate Building
Regulations. The Benchmark Checklist can be used to demonstrate compliance with Building Regulations and should be
provided to the customer for future reference.
Installers are required to carry out installation, commissioning and servicing work in accordance with the Benchmark
Code of Practice which is available from the Heating and Hotwater Industry Council who manage and promote the
scheme. Visit
www.centralheating.co.uk
COLD INLET SET – WHAT ARE THE CONNECTIONS?
EQUIPMENT SUPPLIED WITH THE CYLINDER
WATER SUPPLY
iSteel is capable of delivering over 50 litres per minute when connected to a suitable mains supply. The high quality inlet
control set with its 3 bar operating pressure has been designed to make the most of what is available however the
performance of any unvented system is only as good as the water supply.
In unvented systems both hot and cold services are supplied simultaneously from the mains so the maximum possible
on-site water demand must be assessed and the water supply should be tested to ensure it can meet these requirements.
If necessary consult the local water supplier regarding the likely pressure and flow rate availability.
It is important that site pressure readings are taken under dynamic flow conditions, high pressures under zero flow
conditions are not necessarily indicative of satisfactory performance. A minimum of 1.5 bar at 20 l/m flow should be
available. Where mains inlet pressures are likely to exceed 16 bar then an additional upstream pressure reducing device
should be fitted.
A minimum of 22mm supply pipe-work should ideally be provided and existing 1/2” (15mm) cold mains pipe-work may
need to be upgraded. Hard water treatment should be considered in areas where content it greater than 200ppm, if
required adjust cylinder temperature to below 60 degrees.
SITING THE UNIT
iSteel can be positioned more or less anywhere in the dwelling but it should be remembered that for every 1 metre that
an outlet is above the iSteel, the pressure will be reduced by 0.1 bar. If siting outside the heated envelope of the dwelling
such as in a garage or outbuilding then frost protection should be provided and exposed pipework should be insulated.
iSteel must be supported on a flat base capable of supporting the weight of the cylinder when full. The minimum
recommended cupboard size is 650mm square.
It’s important that consideration is given to access for maintenance of the valves. The immersion heaters are 375 mm
long and access space should be provided for possible future replacement, also adequate access to remove and re-install
the cylinder in the event of a problem.
SCHEMATIC
GENERAL INSTALLATION
COLD MAINS PIPEWORK
Run the cold main through the building to the place where the iSteel is to be installed. Take care not to run the cold pipe
near hot water or heating pipe work so that the heat pick up is minimised. Identify the cold water supply pipe and fit an
isolating valve (not supplied).
A 22mm BS1010 stopcock can typically be used but a 22mm quarter turn full bore valve would be better as it does not
restrict the flow as much. Do not use “screwdriver slot” or similar valves.
Make the connection to the cold feed of the cylinder and incorporate a drain valve. Position the inlet control just ABOVE
the Temperature & Pressure Relief Valve (TPRV) mounted on the side of the cylinder. This ensures that the cylinder does
not have to be drained down in order to service the inlet control set. Ensure that the arrow points in the direction of the
water flow.
Select a suitable position for the expansion vessel. Mount it to the wall using the bracket provided. Use the compression
connection supplied to connect the vessel into the cold water pipe adjacent to the cold feed point on the cylinder. There
must be no obstruction or flow restriction between the cylinder and the expansion vessel.
BALANCED COLD CONNECTION
If there are to be showers, bidets or mono-bloc taps in the installation then a balanced cold supply is necessary. There is
a 22mm balanced connection on the inlet control set. All outlets in the house will be at 3 bar and thus automatically
balanced.
HOT WATER PIPEWORK
Run the first part of the hot water distribution pipework in 22mm. This can be reduced to 15mm and 10mm as appropriate
for the type of tap etc. Your aim should be to reduce the volume of the hot draw off pipework to a practical minimum so
that the time taken for the hot water is as quick as possible.
Do not use mono-bloc mixer tap or showers if the balanced cold connection is not provided, the unit will back pressurise
and result in discharge. Ensure that the top of the vessel is accessible for servicing.
PRIMARY COIL CONNECTIONS (INDIRECT ONLY)
Compression connections are provided for the primary circuit which must be positively pumped. Primary flow and return
connections are interchangeable to suit site conditions without affecting reheat times. These connections are metric and
should be changed by the installer if using Irish size copper tube.
Sealed or vented primary circuits can be used, to comply with normal installation practice the primary pressure should
not exceed 3 bar although the coil in the iSteel is suitable for up to 7 bar if required. The boiler may be Gas, Electric, and
Oil etc. but must be under effective thermostatic control. Uncontrolled heat sources such as some AGA’s, back boilers,
solid fuel stoves, etc. may not be suitable please contact us for guidance. The two port zone valve should be installed into
the primary flow pipework leading to the coil flow inlet. The direction of flow arrow should be towards the primary flow
connection. On twin coil cylinders an extra thermostat boss is provided.
SECONDARY CIRCULATION
Where secondary circulation is required a circulator suitable for potable water should be used in conjunction with a nonreturn valve to prevent backflow. It may be necessary to incorporate an extra expansion vessel into the circuit to
accommodate the increased system water volume in larger secondary circulation systems. Where off peak electrical
tariffs are being used then secondary circulation should be avoided. A secondary return boss is fitted as standard on 210,
250 & 300L. On smaller sizes tee into the cold feed pipe above the drain.
IMMERSION HEATERS
As a requirement of Building Regulations the iSteel immersion heaters are fitted with thermal cut-out in addition to the
normal control thermostat. To help ensure correct replacement the immersion heaters have a special 1¾" thread. They
are of a low noise Incoloy construction and rated at 3 kW at 240 V. Replacement immersion heaters should be purchased
via ourselves otherwise your guarantee may be affected. For commercial / heavy duty installations where constant usage
/ reheat is required Titanium immersion heaters must be fitted in order to comply with the warranty.
The ‘O’- ring on the head of the immersion heater should be correctly positioned and lubricated before fitting. Screw in
hand-tight until almost sealed then gently tighten as the ‘O’ rings will seal easily. The electrical supply to each immersion
heater/s must be fused at 13A via a double pole isolating switch to BS 3456. The cable must be 2.5mm
(85°C HOFR) sheathed flex complying to BS 6141:1981 Table 8. Do not operate the immersion heater/s until the unit is
full of water. If any sterilisation liquid is in the cylinder do not operate the immersion heater/s as this will cause premature
failure. Electric to be supplied by a fused supply compliant with local regulations, and fitted by a qualified Part P
Electrician.
2
heat resistant
ENERGY CUT OUT AND CYLINDER THERMOSTAT (INDIRECT ONLY)
600 mm Max
As a requirement of Building Regulations the iSteel units are fitted with a thermal cut-out in addition to the normal control
thermostat. This unit should be fitted to the dedicated boss on the cylinder and wired to the two port valve controlling
the primary flow (see wiring diagram).
DISCHARGE ARRANGEMENT
This guidance is available as a download of the G3 Approved Document from www.planningportal.gov.uk.
The discharge from both the temperature relief and expansion relief valves can be joined together via a 15mm end feed
tee.
It is important that any discharge water does not collect in this pipe-work and can run freely to the tundish.
The tundish should be mounted in a vertical and visible position located in the same space as the unvented hot water
storage system and be fitted as close as possible and within 600mm of the safety device e.g. the temperature relief valve.
The discharge pipe-work from the tundish must be routed in accordance with Part G3 of the Building Regulations.
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, be of metal and:
• Be at least one pipe size larger than the nominal outlet size of the safety device unless its 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 two sizes larger than the nominal outlet size of the safety device, between 18 and 27m
at least 3 sizes larger, and so on. Bends must be taken into account in calculating the flow resistance. An alternative
approach for sizing discharge pipes would be to follow BS6700 Specification for design installation, testing and
maintenance of services supplying water for domestic use within buildings and their curtilages.
• Have a vertical section of pipe at least 300mm long, below the tundish before any elbows or bends in the pipework.
• Be installed with a continuous fall.
• It is preferable for the discharge to 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 acceptable discharge arrangements are:
1. Ideally below the fixed grating and above the water seal in a trapped gulley.
2. Downward discharges at a 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 play or otherwise come into contact with
discharges, a wire cage or similar guard is positioned to prevent contact whilst maintaining visibility.
3. Discharges at a high level; e.g. in to 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
3m from any plastic guttering systems that would collect such discharges (tundish available).
4. 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 larger 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 blind, infirm or disabled people, consideration should be given to the installation of an electronically
operated device to warn when discharge takes place.
Any queries with regard to discharge arrangement contact your local council planning office.
TWIN COIL FORMAT
Indirect twin coil units can be installed in two separate formats:
• In a solar powered system with a backup boiler.
• In a system with two non-solar heat sources (normally two boilers).
With either format it is essential that the installation meets all current regulations including, in particular, the high limit
cut out requirements of Building Regulation G3.
UPPER COIL
This is connected to the boiler as per the instructions for a iSteel single coil cylinder with the high limit thermostat inserted
into the middle thermostat pocket and wired to control the supplied two port valve in either the primary flow or return
as indicated in the wiring instructions.
LOWER COIL – SOLAR VARIENT
In a solar system the lower coil is connected to the solar heat source. Either primary coil connection may be used for flow
or return. The solar cylinder sensor supplied is inserted into the lower thermostat pocket and the energy cut out into the
upper pocket. The ‘mechanical’ control thermostat is not normally utilised in a solar system. In systems where the panels
are above the cylinder then the energy cut out shall be wired so as to interrupt the power supply to the solar pump or
controller in the event of over temperature.
In systems where the cylinder is above the panels then the energy cut out should be wired to a suitable two port valve
(not supplied) on the return pipe-work to the solar panel.
LOWER COIL – NON SOLAR VARIENT
This is connected to the additional boiler as per the instructions for a iSteel single coil cylinder with the high limit
thermostat inserted into the lower thermostat pocket and wired to control the supplied two port valve in either the
primary flow or return.
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