RM Unvented Cylinder 90ltr Direct Mega Flow Stainless Steel 25 Year Guarantee

Introduction & Maintenance Stelflow

The corrosion resistant Stelflow 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 in Twin Coil and Indirect. Direct Eco units are available in 5 sizes from 150 - 300 litres . There is also a range of slimstyle units from 60 - 210 Litres again in Direct and Indirect versions.
To help ensure compliance with the relevant Water and Building Regulations all Stelflow units are supplied complete with the necessary safety and control devices needed to connect to the cold water mains. In order to ensure high flowrate performance with minimum pressure drop even in lower pressure areas , pre-adjusted. High quality controls have been selected.
Stelflow is approved to demonstrate compliance with Water Regulations and Building Regulations G3 & Part L.

Storage Prior to Installation

Stelflow 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.

Water Supply

Stelflow 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.

Siting The Unit

Stelflow can be positioned more or less anywhere in the dwelling but it should be remembered that for every 1 meter that an outlet is above the Stelflow, 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.

Stelflow 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

Schematic

Run the cold main through the building to the place where the Stelflow 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 minimized. 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 hose to connect to
the inlet control group.

Balanced Cold Connection

If there are to be showers, bidets or monobloc taps in the installation then a balanced cold supply is necessary. There is a 22mm balanced connection on the inlet control set. An alternative method is to split the inlet control set on to two parts. Site the pressure reducing valve immediately after the incomming cold mains stopcock (typically under the kitchen sink). All outlets in the house will be at 3 bar and thus automatically balanced. The expansion relief valve section must still be mounted just above the TPRV on the cylinder. A 3/4”F-22mm compression adaptor will be needed (not supplied).

Hot Water Pipe Work

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 monobloc mixer tap or showers if the balanced cold connection is not provided. The unit will back pressurise the unit 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.

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 Stelfow is suitable for up to 7 bar if required. The boiler may be Gas, Electric, 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 non return 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 Stelflow 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 13/4“ 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.

The ‘O’ring on the head of the immersion heater should be correctly positioned and lubricated before fitting . Screw in handtight until almost then gently tighten as the ‘O’ rings will seal easily. The electrical supply to each immersion heaters must be fused at 13A via a double pole isolating switch to BS 3456. The cable must be 2.5mm2 heat resistant (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.

Energy Cut Out And Cylinder Thermostat Indrect Only

As a requirement of Building regulations the Stelflow 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).

General Guidance

General guidance is provide by the above diagram extracted from the G3 Building Regulation Guidance. This guidance is available as a free of charge download of the G3 Approved Document.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 500mm 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: