Supply requirements

Natural gas supply

For the Greenstar i Junior when on hot water or full output demand will require up to 3.02m3/hr of gas (depending on the model).

For the Greenstar Si when on hot water or full output demand will require up to 3.24m3/hr of gas (depending on the model).

For the Greenstar CDi 42kW appliance when on a hot water or full output demand will require up to 4.4m3/hr of gas (figures for other appliances can be found in the relevant installation manuals).

The gas meter and supply pipes must be capable of supplying this quantity of gas in addition to the demand from any other appliance being served. It is important that a gas supply pipe of at least 22mm diameter is used. Under no circumstances should the size of the gas supply pipe be less than that of the appliance inlet connection. The meter outlet governor should be capable of ensuring a dynamic pressure of 20mbar (8in wg) at the appliance. Particular consideration should be given to the resistance to gas flow created by elbows, bends etc. Pipe work should be sized to overcome this resistance and details of this are given in the table below.

Liquid Petroleum Gas (LPG) supply

All Greenstar combi ranges are available in natural gas and LPG variants. The appliance when on a hot water or full output demand will require up to 2.22 kg/h of gas (depending on the model).The Greenstar Si models will require up to 2.38 kg/h gas (depending on the model) at maximum demand.

The Greenstar CDi 42kW appliance when on a hot water or full output demand will require up to 3.3 kg/h of gas (figures for other appliances can be found in the relevant installation manual).

The gas tank or bottles must be capable of supplying this quantity of gas at a nominal pressure of 37mbar (14.8in wg) at the appliance. The table below shows the LPG discharge through varying lengths of pipe and the resistance to flow created by elbows, bends etc. Pipe work should be sized to overcome this resistance.

Electricity supply

A 3amp fused three pin plug and unswitched shuttered socket outlet (both complying with BS 1362) or preferably a double pole isolator with a contact separation of 3mm in all poles supplying the appliance should be used.

The appliance electrical circuits are also protected by an internal 2amp fuse. The appliance must be earthed.

Mains cold water supply

Water Authority requirement

A direct mains cold water connection is permitted by Water Authorities. However, it is recommended that reference be made to local requirements. In the event of difficulty contact the Worcester Technical Support Department.

Pipe sizing

Unless the mains pressure is low, a standard 15mm diameter service pipe is normally suitable. A 15mm hot water distribution pipe to the first branch is recommended thereafter 15mm and/or 10mm to all draw off points.

Cold water connection

Connection should be made as shown in the pipework detail and the appliance installed generally in accordance with the layout shown on the pipework connections and casing dimensions.

Wherever possible the cold supply to the appliance should be the first connection off the mains supply, in order to minimise hot water flow reduction when cold water services are operated. The final 600mm of piping to the appliance should be of copper only.

Cold water pressure

To achieve the stipulated flow rate a working cold water mains pressure of between 1.3bar is required.

However, for the Greenstar CDi range to achieve the stipulated flow rate a working cold water mains pressure of between 1.2 and 2.3bar is required (dependant on model).

The appliance will operate at a minimum working pressure of only 0.2bar (3psi), however a reduced hot water flow rate should be expected. Back-flow prevention devices, including water meters, can prevent the expansion of hot water into the cold water main. However, this can result in a pressure build-up that may cause damage to the boiler and household devices such as showers, washing machines etc. In these cases we recommend that a mini-expansion vessel (Part No. 7 716 192 105) be fitted adjacent to the boiler in the cold water main.

Hot water supply

For the Greenstar CDi range, a domestic hot water flow regulator, set to give a optimum flow rate of between 9 and 15l/min ±15% (dependant on the model) is fitted to the cold supply of the hot water exchanger.

As with all mains fed systems, the flow rate of water obtainable from individual taps will vary in relation to the number of taps operating simultaneously, and will depend upon the cold mains supply available to the property.

Therefore, in order to avoid excessive starvation of flow to individual taps, flow balancing may be required by the use of proprietary constant volume flow regulators or Ball-o-Fix valves.

Hot water systems

Taps and valves

Hot and cold taps and mixing valves used with the Greenstar CDi Series appliance must be suitable for operating at a mains pressure and temperatures of 65°C (150°F).

Showers

When a loose head shower with a flexible hose is used over a bath or shower tray, the hose must be fixed so that the head cannot fall closer than 25mm (1in) above the top edge of the spill over level of the relevant bath or shower tray.

Alternatively, the feed pipes to the shower should incorporate a double check valve assembly or a check valve and vacuum breaker.

With fixed head showers no provision is necessary.

The use of a thermostatically controlled shower will give added comfort and safeguard against high hot water temperatures.

Alternatively, a pressure balancing shower valve specifically designed for constant temperature water heaters would be suitable.

Bidet

The supply of hot and cold water mains direct to a bidet is permitted provided that the bidet is of the overrim water feed type. The outlet(s) should be shrouded and not to have any temporary hand held spray attached. No other anti-syphonage arrangements are necessary.

Use in hard water areas

As the maximum temperature of the domestic hot water heat exchanger is limited by the electronic control circuit, there is normally no need for water treatment to prevent scale accumulation.

In areas where exceptional water conditions prevail, consideration may need to be given to the fitting of a device capable of preventing scale. In such circumstances the advice of the local water authority should be sought.

Warranty

Worcester Greenstar combi range appliances are offered with a full 2 year guarantee* on parts and labour, a 10 year warranty* on the primary heat exchanger and a 5 year warranty* on the plate heat exchanger. Ongoing service and maintenance contracts can be arranged through the Worcester Customer Service Department.