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Heatranger Models 216SFW, 345W, 355SFW

These models are intended to be continuously alight and will therefore always be producing hot water, the necessary heat being absorbed by the boiler from the surrounding firebox.

The more cooking is carried out, then the more hot water is generated. With average cooking  use, approximately 450 litres (100 gallons) of domestic hot water would be created over a 24 hour period. If the cooker spends longer periods idling, then the hot water production is proportionally reduced, unless of course, a hotter fire is maintained for obtaining central heating. This is assuming that the control damper on the 345W and 355SFW models is set to the cooking position with the firebricks in their appropriate place.

The hot water must be stored in an open-vented, vertical conventional copper cylinder, installed so as to operate from gravity circulation, connected as an indirect system as shown below and suitably insulated. A storage capacity of 190 litre (40 gallon) is required. Electric immersion heaters may also be incorporated.

To maintain performance, the maximum distance between the cylinder and Rayburn should not exceed 10 metres, giving a maximum 'pipe loop' of 20 metres.

To ensure the optimum hot water performance we do not recommend any secondary circulation from the storage cylinder, consequently the feed to the draw-off taps should be 'dead-leg' pipework.

To encourage gravity circulation, the flow & return pipes between the Rayburn and the cylinder should rise continually and be of 28mm diameter, lagged if possible to maintain efficiency. A circulating pump will probably be used to drive the heating system, but the hot water circuits should operate by gravity.

If the demand for hot water is likely to be limited, or the cylinder is situated close to the Rayburn, a heat leak might be advisable. This should take the form of a towel-rail or small radiator, fitted with isolating valves and operating on gravity circulation. Alternatively, a clamp-on pipe thermostat could be fitted to the flow pipe, set to bring the heating circulating pump into operation, if the water temperature becomes excessive. 

An 'injector tee' is supplied with the Rayburn, which should be fitted at the point where the heating return pipe and the hot-water return pipes meet. This ensures that the gravity hot-water circulation is not interrupted whilst the heating pump is running. 

The plumbing system should be fully flushed through and a suitable corrosion inhibitor added.

 Sealed or unvented systems must not be used with these models.

It is possible for the Rayburn to share the domestic hot water load with an additional appliance, this being achieved by the use of a twin-coil cylinder. Both appliances should have their own separate systems and feed tanks, but the Rayburn should be allowed to contribute the bulk of the heat to the cylinder, using the bottom coil. The other appliance should only heat the cylinder on demand using, a cylinder thermostat in conjunction with a motorised zone valve. No valves or restrictions should be fitted to the Rayburn circuit.

The system must be installed in accordance with local water bylaws, Building Regulations and British standards and we strongly encourage that the plumbing be carried out by a competent person.

See also

Domestic Hot-Water   General Questions

Central Heating