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CENTRAL HEATING

Heatranger Oil-fired  Models 440, 460, 480, 499  K & KB, 880K, 8120K, 8150K

These models offer considerable flexibility in central heating system design and are compatible for use with most modern systems.

This can include normal open-vented or sealed systems utilizing conventional radiators or underfloor heating. They may be also used in conjunction with 'Heatstore' type hot-water cylinders.

Whilst it is difficult to predict the total number of radiators which each model will supply, it is more appropriate to refer to the radiators stated output and then check that the total is within the capacity of that particular model Rayburn. Always allow a margin of 10% for pipe-work losses and of course an allowance for the domestic hot water requirements. 

A fully pumped, indirect system is required, similar to that shown below, noting that the diameter of the flow and return pipes should be 28mm, up to the point in the system where the heating and hot water circuits split.

Whatever type of system is used, it must be fully pumped and contain a suitable corrosion inhibitor.

Some heat is generated by the boiler when cooking operations are carried out (max 1kW/hr) therefore the Rayburn incorporates its own pump over-run control, thus it is necessary to provide a bypass loop, in circumstances where zone valves and/or thermostatic radiator valves are fitted which can completely close both circuits. This bypass could incorporate a heat leak such as a towel rail, but otherwise should provide a pipe-work loop of at least 5m from the Rayburn, sufficient to discharge the latent heat. An automatic pressure adjusting valve should be fitted to the bypass.

Since these models incorporate a manual reset overheat device, it is possible to use a sealed system as an alternative to the conventional open-vented arrangement. Sealed systems, set to operate at a maximum pressure of 2 bar, will require the appropriate ancillary equipment, such as expansion vessel, pressure relief valve and filling loop.

Time control for the heating system is obtained from the Rayburn's integral programmer. Motorised valves should be used to provide the necessary control, in conjunction with cylinder and room thermostats and may be of the 2 port zone type or 3 port mid-position variety. They should be sized as follows.

Typical external wiring diagram for controls shown below.

If under-floor heating is to be used, this should be a proprietary packaged system, consisting of all the necessary controls etc. Such systems normally require the water temperature through the plastic pipe coils to be restricted to a relatively low temperature such as 30-50 degrees C., but the Rayburn's boiler thermostat must not be used for this purpose, otherwise the domestic hot water temperature would be insufficient and damage to the heat exchanger may result from condensation. Instead, the under-floor equipment manufacturer will normally supply the necessary thermostats and mixing/blending valves to control the water temperature to the heating coils. Always refer to the manufacturers technical literature and instructions.

Thermal store type hot-water cylinders may be used with these model Rayburns, in which the heat for the radiators is drawn from the cylinder. Note that two circulating pumps will normally be required. A typical system is shown below, courtesy of Albion Cylinders Ltd and featuring their 'Mainsflow' system.

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

See also Domestic Hot Water