Combination Boiler with 2 Heating Zones, 230V Switching A wiring centre or junction box is required to connect all of the devices together. The examples shown here use a 10 terminal wiring centre. This arrangement is only suitable for boilers with a 230V AC switched input. Boilers with 24V or other voltages are covered separately. Wiring. This diagram shows the wiring for all components.[PDF] T6360B Room Thermostat Wiring & Operation It is a diagram drawn to I.E.E. guidelines. The picture above right is a photograph of the actual thermostat terminals. Wire in the thermostat according to the number, not the order the terminals are positioned. The "heating load" could be a pump, boiler or motorised valve. There is NO colour coding in central heating wiring so we cannot recommend