Viessmann Cylinder demand box (System boiler) 7574319

Cylinder Demand Terminal Box

For use when four pipe configuration is used with a third party cylinder.
This transfers 230v AC signal from conventional cylinder thermostat controls (S or Y plan) and converts the 230V to a low voltage signal as required by the Vitodens range of system domestic boilers.

Complete with instructions.

For the new PlusBus Vitodens 200-W just snip the boiler connection plug off and hard wire into 3 & 4 on the cylinder sensor connection block.