One valve for hot water another for heating. Output from the normal cylinder thermostat is connected to the high limit thermostat and the output from that powers the 2 port valve motor.
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S plan wiring diagram with unvented cylinder. Generally only used when installing an unvented cylinder to an existing y plan system. For new installations s plan is a far better choice. Wiring diagrams and further information continues below. Central heating electrical wiring part 2 s plan. This video covers the wiring and electrical operation of an s plan system with two 2 port valves. S plan heating systems are now the most common type of system installed in the uk after combination boiler systems which do not have any external motorised valves.
These are shown at the bottom right of the diagram. X range x plan wiring diagram unvented cylinder option gyellow cut off dhw sl coil. Electrical wiring for central heating systems. The s plan is popular because it is versatile you can add an unlimited number of zones simple to wire and easy to fault find on. We always fit s plans now regardless easier to wire simpler in design. Also you could use your existing combi to run an s plan no need for a replacement boiler if the existing is sound.
As said though the unvented cylinder needs to have its own zone valve so you would be better off using an s plan. Part 2 in the series looks at s plan wiring a system which uses two separate valves. Here coloured wires indicate the permanent mains supply to the boiler and programmer. Heating control ntc cylinder sensor connect timer to the no dhw demand nc no dhw e orange grey 2. This diagram shows the wiring layout using the most typical components. Orange grey wires from ch zone are not required please isolate opentherm make safe.
Wiring is based on the standard y plan with the addition of a high limit thermostat and a 2 port motorised valve.
Gallery of S Plan Wiring Diagram With Unvented Cylinder
