The problem is due to the combined cylinder stat and overheat stat. How does a 2 port valve work.
Nl 7021 Cylinder Stat Wiring Download Diagram
Unvented cylinder y plan wiring diagram. X range x plan wiring diagram unvented cylinder option gyellow cut off dhw sl coil. Unfortunately the installer has not been able to work out how to wire it. It also allows you to satisfy the need for a positive shut off of water flow to an unvented cylinder in order to comply with g3 regulations if the cylinder were to overheat. These are shown at the bottom right of the diagram. Here coloured wires indicate the permanent mains supply to the boiler and programmer. 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.
This diagram shows the wiring layout using the most typical components. The unit has a stainless steel inner vessel which ensures an excellent standard of corrosion resistance. Though they do say that a y plan can be used with the safety zone valve. Connect it as per usual for a hot water cylinder if it is s plan if it is y plan the you need to add the two port valve in to the standard circuit so that the dhw demand from the cylinder stat opens the 2 port valve and then the microswitch of that valve fires the boiler. Y plan is suitable up to 26kw only. The outer casing is a combination of resilient thermoplastic mouldings and plastic coated corrosion proofed steel sheet.
As said though the unvented cylinder needs to have its own zone valve so you would be better off using an s plan. Wiring diagrams and further information continues below. Output from the normal cylinder thermostat is connected to the high limit thermostat and the output from that powers the 2 port valve motor. Adding a 2 port valve and a dual thermostat to a y plan heating system when an unvented hot water cylinder is used. This video covers the wiring and electrical operation of a y plan system. Wiring is based on the standard y plan with the addition of a high limit thermostat and a 2 port motorised valve.
Orange grey wires from ch zone are not required please isolate opentherm make safe. All products are insulated. Page 1 direct indirect unvented cylinder installation maintenance manual. Heating control ntc cylinder sensor connect timer to the no dhw demand nc no dhw e orange grey 2. 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.
Generally only used when installing an unvented cylinder to an existing y plan. Page 23 electrical diagram three port mid position valve y plan. The cylinder is a purpose designed unvented water heater. The problem is that telford only show a wiring diagram for an s plan in the installation manual.
Gallery of Unvented Cylinder Y Plan Wiring Diagram
