Wiring new Worcester Greenstar 40CDI Conventional Boiler

[ManilaMully99]

Hi guys,

Its my first post on here, but I'm going to dive in deep!

Our plumber is currently fitting the CH and HW system in the house we're renovating. I'm doing the wiring for it, and whilst I have just completed an electrical course, I'm unsure on this issue, as its my first Heating system.

We are fitting 2 x 2 port valve system ("S" Plan). The boiler is a Greenstar 40CDI Conventional, which is meant to be wired into the 16 terminal port supplied with the Megaflo unvented indirect hot water cylinder.

Obvioulsy I understand the plan, and where each device (2 valves, room stat and programmer) are supposed to go. The S Plan setup however requires the boiler to be wired into the Wiring Box, taking power through the Zone Values. But as I understand it, this boiler needs a permanent power supply to avoid switching off when needed.

Therefore my question, which I have been unable to find on the internet thus far is; Where do the wires run from the 'External Wiring Controls' on the boiler? I have Ns (Neutral supply), Ls (Live supply) and Lr (Live return). But according to the plan, the boiler has a N and L, which are to be wired to the connecting Neutral ports and Zone Valves (Orange cable) respectively.

So, any ideas? The help would be very beneficial, as the plumber is back next week.

Also, I am aware that this boiler also requires the pump to be connected through the boiler (Not as stated in the S plan), for the overrun.

 

[ServiceNumpty]

Orange wire gets connected to boiler live return.
Permanent Live is from live in wiring centre.
As you're wiring an unvented as well what gets wired into the overheat thermostat.

 

[Tibbot]

The S-Plan diagram will be generic so you follow the MI's. In this case you wire permanent L,N,E to the L,N,E on the boiler. Then your LS and NS (with E) supply power to the wiring centre. Pump is wired from the boiler. You then do your controls as a normal S-Plan returning your switched live from the zone oranges to LR on the boiler. This way when you turn off power to the boiler all controls are electrically isolated.

 

[ManilaMully99]

Orange wire gets connected to boiler live return.
Permanent Live is from live in wiring centre.
As you're wiring an unvented as well what gets wired into the overheat thermostat.

The permanent Live has to be direct from the supply, which is isolated from a 2 pole fused switch. I think you mean the Ls get wired to the Wiring Box?

 

[ManilaMully99]

The S-Plan diagram will be generic so you follow the MI's. In this case you wire permanent L,N,E to the L,N,E on the boiler. Then your LS and NS (with E) supply power to the wiring centre. Pump is wired from the boiler. You then do your controls as a normal S-Plan returning your switched live from the zone oranges to LR on the boiler. This way when you turn off power to the boiler all controls are electrically isolated.

Thanks Tibbot. Everything seems to make sense when someone explains it to you! Maybe I need to sit and think things over a little more! lol.