Live wire from old pump on vented to system boiler

rhinosaw · 8 Aug 2019

A couple of installers have mentioned this,
So going from vented system to system boiler WB 15i, possibly.
They tell me that they have to take a live from where the old pump would be removed to the new system boiler.
I don't understand this as I would have thought that when the microswitch opens and connects on the 2 port valve this would then turn the boiler on. Where does the pump come into the equation?

ianmcd · 8 Aug 2019

The WB 15I is a system boiler and the pump is built within the boiler and controlled by the boiler, do you mean the 15Ri ? If it is the Ri it is a heat only boiler and the external pump must be wired from the boiler for the pump over run function to work

rhinosaw · 8 Aug 2019

No it is definitely a 15i system boiler.
So I presume that u just disconnect the old pump on the old vented system and the microswitch will turn the boiler on or the system boiler will sort out the start up itself

jeff the gasman · 8 Aug 2019

You need a permanent and a switched live. You probably only have switched.

rhinosaw · 8 Aug 2019

Thanks J the G, why do I need both?

jeff the gasman · 8 Aug 2019

The Boiler needs a permanent live to run overheat protection when you or the thermostat switches it off.
Residual heat removal.

rhinosaw · 8 Aug 2019

For the pump overun , is that the same?

jeff the gasman · 8 Aug 2019

rhinosaw said:
For the pump overun , is that the same?

Yes

rhinosaw · 8 Aug 2019

Sorry to be a bit thick but could u not take the permanent live from the main boiler switch on the wall and use the switched one from the zone valves? Currently my old vented boiler doesn't have pump overun so as u said before, just a switched live from zone valves.

ianmcd · 8 Aug 2019

yes you can

jeff the gasman · 8 Aug 2019

What he said ^^^^^^^^^^

rhinosaw · 8 Aug 2019

Not sure what Jeff's response is, did I say something wrong,?

jeff the gasman · 8 Aug 2019

rhinosaw said:
Not sure what Jeff's response is, did I say something wrong,?

No you wally it means what the one above said. ^^^^ lol

rhinosaw · 8 Aug 2019

Ok, that's a relief,
I blame it all on these installers coming round to give me quotes for a system boiler from a vented system.
A couple have said , have to take a wire from the old pump (in the airing cupboard) back to the new boiler.
But looks like, switched live comes from the zone valves and permanent live can really come from a live near the boiler.
I knew that I should have been an electrician really.
Thanks to u and Ian

jeff the gasman · 8 Aug 2019

The live has to be switched from the central heating isolation switch not a separate one. Just sayin.

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Live wire from old pump on vented to system boiler

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