Boiler Replacement Wiring

[Nicky Tesla]

A colleague replaced a boiler today and i got the job of wiring it.  The boiler is a worcester greenstar (i think), as a replacement system boiler with an existing Y plan and cylinder.

The problem is that the boiler is not a direct replacement electrically,  i have to fit an extra cable all the way from the boiler downstairs in the kitchen to the pump in the airing cupboard upstairs. I also have to wire a permanent live to the boiler from the programmer NEAR to the boiler.

Is this normal for a new style system boiler or are other makes available that do not require this?

 

[steptoe]

pump over-run then I take it.

there are ways around it if the plumber knows his stuff/is willing to do it.

 

[wozz]

WB want their boilers wired to the boiler first then to the wring centre,  presumably so their engineer can take out the power to the wiring centre link it and prove the boilers functionality.  I try to wire it how they want it, but in the past it has not been possible, my mate installs alot of WB and knows the local engineer i dont think he looses any sleep whichever was is easiest.  

 

[Nicky Tesla]

yeah pump over-run

WB ?  is that worcester Bosch?

Are they all like this these days

 

[steptoe]

not all boilers have pump over-run

if it does have an over-run then it deffo needs either a cable from boiler to pump, or a different configuration to the plumbing.

 

[Steve3948]

Most internal but not all have L&N then Trigger & Pump, I tend to run a 6242Y & 6243Y, that covers most requirements.

Did an outside boiler yesterday, L&N + trigger, Oil Fired.

 

[steptoe]

check the wiring, you may find a spare wire from boiler to wiring centre,

I normally run 2x 3c&E between prog and centre, same again from boiler to centre.

 

[Nicky Tesla]

ok  but at the moment it looks like im gonna have to start knocking kitchen tiles off the wall to get my cables through.

 

[Sharpend]

Is the fused spur to isolate the boiler close by, could you not pick up a live feed from there ?

 

[Nicky Tesla]

yes but its  on a different tiled wall,  but i still have to get my pump cable upstairs and the bathroom is above the boiler so i think i will go all the way up the stench pipe boxing and into the loft otherwise its trunking or floorboard lifting..........sod that!

 

[sellers]

Yes this is very common, I've heard its so the heat exchanger can cool down after the boiler has been used.

Very simple to wire, just need a spare or extra core!  Not the CPC!!!

 

[wozz]

The previous boiler probably had a cast iron heat exchanger so doesnt need a pump over run to get the heat out, the new boiler would have a ali heat exchanger and need the pump to over run to get the heat out of it. This problem is usually allowed for by plumbers when pricing.

 

[Nicky Tesla]

the plumber said today that this is a regular boiler and it is easier to fit a system boiler (i dint know the difference)  and then get rid of the tank and put a filling loop in.   Then there is no need for extra cables to the pump because the pump will be in the boiler.  

Makes sense.

 

[steptoe]

Nicky, your post is mixing up system boilers.with combis,

Im not sure what you mean therefore.

 

[Nicky Tesla]

not combis.............regular and system..

They both use a cylinder for hot water but the system one has a built in pump and expansion vessel etc

http://www.worcester-bosch.co.uk/homeowner/boilers/what-is-a-system-boiler

 

[Sharpend]

What you need here, is a five core flex to boiler, carrying perm live, neutral, earth, outgoing live from boiler to system controls, return switch for boiler.

You can probably utilise an alternative live for system controls.