Central heating wiring

[KevinS]

Certain this topic has been covered loads of times - sorry
i have had very little experience of central heating wiring in the past, basically it was one person who did the vast majority of it, but now he has left the company and now it has fallen into my lap.
i can wire up systems but usually have to take it back to basics, ie take the wiring apart and trace the wires back then rewrire it up
i know this is the long way and I am certain it will get easier,
couple of weeks ago I had a fault which was giving me 240 at the room stat when it was calling for heat but 78v when it was not calling for heat - turned out to be the cylinder stat.
yesterday, I had a fault where the heating could be on, the hot water could be on, but not at the same time.


i have downloaded the wiring diagram from Honeywell, but still get stuck when something isn't working, do any of you guys have a flow chart or something so I can work out what the problem is in an easier methodical way


hope this makes sense. Any advice is better than what I currently have


i am also led to believe most of the systems are y plan, but some of the boilers have a pump over-run, how will I know this and is it blatantly obvious if the system isn't a y plan.

 

[mikegas]

Do you have an iPhone/iPad?

 

[stevetheplumber]

was going to post a wiring query my self so ill hi jack this thread vaillant system boiler think its a 612, wired to a y plan the sparks is strugling and i tried to help but didnt work i thought you used the feed to terminal 1 from the spur as your permenant live to boiler then fed terminal one from terminal 3 on the boiler then used the orange from the threeway to terminal 4 on the boiler if that makes sense so boiler has permenat live ,feeds out to controls and is fired from external controls
im pretty sure this was true of the earlier vaillants as the overheat stats worked by cutting the feed out on 3 it may not be the case now