Boiler novice.

[Andy B]

I`ve been asked to wire some different boilers recently for a heating company. Its not something I`ve done before. I basically want to know. When and why do you need a satisfied signal from the stat and what does it go to? Why on a lot of boilers does the controls (ie stat and programmer) have there own supply from the boiler terminals to switch but still use the power from the live neutral boiler connections to power them? Why not just wire the common out from the live terminal of the boiler?

Hope these questions make sense.

 

[vernam616]

Sounds like we are talking about a Combi system

In the boiler you will have L-N-E and stat control which basiclly is a 230v out and a 230v back in when thermostat is switched to tell the boiler to turn on

The programmer fits inline, so you would wire L-N-E from the spur to the boiler (because combis have a "water only" function so even if the programmer /stat is turned off you can still draw hot water from the boiler hence why it needs a permanent supply)

You would take a LNE from the spur to the programmer/a cable from the programmer to the stat and a cable from the programmer to the boiler

most common programmers i have used have N L 1 2 3 4, the switching diagram is shown on the rear usually, the programmer switchs the live going to the stat, the return from the stat is put into a connector block behind the programmer(in a back box) and joined to the cable which you have took to the boiler which joins into stat control block

I hope this makes sense, its hard explaining, easier to show someone in person haha

EDIT: if you wernt using a programmer, you would just take a LNE to boiler and a twin/3 core(depending if stat requires neutral) to the stat