Alpha boiler wiring

[fixitflav]

Can anybody explain what Alpha are getting at with the attached wiring diagram?

Where it says Note: To connect external control, remove link etc….As far as I can see, you could leave the link in and put 230V on 1 or 2 (from a stat). Or remove the link and put 230V on 1. It doesn’t say what the link is for. It suggests there’s a 230V output from 2, with the link in, but I can’t see why you would want that, and if you did, it’s available between the stat and the boiler.

I don’t suppose there’s a problem in practice, but it puzzles me.

 

[RandomGrinch]

As far as I can see, you could leave the link in and put 230V on 1 or 2 (from a stat).

If you left the link in place, the boiler would constantly be receiving a live supply from terminal 2 on its call for heat terminal 1, the heating would be permanently on (dependent on the built in clock).
Note the arrows on the diagram - terminal 2 is a live out, terminal 1 is the switched live return...

remove the link and put 230V on 1.

This would be the usual method.

It suggests there’s a 230V output from 2, with the link in, but I can’t see why you would want that,

You could use the 230V feed from terminal 2 to provide a live to power the thermostat (the neutral would need to be piggy backed on the boilers N terminal) - it simply provides a convenient extra L terminal to use.
There is also the possibility of connecting a battery powered stat, with volt free switching - terminal 2 would connect to common of the stat and terminal 1 to normaly open.

 

[fixitflav]

Thanks for reply. I should have said, I was thinking of the situatiion without the internal clock.

f you left the link in place, the boiler would constantly be receiving a live supply from terminal 2 on its call for heat terminal 1, the heating would be permanently on

Yes, obvs you wouldn't want that. So T2 is permanently live (from an internal connection)? If so you couldn't leave the link in, as I suggested. The only time you'd want the link in is if you want to switch the boiler On/Off at the fused plug. And that wouldn't be right, as the pump stops immediately, losing the overrun feature.

You could use the 230V feed from terminal 2 to provide a live to power the thermostat (the neutral would need to be piggy backed on the boilers N terminal) - it simply provides a convenient extra L terminal to use.

That's a possibility, but I'd have thought more likely there's 230V avilable elsewhere, and just put power to T1 via the (external) clock and stats.

There is also the possibility of connecting a battery powered stat, with volt free switching - terminal 2 would connect to common of the stat and terminal 1 to normaly open.

That's a good point.

 

[RandomGrinch]

So T2 is permanently live (from an internal connection)?

Yes, although it appears there is the option to control it as a channel 1 out, but that would involve connecting the internal clock.
In most cases, this would be a permanent live.

That's a possibility, but I'd have thought more likely there's 230V avilable elsewhere, and just put power to T1 via the (external) clock and stats.

It's considered best practice (and quite sensible), that the power for the stat is on the same circuit as the boiler - whether that be from the same FCU, or from a flex coming from the boiler itself.
In the case of smart stats, it makes sense and is least effort to run a short flex from the boiler to the RF receiver.
Being on the same circuit means at a boiler service, there is a single point of isolation; the internal circuitry of the boiler is completely isolated from the mains. If there were an alternative power source to the stat, a switched live may still be received at the boiler, with shocking consequences for the RGI!

 

[fixitflav]

It's considered best practice (and quite sensible), that the power for the stat is on the same circuit as the boiler - whether that be from the same FCU, or from a flex coming from the boiler itself.

OK, I take the point, if the boiler needs a permanent live. My whole system is powered from a 3A plug, but the boiler has no permanent live, just fires when given 230V.
Thanks for the comments

 

[Stuckinarut]

OK, I take the point, if the boiler needs a permanent live. My whole system is powered from a 3A plug, but the boiler has no permanent live, just fires when given 230V.
Thanks for the comments

Are you sure about that? According to the instructions there should be a LNE.

 

[fixitflav]

Are you sure about that? According to the instructions there should be a LNE.

That was my existing boiler. It's not an Alpha, it's a 25-year old Ideal Minimiser 50. The system has N & E of course.