wiring for new digital room stat?

[Zarty]

I have seen a similar post, which was helpful but need to be sure so...

I have an exisiting mechanical room stat controlling a combi boiler.
I have purchased a new digital room stat (Drayton Digistat+3) and want to swap the stats over.
When I opened up the old room stat, I found 3 wires. That would be one Live and two Neutral. From what I understood from the other similar post, I need to just tape up and forget one of those Neutrals? If so, I just need to be sure which one of those Neutrals to tape up...

The old stat has this wiring on the block:-

Number 1: Brown, Live
Number 3: Black, Neutral
Number 4: Grey, Neutral

There is a little wiring diagram on the lid of the old stat and it would appear that Grey on Number 4 is the one that should be taped up and ignored? The old stat, by the way, is a Towerstat RS.

The new digital stat has a wiring diagram on the lid plus what's shown in the installation document thus:-

Number 1: C
Number 2: On (Load)
Number 3: Off

I assume that I would connect the Brown/Live to Number 1 (C) and Black/Neutral to Number 2 (On) ?

Thanks in advance,
Clive

 

[Zarty]

It's ok, I got it sorted out. I looked a bit closer at the old stat's wiring diagram and realised that the two neutrals join together at the boiler anyway so either one would do. The new digital stat works like a charm.

Clive

 

[canalman]

Are you quite sure of this?
I would expect a mains stat cable to have one Permanent Live (usually Brown), one Switched Live, and a Neutral. It needs the Sw L to take the switched live back to the boiler.
The Neutral in a conventional stat is there to make the 'accelerator heater' inside the stat operate correctly, to cycle the stat more efficiently. An electronic stat will not need this wire - disconnect it but insulate the end.
You must have had a switched live, and perhaps you found it 'by accident'?
Take advice from an electrician on this one, I beg you.