replacement room thermostat wiring

[newbuyer17]

I'm trying to replace an old analog room thermostat with a programmable digital one.

The new one has 3 terminals - Common, Normally open and Normally closed
Instructions say connect heater to Common and Normally Open. The diagram associated with this shows LIVE wire to Common, and Neutral to Normally Open. NC is left empty.

However, my old drayton one has 3 wires + an earth:
One is grey with blue/neutral sleeving over, one is brown/live, and the other is black with brown sleeve over it. The earth wire just connects to the chassis.

The wiring diagram on the back of the old drayton says Neutral to Neutral, Live to Live, and CALL to terminal 3. Terminal 3 is wired to the black wire described earlier. The neutral and live wires are wired to the N and L terminals.

So what do I wire to the new thermostat?

On top of this it recommends a 5A fuse. The old Drayton recommends a 3A one, but it aint there. House rewired 5 years ago and has RCDs, so I assume I am OK to forget about the fuse?

I was expecting a straight swap, so I'm a bit confused.

Thanks in advance
EDIT:
Its one of these:
http://www.tfc-group.co.uk/_sa_webapp/runa2a3.html?page=320

The instructions online are different to what I have, and slightly more detailed.

 

[seco services]

live to common
sw/l which you say is black to hc
neutral not needed make safe.

 

[mikely]

On top of this it recommends a 5A fuse. The old Drayton recommends a 3A one, but it aint there. House rewired 5 years ago and has RCDs, so I assume I am OK to forget about the fuse?

No. RCDs do not provide short circuit or overload protection, only earth fault protection. Your heating system and boiler should be protected by a 3A fuse normally supplied via a switched fuse unit.

 

[newbuyer17]

Thanks guys.
All working now.

I guess the old one must have used power off the mains for it's own operation, hence the neutral - mine is battery powered. Should have worked that out myself, but understand now anyway.

Fuse is also OK - boiler is fused and does have a switch next to it. I was assuming I had to fit a fuse in with the thermostat, which was why I was confused.

Thanks again for the assistance.