central heating programmer re-wiring

[Mark Downey]

my switchmaster 905 programmer has just packed in so i thought it was about time to get a digital one ,Just come back from B&Q with a drayton tempus 7. After taking the front off the switchmaster it revealed this layout on the backplate

N-L-1-2-A-B-C-3-4

n-neutral l-live

1 central heating ON 2 CH OFF A.B,C- SPARE 3 HW ON 4 HW OFF

feeding this I had 2* 3 core cables

1st Cable - live neutral and the green cable screwed into the spare A 2nd cable - Brown into no1(CH ON) Blue into no 3(HW ON) and Green into No4(HW OFF)

OK the new Drayton has this layout on its backplate

N-L-1-2-3-4

N-neutral L-live

1 HW OFF 2 CH OFF 3 HW ON 4 CH ON

so i connected the cables up as per diagram but did not know where to put the green cable from cable 1 - and assumed it was an earth cable so i plugged it into the earth socket . This configuration now leaves me without a connection into no 2 (CH OFF). I powered up the programmer and everything came on , Great I thought.Set the time ,adjusted the timer settings and set to auto. When the time came for the heating to come on - Nothing - No pump running or

3 port valve switching over Also nothing comes on in manual either.

So can any of you kind people help me.

Mark

[Set Square]

Is your room stat turned up high enough to make the heating come on?

If you have a Y-plan system [See

] you don't need CH-OFF connected (but you *do* need HW-OFF).

Do you have a central junction box where all the wires are connected? If all else fails, you'll need to trace the cables to find out what the other ends of these 2 x 3-core cables connect to.

Incidentally, it's *extremely* bad practice to use the green or green/yellow earth conductors for carrying live signals such as HW-OFF - *and* very dangerous!