Relocating CH 'programmer' - What cable size

[jpdw]

Hi.. First post after weeks of lurking, so please be nice to the newbie!

I want to relocate my CH programmer/timer from the back of my first floor airing cupboard to room immediately below.

It is currently connected via 2 3-core flexes to the wiring centre which in turn is connected to a dodgy looking 3-pin socket in the airing cupboard, fused at (I think) 3 amps.


What size cable should I use for the drop to the new location? I assume 2.5mm T&E ( x 2 ) but anything smaller would be a bonus as it would be easier to run -- and the flex currently there - albeit for the very short 1 metre run - looks much smaller.


In case it's useful, info to help with answers:
- Access for a cable run is straight forward & approx 3-4 metres.
- The programmer/timer is a modern (honeywell) with standard backplate
- I'd also change to pick up power for the programmer / CH from the new location rather than the current dodgy looking 3pin which will have one of those safety 1-pin cover things put in so that it's out of use, pending an electrician removing it completely when the CU is changed next year - but I still need both cables as I'll have to take the unswitched supply back up to the CH wiring centre (& on to the boiler etc).
- The new supply connection will be switched FCU with same fuse rating as current plugtop.

Thanks!

 

[Steve3948]

1.0mm² 6242Y or 6243Y is fine and fused at 3 Amps.

Do you have a Y-Plan or S-Plan, as the Y-Plan requires 1 extra conductor.

5 + E for Y-Plan and 4 + Earth for S-Plan.

 

[jpdw]

1.0mm² 6242Y or 6243Y is fine and fused at 3 Amps.

Do you have a Y-Plan or S-Plan, as the Y-Plan requires 1 extra conductor.

5 + E for Y-Plan and 4 + Earth for S-Plan.

It's an S-Plan - more-or-less *. I've had the lid off the HC wiring centre and traced it all back because it wasn't immediately appearent which std plan it was. But still with S-Plan I need (as you say) 4+ Earth, so I will need two cables whether I used 2 or 3 core (+E).

If 1.0mm2 will do then I'll probably run 1.5mm instead as I've got loads... both are a heck of a lot more "workable" than 2.5mm --- unless someone else wants to contradict and say I need to use 2.5mm...

Thanks for the reply,

jpdw

----
* For some reason the switched-live from the zone valve "switches" to the boiler goes via a further stat which is clamped to the output circulator pipe of the boiler... best theory is that it was a bodge when the boiler wasn't functioning okay (before we bought the place)... which is it now & the boiler will be replaced next year anyhow.

 

[Steve3948]

As the system is fused at 3A and 1.0mm rated at 11A, no need for 2.5mm rated at 27A.

 

[jpdw]

I've been checking the exact route today and think my 3-4 m estimate is a bit low ... It may be as much as 8 metres by the time the cables are routed from end-to-end.

It will be a mix of surface conduit and cable clipped. With some of the cable clipped stretch in the ceiling/floor void.

Will this make a difference to the cable choice? Whilst there is some "headroom" in current carrying max of 11A (from the 3A rating of the FCU supplying it), will this new distance & installation method make a significant enough distance to have to use something bigger?


Thanks...

 

[Steve3948]

No, Max 72M in length, 3A Load for 1.0mm² with a 6A B Type Mcb.