Questions on: Immersion switch replace with timer

[NickNock]

I want to install a TimeGuard inline immersion timer (model NNT03 as here: http://www.timeguard.com/products/t...ompact-electronic-immersion-heater-timeswitch ) in the airing cupboard, for summertime immersion control (use boiler in winter). This timer required no separate power supply, deriving power for it's circuitry from the supply it switches.

At present, immersion heater is fed from a dedicated MCB in the consumer unit, to an unfused dual pole single throw (DPST) switch with flex outlet, located in the airing cupboard.

I propose to do a straight swap, new timer for old switch.
Question: Is this acceptable and still compliant to regs?
I have checked PartP guide and BS7671 and can find no clear guidance.

(Small aside, the TimeGuard has no flex outlet and no flex clamp to relieve strain, so I will need to add an unfused flex outlet plate between the timer and the existing heater flex).

My reason for my question above is this: If the timer were to fail catastrophically (fire) it might not throw the MCB (or would it?). But clearly a low current fuse to protect the timer will not allow the immersion to operate.

Limitations: The wall space I have will only allow two single patresses.

 

[NickNock]

Not sure if my sketch attached to original post so here it is again.

 

[SimonH2]

If you provide an external flex clamp - fairly easy to make - then you could retain the switch while adding the timer.
Also, it would be better in the electric forum - I've reported it for a mod to move the thread.

 

[NickNock]

SimonH, many thanks for pointing out the correct sub-forum - I didn't see it. I'll have a more in depth shufti around all the categories for next time.
Thanks also for the suggestion about fabricating a clamp. As tempting as it is, and easy indeed to fabricate, I'm not convinced that this would be compliant, as all electrical devices are CE marked and should not be adapted otherwise the CE Mark is invalidated. In the (incredibly) unlikely event that something went catastrophically wrong like my completely impractical girlfriend snagging the flex resulting in sparking and a terminal overheating, the penalties are high both in terms of safety and legally.
I'm also keen to stick to Regs in the event we sell up and move, and a buyer's over-enthusiastic surveyor decides to make an issue of such mods.
When I think of my childhood in the 70's, rewiring things, extending cables with insulating tape etc and it wasn't an issue. How times have changed!

 

[Iggifer]

I would never want to lose local isolation of an immersion heater

I did basically the same job on friday, but there were two immersion heaters. I used these timers, which have built in strain relief

I was lucky that they were wired into a stud wall, so I could keep the existing switches, fish in the wall so the cable came out by the bottom cable entry, and then out to the immersion elements.

You could just loop out of the current switch, into the timer, then back onto the element

For strain relief you could use these and to keep your cables tidy too.

 

[NickNock]

Iggifer, many thanks. Though I've already got the TimeGuard NNT03, the cable clips look excellent if they grip the flex tightly enough to prevent the flex from slipping.
I'm also fortunate the wall in question is a stud wall - I've done plenty of single to twin socket conversions in solid brick and block walls - horrid!
Ta.

 

[Iggifer]

Oh yea those clips will hold the flex tight enough, assuming it's the right size flex!

 

[NickNock]

Thanks Iggifer, I'll definitely try to get some of those P clips and will check the flex diameter to make sure they are tight. I like that these are standard industry items. Ta very much.

 

[securespark]

The other way to do it is to leave the DP switch in place, butt another 32mm pattress up to it (of the PVC variety) to fit the timer to. Why PVC?

You can fit a gland to provide the strain relief.

 

[NickNock]

Thank you Securespark, that's ingenious too. Such a shame that this TimeGuard timer doesn't have the strain relief built in. Otherwise it's a nice compact unit.
Cheers.

 

[securespark]

No worries!

 

[SimonH2]

Thanks also for the suggestion about fabricating a clamp. As tempting as it is, and easy indeed to fabricate, I'm not convinced that this would be compliant, as all electrical devices are CE marked and should not be adapted otherwise the CE Mark is invalidated.

Hmm, now that could start a whole new "discussion". Lots of what gets installed is, by the nature of installations, fabricated or modified. OK, so a lot of stuff is intended to be adapted (eg having knockouts for cable entries/conduits), but where would you draw the line ? For example, some of what I do (occasionally) involves making brackets etc for trunking or wire basket - those aren't CE marked, nor could they be. I think all the regs have to say about it would be about "good workmanship" and "suitable for the task" (and as of recently, of metal if supporting cables above a fire escape route).

 

[Taylortwocities]

Such a shame that this TimeGuard timer doesn't have the strain relief built in.

It is designed to go into a recessed or surface box. Exactly the same as say a socket or a light switch. None of these have strain relief for the cables themselves. Strain relief would be a function of the enclosure that you select.

 

[DaveHerns]

Why does this only switch LED's up to 80w ?

 

[stillp]

all electrical devices are CE marked and should not be adapted otherwise the CE Mark is invalidated

I don't think the clamp would fall under the Scope of any of the EU Directives that require CE marking, since it is not dependent on electrical energy for its function.