NVR & Cuttoff switches


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Whilst building my workshop, I constructed a simple safety circuit that has 2 features.

- A series of mushroom switches, pressing any of which will cut the power to the whole circuit.

- NVR for the whole circuit.

So I now have a mushroom switch within easy reach of any of my 240V outlets, and in the case of loss of power, I have NVR on the entire circuit. Resetting is a matter of walking up to the wall-mounted box and hitting the reset button to re-energise the relay.

Parts cost approx £20 from Maplin and take about an hour or so to put together. Is anybody intersted in me posting detals of how to build these?

I will eventually have 3 of these for the 3 separate spurs I will wire into the workshop, but my priority now is battery backup for the lights. If there is a power loss (e.g. RCD trips out), I don't relish the idea of the lights going off and things are still spinning down (lathes, saws, drills) so I'm ensuring the lights will remain on for a good few minutes.


Established Member
17 Sep 2002
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Castell Nedd, De Cymru
Hi Elvch, I`ve wired my shed on the Ring Main principle would that setup work,or put it this way will a NVR switch work on a Ring Main.

Good Idea as not all power tools has NVR switches i.e. hand drill in a drill press mode. :eek:


can't see any problem with it working on a ring-main arrangement. You would have a single feed from the consumer unit (fuse box) to the black box and then run the ring-main from the output side.

One word of caution however, this wasn't designed as a substitute for NVR

... When you reset the switch box e.g. after a power cut, any tools without their own NVR switches would start up as power is restored to the outlets.

The gizmo was originally designed so I could use "mushroom" cut off switches mounted strategically around the shed as an emergency cut-off system. The NVR type behaviour is a side-effect.


Don't bother with batteries for lights beleive that can work out expensive.
Why don't you try putting in a small consumer unit with an isolating switch for the whole off the electrical circuits and a seperate rcd for the power circuits within the same board as you would in a normal house so that if the rcd trips you still have lighting



thanks for the advice Steve and your idea was my original plan, but I know somebody who works for a computer repair outfit and for a couple of pints I got a small Uninterruptable Power Supply that will take 500VA load for 10 minutes. That's why I'm going down the battery backup route.