Reinstate cable - best way to test which it is.

[rarara]

I want to use again what looks to be one of the decommissioned cables that (previous storage heating at a guess?) run to the old, unused fuse box. The idea being to make it live again by having it connected to the existing RCD. There are quite a number of these old cables all running to the same point, and no way of tracing the cable I want physically. What is the best was to find the cable I want??

I thought maybe use the continuity test on my multimeter, connect it to L+N at the far end, then work through the decommissioned cables at the old fuse box side and connecting their L+N in turn I should hear the beep when I find the correct one.

Will that work? The cable is getting on for 10m in length, so maybe a multimeter is too puny?

 

[Taylortwocities]

Continuity on a multimeter will be fine.

Do check that the cable is not live before you test it for continuity!!@!!!!

 

[cjard]

Do check that the cable is not live before you test it for continuity!!@!!!!

I dare say he might even want to test it for live before he joins L and N together at the far end before coming to the meter end to test for continuity

rarara, cable resistance is resistance regardless of the voltage (heating effects aside): if your meter says it has a resistance of 2 ohms then it has a resistance of 2 ohms - there isn't the concept that the 9v battery in your meter meter can be "too puny" to measure the resistance of 10 metres of wire. In service, with 240v pushing current through it, the wire will still exhibit a resistance of 2 ohms

 

[Taylortwocities]

In fact, the thicker the cable, the less resistance there will be.

Given this VERY basic gap in your electrical knowledge, I am wondering if it might be better to get an electrician to do this work for you?

 

[flyingsparks]

What do you want to do with this 'redundant' cable? What size is it?

 

[PrenticeBoyofDerry]

I would highly recommend that you removed all old redundant cable and started a fresh with new cable. It is highly likely the cable has been left out of service for a reason. The cable could well present a danger if re-used. At the very least I would do a complete visual inspection of the cable routing and any junction and besides continuity tests , a insulation resistance test would be required. The cable could well be VIR cable and should not be reconnected.

 

[rarara]

Hi, guys - thanks for the input. Just to confirm, the cable (despite being redundant) is modern, correctly sized, not VIR etc - I would guess it was upgraded just prior to central heating being installed at some point in the past. I will do a visual inspection of as much as possible when next in the loft. I need a new socket to relocate a phone/modem in a central position in the property so the range covers all rooms - so a pretty light load.