Buried-cable detector

[Michael GilliganParticipant @michaelgilligan61133]

[Michael GilliganParticipant @michaelgilligan61133]

Can anyone kindly recommend a good device for detecting/tracing U.K. domestic mains cables that are buried in plaster ?

For the procurement specialists amongst us … my outline requirement is:

MUST be suitable for hand-held operation

MUST be capable of detecting a dead, or a live, cable buried 30mm deep within plastered block-work

MUST be capable of locating the cable location to +/- 30mm

NICE TO HAVE the ability to discern between dead and live cables

NICE TO HAVE a reasonable price point [not necessarily low, but capable of being reasoned]

OPTIONAL either a commercial item or a DIY design

Thanks

MichaelG.

[bernard towersParticipant @bernardtowers37738]

I use a Draper one that can tell the difference between nails and screws and power cables

[SteambuffParticipant @steambuff]

I use the "Bosch Pro Stud Finder GSM120" Not cheap but has worked for me.

Currently on Amazon (Follow link for details) Bosch GSM-120

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, both

… I will have a look at those

MichaelG.

[old martParticipant @oldmart]

Visit an electrical firm which supplies electricians and ask them what the options are. I had a little gadget that worked very well and could be checked against known wiring easily. I got rid of it as soom as it became unreliable.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi MichaelG, the Bosch Truvo TL19792 in cpc.farnel's list might be worth looking at. I've not had or used one, but reading the technical docs, it seems to cover your depth requirement and is a reasonable price that I would pay.

Regards Nick.

[Andy StopfordParticipant @andystopford50521]

I have yet to find one of these gadgets that works reliably.

I presume the very expensive (£300+) ones work – these all seem to use a separate transmitter and receiver, and some work by injecting a signal into the cable so that it functions as an antenna (the ones you see being used to find buried cables in roads work this way).

Here's an example of a posh one – I have no idea whether it's actually any good:

Chauvin Arnoux CA6681 Cable Detector

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nicholas Farr on 03/06/2022 20:58:05:

Hi MichaelG, the Bosch Truvo TL19792 in cpc.farnel's list might be worth looking at. I've not had or used one, but reading the technical docs, it seems to cover your depth requirement and is a reasonable price that I would pay.

Regards Nick.

.

That looks promising, Nick

**LINK**

MichaelG.

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But there are mixed reviews on the B&Q website …

 

Edited By Michael Gilligan on 04/06/2022 06:55:11

[Michael GilliganParticipant @michaelgilligan61133]

The Bosch ‘Professional’ may be worth the incremental cost, but it is physically large, and I note that it is specified for use on ‘Drywall’ : **LINK**

https://www.bosch-professional.com/gb/en/pdf/productdata/gms-120-sheet.pdf

My present requirement involves plastered blockwork …

MichaelG.

[Joseph Noci 1Participant @josephnoci1]

I have an oldish Bosch – PDO Multi and it works well, even does a good job of detecting wood 20mm inside a wall…! I have found sensor orientation has some influence on the center of detection – hold the unit vertical battery down gives a sense centre that is approx 15mm lower than if the unit is vertical battery up – the average of the two seems always to work..Left / right position is good, irrespective of unit held up or down.

Live cable sense very good, dead cable sensed in metal detect mode and depends on cable thickness – 2X14 gauge copper wires detect easily at 30mm below plastered wall. 50mm panel-pin head detects @ 25mm.

The PDO is no longer available and Bosch intimates the GMS120 is its successor – I would go for that.

Bosh PDO Multi Manual

Bosch GMS-120

[Nicholas FarrParticipant @nicholasfarr14254]

Hi MichaelG, that Bosch Truvo one is significantly cheaper in B&Q, but a similar price to CPC/Farnell's one in Screwfix, the mind boggles sometimes.

Regards Nick.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nicholas Farr on 04/06/2022 08:39:32:

… the mind boggles sometimes.

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It does indeed, Nick

MichaelG.

[Clive Brown 1Participant @clivebrown1]

I bought one of te cheaper brands from a DIY shed. My need was to detect wall studs, I was not very impressed. Positional indication was vague, tapping the wall with my knuckles seemed just as good. When I tried it for mains wiring results were just as unimpressive. I certainly wouldn't trust it to avoid hitting a buried wire.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Joseph Noci 1 on 04/06/2022 08:24:23:

I have an oldish Bosch – PDO Multi and it works well, […]

The PDO is no longer available and Bosch intimates the GMS120 is its successor – I would go for that.

.

Thanks, Joe … I welcome your opinion

There are only two things stopping me from rushing out to buy one

1. It is, as I mentioned, rather large at 200mm tall, and I can see that presenting some difficulty in confined spaces.
2. Although the ‘Truvo’ is unlikely to be as rugged, I do wonder if it might be a more modern implementation of the Bosch circuit design [i.e. more integrated] because it runs on three AAA cells instead of the 9v brick. That would maybe explain the smaller size and cheaper price

I can’t justify buying both, just to find-out, though

I will probably just waste a few more days on “Research” before buying

MichaelG.

[Dave HalfordParticipant @davehalford22513]

There's a bloke Bristol way who use a drill the find the power cable in his front lawn. So much for 3 ft down.

[SamsarandaParticipant @samsaranda]

Definitely use an instrument to find buried cables in your walls, about 30 years ago I was refitting our kitchen and believed that I knew where all the buried cables and pipes were, Sods Law I found a cable buried where there was no reason to suspect one, I was drilling with a mains powered drill and suddenly there was an almighty bang and flash of light, I had hit a ring main cable. With luck the drill had penetrated dead centre on the twin and earth cable thereby sending most of the current straight to earth, the blow was powerful enough to destroy the main input fuse, requiring the electricity company to attend for the renewal. My masonary bit that I was using had vaporised, I considered myself extremely lucky to have not suffered any injury, the wife was out when it happened, you can imagine what transpired when she came home!!! Dave W

[Michael GilliganParticipant @michaelgilligan61133]

Joe,

may I just ask if this is consistent with your experience of the earlier model ?

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I am still a little concerned by the specific reference to drywall

MichaelG.

[Joseph Noci 1Participant @josephnoci1]

Michael,

That tool does everything mine does, and a lot more! If I were still mucking around building my house I would ditch mine and get one of those. I think the Drywall reference is for our American friend's peace of mind – I have found on numerous older reviews the American have regularly asked if it works with drywall – since that is the primary construction method there I guess.

Here are some reviews that show it's ability against brick and concrete as well. ( Forgive the patronising video – not my doing..)

**LINK**

**LINK**

The dielectric constant of the materials do play a role in the detection capability, and drywall tends to be air or foam etc in the cavity and the detection signal is less masked compared to when in concrete/brickwork, so the unit is perceived to be more sensitive – meaning that a 'conventional' detector would probably battle to localise the detection area due to the heightened sensitivity. The self calibration of the unit held against the drywall would correct for that I guess.. A the risk of placing myself in the line of fire, I would recommend that unit – if you can live with the size in your application.

[Michael GilliganParticipant @michaelgilligan61133]

Brilliant response, Joe … just what I needed to hear !

Thanks

MichaelG.

[egaParticipant @ega]

Buying a replacement 9V brick (or block) battery for this kind of device seems to be something of a minefield, particularly if you are considering a rechargeable one.

My Bosch DMF 10 detector is quite fussy about voltage but I understand that some devices will tolerate much less than the nominal 9V.

[Joseph Noci 1Participant @josephnoci1]

Posted by ega on 05/06/2022 09:54:50:

Buying a replacement 9V brick (or block) battery for this kind of device seems to be something of a minefield, particularly if you are considering a rechargeable one.

Why is that? Are they scarce because of environmental issues in your country? There appear to be many sources for 9v NiMH rechargeable blocks..

[Mike PooleParticipant @mikepoole82104]

I think the wiring regulations require the wiring to be vertical or horizontal from any wall mounted sockets and switches, a band below the ceiling is also specified for wiring. Of course the shortest route cowboys may have been at work so it is best to check as far as possible.

Mike

[egaParticipant @ega]

Posted by Joseph Noci 1 on 05/06/2022 15:08:11:

Posted by ega on 05/06/2022 09:54:50:

Buying a replacement 9V brick (or block) battery for this kind of device seems to be something of a minefield, particularly if you are considering a rechargeable one.

Why is that? Are they scarce because of environmental issues in your country? There appear to be many sources for 9v NiMH rechargeable blocks..

Certainly not scarce so far as, eg, Amazon UK is concerned but the entries there are littered with adverse comments, particularly about LiOn rechargeables. It's no doubt less of a minefield to those more knowledgeable about battery technology than I and I was hoping someone would weigh in with some advice. I was looking for a replacement for an alkaline non-rechargeable.

Incidentally, the battery rejected by my cable detector at about 8.5V was happily accepted by my moisture detector.

I have always found the standard 9V connector with male and female press studs rather awkward to use.

[EmgeeParticipant @emgee]

I believe it will be difficult to buy a device that will reliably detect live or otherwise cables in a stud wall where they will be 60mm deep if in 2"x4" stud, even is a 3" stud the depth will be over what can be detected by any low cost meter.
Lots of partition walls these days are formed from pressed steel U and Z section so are more easily detected than a wood structure, any cables though may be difficlt to locate.

As said by others the cables are likely to be almost vertical above/below electrical equipment but may also be horizontal in such areas where there are multiple outlets at the same height and on the same circuit.

Also I think it may have been said another cable zone to avoid is at ceiling level and 400mm below.

Emgee

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