Garden path lights - rethink

[ash_scotland88]

Interestingly (for me) an RCD tripped over night, but not the one protecting the circuit I was working on.

 

And I was told installing an RCBO box was overkill for a residential property....

[MJNewton]

2 minutes ago, ash_scotland88 said:

And I was told installing an RCBO box was overkill for a residential property....

 

Can you elaborate? What specifically were they referring to? 

[ash_scotland88]

13 hours ago, MJNewton said:

 

Can you elaborate? What specifically were they referring to? 

 

Spark (friend from previous company) said it wasn't something he had installed much beyond a commercial sense.

I put forward my point I personally felt it was the way forward and would be a beneficial in the long run, and in work on rubber box distros any requiring any significant work we were rewiring to RCBO.

Other half also didn't like the price increase and jumped on it being overkill for residential band wagon, but in hindsight I gave him too much credit for understanding different protection types...

 

Anyway:

 

We think it was the fridge freezer we inherited with house but never previously turned on, it probably reach a temperature and then tripped.

[MJNewton]

I might be misunderstanding the context, but RCBOs have been common for a while now - and I'm not quite sure what the residential aspect is. Cost perhaps I suppose?

 

Certainly they are useful for outdoor circuits as they are more prone to nuisance trips and so it can be really beneficial to not have those trips take circuits down in the house if they happen.

[ash_scotland88]

I know they've been common, just my friend was saying not that common and overkill for residential use in his experience.

 

Compromise was a high integrity board allowing a stand alone (or two) RCBO. Atleast I hope that's what's been installed, not looked beyond the outside yet but an RCBO is placed in ready to go.

 

Also explored this evening that a service void is accessible from the bedroom above the front door. This is the bedroom where I've already been able to put a short twin and earth* from the front door light into the floor void. Tomorrow exploring the crawl space to see if the next route is down or up into the attic to get back outside. All this routing to avoid a cable along the front of the house!

 

And at some point really should explore my presumption from the old CU markings that the light switch is on it's own circuit (along with the understairs cupboard light).

 

*Will try and make it all one length when running in properly.

[ash_scotland88]

GAH,

 

Just looked at all the bits, after sitting there for a week.

Wiska 308 box

Wiska 308 earth clamp bar

And Tower SWA glands, the glands are too big for the box. Due to internal plastic webbing means the locking nut doesn't align over the hole to centre.

As well as the earthing rings (don't know correct term) are too long for the clamp bar but that would have been an easy fix.

 

Any one know a Screwfix / Toolstation / somewhere else shopping list? Cable is 4core 2.5mm to give an idea of sizing, I'm sure when I looked on a chart it's 15mm but could be wrong.

 

 

Edit; misunderstood what I was doing.

The glands screw into the box. But then with the earth clamp bar there isn't any thread left on top for the earth ring, so does the bar replace the ring?

Edited September 30, 2021 by ash_scotland88

[TonyT]

Use the bar instead of the banjos/frying pans.

They do the same job.

 

[ash_scotland88]

On 30/09/2021 at 23:30, TonyT said:

Use the bar instead of the banjos/frying pans.

They do the same job.

 

Worked it out, was admittedly being an idiot.

On 26/09/2021 at 22:54, MJNewton said:

 

If you plug an extension lead in somewhere and take it out to the light you can measure the resistance between the earth at the light and the earth in the extension socket and it should ideally be less than a couple of ohms. (Passing this test will also require your socket circuit earth to be present of course so two tests for the price of one!)

Done this, can confirm earth is present!

 

Made up the extension lead for earth only. Tried testing the extension with my cheap multi, don't think it can measure low enough as it was showing -1* but noticed if I stroked the copper I could get it to show changing numbers. Also used the beep function and got a circuit.

Plugged in the Martindale on socket to confirm earth is present there (again cheapish and just gives a a-b ,b-c, c-d earth reading). Used the earth-only extension and same technique (tickle and beep) as above confirmed earth was present in the lighting circuit.

 

Also explored the service void route, no access from the crawl space so looked like we'll be going up it instead of down and coming out from the eaves from the attic. In possibly the most convoluted route to get a cable somewhere....

[Onoff]

13 minutes ago, ash_scotland88 said:

showing -1*

 

First stay in the Ohms setting. Sounds like you need to switch up a range. You also need to take into account the resistance if your long test lead wire. "Stroking the cable". You need to make good contact so use connector blocks or Wagos etc. Record the lowest reading you get.

 

Do yourself a favour and buy a copy of this, today:

 

https://www.amazon.co.uk/IET-Wiring-Regulations-Inspection-Certification/dp/1138606073/ref=mp_s_a_1_5?

 

Tbh you can pick up an earlier 17th edition for pence which would do you for the basic testing.

 

Tbh any book by Brian Scadden is good.

 

Actually I might have an old edition of the test & inspect book you can have. PM me your address. If I've got one it's yours.

Edited October 2, 2021 by Onoff

[MJNewton]

1 hour ago, ash_scotland88 said:

Worked it out, was admittedly being an idiot.

Done this, can confirm earth is present!

 

Made up the extension lead for earth only. Tried testing the extension with my cheap multi, don't think it can measure low enough as it was showing -1* but noticed if I stroked the copper I could get it to show changing numbers. Also used the beep function and got a circuit.

 

For future reference, '-1' means out-of-range i.e. the resistance was greater than that for the set range. Given that you were measuring something that should've only been a couple of ohms tops and that 'striking the copper' gave a reading shows that you weren't making contact.

 

Note that 'changing numbers' is not the result you were seeking for this test. Even a wet piece of string or even the probes held in each hand would give you changing numbers if the range was set high enough. Don't be misled by the continuity beep test either as that can often sound at resistances up to a couple of hundred ohms (the meter should say what the detecting range is). 

 

If you want to be sure then get an actual, stable, reading. 

[ash_scotland88]

Cheers, guys.

 

My understanding of my multi meter was that if it showed 1 reading was too high if it showed -1 then too low, lowest resistance setting is 200 and if I'm understanding my online manual this does from 0.1. Its a West169 if anyone is nosey.

 

I closest I was able to get to a stable reading on just the extension cable was after scratching the earth pin on the plug and even then it was slightly changing. Sat around 18-20ohms.

 

Further exploration, couldn't go up on in that service void. So next plan, take it from the light switch on the understairs cupboard as the original CU marked this as being linked with the front door and flood....oh how wrong. It appears to be on a circuit by itself, so will get that swapped over to the RCBO and will have to live with the light switch in there. But being smart/sensors shouldn't have a need to manually turn them off often.

 

That saga and education continues.

 

 

(If anyone is wondering why not direct to CU it sits centre of house, concrete floors below that section and don't have a clue how to get cables to it without ripping up half the floors)

[MJNewton]

2 hours ago, ash_scotland88 said:

My understanding of my multi meter was that if it showed 1 reading was too high if it showed -1 then too low, lowest resistance setting is 200 and if I'm understanding my online manual this does from 0.1. Its a West169 if anyone is nosey.

 

 

There's no such thing as 'too low' on a multimeter. Do you have a link to the manual? A meter scale goes from zero to whatever the scale range is for the position you've set it to. The '200' resistance position measures 0-200 ohms, with a higher resolution than that which would be achieved for the next one up - say 0-2000 or whatever it is.

 

Quote

I closest I was able to get to a stable reading on just the extension cable was after scratching the earth pin on the plug and even then it was slightly changing. Sat around 18-20ohms.

 

That's pretty poor and in my opinion warrants further investigation to work out where the high resistance is coming from - is it the meter leads (connected them together and take a reading), the extension lead (measure from one probe to the other) or is it your circuit (subtract the first two readings from the total) which might be in the circuit you're tapping into or the one you plugged the extension lead in.

 

With a 20 ohms earth path a dead short would draw 240/20 = 12 amps. Whilst that'd trip a 6A MCB it wouldn't trip anything much higher. To put it into context - a 2 ohm earth path would result in 240/2 = 120A which would trip any sized MCB and in the shortest possible time.

Edited October 2, 2021 by MJNewton

[TonyT]

If you are tying into the lighting circuit -and finding not difficult why not spur off the ground floor sockets?

 

drill out the back of a socket and away you go.

 

easier for cable run!

 

 

[Onoff]

You're welcome to the earlier 6th edition:

 

[ash_scotland88]

@tonyT going to do that for an outdoor socket.

Well hopefully (not explored) come down the conduit under the floor and out at the some point as lighting exits from underground.

 

@MJNewton just here testing the extension again. Before hand on the cable I was getting -20ohm (brass screw to brass screw on inside of plug/socket) when it settled.*

The 20ohms was cable.

On cupboard light I got -30. Reading this post I thought I would do your suggestion and probe to probe is -30. So no idea what's happening here.

*Numbers start high (or is it lower when negative?) then settles.

 

Closest I can find to my manual. Will download automatically FYI

https://www.faithfulltools.com › ...PDF

Web results

Instruction Manual - Faithfull Tools

 

I had in mind that it's not just 0-200 range reading but also some decimal point moving had to be done as well, so may be something like 0.2 or 0.02. ?

Edited October 3, 2021 by ash_scotland88

[MJNewton]

There's no such things as negative resistance reading so on that basis I'm assuming your meter it broken.

[dpmiller]

Suggest you get a trained electrician to have a look- wierd readings on the ohms range can often mean there's a voltage where there shouldn't be.

[ash_scotland88]

@dpmiller it's doing when just measuring the extension lead.

 

I've got a sign off from a spark when CU was upgraded and this was more in checking to ensure an earth was continuous where I was originally going to go. Might see if I can borrow one from work.

 

Not sure if I read on here but for cable running through brick wall, but should I put in a plastic conduit? I understand why, protect twin and earth, but at 20mm it's a pretty big hole.

[TonyT]

So you are planning to do an outside socket, great so fit an IP rated socket and adjacent to it fit a switched spur for the outside lights.

 

spur let’s you isolate the lighting

swa cabling straight into spur.