Earth Leakage Query.

[telectrix]

might be having a blonde moment here, but.... if an installation has earth leakage, could this be measured with an earth leakage clamp meter on the main earthing conductor and/or the main bonding conductors as logically, if there is leakage , you would expect the current to travel to earth through these conductors?

 

[malcolmsanford]

Well you certainly would get a reading on your CPC, and I suspect in theory also on the bonding but I have never clamped a bonding conductor to see.

Of course if the leakage started say on a refrigerator compressor, then you would get the full leakage current on that circuit CPC, and it will obviously dissipate as it comes to the MET and go off in it's various paths, obviously the easiest path to earth would have the highest reading, but i'm sure you will get smaller readings on other paths, ie your bonding.

Love the avatar mate " and they smash them all to bit"

 

[telectrix]

Well you certainly would get a reading on your CPC, and I suspect in theory also on the bonding but I have never clamped a bonding conductor to see.

Of course if the leakage started say on a refrigerator compressor, then you would get the full leakage current on that circuit CPC, and it will obviously dissipate as it comes to the MET and go off in it's various paths, obviously the easiest path to earth would have the highest reading, but i'm sure you will get smaller readings on other paths, ie your bonding.

Love the avatar mate " and they smash them all to bit"

that's what i thought. just clamped the main earth in the house install, my lady,s got the oven running there's 2 freezers, 2 fridges ( though maybe not running ) and i read 7mA. just thought it might be a quick test before going through the whole rigmarole of IR testing before a CU change.

 

[Chr!s]

that's what i thought. just clamped the main earth in the house install, my lady,s got the oven running there's 2 freezers, 2 fridges ( though maybe not running ) and i read 7mA. just thought it might be a quick test before going through the whole rigmarole of IR testing before a CU change.

It can be misleading, take a pme supply like mine. Now when i place my leakage tester around the main earth i have close to 1 amp.

If i place me clamp around the live conductors i have 12 mA at the origin.

Obviously there is some diverted current which can mislead.

Regards Chris

 

[malcolmsanford]

Also if the next house on the phase does not have good or any bonding you will pick a little of theirs up as well, not sure how well you would get on using this as a test squence to be honest Tel, as if you got the amp as in chr!s scenario you would think your RCD would be tripping.

 

[telectrix]

yeah, not proposing it as an actual test. if a high reading was obtained, would need investigating. just thoght of it as a starter point , like a socket tester before opening sockets to check polarity etc. anything amiss, get the megger out!

 

[topquark]

If you're looking at leakage for the property best to get a differential reading (clamp around live/neutral coming in). That'll give you an idea of how much current bleed you have (but don't expect that to add up to the total leakage at the main earth/bonding).

 

[pushrod]

Putting clamp on live and neutral tails should do the trick.
oops just beaten to it by top quark

 

[telectrix]

won't work of thre's any load on the installation though as the clamp meter would have to be set to a higher range and would not have the sensitivity to read a mA difference.

 

[topquark]

won't work of thre's any load on the installation though as the clamp meter would have to be set to a higher range and would not have the sensitivity to read a mA difference.

As it's taking a differential reading the two magnetic fields will interact and, to a degree, cancel each other out. So your mA setting should still be OK by-in-large (unless you have a very high leakage).

 

[telectrix]

As it's taking a differential reading the two magnetic fields will interact and, to a degree, cancel each other out. So your mA setting should still be OK by-in-large (unless you have a very high leakage).

do you mean you're clamping round both tails together on mA range and the meter will measure the difference? ( only just got E/L clamp meter, been used to only using IR testing )

 

[topquark]

do you mean you're clamping round both tails together on mA range and the meter will measure the difference? ( only just got E/L clamp meter, been used to only using IR testing )

Yes mate, exactly that. Both the incoming live and neutral (have to be before the main incommer for obvious physical reasons).

The clamp will then use the combined magnetic field created by both cables and measure the induced current from that.

 

[telectrix]

if only. i have the alphatek tek633. the jaws won't close around 2 tails.

 

[topquark]

Probably best to work of the cpc for each circuit in that case. With the usual proviso that some things (immersion etc) will have another parallel path to earth so you may not see all of the leakage.

That's one of the advantages of a nicely laid out set of terminations like in Nick's CU

 

[telectrix]

obviously the way to go is to investigate each cct. individually, but i was thinking similar to global IR test to get a rough idea before any serious testing was undertaken.

 

[topquark]

If you have dedicated use of the circuits/house you could try this, with the usual precautions. Isolate each circuit and check the main earthing conductor for leakage. Then engage each circuit one by one checking the leakage (the last one(s) to engage should be the RFC's as that's where most of the "good" leakage tends to be). That should give you a rough idea of how leaky the installation is likely to be.

That should give you an idea as to whether you want to investigate one circuit more fully before changing the CU or if there's a circuit that you don't want to RCD/RCBO protect, at least to start with.

If you had dedicated use of the house you could disconnect the main bonding as well (but there's an obvious risk to doing that ).

 

[pushrod]

if only. i have the alphatek tek633. the jaws won't close around 2 tails.

Get your mole grips out and squish them first :smilewinkgrin:

Sticking it on your main earth could give you an indication of possible probs and a definite all-clear if you are getting just a few mA when everything is on.

 

[telectrix]

Get your mole grips out and squish them first :smilewinkgrin:

Sticking it on your main earth could give you an indication of possible probs and a definite all-clear if you are getting just a few mA when everything is on.

exactly my tinking. if there's only, say 5 or 6 mA flowing through the main earthing conductor ( and/or the main bonding conductors ) then i would expect that all the circiuts were healthy. obviously, some circiuts could be breaking down under a load not present at the time, so that's why i stressed that it should only be a rough guide to help in deciding whether or not there might be issues when fitting RCD protection.

edit. didn't think of squishing the tails. bloody good idea. they would look better flat, saves buying round clips :yesnod:

 

[topquark]

Just had a quick check on mine 11.5mA (give or take) on both main earth and differential on live/neutral. That's on a PME based earthing system.

 

[pushrod]

Just had a quick check on mine 11.5mA (give or take) on both main earth and differential on live/neutral. That's on a PME based earthing system.

You're lucky mine is 40+ then my ELCM goes over range on the tails, on the bright side it's less than 0.1A :thinking: , but i've still got 40+mA in the earth when the whole installation is isolated, obviously a lot of investigation to do before i change my own CU.(that's on a tn-s)

 

[telectrix]

You're lucky mine is 40+ then my ELCM goes over range on the tails, on the bright side it's less than 0.1A :thinking: , but i've still got 40+mA in the earth when the whole installation is isolated, obviously a lot of investigation to do before i change my own CU.(that's on a tn-s)

wel that's an easy one. convert it to TT, that will incrfease the Ze, thus reducing your leakage current to a manageable level :carolers:

and noo commentz on the typos, jusd got back from the Polish Club, 110 proof vodska.

 

[tony mc]

tel

I had a board change last week and only had 7 mA leakage on the tails prior to doing a globle IR.

On testing I found that the up lights CCT was 0.00 Meg and when changed to ohms it was just over 99k ohms between Neutral and CPC.

Even with that reading the RCD will hold and no leakage was found when the tails were clamped the 7 mA was from the 2 ring finals.

I suppose ot would have to drop below 7666 omhs or there abouts.


Loads of faults at swiches neutrals nicked etc.

 

[topquark]

You're lucky mine is 40+ then my ELCM goes over range on the tails, on the bright side it's less than 0.1A :thinking: , but i've still got 40+mA in the earth when the whole installation is isolated, obviously a lot of investigation to do before i change my own CU.(that's on a tn-s)

When doing the tails clamp, then turn the meter on (or off/on again (whilst clamped)) and see if that makes any difference to the reading, I've noticed that some meters are a little too sensitive to being open/closed when on.

I did spend a little while getting to the bottom of all of my leakage before changing my CU. Most was down to the downstairs sockets (hence the suggestion to re enable them last). Tv/Sat/Surround sound/laptop/computer and a couple of Tvs on standby. Nothing out of the way but it does soon mount up.

 

[pushrod]

tel

I had a board change last week and only had 7 mA leakage on the tails prior to doing a globle IR.

On testing I found that the up lights CCT was 0.00 Meg and when changed to ohms it was just over 99k ohms between Neutral and CPC.

Even with that reading the RCD will hold and no leakage was found when the tails were clamped the 7 mA was from the 2 ring finals.

I suppose ot would have to drop below 7666 omhs or there abouts.


Loads of faults at swiches neutrals nicked etc.

I think the real advantage of using an ELCM is to check the appliances of the customer (it is not a substitute for IR testing) before changinging the CU so that you can identify the culprit(s) or at least warn the customer of what is going to happen. Otherwise on completion of the job you might hear those words from time immemorial "it was ok before you started working on it"!

When doing the tails clamp, then turn the meter on (or off/on again (whilst clamped)) and see if that makes any difference to the reading, I've noticed that some meters are a little too sensitive to being open/closed when on.

I did spend a little while getting to the bottom of all of my leakage before changing my CU. Most was down to the downstairs sockets (hence the suggestion to re enable them last). Tv/Sat/Surround sound/laptop/computer and a couple of Tvs on standby. Nothing out of the way but it does soon mount up.

Have tried that, unfortunately my house does have real issues and the wiring is pretty ancient in places; but the current in the earth, when the power is off, is the real puzzler.

 

[telectrix]

I think the real advantage of using an ELCM is to check the appliances of the customer (it is not a substitute for IR testing) before changinging the CU so that you can identify the culprit(s) or at least warn the customer of what is going to happen. Otherwise on completion of the job you might hear those words from time immemorial "it was ok before you started working on it"!



Have tried that, unfortunately my house does have real issues and the wiring is pretty ancient in places; but the current in the earth, when the power is off, is the real puzzler.

that's an easy one. you live in leicestershire, where it's as flat as a pool table. there ain't no hills for the current to run down. sssimples.

 

[topquark]

Have tried that, unfortunately my house does have real issues and the wiring is pretty ancient in places; but the current in the earth, when the power is off, is the real puzzler.

With only one supply, spooky perhaps your house is working as a large solar cell and with the power off it has no where else to go

Ignore me now, I've been on the vino again! :17: :54:

 

[pushrod]

[/COLOR]

that's an easy one. you live in leicestershire, where it's as flat as a pool table. there ain't no hills for the current to run down. sssimples.

LOL well that is as good as any of my ideas.

With only one supply, spooky perhaps your house is working as a large solar cell and with the power off it has no where else to go

Ignore me now, I've been on the vino again! :17: :54:

The best i could come up with was the house was acting as a giant capacitor:thinking:

 

[topquark]

LOL well that is as good as any of my ideas.



The best i could come up with was the house was acting as a giant capacitor:thinking:

Ah, but capacitors don't generate charge, they store it, well rather they allow a PD to be built between two dielectrics .... more beer needed !

 

[topquark]

Ah, but capacitors don't generate charge, they store it, well rather they allow a PD to be built between two dielectrics .... more beer needed !

No one was in the mood for taking the hiss then

 

[telectrix]

i have a healthy respect for capacitors, ever since working on 1970's colour TVs. when a section of the crude wire wound dropper resistor went o/c. there would be a nice 200v charge left on the smoothing capacitor. the usual method of discharging this before getting bit big style was to use a 10" blade pozidriv screwy. to s/c the cap. to chasssis. still got my old one with little blackened nibbles.

 

[mayfair]

Nothing like the old sets LOPTY big and ugly , nice heat in the workshop off the old PL405 valves.

i have a healthy respect for capacitors, ever since working on 1970's colour TVs. when a section of the crude wire wound dropper resistor went o/c. there would be a nice 200v charge left on the smoothing capacitor. the usual method of discharging this before getting bit big style was to use a 10" blade pozidriv screwy. to s/c the cap. to chasssis. still got my old one with little blackened nibbles.

 

[telectrix]

mmmm and the old PL519 with 8kV sitting on the top cap.

 

[mayfair]

Ouch !!!!!!!!!!!!!!!!!!! Showing our age now Tel I was apprentice with Redifusion in 1975 FFS that 36 year ago

mmmm and the old pl519 with 8kv sitting on the top cap.

 

[telectrix]

i was with rediffusion 1972-3. average 18 service calls per day.

 

[mayfair]

Where at m8 ? btw how Mrs Tel mine has test results tomoz ......not happy puppy (me)

i was with rediffusion 1972-3. average 18 service calls per day.

 

[telectrix]

was at the rediffusion depot in stoke. my lady's had the all clear last check up. next one in about 4 months time. fingers crossed.

 

[Mike Me Mate]

That's brilliant! I was looking for a fast and easy way to check if was going to hold. Do most clamp meters have a m/a range?
I defiantly try it next time I change a board. Tip top!

 

[telectrix]

most clamp meters don't have milliamp range. you need a earth leakage clamp meter.

 

[Mike Me Mate]

Are they expensive or can you pick them up in maplins?

 

[telectrix]

not in maplins i don't think . the alphatek 633 is around £65 + VAT. it's about the cheapest going. try ebay.