recommended entry level pro tester

[NickTG]

hi there
can anyone recommend a test device that I can use for anything i need in the home (I think my basic multimeter is limited ....im probably looking for an entry level professional unit as im even thinking of becoming a trainee electrician as a change in career in the post covid world).

(I had an appliance fixed under its first year guarantee the other week and the guy advised my earth / ground resistance value was a bit high - ive done some research and im thinking of putting an additional earth spur and earthing rod but first it would be good to have a meter where i can test the earth resistant values .... i think in the UK it should be less than 5 ohms)

 

[SparkyChick]

Welcome to the forums...

Kewtech do testers that are good value for money but you can also pick up second hand units on eBay (you should try and get one that is calibrated). If you are seriously considering a career switch then I would go for the best you can afford. When I started 5 years ago I bought a tester that far exceeded my requirements at the time and I don't regret that decision (it was a Megger MFT1731).

That being said, a basic tester that can do all the tests defined in Guidance Note 3 will suffice. But the most important part of testing is being able to understand (a) what you are testing and why, (b) how the testing works (so you can pick appropriate tests) and most importantly, (c) how to interpret the results you are seeing.

Unless the appliance bod carried out an earth fault loop impedance test with an earth fault loop impedance tester, I wouldn't necessarily put much stock in what he told you, but EFLI is important as it will tell you whether the devices protecting your installation (and you) will trip in the times required. It's also important to understand the earthing system at the property. A reading of 5 ohms could be considered spectacular for a TT earthing system, or a lighting circuit covering the whole house wired in 1.0mm twin and earth cable on a TNCS or TNS earthing system, whilst for a ring final circuit on a 32A breaker, wired in 2.5mm T+E cable on a TNCS system it would be non-compliant and would require investigation.

Just be aware that if you have a TNS earthing system (this is where the main earth is connected to the sheath of the incoming cable), if it has a clamp around the cable before the service head, under no circumstances should you mess with that clamp. If it's a screw clamp it's possible you could crush the cable and cause an internal short which would shower you with molten lead, copper and the resulting arc plasma... in other words, huge chance of permanent injury or death.

If I was in your shoes, I would simply get an electrician in to do a quick check (I'm thinking an hour of their time) and take it from there.

 

[Mike Johnson]

As above first check what supply system you have and its Earthing arrangements.

Assuming your main supply is a TT earthing system, In reality you want the Ω reading to be as low as possible, but anything below 200Ω is compliant, but in my eyes not acceptable, below 100Ω is the minimum I personally would accept, better to upgrade your current TT system if that is what you have with additional rods connected to your current rod in series, these additional rods will need to be at least the depth of your current rod horizontally away from it, i.e. outside the zone of influence, finding out how long your current rod may be is anybodies guess, test device's for this sort of thing are specialised if a dedicated instrument, but can be picked up for about £100.00, however if you are seriously looking to train as an electrician then a Multi Function Tester (MFT) is what you need, but do ensure it has the functions you are looking for, some of the lower specified MFT's are not capable of measuring Earth resistance, if I remember correctly in the Fluke range its only the 1663 and above that can do that.

 

[NickTG]

Welcome to the forums...

Kewtech do testers that are good value for money but you can also pick up second hand units on eBay (you should try and get one that is calibrated). If you are seriously considering a career switch then I would go for the best you can afford. When I started 5 years ago I bought a tester that far exceeded my requirements at the time and I don't regret that decision (it was a Megger MFT1731).

That being said, a basic tester that can do all the tests defined in Guidance Note 3 will suffice. But the most important part of testing is being able to understand (a) what you are testing and why, (b) how the testing works (so you can pick appropriate tests) and most importantly, (c) how to interpret the results you are seeing.

Unless the appliance bod carried out an earth fault loop impedance test with an earth fault loop impedance tester, I wouldn't necessarily put much stock in what he told you, but EFLI is important as it will tell you whether the devices protecting your installation (and you) will trip in the times required. It's also important to understand the earthing system at the property. A reading of 5 ohms could be considered spectacular for a TT earthing system, or a lighting circuit covering the whole house wired in 1.0mm twin and earth cable on a TNCS or TNS earthing system, whilst for a ring final circuit on a 32A breaker, wired in 2.5mm T+E cable on a TNCS system it would be non-compliant and would require investigation.

Just be aware that if you have a TNS earthing system (this is where the main earth is connected to the sheath of the incoming cable), if it has a clamp around the cable before the service head, under no circumstances should you mess with that clamp. If it's a screw clamp it's possible you could crush the cable and cause an internal short which would shower you with molten lead, copper and the resulting arc plasma... in other words, huge chance of permanent injury or death.

If I was in your shoes, I would simply get an electrician in to do a quick check (I'm thinking an hour of their time) and take it from there.

thank you so much for that detailed answer

 

[NickTG]

As above first check what supply system you have and its Earthing arrangements.

Assuming your main supply is a TT earthing system, In reality you want the Ω reading to be as low as possible, but anything below 200Ω is compliant, but in my eyes not acceptable, below 100Ω is the minimum I personally would accept, better to upgrade your current TT system if that is what you have with additional rods connected to your current rod in series, these additional rods will need to be at least the depth of your current rod horizontally away from it, i.e. outside the zone of influence, finding out how long your current rod may be is anybodies guess, test device's for this sort of thing are specialised if a dedicated instrument, but can be picked up for about £100.00, however if you are seriously looking to train as an electrician then a Multi Function Tester (MFT) is what you need, but do ensure it has the functions you are looking for, some of the lower specified MFT's are not capable of measuring Earth resistance, if I remember correctly in the Fluke range its only the 1663 and above that can do that.

thanks Mike - the earth at the moment runs from the consumer unit (i guess) to the gas pipe as it exits the house (as it see it strapped onto that pipe )

 

[pc1966]

thanks Mike - the earth at the moment runs from the consumer unit (i guess) to the gas pipe as it exits the house (as it see it strapped onto that pipe )

There should be a proper "means of earthing" and not relying on service pipes (though in that distant past that happened).

So normally in the UK (the common "TN" systems) you would have the main earth coming from the supply (DNO) cut-out to either a main earth terminal block nearby, or in to the CU. Under no circumstances should you attempt to add or modify this (DNO end) yourself! If it looks flaky or missing then contact the DNO and ask them to investigate. Typically the DNO earth will be under an ohm.

Less common here, but the norm in the EU, are TT systems where there should be a dedicated earth rod. Relying on service pipes for it is prohibited as they can and do get replaced by plastic by the utilities who have no obligation to provide earthing to the homes! If you are on a TT system you will either have an incoming RCD (probably 100mA delay) or an all-RCD/RCBO board. As mentioned above, a typical TT system should be under 200 ohms (for 30mA or 100mA RCDs, less than 167 ohms for 300mA etc), but the lower the better.

But it should be one or the other:

• A proper DNO earth, or
• A dedicated and tested rod.

If you can post some photos of your supply arrangement and CU folks here might be better able to advise you on what is your best course of action.

 

[pc1966]

As @Mike Johnson mentioned, not all MFT have the option for measuring an earth rod directly (e.g. with 2 ground spikes, etc) however, in most cases doing a "Ze" test to the rod in isolation is often the simplest means of verifying it is OK, and all MFT can do that.

The earth spike test is more accurate, and if you are installing and have no AC power yet possibly the only means to verify an earthing arrangement, but in built up areas where the rod might go through tarmac/concrete and you simply cannot put test spikes in anyway, then the "Ze" approach is fine.

 

[NickTG]

There should be a proper "means of earthing" and not relying on service pipes (though in that distant past that happened).

So normally in the UK (the common "TN" systems) you would have the main earth coming from the supply (DNO) cut-out to either a main earth terminal block nearby, or in to the CU. Under no circumstances should you attempt to add or modify this (DNO end) yourself! If it looks flaky or missing then contact the DNO and ask them to investigate. Typically the DNO earth will be under an ohm.

Less common here, but the norm in the EU, are TT systems where there should be a dedicated earth rod. Relying on service pipes for it is prohibited as they can and do get replaced by plastic by the utilities who have no obligation to provide earthing to the homes! If you are on a TT system you will either have an incoming RCD (probably 100mA delay) or an all-RCD/RCBO board. As mentioned above, a typical TT system should be under 200 ohms (for 30mA or 100mA RCDs, less than 167 ohms for 300mA etc), but the lower the better.

But it should be one or the other:

• A proper DNO earth, or
• A dedicated and tested rod.

If you can post some photos of your supply arrangement and CU folks here might be better able to advise you on what is your best course of action.

thanks PC1966 - i attach a pic and a drawing of the earth cables ( looks a bit neater in the drawing ;-) ). The "metal T" is the main electric input and there is an earth cable strapped to that metal casing which houses the electric cable that comes into the house. That earth cable is connected to an all metal connection strip (that is in three sections ). The property is in two flats - the two earth cables from the consumer units of each flat enter single fuse boxes and then out to connect to the metal connection strip. From that connection strip there are two further earth wires that come out and connect to the service pipes (maybe once upon a time that was extra precaution)
what i was planning on doing is buying an earthing rod from toolstation and connecting it to the metal connection strip and do some testing ive always loved electrics

 

[pc1966]

That looks quite ropey. It also appears (as far as I can see?) as if the lower meter reads all power, and the upper meter just the power to the 2nd flat?!

That is connected as a TN-S system, but that is not looking like the usual DNO connection to the incoming cable. From its age, etc, I would say you must not touch it at all. I have no idea who the DNO is in your area, but maybe some of the other forum members with a bit more knowledge in this area can advise you on who to contact to get the supply earth checked.

Since it is a TN-S arrangement expecting a low impedance earth adding a rod will not do anything, as you simply won't get a low enough impedance that way to allow the over-current protection devices to go an an earth fault.

Basically if the supply earth is not good enough then the DNO should fix it. If they can't / won't then it means converting to a TT system and that means both of the flats would need their CU checked and (most likely) upgraded to have the required RCD protection on all circuits.

Really this is something that needs the DNO and/or a full professional assessment if any changes are to be made.

 

[NickTG]

That looks quite ropey. It also appears (as far as I can see?) as if the lower meter reads all power, and the upper meter just the power to the 2nd flat?!

That is connected as a TN-S system, but that is not looking like the usual DNO connection to the incoming cable. From its age, etc, I would say you must not touch it at all. I have no idea who the DNO is in your area, but maybe some of the other forum members with a bit more knowledge in this area can advise you on who to contact to get the supply earth checked.

Since it is a TN-S arrangement expecting a low impedance earth adding a rod will not do anything, as you simply won't get a low enough impedance that way to allow the over-current protection devices to go an an earth fault.

Basically if the supply earth is not good enough then the DNO should fix it. If they can't / won't then it means converting to a TT system and that means both of the flats would need their CU checked and (most likely) upgraded to have the required RCD protection on all circuits.

Really this is something that needs the DNO and/or a full professional assessment if any changes are to be made.

thanks pc1966 - ill check who the DNO is for finsbury park north london ...thanks for the advice i wont go down the route of adding a rod then (you are right on the meters - as one of the flats is just a self contained granny anex) -im not sure if the supply earth is good enough so i do need to do some tests but ill get in touch with DNO once all this covid stuff is over - many thanks

 

[DPG]

Those two twin and earths are abysmal.

 

[NickTG]

Those two twin and earths are abysmal.

once upon a time im told the place used to be a dental practice and the dentists home - when i got the place 6 years ago i remember asking the Electric Board/Grid (may have been the DNO) if i could have an updated supply as someone did say it was a very old inlet but they wanted something like £2k - 3k to update the inlet !! - while the gas board fitted all new free of charge. However thanks to this forum i will now contract the DNO for the area and specifically talk to them about the earth - I do really appreciate all your help

 

[UNG]

what i was planning on doing is buying an earthing rod from toolstation and connecting it to the metal connection strip and do some testing ive always loved electrics

I've seen an installation that someone had done that although the person that did it worked for an NICEIC contractor and should have known better. It was on a looped supply from nextdoor it turned out that having got the DNO involved the rod was the earthing point or 6 - 8 properties, the DNO engineer was far from happy

 

[Pete999]

hi there
can anyone recommend a test device that I can use for anything i need in the home (I think my basic multimeter is limited ....im probably looking for an entry level professional unit as im even thinking of becoming a trainee electrician as a change in career in the post covid world).

(I had an appliance fixed under its first year guarantee the other week and the guy advised my earth / ground resistance value was a bit high - ive done some research and im thinking of putting an additional earth spur and earthing rod but first it would be good to have a meter where i can test the earth resistant values .... i think in the UK it should be less than 5 ohms)

Just stand on the corner and shout !ban the bomb! to become a pro tester.

 

[Dartlec]

Just stand on the corner and shout !ban the bomb! to become a pro tester.

That was worth the 4 month wait ?

For future viewers, the Megger 1552 has to be a good shout - available on ebay for less than £200 and still does pretty much everything for basic testing - also pretty much bullet proof if you don't heavily abuse it.