Safe electrical isolation check before servicing boiler

water and gas · May 31, 2016

Hi all,
Just spent a week placement with British Gas. Part of the boiler service is to complete a Dynamic Assessment Checklist, and so, first perform a safe electrical isolation check. Now this involves 2 tasks: 1st using an electric pen voltage tester over the boiler and 2nd using a socket and see device.
Where I get confused is does the pen tester to check earth continuity and the socket and see device to check the resistance polarity or the way around?
I am a newbie in the trade and need some clarification also as to what both tests differs from each other?
I thank in advance anyone who will offer its support.
Really appreciated guys!!
Thank you!!!

steptoe · May 31, 2016

Neither of those methods are any sort of meaningful test whatsoever

Rob. · May 31, 2016

Any chance you can post a copy of this document.

I've a strong feeling they haven't taught how to safely prove dead or isolate. Or even in fact use the correct equipment.

Essex1 · May 31, 2016

Both those examples of testing do not meet the HSE guidance on safe isolation. If they are asking you to work to these guidelines then you must challenge them under H&S.

binky · May 31, 2016

assumes boiler is on a plug, which it shouldn't be.

Pen tester, or rough voltage indicator is a more accurate description, is only a rough test for voltage being present, ie cabling may be live. These can easily be confused by other live equipment being in close proximity.

Socket tester - some have an indication of Zs built in, but most don't. These are more for checking polarity and presence of a live earth and neutral. Fairly meaningless and only useable with a socket.

What you should be using is Voltage Probes to confirm electrical supply is dead to the boiler. They should also be teaching basics like switching circuit off at the Consumer Unit, and removal of fuses at a fused spur whilst working on boiler to prevent accidental re-energising.

Sharpend · May 31, 2016

Oh dear another BG scam!

Sidewinder · May 31, 2016

Duplicate threads merged.

ProDave · May 31, 2016

So enlighten me, just where do you plug the socket and see, when you encounder a boiler hard wired into an FCU on it's own dedicated circuit?

Unfortunately you have NOT been taught anything whatsoever about proving a circuit is dead and safe to work on. Sounds like another short course failure.

binky · May 31, 2016

sounds like the same course Currys oven fitters have been on, whatever they use fails every TT system... :shakehead

water and gas · May 31, 2016

water and gas said:
Thank you for your help really! This is a short track course and spent only 1 week with BG so no time really to assimilate everything and obviously well aware 1 year practise with a mentor will be required before I fully understand the science behind it.

What I understand is what is the pen used for and what the socket and see used for? They told me but did not manage to put down notes and just forgot what they said about it.

So, here is what I am writing on my portfolio and does it make sense?

“Part of British Gas boiler service procedure is to complete a Site Specific Dynamic Assessment Checklist. I first check safe electrical isolation by performing a dead test for both resistance to earth and earth continuity. I touched an electric pen voltage tester over a switch to check the good working order of it which has been confirmed by the red light at the tip of the detector, and then make contact of it all over the boiler. The pen did not react confirming the boiler was safe isolated and therefore safe to use. The detector was then touched back over the same switch where it turned red confirming it did well work when checking the boiler safe electrical isolation.

The control box was then opened to perform a polarity test. Using a socket and see device I firstly put the blue lead from device to the E terminal block on the boiler and secondly the brown lead to the N terminal block on the boiler. All results were satisfactory and therefore the boiler was safe to work on.

Finally, I checked the boiler socket was on a 3Amp which it was.”

ProDave · May 31, 2016

I am sorry, what's said in post ID11 is a load of meaningless tosh and in NO WAY has it PROVED the boiler is dead.

I despair if that is what is being taught. :C

water and gas · May 31, 2016

Thanks for the reply...

So what is the pen, and the socket and see for when checking safe electrical isolation before servicing a boiler?

Andy™ · May 31, 2016

at best, its a complete bodge. those non-contact voltage detectors can be useful to give an indication something is live (and i do own one), however it is useless for testing dead and can easily give false reasings resulting in your death. for safe isolation you need a proper device, like a fluke T140 (probably different model by now, mine is a good few years old) or similar, and enough knowledge to be able to use it correctly & safely. from your posts, you do not even know the basics. for a start, you dont check for 'resistance to earth and earth continuity' . and putting a blue lead to earth and brown to N does not prove polarity either

if this really is your training, then your employer is in breach of EAWR, and you are at a very serious risk of electrocution if you keep going the way you are

ProDave · May 31, 2016

The biggeest ommision that I saw was there was no mention of touching ANY probe to the boilers L terminal. headbang

water and gas · May 31, 2016

So what probe should be touching the boiler L terminal? Are we well checking for polarity here?

And do you know how to perform earth impedance on boiler? what is the procedure?

As said I am building my gas portfolio through short track course and also new in the trade so even the basic are not there and that's a work in progress, hence why I came over the forum and kindly ask for some clarification. I just need some help and trying to make sense between earth impedence and polarity. Thank you guys

Andy™ · May 31, 2016

you need to use a proper voltage tester (like i said in post 14) between L&N, L&E, N&E. many decent ones will also warn you if something is live (but not what voltage) with only 1 probe touching

for safe isolation, you have no need to test polarity. this only needs done if any modifications / work has been done / periodic inspection of the fixed wiring. by impedance check, if you mean earth loop impedance, then it is done with an earth loop impedance tester by connecting probes to L, N & E (or in some cases, L&E only). but as polarity, you have no need to do this for boiler maintenance. there are also a few different earthing systems which will give different results. a reading may be acceptable on one type but unacceptable on another. we often go to properties where the 'gas engineer' has 'failed' the wiring when there isnt actually anything wrong, he is just incompetent at electrics

you really need to learn a lot more about this before working on anything electrical

and if there is anything written down saying you test for dead the way you are, any chance of a copy / picture of it? stuff like that is always entertaining for us

Essex1 · May 31, 2016

This is a blatant wind up. Cannot belive I bit earlier.

water and gas · May 31, 2016

Andy, thank you for your post which is a constructive post not like some others where they are just negatively qualifying my incompetence which is fair enough as I am a starter but they are not helping me to understand what I am missing on.

So because I am new in the trade I don't express myself clearly and not using the right wording!

Through your post I better I understand that the pen was to check if the boiler was not live, and the socket and see (the one we used has the loop impedance button) to test the earth loop impedance.

Seems like the polarity is not relevant here as we haven't carried out any electrical work. Somehow with the gas engineer we briefly talk about polarity but that was then surely regarding a different matter where I got confused.

As said I won't carry out any electrical work till I am confident and this should take me a year at least and under supervision till then.

ProDave · May 31, 2016

water and gas said:
So what probe should be touching the boiler L terminal? Are we well checking for polarity here?

L is (normally) the one that will hurt or KILL you if you touch it, so it begars belief that you have been "taught" to "test for dead" without actually making any measurment form the boilers L terminal.

As already pointed out, to properly "test for dead" you need to take 3 measurements as already described from all 3 terminals. Preceeded and followed by "test your tester" (i.e make sure it actually works and reads a voltage when really live)

I would go back to your course priovider and ask for a refund because what they have taught you is somewhere between incompetent / dangerous and fraud.

kerching · May 31, 2016

What is the model number f the Socket and See?

originally they only made a plug in tester but now they do a lot more. Including a Proving unit which i believe is made by Megger

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