Live testing - could this be a Part P assessment failure?

[Tuttle]

Another Part P assessment related question ...

What is the correct way of carrying out RCD tests on RCBO protected circuits that have no socket outlets, e.g. lighting, alarms, immersion heaters, etc?

I would be tempted to switch on the main switch and the RCBO for the circuit to be tested with the CU cover removed, just for the duration of the test, and probe the neutral and live terminals on the top of the RCBO with my multifunction tester's leads (with GS38 covers fitted) but I am a little concerned that this would be classed as working live.

Is it acceptable to energise the CU with the cover off in this case or would I risk failing my assessment?

Anyone done this on an assessment? Was it ok or frowned upon?

Seems like the safest way to do it to me but I am not sure if switching on with the cover removed is a big no no in all situations.

 

[johnboy6083]

live working is a part of testing that cannot be avoided if it is to be done properly

 

[Tuttle]

Another Part P assessment related question ...

What is the correct way of carrying out RCD tests on RCBO protected circuits that have no socket outlets, e.g. lighting, alarms, immersion heaters, etc?

I would be tempted to switch on the main switch and the RCBO for the circuit to be tested with the CU cover removed, just for the duration of the test, and probe the neutral and live terminals on the top of the RCBO with my multifunction tester's leads (with GS38 covers fitted) but I am a little concerned that this would be classed as working live.

Is it acceptable to energise the CU with the cover off in this case or would I risk failing my assessment?

Anyone done this on an assessment? Was it ok or frowned upon?

Seems like the safest way to do it to me but I am not sure if switching on with the cover removed is a big no no in all situations.

BTW. I meant neutral and line terminals - thought I'd get that in before anyone points out that the neutral is a live conductor

 

[needasparks]

There is not normally any reason to remove the cover without the main switch off that i can think of (although we all do it ) but don't do it on an assesment.
Why are you testing the circuit(rcd) at the origin and not at the end of the circuit under test ? What is this going to achieve ?

 

[Tuttle]

There is not normally any reason to remove the cover without the main switch off that i can think of (although we all do it ) but don't do it on an assesment.
Why are you testing the circuit(rcd) at the origin and not at the end of the circuit under test ? What is this going to achieve ?

The reason for testing at the origin is that it is easier (safer I think) than trying to probe live connections in a ceiling rose or dismantling a live fused connection unit or alarm panel. Also, I'd have to walk away from the dismantled equipment to reset the RCBO.

 

[trev]

Another Part P assessment related question ...

1)What is the correct way of carrying out RCD tests on RCBO protected circuits that have no socket outlets, e.g. lighting, alarms, immersion heaters, etc?

2)I would be tempted to switch on the main switch and the RCBO for the circuit to be tested with the CU cover removed, just for the duration of the test, and probe the neutral and live terminals on the top of the RCBO with my multifunction tester's leads (with GS38 covers fitted) but I am a little concerned that this would be classed as working live.

3)Is it acceptable to energise the CU with the cover off in this case or would I risk failing my assessment?

Anyone done this on an assessment? Was it ok or frowned upon?

Seems like the safest way to do it to me but I am not sure if switching on with the cover removed is a big no no in all situations.

1) Instead of the lead with the plug top use the one with the probes and fit your crocs on th ends, attach relevant croc to terminal and hit button for test as normal
2) What would you be hoping to achieve with this method? The way to do it is to test at the point furthest remote from the origin. You would be testing live at this stage. To complete the testing function properly live tests are inevitable
3) Don't know for sure whether it would fail you your part p assessment but I do remember that taking the cover off a live CU during 2391 practical was an instant fail

 

[trev]

The reason for testing at the origin is that it is easier (safer I think) than trying to probe live connections in a ceiling rose or dismantling a live fused connection unit or alarm panel. Also, I'd have to walk away from the dismantled equipment to reset the RCBO.

If you did that and something went wrong and it ended up in front of a guy in a wig and a robe what would your reply be to the question "Why did you not conduct the tests in accordance with normal custom and practice and as laid down in guidance note 3?"

 

[needasparks]

But you would not have resistance values added to the result of the rcd triping time would you ?
We have also got to find a way of a safe testing method for the situation which is why we are assesed on our proceedures. sometimes we have to use two people for live testing for that reason if concidered needed. It goes with the job i'm affaid.

 

[trev]

Even if you didn't have someone with you you could establish exclusion zones around the open live points with barriers around them + big signs "DANGER 230/400 VOLTS NO ENTRY DANGER OF DEATH" etc.
Put em up take photos on your phone as proof they were there, test as per usual, jobs a goodun

 

[Tuttle]

The on site guide says that RCD tests are made on the load side of the RCD "as near as practicable to its point of installation" which seems to me to say that the tests don't need to be carried out at the furthest point, in fact I think that it says that test should be carried out near to the origin if that is where the RCD is installed, or have I misunderstood?

I've got GN3 here so I'll have a look through that as well (can anyone point me at the relevant bits?).

 

[Tuttle]

I can't find anywhere in GN3 that specifies where RCD testing should be performed, e.g. the origin / point of installation or the furthest point. Actually, I wouldn't have thought that it would make much difference anyway because the tester draws a constant current so circuit resistances should not have an effect, and the aim of the test is to test the RCD not the wiring. I thought the CU would be a good place to do live testing (if there is no better alternative) as there is good access, it is fixed to the wall not floating around, and on a modern unit with the bus bar cover fitted there is not really that much to accidentally touch - much safer than an old CU switched off with the lid off! - but maybe I need to rethink

 

[netblindpaul]

You should NOT undertake RCD tests at circuit extremities as the testers that are in use for this are in adequate to deal with this scenario.
RCD tests must be undertaken at the output of the RCD to be accurate unless you have an RCD tester which is genuinely costing about £10k+!

 

[jaresquire]

My NIC inspector has no problem with testing rcd/rcbo at the cu.

 

[trev]

Fair enough chaps, I appear to be wrong. Although I've always carried out RCD test at the furthest point and did so on my 2391 practical too. I stand corrected

 

[Tuttle]

You should NOT undertake RCD tests at circuit extremities as the testers that are in use for this are in adequate to deal with this scenario.
RCD tests must be undertaken at the output of the RCD to be accurate unless you have an RCD tester which is genuinely costing about £10k+!

I had wondered why OSG says to test close to the point of installation, and that could explain it, thanks

 

[spark 68]

Hi Trev,

I don't think it makes much difference in reality, as the Zs of the circuit under test should have a negligable effect wrt the RCD tripping current.

IIRC there was an article in one of the wiring matters magazine a while back about this, I think it comes down to which ever way is the safest/most convenient.

 

[trev]

I think I've got all the egg wiped off my face now.
Ah, no there's a bit right there

 

[Engineer54]

Well from the start of this thread until post#12, i was amazed at the lack of understanding on the simple testing of an RCD device. All this nonsense about ''live working'' seems to be clouding the waters somewhat!! Live working and conducting required tests such as RCD and ELI, necessitates the circuit and the CU being live, there is no-way around it.

As for testing RCD's at the furthest point, that's acceptable for checking the RCD is functioning, but to conduct accurate parameter testing you really need to take those readings at the RCD terminals. Some manufactures state that there units need short length of wire to test from rather than directly on the terminals. But you can safely say that RCD test should be conducted at the CU and not in the field.


As for live working, just the use of your commonsense will normally suffice in the real world.... lol!!

 

[Chr!s]

This may help a little.


https://www.electriciansforums.net/attachments/indg354-pdf.120236/

Regards Chris

 

[spark 68]

Hi E54,

As for testing RCD's at the furthest point, that's acceptable for checking the RCD is functioning, but to conduct accurate parameter testing you really need to take those readings at the RCD terminals.

Whilst I usually prefer to test at the terminals, as this is more convenient for re-setting the device in question (auto testing aside), some scheme providers prefer you to test at a nearby socket (if and when this is possible re:split load boards) as this is deemed safer using a plug in lead.

The wiring matters article I referred to earlier (I will see if I can find it), seemed to suggest it makes little difference to the trip times recorded (or perhaps the worst case scenario), maybe different organisations have in the past, rightly or wrongly "their own way of testing"

Iam not disagreeing with anyone, as I said I prefer to test at the devices out going terminals.

 

[Farmelectrics]

no you havnt misunderstood nothing wrong with you testing rcbo at board make sure you have warning sign hanging from board and you dont leave area with board cover off do your live rcd tests and replace cover job done

 

[Engineer54]

Hi E54,

Whilst I usually prefer to test at the terminals, as this is more convenient for re-setting the device in question (auto testing aside), some scheme providers prefer you to test at a nearby socket (if and when this is possible re:split load boards) as this is deemed safer using a plug in lead.

The wiring matters article I referred to earlier (I will see if I can find it), seemed to suggest it makes little difference to the trip times recorded (or perhaps the worst case scenario), maybe different organisations have in the past, rightly or wrongly "their own way of testing"

Iam not disagreeing with anyone, as I said I prefer to test at the devices out going terminals.

Think you'll find if you check with the manufacturers themselves, will recommend testing at the outgoing terminals. These Scam providers often seem to try and make-up there own rules, about doing things. Make them sound official too, but they are anything but official, ....Just there own slant on things, that can often be at least confusing and at worst ...Wrong!!

 

[netblindpaul]

One other point.
HSE do not consider live testing as live working.
Live testing is live testing, an essential part of ensuring that electrical equipment is safe for continued use.
Live working is live working, disconnecting and making connections say on an energised circuit carrying current. This is very highly regulated and controlled. Mess this one up & you are in heap big doo doo's!
Hence why live working is not acceptable.

 

[mogga]

if taking a C.U. cover off is a fail then I would fail every day of the week
I work mainly in commercial situation and would never get away with puting in the lim box "Unable to take off DB cover as it would be live " Im an approved electrician and as such have been trained and know the risks and how to use test equipment in live situations FFS
I cant imagine the manager of a resteraunt allowing me to turn off all his/her electricity while I remove covers ect its not practical I have limited dbs that I deem unsafe to work on while they are live MEM Dorman smith LM Crabtree C50 ect this is getting to be a JOKE seems like they want trained monkeys who have no clue how to work on old stuff just want to install nice shiney new equipment What else do they expect from 5 week wonders ?????????????

 

[Tuttle]

Thanks guys. So the answer is that I shouldn't get into any bother if I energise a circuit with the CU lid off to do RCD tests, which is exactly what I do when I don't have an inspector looking over my shoulder

I thought that would be the case but I just wanted to make sure. I think that assessment paranoia is starting to kick in and sometimes H&S rules do seem to go a little bit too far, especially when you're dealing with large organisations!

Actually I used to work in a TV repair shop, over 20 years ago now, and we used to have unattended TV's switched on with screens facing the wall and backs off all over the place, and nobody thought anything of it. We used to have customers coming into the workshops sometimes as well. I wonder what modern H&S would think of that!

 

[Engineer54]

One other point.
HSE do not consider live testing as live working.
Live testing is live testing, an essential part of ensuring that electrical equipment is safe for continued use.
Live working is live working, disconnecting and making connections say on an energised circuit carrying current. This is very highly regulated and controlled. Mess this one up & you are in heap big doo doo's!
Hence why live working is not acceptable.

How about ''Live'' HV/MV overhead line/string and insulator cleaning, with high pressure water equipment from the ground??

 

[netblindpaul]

Different ball game E54, this would only be done by (in the UK) NG, the DNO's, or their approved and trained, competent contractors.
The problem you have in the LV electrical industry is that there are too many who are incompetent out there, so they "police" that by making these rules.
Mind to be honest I've never come across the work you describe being done.

 

[telectrix]

Thanks guys. So the answer is that I shouldn't get into any bother if I energise a circuit with the CU lid off to do RCD tests, which is exactly what I do when I don't have an inspector looking over my shoulder

I thought that would be the case but I just wanted to make sure. I think that assessment paranoia is starting to kick in and sometimes H&S rules do seem to go a little bit too far, especially when you're dealing with large organisations!

Actually I used to work in a TV repair shop, over 20 years ago now, and we used to have unattended TV's switched on with screens facing the wall and backs off all over the place, and nobody thought anything of it. We used to have customers coming into the workshops sometimes as well. I wonder what modern H&S would think of that!

that takes me back a while. mirrors at back of bench, line output valves with around 8kV sitting exposed, metal chassis connected direct to neutral, except when some idiot had wired the plug wrong way round. O/C dropper resistor leaving caps chasrged to 200V d.c. happy days.

 

[Engineer54]

Different ball game E54, this would only be done by (in the UK) NG, the DNO's, or their approved and trained, competent contractors.
The problem you have in the LV electrical industry is that there are too many who are incompetent out there, so they "police" that by making these rules.
Mind to be honest I've never come across the work you describe being done.

Only jiving with you mate...lol!!

Yes they do use this form of cleaning (among others) in the UK. Mainly in and around heavy industrial areas and complexes where prone to industrial build-up of contaminates. Depending on the type and severity of the build-up, anything between every 10 to 15 year periods. Obviously water needs to be high purity deionized water.

If you look at some of Tony's photo's of the heavy industrial plants that he's worked in you will see for yourself the build up that can and does takes place. Now imagine that build-up on 33/66KV and above strings and there insulators. Heavy carbon producing plants tend to need more frequent line cleaning...

 

[netblindpaul]

E54,
I know HV stuff needs cleaning, and I had envisaged a method, as you say, along with the same principles also that are used for water fire extinguishers which are used on LV electrical equipment.
However, I was under the impression that it was normally dry blast cleaning or dry ice cleaning that was used.
Though I can believe it possible to use water, after all water is an insulator...

 

[Engineer54]

E54,
I know HV stuff needs cleaning, and I had envisaged a method, as you say, along with the same principles also that are used for water fire extinguishers which are used on LV electrical equipment.
However, I was under the impression that it was normally dry blast cleaning or dry ice cleaning that was used.
Though I can believe it possible to use water, after all water is an insulator...

Only if it's deionised water at those sort of voltages!! Samples of water in the water wagon need to be tested, prior to firing up at the lines/strings. If parts per million exceed the maximum allowable then it can't be used. Never seen those other methods you mentioned used, probably raw material and the means to get those materials to the lines/strings etc, would be too expensive. Air blasting as i remember was tried, but some of these built-up deposits are set like concrete, and need soaking and pressure to shift them...

 

[netblindpaul]

E54, You bit, as I thought you would!
Remember water is H2O and that is that.
We used dry ice on our drives which had deposits set like concrete almost.
Also there seems to be a Co. 'tother side of the pond that uses walnut shells and other stuff, like we use over here for delicate blasting of soft materials.

 

[Engineer54]

E54, You bit, as I thought you would!
Remember water is H2O and that is that.
We used dry ice on our drives which had deposits set like concrete almost.
Also there seems to be a Co. 'tother side of the pond that uses walnut shells and other stuff, like we use over here for delicate blasting of soft materials.

Dry ice is water yes, but in a completly different form and not as easy to store. The equipment is going to be far more expensive to blast at what can be high distances too,. They use water because it's cheap, the equipment to pressurise it, is also relatively cheap. I'm not saying there are not other means of achieving the same ends, just that all are going to be a more expensive proposition to run and maintain, than water and a simple high pressure pump!! It's a proven system that Works!!! ...And great fun to operate too! ...lol!!!

 

[netblindpaul]

No mate Dry is is solid CO2 (excuse the lack, of subscript).

 

[Engineer54]

Sorry thinking of something completly different ... that and age is my excuse!!...

Oh, ...and H2O is not just water, and that is that!!! If it was there would be an awful lot of water chemists and engineers out of a profession!! Water is full of contaminates depending on the source. Would you really use tap water to top-up a battery?? No you would use deionised or distilled water, or that battery ain't gonna last too long....

 

[Les Dove]

I would have to agree with tuttle, if you look at page 140 OSG (little red book) there is just one RCD reading per group of circuits not one RCD reading per circuit. I contacted Hager a year or so ago and their tech dept said to test at the origin of supply otherwise you would need to dis-connect all the other neutrals to get correct readings.

 

[hyperloop]

Tuttle, The WHOLE POINT of doing RCD test times from points of utilisation is to see that the tripping time comlies in the event of a fault at the remotest part of the circuits, if you just test in the board, how on earth does that show this? you can take it as gospel that this is the case, if you tested the load side on your assessment the guy would just see you dont understand the point of the test or how to conduct it.

 

[HandySparks]

Tuttle, The WHOLE POINT of doing RCD test times from points of utilisation is to see that the tripping time comlies in the event of a fault at the remotest part of the circuits, if you just test in the board, how on earth does that show this? you can take it as gospel that this is the case, if you tested the load side on your assessment the guy would just see you dont understand the point of the test or how to conduct it.

No. The point of doing RCD testing is to verify the performance of the RCD. The tester causes a specific differential current to flow and checks for time to trip. Since the test current is determined by the test instrument, independent of the circuit resistances, it makes no difference where on the load side the test is made.

Testing of the circuit wiring should be done by R1, R2, Zs prior to the RCD test.

 

[Engineer54]

Tuttle, The WHOLE POINT of doing RCD test times from points of utilisation is to see that the tripping time comlies in the event of a fault at the remotest part of the circuits, if you just test in the board, how on earth does that show this? you can take it as gospel that this is the case, if you tested the load side on your assessment the guy would just see you dont understand the point of the test or how to conduct it.

I'm sorry to say, that it's you that don't understand the point of RCD testing, or indeed how to conduct them!!!

Check with the manufacturers, all will tell you to test there RCD's/RCBO's outgoing/load terminals... There are one or two that require a short conductor(s) (a matter of a few inches) connected to the load terminals and test from those conductor ends.

Nothing to stop you testing from remote locations mind, but just as confirmation of tripping, but not for your actual notifiable readings...

 

[deploydasausage]

thanks to everyone that posted, i only just discovered that i was conducting rcd tests wrong. ...testing at the board will save me loads of time!!!