Proving dead & safe iso on Economy 7

[NickD]

Interested to hear people's thoughts on best practice for proving dead and achieving safe isolation on an Economy 7 board - the problem being, (unless you work 0000-0700 GMT :wink5 the Economy 7 supply is unenergised. So 'proving' your means of isolation achieves dead actually proves nothing, because even if you had failed to isolate it'd be dead anyway - the supply is unenergised. And the energisation of the Economy 7 is outside your control, and for life criticality it's not good enough to assume it can only ever come live during the wee small hours - accidents and errors happen.

In increasing order of derangement, my thoughts currently include
- pulling the cutout fuse (would you do it if you were being assessed though?)
- carefully (no touchee copper) removing the Economy 7 tails from the main switch and isolating them in connector block
- insulation testing supply-to-load on both the L and N side of the main switch after turning off, to prove the switch open

(tin hat on, finds parapet)

 

[Lee Marshall]

just go during the day lol

 

[Octopus]

I was testing an E7 system a few months ago and then at 3pm, just as I was finishing, the timer switched it on. Thankfully I didn't have my fingers in the board at the time. lol

 

[BrianDB9]

Get a contractor switch fitted.

Prove GS38 Testers on known live source and check circuit is dead is about as much as i can think of - HSE wouldnt take kindly to any risk.
They've even stopped us doing live tests only Zs = Ze +r1+r2 now

 

[Lee Marshall]

I was testing an E7 system a few months ago and then at 3pm, just as I was finishing, the timer switched it on. Thankfully I didn't have my fingers in the board at the time. lol

did the heatwise kick in for an hour? lol

 

[NickD]

just go during the day lol

I am. That's the problem dude!

 

[NickD]

Prove GS38 Testers on known live source and check circuit is dead is about as much as i can think of

But that's my point. This proves naaaaathing when the supply is dead anyway, but can be energised outside of your control. Same problem must pop up for PV I guess when it's dark, very cloudy or Wales.

 

[lauriehurman]

I agree with Murdoch
Watch out for the "afternoon boost".
Laurie

 

[Guest55]

wtf is this sh**e ?
why cant you just turn off the main sw ?
it wont matter if the teleswitch is energised or not.
and as for pulling out tails and sticking in connector blocks ?? get a grip or just pack in electricals before you have an accident..

 

[Octopus]

I agree with Murdoch
Watch out for the "afternoon boost".
Laurie

Wasn't an afternoon boost, the clock was very wrong.

 

[NickD]

wtf is this sh**e ?

Risk management.

why cant you just turn off the main sw ?

You can. But how do you know the main switch has done its job and isolated from the supply? Proving dead proves NOTHING because the supply side of the switch is dead. Even if you left the switch closed it'd still show dead.

it wont matter if the teleswitch is energised or not.

It will if your safe isolation didn't actually work but you glibly assumed it did because it all looked dead, and then you're working on it when the teleswitch switches live. It might matter more than anything has ever mattered to you ever.

and as for pulling out tails and sticking in connector blocks ?? get a grip or just pack in electricals before you have an accident..

I did say it was a bit of a random idea; question is whether doing so carries more risk than a possible failed main switch allowing the system to go live while-U-work. Bear in mind you can confirm the tails are dead before you do it. Care is required because the means of energising them is outside your control.

 

[Guest55]

why dont you take your multi quotes and jog on over to the screwfix forum where this sort of topic is highly valued.

 

[Robert Turnbull]

Risk management.



You can. But how do you know the main switch has done its job and isolated from the supply? Proving dead proves NOTHING because the supply side of the switch is dead. Even if you left the switch closed it'd still show dead.



It will if your safe isolation didn't actually work but you glibly assumed it did because it all looked dead, and then you're working on it when the teleswitch switches live. It might matter more than anything has ever mattered to you ever.



I did say it was a bit of a random idea; question is whether doing so carries more risk than a possible failed main switch allowing the system to go live while-U-work. Bear in mind you can confirm the tails are dead before you do it. Care is required because the means of energising them is outside your control.

It would take about 5 seconds to prove the main switch was working

 

[NickD]

why dont you take your multi quotes and jog on over to the screwfix forum where this sort of topic is highly valued.

Because I thought I might get a more professionally informed answer here, and because they don't have the same quality of troll.

 

[NickD]

It would take about 5 seconds to prove the main switch was working

Cool, that's what I need - how would you do that, please? Isolation test across the switch, both L and N?

 

[ipf]

I am. That's the problem dude!

1.00 am solves the problem, dunnit ?

 

[snowhead]

The logic of pulling the E.7 tails would apply to the normal supply, if you don't trust the main switch working.

Minimum required;

Prove continuity on the E7 Main switch whilst ON.
Switch off and prove NO continuity.

If you're replacing C.U or tails, work as you would for a normal supply.

 

[Robert Turnbull]

Cool, that's what I need - how would you do that, please? Isolation test across the switch, both L and N?

test continuity on both poles. with switch open then closed.

Loss of continuity would prove the switch is working.



Not been rude.....

That should have been a fairly obvious one

 

[NickD]

That should have been a fairly obvious one

Yebbut I don't like to think thoughts like "well it's obvious" around safe isolation.

And with due respect I don't think it is that obvious because mere loss of continuity at closure doesn't prove the airgap will withstand the supply voltage. Hence my suggestion of actually IR testing rather than continuity testing. I know this may appear pedantic but I'd rather be a live pedant than an electrocuted whatever-a-smoking-corpse-that-when-alive-was-not-a-pedant-is-called.

 

[John Toomey]

Your not a real sparks till youve had a 400volt belt, all this 230volt stuffs kids play :dizzy2:

 

[NickD]

Your not a real sparks till youve had a 400volt belt, all this 230volt stuffs kids play :dizzy2:

Which reg is that? :wink5:

 

[DNS1]

Where it all gets really confusing is when you have an economy 10 supply... It kicks in for a few hours a couple of times during the day...

 

[John Toomey]

Which reg is that? :wink5:

its in AMD 2 2013 BS7671:2008 lol

 

[Robert Turnbull]

Yebbut I don't like to think thoughts like "well it's obvious" around safe isolation.

And with due respect I don't think it is that obvious because mere loss of continuity at closure doesn't prove the airgap will withstand the supply voltage. Hence my suggestion of actually IR testing rather than continuity testing. I know this may appear pedantic but I'd rather be a live pedant than an electrocuted whatever-a-smoking-corpse-that-when-alive-was-not-a-pedant-is-called.

An IR Test would be just as quick,

do both, would still be quicker than writing your OP.

Also if you turn all the breakers off you will have double protection whilst working and no load if it was to energise, so it wouldn't hurt to much anyway

 

[John Toomey]

- pulling the cutout fuse (would you do it if you were being assessed though?)

tut tut tut
1) do you carry approved seals to reseal the cut out?
2) under your risk management what do you do with the live side which you could insert a BS finger?
3) have you not read the 17th edition OSG which states that the cutout fuse is not to be removed by electricians and only by a supplier?

Now if you are really worried about the failure of the main switch carry out your usual procedure for proving its dead, you know live source, dead source, live source. Then when you are happy IR test both poles with the isolator open and closed at 500volt or 1000 volt if you really want to.
Incidentally why do you want to do this? what are you doing to the board?

If you still have problems ask a grown up to help and do remember side cutters can be sharp!:daisy:

 

[Robert Turnbull]

Ring the DNO and wait for them to fit a isolator.

which can then be turned off

don't megger that because it will be live, unless you pull the fuse to check it

 

[chrish_1977]

I was testing an E7 system a few months ago and then at 3pm, just as I was finishing, the timer switched it on. Thankfully I didn't have my fingers in the board at the time. lol

I had exactly the same thing, all packed up and noticed the neons were on on the spurs for the storage heaters, spoke to the owner and she said its a kind of boost in the afternoon, nice if her to let me know.ad I was changing the off peak board

 

[John Toomey]

Ring the DNO and wait for them to fit a isolator.

which can then be turned off

don't megger that because it will be live, unless you pull the fuse to check it

But how will he know that isolator is operating correctly?
Modern Insulation Resistance Testers will not work on a live circuit. Whats all this talk of pulling the fuse, nobody illegally does that.. do they? lol

 

[John Toomey]

I had exactly the same thing, all packed up and noticed the neons were on on the spurs for the storage heaters, spoke to the owner and she said its a kind of boost in the afternoon, nice if her to let me know.ad I was changing the off peak board

Thats why im packed up and gone by 2.30! :wink5:

 

[Robert Turnbull]

I had exactly the same thing, all packed up and noticed the neons were on on the spurs for the storage heaters, spoke to the owner and she said its a kind of boost in the afternoon, nice if her to let me know.ad I was changing the off peak board

Thats why im packed up and gone by 2.30! :wink5:

That's the best way to do a fast board change when you know it'll go live any minute.

 

[HandySparks]

Whats all this talk of pulling the fuse, nobody illegally does that.. do they? lol

Yes, I pull the fuse, but not illegal. SSE area. They'll give you some temporary seals and you just e-mail them to say where you've used them. Great system.

 

[John Toomey]

Thats a great system, we dont have that system. So touching their equipment is still technically still an offence. hopefully it will all change soon! I found one guy who used to use to stick a bit of 1mm through the meter or cutout twist it up and solder it...nice

 

[John Toomey]

Yes, I pull the fuse, but not illegal. SSE area. They'll give you some temporary seals and you just e-mail them to say where you've used them. Great system.

Thats a great system, we dont have that system. So touching their equipment is still technically still an offence. hopefully it will all change soon! I found one guy who used to use to stick a bit of 1mm through the meter or cutout twist it up and solder it...nice

 

[NickD]

tut tut tut
1) do you carry approved seals to reseal the cut out?
2) under your risk management what do you do with the live side which you could insert a BS finger?
3) have you not read the 17th edition OSG which states that the cutout fuse is not to be removed by electricians and only by a supplier?

Now if you are really worried about the failure of the main switch carry out your usual procedure for proving its dead, you know live source, dead source, live source. Then when you are happy IR test both poles with the isolator open and closed at 500volt or 1000 volt if you really want to.
Incidentally why do you want to do this? what are you doing to the board?

imhotep imhotop imhotep
1) No. Seals are American. I bring the SBS.
2) Lock the meter cupboard and label across the lock ELECTRICIAN WORKING - DO NOT OPEN
3) Yes <waves 2382>, but we all know Hans Christian Andersen was the committee member responsible for that clause.

IR test @ 500Vdc both sides of switch is I think enough to keep me happy. By the way, for those who say you can't, it's live - the whole point is the supply's not live. If it was live I wouldn't need to bother.

Adding a radial circuit for a dehumidifier for my NAPIT assessment.

Side cutters can be sharp? Oh. That's where I've been going wrong then. Lovely lovely Aldi tools.

 

[ian.settle1]

All I can say is if you have to ask questions like this then you are NOT competent to do the job and should be given to someone who knows what theer doing.

 

[NickD]

All I can say is if you have to ask questions like this then you are NOT competent to do the job and should be given to someone who knows what theer doing.

Jolly good. Which question(s) are you talking about exactly, by the way? Based on responses (no offence intended to those who have constructively contributed), it looks like many of the people who know what they're doing would just safe isolate and prove dead at the load side of the switch, when in fact if the supply is unenergised this alone proves nothing.

 

[John Toomey]

imhotep imhotop imhotep
1) No. Seals are American. I bring the SBS.
2) Lock the meter cupboard and label across the lock ELECTRICIAN WORKING - DO NOT OPEN
3) Yes <waves 2382>, but we all know Hans Christian Andersen was the committee member responsible for that clause.

IR test @ 500Vdc both sides of switch is I think enough to keep me happy. By the way, for those who say you can't, it's live - the whole point is the supply's not live. If it was live I wouldn't need to bother.

Adding a radial circuit for a dehumidifier for my NAPIT assessment.

Side cutters can be sharp? Oh. That's where I've been going wrong then. Lovely lovely Aldi tools.

hahaha superb! I look a good sense of humour, unlike some i could mention

 

[Richard]

Isn't the answer to this thread - a proving unit?

 

[NickD]

Isn't the answer to this thread - a proving unit?

Or....a shrubbery!!!!

I have a proving unit. If you mean use it to prove the voltage indicator, no it's not the answer as far as I can see (but see below). Please feel free to correct me on this, maybe I've misunderstood you. But the issue is not in proving that the voltage indicator is working.

I get the abiding sense people are not getting what I'm saying. Let's try again :-
1. If you have a board where the supply tails are unenergised, and you switch off lock off and 'prove' dead on the load side, you haven't proved you've isolated the board from the supply. A knackered switch with a load-to-supply short on the live side would give you the same 'dead' result. So would leaving the switch closed for that matter.
2. An isolation test which cannot tell the difference between isolation and non-isolation is worthless. This is just going through the motions, as if the mere ritual of safe isolation will save you. (Ooh, came over all lyrical there. Never mind. Welsh blood. Sorry.)
3. If the means of energising the tails is not under your control (for example Economy 7 teleswitch) and you have not really proved isolation, you are working at unreasonable risk. You might die or, even worse, breach the Elec @ Work Regs 1989.

Best solution to date in my personal (inexperienced, incompetent, clearly unsafe to practice and probably with questionable personal hygiene to boot) opinion is safe isolate and 'prove' dead, then check if the supply is itself dead. If it is but could become live (e.g. Economy 7), then IR test at 250V-then-500V across both sides of the open switch* to prove isolation. Neither side should be live (tails are currently unenergised) so IR test instrument should not complain. (Testing on continuity range only shows that at 24Vdc the open contacts provide >2000 ohms resistance, on my MFT anyway - my lust for life much prefers to know it is >1000 Mohms at 500Vdc.) I AM MAKING THIS UP FROM FIRST PRINCIPLES. IT IS NOT LAID-DOWN BEST PRACTICE. DO NOT TAKE THIS AS GOOD PRACTICE JUST BECAUSE YOU READ IT HERE.

The only way I can think that a proving unit helps is (NOTE TO ANYONE READING - HERE FOLLOWS REALLY STUPID IDEA - DO NOT DO) if you rig it up to apply the proving voltage across the supply side of the switch and then check the load side is dead. On any proving units I've ever seen, the arrangement would have to be seriously Heath Robinson - I wouldn't go there. Might be a good way to blow up your proving unit if the supply gets energised while doing it.

Any of you experienced guys out there care to shout out if you have ever come across a main switch which does not actually isolate on one or both poles, just to show me I'm not in cloud cuckoo land here?

(*Worth bearing in mind that, assuming the supply neutral tail is connected to earth potential, the IR test on the neutral side of the switch will have the effect of applying the test voltage E-N within the board, and so potentially E-L as well through any loads not disconnected.)

 

[Robert Turnbull]

Does the neutral go though the teleswitch?

if not it has potential for voltage.

do a voltage check before u megger it

 

[NickD]

Does the neutral go though the teleswitch? if not it has potential for voltage. do a voltage check before u megger it

When I said check the supply side for live I meant L-E, L-N, E-N. Sorry, probably should have made that clear.

 

[Dave 85]

wtf is this sh**e ?
why cant you just turn off the main sw ?
it wont matter if the teleswitch is energised or not.
and as for pulling out tails and sticking in connector blocks ?? get a grip or just pack in electricals before you have an accident..

Once again you have well and truly hit the proverbial nail on the head Biff.
Your ability to always say what I seem to be thinking never ceases to amaze me!
"How do I prove a dead supply is dead"....what will they think of next...

 

[NickD]

"How do I prove a dead supply is dead"

And the Oscar for Best Performance In The Role Of Someone Not Actually Understanding The Question goes to...

(Although you may get a nod in the Deliberately Just Trying To Wind Me Up category too.)

It comes down to: how do you prove the main switch has done its job, if the supply to it is dead anyway at the time?

 

[Knobhead]

If in doubt connect to earth. Works for the LV side of a distribution transformer, just scale it down a bit.

 

[NickD]

If in doubt connect to earth. Works for the LV side of a distribution transformer, just scale it down a bit.

I suppose risking blowing the cutout fuse is better than risking blowing your mind.

 

[Stroppy]

Here's what I would do:

check the times that the eco7 will be on or on the boost period, and work when it will be well in the "off" period

isolate it with the switch, and if it seems to switch normally (doesn't feel 'crunchy' and makes a positive movement and clicks to off) trust that it has disconnected as it should do. (Come to think of it can't you take the top off this isolator and prove its operation with a continuity tester??)

if you're still terrified that it may energise unexpectedly, work as if it is live - ie use only insulated tools, safety spectacles (!), don't touch the shiny bits etc. Maybe prop your volt stick on the Line conductor so if it suddenly comes live it will beep at you.

 

[TaffyDuck]

4 pages on how to use a continuity tester. Will wonders never cease? What`s next, which end to I hold a screwdriver? or perhaps why does it hurt when I attach croc clips to my testicles? :45::45:

 

[Dave 85]

And the Oscar for Best Performance In The Role Of Someone Not Actually Understanding The Question goes to...

(Although you may get a nod in the Deliberately Just Trying To Wind Me Up category too.)

It comes down to: how do you prove the main switch has done its job, if the supply to it is dead anyway at the time?

If having isolated a dead ECO 7 board, tested for voltage and found none, tested continuity across the main switch in the open position and found none (which is surely obvious to anyone who has even the most basic understanding of electricity) you are STILL scared to work on said supply, then Im afraid you are very much in the wrong game my friend.

 

[bigbaddave]

Yebbut I don't like to think thoughts like "well it's obvious" around safe isolation.

And with due respect I don't think it is that obvious because mere loss of continuity at closure doesn't prove the airgap will withstand the supply voltage. Hence my suggestion of actually IR testing rather than continuity testing. I know this may appear pedantic but I'd rather be a live pedant than an electrocuted whatever-a-smoking-corpse-that-when-alive-was-not-a-pedant-is-called.

Its a frigging continnuuity test bud... When is your homework due in bud?

 

[Rampantchilli]

You could just do the work at night, that way you will be sure the supply is on, so when you isolate you can carry out your 'normal' safe isolation and get the correct results.

btw, E7 is on for 7hours overnight, e10 doesn't exist, it commonly know as d rate or d10 and depending on which company put it in historically, it usually still does 7 hours over night, and the other 3 hours are afternoon boost, there's also a 12 hour rate version available, with 3 'off peak' periods, but that will just blow your mind if your scared of e7 lol