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.