Isolator switch
- Thread starter Digger
- Start date
Help Support Talk Electrician Forum:
just a guess, but perhaps the isolator could be used for isolating?
- Joined
- Mar 28, 2008
- Messages
- 14,320
- Reaction score
- 967
Most often when the tails are longer than 5m.
some DNO's specify this..
its not actually a reg...
Personally anywhere that the CU is not within spitting distance of the main cutout fuse tis best to have some form of additional isolation.
Also remember some isolators also have an overload protection device built into them as well..
So tis isolate and fuse the tails as well.
In a real nice perfect world where money is no obstacle it would be nice to have an isolator on all installations..
make it super easy if you need to change a CU or split the tails...
Oh by the way...
Welcome...
Just make sure you keep posting now you have started.
:^OGuinness
some DNO's specify this..
its not actually a reg...
Personally anywhere that the CU is not within spitting distance of the main cutout fuse tis best to have some form of additional isolation.
Also remember some isolators also have an overload protection device built into them as well..
So tis isolate and fuse the tails as well.
In a real nice perfect world where money is no obstacle it would be nice to have an isolator on all installations..
make it super easy if you need to change a CU or split the tails...
Oh by the way...
Welcome...
Just make sure you keep posting now you have started.
:^OGuinness
Sorry Special location, some of that is wrong. An isolator is a switch & has no overload protection (ie, fuse).
If the distribution board is any distance away from the supply origin (normally more than 3 m) then a switch fuse has to be fitted.
Most new installs now have an isolator, which is fitted soley so you can work on the consumer unit safely without having to break a DNO seal and remove the main fuse (which is not allowed anyhow)
If the distribution board is any distance away from the supply origin (normally more than 3 m) then a switch fuse has to be fitted.
Most new installs now have an isolator, which is fitted soley so you can work on the consumer unit safely without having to break a DNO seal and remove the main fuse (which is not allowed anyhow)
- Joined
- Mar 28, 2008
- Messages
- 14,320
- Reaction score
- 967
I stand corrected by sir Slips of the Shod lands...
:Salute
I know what I meant
I had assumed the op may have been referring to both an isolator and/or a switch fuse by the same generic name...
As you say the common fuse+switch is "A switch fuse"
such as..
http://www.alertelectrical.com/prod/842/click-80a-double-pole-switchfuse-100a-max
which by its very nature.. can still Isolate the supply from getting to the CU....
BTW..
They don't fit isolators round here yet (unless installing spark puts one in!)
5m / 3m whats a couple of 'm' between friends... :Salute
I think between us we have covered the bases to answer the ops question!
:Salute :x
- Joined
- Mar 28, 2008
- Messages
- 14,320
- Reaction score
- 967
Indeed!
safedepth
Well-known member
First of all sorry to drag this thread back up.
Slipshod,
Is this a reg or a "like to have" from some DNO's?
The reason I ask is I am frantically looking for it in the BRB now. I'm pricing for a job which involves moving the service head. It will eventually leave it some 15m from the nearest CU, (there will be 2 in the end). If I do put a switched fuse in, where is the difference between my fuse and the DNO's? They would after all both be the same rating and quite possibly the same type.
Cheers.
Incidentally, it might say Slipshod but you can all chip in of course!
ray
your wiring must comply with regs from the meter onwards. that includes overload/fault protection to tails. so a fuse is required. however, DNO allow you to use their fuse as this protection, providing its less than a set distance
safedepth
Well-known member
[quote name='Andy
sparkytim
Well-known member
- Joined
- Mar 14, 2010
- Messages
- 1,809
- Reaction score
- 1
The isolator between the Meter and Consumer Unit came into use on New housing developments to enable connection of the Supply and fitting of the Meter to be completed PRIOR to completion of the internal installation. Contractors were then allowed to "self connect" safely to the outgoing terminals of the 100 Amp double pole isolation switch and a PME earth connection point pre fitted.
Manator
©Honorary Essex Boy™
safedepth, as with all regulation some will and do interperate differently. If you look through the regulations about isolation there are clear indications as to why isolation is provided and when it should be used. Again we often have a bleed over of regulations some taking precedent over the others.
I have had a few drinks tonight and I am not of clear thought, so what I say is from memory only, I do know that any length over 3m should be isolated at or near the in comming supply, if this is a building regulation or a DNO imposed regulation I can not remember, but from a BS7671 point of veiw I can see a requirement under isolation for any single point of use ( consumer unit) , in this case, will require safe isolation, some DNO's now fix this as standard, some do not.
As with all regulation, the best aproach to any works is to follow the best practice guides, its the no nonsense, does what it says on the tin, approach to all electrical installations.
I have had a few drinks tonight and I am not of clear thought, so what I say is from memory only, I do know that any length over 3m should be isolated at or near the in comming supply, if this is a building regulation or a DNO imposed regulation I can not remember, but from a BS7671 point of veiw I can see a requirement under isolation for any single point of use ( consumer unit) , in this case, will require safe isolation, some DNO's now fix this as standard, some do not.
As with all regulation, the best aproach to any works is to follow the best practice guides, its the no nonsense, does what it says on the tin, approach to all electrical installations.
safedepth
Well-known member
Thanks. I'm into a bottle of red myself now but can see your point. I'm going to incorporate a switched fuse to cover the eventualities.
Cheers sparky. It wasn't so much the isolator but the fuse I was querying. For what it's worth I think a switch should always be incorporated between the DNO fuse and cu. These cu's will be 15 m from the head.
gordy,
There is no requirement for isolation every 3m, the 3m thing comes from most DNO's only allowing 3m max of tails to be protected by their fuse.
Any more than this (DNO requirements notwithstanding) requires a fused isolator aka KMF to protect the tails, even if the fuse is identical to the DNO device directly upstream.
It should be on the DNO website or available from them FOC, under ESQCR requirements.
As I have said again numerous times we are lucky around here we have a good DNO.
There is no requirement for isolation every 3m, the 3m thing comes from most DNO's only allowing 3m max of tails to be protected by their fuse.
Any more than this (DNO requirements notwithstanding) requires a fused isolator aka KMF to protect the tails, even if the fuse is identical to the DNO device directly upstream.
It should be on the DNO website or available from them FOC, under ESQCR requirements.
As I have said again numerous times we are lucky around here we have a good DNO.
jameseye12
Well-known member
- Joined
- Sep 20, 2010
- Messages
- 261
- Reaction score
- 0
Would an isolator also be fitted if there is more than one CU, so that there is one point of isolation for the whole house?
jameseye,
I feel that this is good practice, but it seems that it is not considered essential to comply with 7671
I feel that this is good practice, but it seems that it is not considered essential to comply with 7671
In that instance you'd just use a TP&N isolator.... not a problem at all
