Good morning. I'm in the process of doing a bit of work on a house I'm about to sell. A couple of 2.5mm ring circuits had been changed by a qualified electrician who incorporated crimped joints with heatshrunk sleeving. Out of curiousity, I was under the impression that mains cable had to have another layer of insulation too, to replace the external sheathing . Is this not the case?
Double insulated ring main joint?
- Thread starter Dextraneous
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Where were the joints made , ie in accessory boxes or on exposed runs?
Were insulated crimps used?
I ask the above questions, as if enclosed in accessories, such as back boxes with covers or joint boxes it will be fine, even without heatshrink being applied, also if in containment such as trunking or conduit.
If insulated crimps have been used and then heatshrunk, you will then have double insulation.
Were insulated crimps used?
I ask the above questions, as if enclosed in accessories, such as back boxes with covers or joint boxes it will be fine, even without heatshrink being applied, also if in containment such as trunking or conduit.
If insulated crimps have been used and then heatshrunk, you will then have double insulation.
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Exposed runs (under floorboards). Without taking one apart, I'm not sure whether the crimps were insulated or not, but clearly heatshrink sheathing has been used? If the crimps were insulated anyway, then the sheathing would then presumably be the second layer of insulation? If not then...er..??
I'm basing my indepth knowledge of such connectors from a 2 minute youtube clip
I'm basing my indepth knowledge of such connectors from a 2 minute youtube clip
In general I would expect any qualified electrician, who is skilled electrically/competent, to have installed your joints compliantly. Without any evidence otherwise, it would be very difficult/impossible to offer any other informed opinion.
Insulated crimps are commonly used, in these instances.
Insulated crimps are commonly used, in these instances.
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I can't find a single rule to say the outer insulation must be replaced however there are may situations where it would need replacing. With twin and earth cable one problem is the earth wire would not be protected so unless the earth was 4mm² or above then technically one would need a sleeve to protect the earth. Also there is the problem of retaining the cables strength normally some form of cable clamp is required.
The problem with using shrink crimps is their size and to get a shrink sleeve which will pass over the crimps but with shrink to the outer size is hard and it would also need epoxy resin lining to ensure it can't be pulled free so only real way is to western role the wires then tin with solder (not lead free as the flux can damage cables over time) and shrink sleeve the joints the outer being epoxy resin lined which is very time consuming the other method is to use maintenance free junction boxes which are bulky and also where many are used have a price consideration.
So the electrician has to do a risk assessment and decide if the measures are really required. Personally I hate joining cables clearly in some cases there is no option, but using epoxy resin filled boxes or lined shrink sleeve is really only used outside. Because behind walls routes are limited to the safe zones one can't simply remove a socket one has to also remove the cable so in the main one only joins cables where they have been damaged not to add or remove sockets.
The problem with using shrink crimps is their size and to get a shrink sleeve which will pass over the crimps but with shrink to the outer size is hard and it would also need epoxy resin lining to ensure it can't be pulled free so only real way is to western role the wires then tin with solder (not lead free as the flux can damage cables over time) and shrink sleeve the joints the outer being epoxy resin lined which is very time consuming the other method is to use maintenance free junction boxes which are bulky and also where many are used have a price consideration.
So the electrician has to do a risk assessment and decide if the measures are really required. Personally I hate joining cables clearly in some cases there is no option, but using epoxy resin filled boxes or lined shrink sleeve is really only used outside. Because behind walls routes are limited to the safe zones one can't simply remove a socket one has to also remove the cable so in the main one only joins cables where they have been damaged not to add or remove sockets.
Thanks fellas. I really do trust the pro that did it and was asking out of mild curiousity.
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I was always taught it is a no-no to have single insulated conductors visible outside of an enclosure, unless it is an SEB / PEB.
Me too, and you would have failed your 2391 if you had not noticed this when inspecting for non-conformities, not sure what the regs state about this.
But I don't think that is what Eric was getting at?
As others have said, you are surely aware of the regulation which requires any non-enclosed live conductors to be 'double insulated' (insulated and sheathed)? Hence, if the outer sheathing is removed or damaged, something has to be done to 'replace' it in order for the situation to be compliant.
Kind Regards, John
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I hunted for the regulation as if the poster is going to confront the electrician he must be certain it is against the rules.
I would agree that likely the outer insulation of the cable is the sheath but then we have a second problem. If contained within a wall then the degree of protection would exceed IP4X or IPXXD so one has to decide if the wall forms cable trunking. Here the regulations help "A closed enclosure normally of rectangular cross-section, of which one side is removable or hinged, used for the protection of cables and for the accommodation of other electrical equipment." I would say a wall does not fit into that.
Section 543 is more of a problem it would seem under 2.5mm² when enclosed or 4mm² when not enclosed would come in so for lighting cable it would clearly not be allowed but 543 is not easy reading and I would not really want to stick my neck out here.
As an electrical engineer I was lazy and often wrote into contracts unless written permission is obtained the current version of BS7671 must be complied with. It was a simple line which allowed me to reject poor workmanship. However so often I found what I considered as poor was not actually against the regulations we have on here many times argued about the 3 meter rule and using an earth coloured core for line. And it does need very careful reading and use of English language.
Personally I think it is wrong not to protect the whole cable but also I think if you are going to criticize another electrician then you need to quote the regulations not simply say not permitted.
The above is likely what you refer to however in my definitions it does not define sheathed looking else where we get "encase (something) in a close-fitting or protective covering. "her legs were sheathed in black stockings"" and one has to decide if the PVC which is around each wire is the sheath or if the insulation which binds the cables together is the sheath.
I would agree that likely the outer insulation of the cable is the sheath but then we have a second problem. If contained within a wall then the degree of protection would exceed IP4X or IPXXD so one has to decide if the wall forms cable trunking. Here the regulations help "A closed enclosure normally of rectangular cross-section, of which one side is removable or hinged, used for the protection of cables and for the accommodation of other electrical equipment." I would say a wall does not fit into that.
Section 543 is more of a problem it would seem under 2.5mm² when enclosed or 4mm² when not enclosed would come in so for lighting cable it would clearly not be allowed but 543 is not easy reading and I would not really want to stick my neck out here.
As an electrical engineer I was lazy and often wrote into contracts unless written permission is obtained the current version of BS7671 must be complied with. It was a simple line which allowed me to reject poor workmanship. However so often I found what I considered as poor was not actually against the regulations we have on here many times argued about the 3 meter rule and using an earth coloured core for line. And it does need very careful reading and use of English language.
Personally I think it is wrong not to protect the whole cable but also I think if you are going to criticize another electrician then you need to quote the regulations not simply say not permitted.
I suppose you are strictly correct, but I really don't think that many people have any problem in deciding what (in the context of a cable) "sheathing" means.
Again, although you are probably strictly correct, I do not think that many people would regard the masonry/plaster of a wall as constituting "conduit, ducting or trunking", would they?
Kind Regards, John
wouldn't have been that hard to stick a chocbox over the joint, but if it's crimped then heat shrunk, it's better than just being crimped
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