Mulberry View Posted December 13, 2021 Share Posted December 13, 2021 Here's my kiosk, with 3-Phase installed. It's 35m from the base of the pole. The house will be a further 40m ish on from this. Our caravan needs 45mm of cable from the kiosk. British Gas are coming later this week to install the meter, I think they'll leave me with a 4-pole isolator, unless others disagree? The caravan has it's own consumer unit. So, what will be needed in addition to make the connection? Or can the isolator be connected directly to the CU? My sparky suggested 10mm SWA, presumably 2-core? I have asked him, but his replies are painfully slow! I guess I need a TT earth at the caravan. Does anything need doing with the earth terminal on the side of the 3-Phase head? Is this for me to use to earth the SWA? Link to comment Share on other sites More sharing options...
ProDave Posted December 13, 2021 Share Posted December 13, 2021 You will need a switch fuse to connect to the caravan, you need one with a metal enclosure to take the gland of the SWA cable. Terminate the SWA at the supply end but at the caravan end, insulate and do not connect the SWA (use a large plastic stuffing gland) and connect the caravan to a TT earth. Get a door on that cubicle, the meter and it's connections are not waterproof and it would not surprise me if BG refuse to connect a meter without a door on the cubicle. 3 Link to comment Share on other sites More sharing options...
Mulberry View Posted December 13, 2021 Author Share Posted December 13, 2021 1 minute ago, ProDave said: You will need a switch fuse to connect to the caravan, you need one with a metal enclosure to take the gland of the SWA cable. Terminate the SWA at the supply end but at the caravan end, insulate and do not connect the SWA (use a large plastic stuffing gland) and connect the caravan to a TT earth. Get a door on that cubicle, the meter and it's connections are not waterproof and it would not surprise me if BG refuse to connect a meter without a door on the cubicle. The kiosk has a large OSB 'door' that gets screwed in place while I sort the permanent doors. As for the connection, do I need to do anything before BG come in respect of the switch fuse or can I just figure it out based on what they leave me with? Link to comment Share on other sites More sharing options...
TonyT Posted December 13, 2021 Share Posted December 13, 2021 They should add their meter and 4pole switch. ask nicely for them to keep it nice and high in the top left corner to give you as much room for your own switch fuses in the remaining space to the right of the cutouts Link to comment Share on other sites More sharing options...
Mulberry View Posted December 20, 2021 Author Share Posted December 20, 2021 So, here's what British Gas installed... I've bought an Earth Rod with which to provide a TT earth at the Caravan. I've pulled 45m of 10mm 2-Core SWA Cable. I have a metal-clad 40a Switch Fuse Disconnector on the advice of my sparky for the sole supply of the caravan, I presume I can earth that to the PME? Assuming I'm only using one phase for now, which I anticipate will need to feed the Caravan and maybe a TBS for the house. I might want to fit a consumer unit in the Kiosk, but none of that is decided yet. Should I split the live of Phase 1 with a Henley Block, then split the Neutral with a second Henley Block? This would allow me to connect to the Switch Fuse to supply the Caravan and be able to add further loads to that phase later on if required. What size gland kits for the 10mm SWA? I've got both 20 and 25mm here. I have a plastic junction box to terminate the SWA in the caravan, isolating it from the TT earth that I'll have installed. As a reminder, my sparky is one of my mates, as I said above, he will be round at some point to check this all over, but I don't want to keep bombarding him with questions! 1 Link to comment Share on other sites More sharing options...
Randomusername Posted December 21, 2021 Share Posted December 21, 2021 (edited) You’ll need an earth rod and MET next to the cutout/meter assembly, this will only provide the earthing for the SWA cable armour up to the caravan but you shouldn’t export that earth right into the caravan itself. You will then need a separate earth rod at the caravan CU to provide the TT earth as close to it as possible. Site/temporary supplies are not usually allowed to be supplied as PME, so even if there is an earth terminal at the cutout, you shouldn’t connect up to it. You're basically making a TT earth at the meter cabinet to protect cable armour earths, and then a separate TT earth to locally earth any “temporary” structure that you have taken the supply to. Edited December 21, 2021 by Randomusername Link to comment Share on other sites More sharing options...
Randomusername Posted December 21, 2021 Share Posted December 21, 2021 (edited) EDIT: I notice that the DNO seem to have provided a connection from the service head/cutout to an earth block which you might well expect to provide a suitable MET tied to the PME. This goes against everything which I’ve been advised and have read about temporary/site supplies. THEREFORE it’s entirely possible that the DNO views this as a permanent supply due to the nature of its construction and the fact that any supplies taken from here will be classed as private sub mains? Should this be confirmed I would immediately rescind my previous assertion that the PME cannot be used to provide cable armour earthing up to (but still not including) a temporary structure. Edited December 21, 2021 by Randomusername Clarification Link to comment Share on other sites More sharing options...
ProDave Posted December 21, 2021 Share Posted December 21, 2021 32 minutes ago, Randomusername said: EDIT: I notice that the DNO seem to have provided a connection from the service head/cutout to an earth block which you might well expect to provide a suitable MET tied to the PME. This goes against everything which I’ve been advised and have read about temporary/site supplies. THEREFORE it’s entirely possible that the DNO views this as a permanent supply due to the nature of its construction and the fact that any supplies taken from here will be classed as private sub mains? Should this be confirmed I would immediately rescind my previous assertion that the PME cannot be used to provide cable armour earthing up to (but still not including) a temporary structure. Were you only expecting this to be a temporary supply and you were expecting the DNO tomove the supply head somewhere else in the future? Yes they seem to have supplied a PME earth terminal as they did with ours. You will need that if keeping the supply head there and yes it would then be a private submain to the house eventually. 1 Link to comment Share on other sites More sharing options...
Mulberry View Posted December 21, 2021 Author Share Posted December 21, 2021 4 hours ago, ProDave said: Were you only expecting this to be a temporary supply and you were expecting the DNO tomove the supply head somewhere else in the future? Yes they seem to have supplied a PME earth terminal as they did with ours. You will need that if keeping the supply head there and yes it would then be a private submain to the house eventually. No, this is permanent kiosk. It's all staying here. It's about 40 metres to the plant room for the planned house and 45 metres to the caravan (which of course is only temporary). The kiosk was positioned 35 metres from the pole, being the furthest it could go without needing a 'mains extension' and lots of extra cost apparently. I already plan a TT earth rod at the caravan, which will be within about 3 feet of the CU. As I said earlier, the SWA will be terminated via a gland to a plastic junction box just underneath the caravan CU, so as to isolate the earth. So, back to my original point, can the SWA for the caravan supply be earthed to the PME supplied at the head? In the longer term, more of a plan will be created for what will be connected there and if an earth rod is needed at the kiosk, then so be it. In fact, if I'm better to install an earth rod now, then I will, it's not as though it's very hard, is it? As a further point, the 2 meter boards that are fitted into the kiosk were supplied by UKPN. They are fire retardant chipboard and have been spaced using spacers they provided. I now want to add a further boarded area to fill the space in to the right, but my local leccy wholesaler told me that I'm not allowed to space the boards off any more and that they need to be direct onto the brickwork? Any intel on this? It'll obviously make the install a bit of a shyte show. 1 Link to comment Share on other sites More sharing options...
Randomusername Posted December 22, 2021 Share Posted December 22, 2021 (edited) 15 hours ago, Mulberry View said: So, back to my original point, can the SWA for the caravan supply be earthed to the PME supplied at the head? In the longer term, more of a plan will be created for what will be connected there and if an earth rod is needed at the kiosk, then so be it. In fact, if I'm better to install an earth rod now, then I will, it's not as though it's very hard, is it? Yes, you should definitely use the PME earth terminal in the kiosk to provide earthing for the wire armour up to the caravan. There shouldn’t be any need to put any additional earthing into the kiosk at any point, HOWEVER there are some new regs coming in which are not terribly clear, but seem to suggest that from some point in the future in new houses and structures, there will need to be an additional earthing arrangement built in - effectively putting a TT onto every new PME installation! Exactly what form that will take is still unclear… These guys probably explain it better than I can… and they’re well worth following. Very clear and informative electrical insight. Edited December 22, 2021 by Randomusername 1 Link to comment Share on other sites More sharing options...
ProDave Posted December 22, 2021 Share Posted December 22, 2021 PME is Protective Multiple Earthing. There is nothing wrong with adding to that with a local earth rod. I have once encountered a house where the Outer PNE conductor of the concentric feed cable had failed and the N / E of the whole house was floating somewhere close to L potential. It was really weird as you didn't get a shock touching e.g. the radiators or kitchen sink. This is of course the reason for not connecting PME to a caravan as standing on the ground next to it and touching the metal skin would be very bad indeed. Link to comment Share on other sites More sharing options...
Randomusername Posted December 22, 2021 Share Posted December 22, 2021 11 minutes ago, ProDave said: PME is Protective Multiple Earthing. There is nothing wrong with adding to that with a local earth rod. I do agree with you, but not everyone will… To my mind, it’s a sensible way to effectively reduce the possibility of dangerous PEN faults, in the event that the supply cable becomes damaged on its way to the property. But there’s likely to be an inference by many that the DNOs are attempting to shift the responsibility for effective earthing arrangements from themselves on to the end user. Which is quite a regression from the modern tendency to provide PME wherever available, with TT only being used where the supply arrangement was considered to be too outdated to provide a sufficiently “safe” assurance of protective earthing? Regardless of the changes it’s likely that provision of safety features such as automatic disconnection of the protective earth connection in the event of a probable PEN fault being detected will still need to be routinely fitted into electric car charging installations, going into the future… Link to comment Share on other sites More sharing options...
joth Posted December 22, 2021 Share Posted December 22, 2021 1 hour ago, ProDave said: PME is Protective Multiple Earthing. There is nothing wrong with adding to that with a local earth rod. Slightly OT, but my "new" EV Charger is an old school design that requires TT earthing rod (much to the sparky's disgruntlement). It was installed with the SWA earthed at the meter head end, but not connected to the TT earthing rod at all at the charger end. The armour and spare earth core from the SWA are isolated floating loose inside the case. This is the correct way to provide a TT earth I understand? 1 Link to comment Share on other sites More sharing options...
ProDave Posted December 22, 2021 Share Posted December 22, 2021 My "add an earth rod to your PME" was intended to apply to a situation where you are allowed to use PME. e.g. the sub main that feeds our house is PME and I have an additional earth rod at the house reinforcing the PME earth. 1 Link to comment Share on other sites More sharing options...
Randomusername Posted December 22, 2021 Share Posted December 22, 2021 (edited) 1 hour ago, joth said: Slightly OT, but my "new" EV Charger is an old school design that requires TT earthing rod (much to the sparky's disgruntlement). It was installed with the SWA earthed at the meter head end, but not connected to the TT earthing rod at all at the charger end. The armour and spare earth core from the SWA are isolated floating loose inside the case. This is the correct way to provide a TT earth I understand? Yes. The problem with earth rod protection to car charger unit supplies, as I understand it, is that the charger lead length could be such that the “local” charging unit earthing arrangement is no longer sufficiently near to the large metal object which it supplies… In this respect, a fault-based disconnection system is likely to be far more “end-user proof”… Edited December 22, 2021 by Randomusername Link to comment Share on other sites More sharing options...
epsilonGreedy Posted December 30, 2021 Share Posted December 30, 2021 Nice mortar colour between the kiosk bricks. Link to comment Share on other sites More sharing options...
SteamyTea Posted December 30, 2021 Share Posted December 30, 2021 That youtube video was more fun than watching a murder or two on Endeavour. Link to comment Share on other sites More sharing options...
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