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Baddegg

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I need to run power from a basement to a shed, approx 30 mtrs, customer already has 40 mtrs of swa on site, lights couple of sockets and electric gates to be powered from the shed, normally I install an isolator as a single point of isolation an them split the incoming through a Henley and then to a sp&n unit....but I can only find units that come with 60/80 and 100a fuses.....tlc are saying they don’t do 40/45a bs1361 to go in the units?.....are these available or would you just install a small garage unit 100a main switch with 40/45a mcb as protection for the swa.....adiabatic permitting for the 6mm obviously.......
 
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Baddegg

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Thanks @wheeto, that was my first idea but when TLC said they don’t do them it got me wondering...
 

Gavin John Hyde

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Denmans and rexel stores will have the fuses available on 2 day order if not in stock. Failing that CEF will almost certainly have them for next day delivery
 

Baddegg

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Thanks chaps.....out of interest what’s the preferred method for others?.....sp&n I fused isolator or the mcb route?
 

davesparks

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As far as I know 45A BS1361 fuse won't fit in a 60A bs1361 holder. They come in a range of different sizes, the 60,80 and 100A are all the same size whereas, as far as I know, the 45,32,20,16,10 and 6A get increasingly smaller.
In this situation the wylex standard range 1 way CU/switchfuse used to be perfect for the job but I don't think you can get them anymore.

You could use a switchfuse which uses BS88 bolted fuses, the full range of fuses uses the same fixing centres.
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Thanks chaps.....out of interest what’s the preferred method for others?.....sp&n I fused isolator or the mcb route?
Switchfuse wherever possible
 

Baddegg

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As far as I know 45A BS1361 fuse won't fit in a 60A bs1361 holder. They come in a range of different sizes, the 60,80 and 100A are all the same size whereas, as far as I know, the 45,32,20,16,10 and 6A get increasingly smaller.
In this situation the wylex standard range 1 way CU/switchfuse used to be perfect for the job but I don't think you can get them anymore.

You could use a switchfuse which uses BS88 bolted fuses, the full range of fuses uses the same fixing centres.
Thanks Dave appreciate that 😁
 

davesparks

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Found this via Google, it illustrates it quite well.
The two largest sizes are available as 60,80,and 100A the larger size normally being used in cutouts up to 100A and the smaller usually in switchfuses (though either could be used for either purpose)

bs1361fuses.800.jpg
 

telectrix

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try here. the dreaded ebay:
 

happysteve

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What's max demand (of the subboard, after diversity)? If 30A or 32A will do, how about a fuse carrier, with a standard little "garage board" (with 63/80/100A main switch)? Hager, for example, make them for 30A BS1361 (LB118) or 32A BS88 (LS201).
 

Baddegg

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Thanks Steve at the moment max after diversity is about 23a calculated but probably no where near realistically....led lights inside and garden plus electric gates motor, he wants them all the circuits on they own separate single rcbos (he’s paying) and 16a radial to charge a drill occasionally.I’d like to future proof best I can around the 6mm swa..
 
The likes of CEF have a range of switch fuses, etc. The data sheet for the Eaton 800KMF, for example, says you can fit fuses from 45-80A, lower limit presumably the limit of interchangeable fuse sizes?

Unfortunately the Schneider "Electrical Calculations Tool" is still down for maintenance, but I found an Eaton document "Discrimination and Back-up tables" TD01400002U (dated April 2013) with some tables. Don't know the sort of MCBs you have planned but at a guess from this doc:
  • 6A MCB/RCBO (say lights, maybe the gate?) is OK to 2kA fault current
  • 20A MCB/RCBO (for sockets) is OK to 1.3kA fault current.
I don't think you will see more than 1kA PFC at the end of the cable anyway!
 

Baddegg

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Thanks @pc1966, the circuits after the sub db will all be protected by individual rcbos (customer request) which on paper skews any diversity calc as realistically I could run the kit from one 20a rcbo and fuse down accordingly, the customer is concerned for nuisance trips, my question is more protection for the swa from the DNO incomers upto the shed db 😁
 
Looks like the Lawson ME series of fuses might be the right size for that Eaton/MEM fuse-switch so you can also get 32A and 40A if you need less than 45A, but 32A is unlikely to be coordinated in any sane way with the breaker for the sockets!
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Thanks @pc1966, the circuits after the sub db will all be protected by individual rcbos (customer request) which on paper skews any diversity calc as realistically I could run the kit from one 20a rcbo and fuse down accordingly, the customer is concerned for nuisance trips, my question is more protection for the swa from the DNO incomers upto the shed db 😁
I missed your earlier post about the 16A RCBO, etc, that makes it a bit easier.

Yes, always best to put circuits on separate RCBO and you can be thankful the customer understands is willing to pay for the increased reliability!
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Actually, looking at the coordination tables for 16A it is not any different to 20A, but I suspect a more accurate tool would show a difference (also that table also has no choice of B/C/D curve MCB but perhaps they are all much the same break times at 50x current).

Might be worth getting C-curve RCBO for the gate even if its only a 250W motor or whatever.
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One last comment: if the customer is concerned about reliability and you are basically installing a small CU in the shed then you might want to suggest fitting an SPD there as well.

It is unlikely to matter for infrequency used stuff like the lights/sockets for power tools as most folks are not doing that in lightning storms (Igor, throw the the third switch!) but if the door opener is on permanently and any faults a major inconvenience then it is something to consider.
 
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