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Evening everyone
I've a few questions and it would be helpful if someone could answer them but also point me in the right direction for the answers so that I can mark the places for future reference.

I've just fitted a small garage unit in a house to allow me to power 3 double sockets in the garden I know one of the sockets will power a filter for a free standing pool and possible a heater both running off of 13 amp plugs.

I allowed for 9Kw
on a 35 metre run
with approximately 5 metres buried underground
So ended up using 6mm 3 core SWA
on a 32 amp mcb

I think that I could have got away with a smaller cable but as I could not prove it because of the section that was going under the ground. I went with the bigger cable to be on the safe size,
thought it was a tight fit getting two 6mm into the socket.

This is not a cost saving exercise more a learning curve on how to properly size my cable with the information to hand.

And as a side question ferrules how many people use them all the time on stranded cables or only up to a certain size and whats the best crimping tool for ferrules.

Thanks in advance
 
How did you get your design load for the circuit?
 
9Kw seems a bit on the high side. More info?
..and ferrules are for flexible rather than stranded.
 
A quick check on the Doncaster cables calculator (yes, a bit lazy) for 9kW has 6mm for 90C cable or 10mm for 70C cable (buried in duct conditions). Going 90C is risky if you are not sure the end terminating equipment is up to those temperatures!

However, as already mentioned, 9kW seems a lot for a couple of 13A socket outlets, also it is 39A which is more than your MCB! So repeating with 32A as the load give 6mm for 70C which is now fine.

As you discovered 2*6mm is a bit much for most 13A sockets, typically they only expect up to 2*4mm for a 32A radial (or ring above 106m total length).

Depending on the distances and load distribution you could drop to 4mm at first outlet but you would have to check the voltage drop, etc, with a bit more effort in calculating (and might find it more trouble to buy two different cable types, etc).

Also already mentioned is ferrules are used for fine stranded flexible cables (such as tri-rated for control panels, or H07RN-F rubber outdoor) and not usually for the 7-stranded cables used for "fixed wiring". If you only use up to 10mm cables (probably the majority of cases) then I would go for the self-adjusting crimp as they save you having to get it in the right slot (and leaver it out if it is stuck in one too small). This is a high quality example:

But you get adequate ones off eBay for 1/10 the cost (probably less than 1/10 the operating life as well, but for light use adequate). Something like:

Again for light use one of the kits with crimp tool and a box of various ferrules is handy.
 
9Kw seems a bit on the high side. More info?
..and ferrules are for flexible rather than stranded.
Morning
what info would you like?
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How did you get your design load for the circuit?
as they only asked for 3 outside sockets with one of them running a stand above ground pool filter I went on the basis of 3Kw per socket as 6Kw per socket seemed unlikely and excessive.
if all of the cable had been above ground I could have used 4mm but as some was buried it went up to 6mm.
So I trying to find out where do I look so that I can calculate for the length of buried cable so that I might have been able to use a small cable.
If that makes sense
 
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as they only asked for 3 outside sockets with one of them running a stand above ground pool filter I went on the basis of 3Kw per socket as 6Kw per socket seemed unlikely and excessive.
You need to know what current draw the equipment has. When it comes to socket-outlets you can't assume full load current for design unless you know what will be plugged in. Also heaters may not be running all the time, going through a cycle once up to temperature.

Any load over 3KW should be on it's own circuit and preferably hard wired as most 13 amp plugs will burn out with constant use.

If this is all the circuit is going to power plus possibly an music system and possibly some LED garden lights I would base my design current on the load of the heater plus 500W for the filter and a couple of amps for the other socket-outlets.

More than likely get away with a 20 amp radial but would need to account for a 3KW fixed load on a separate circuit if required.

It would make sense to split the incoming tails and have a switch fuse feeding SWA then a suitable DB near the intended pool location for high fixed loads and socket-outlets. But would need to know the layout of the property and any suitable locations for a DB.
 
You need to know what current draw the equipment has. When it comes to socket-outlets you can't assume full load current for design unless you know what will be plugged in. Also heaters may not be running all the time, going through a cycle once up to temperature.

Any load over 3KW should be on it's own circuit and preferably hard wired as most 13 amp plugs will burn out with constant use.

If this is all the circuit is going to power plus possibly an music system and possibly some LED garden lights I would base my design current on the load of the heater plus 500W for the filter and a couple of amps for the other socket-outlets.

More than likely get away with a 20 amp radial but would need to account for a 3KW fixed load on a separate circuit if required.

It would make sense to split the incoming tails and have a switch fuse feeding SWA then a suitable DB near the intended pool location for high fixed loads and socket-outlets. But would need to know the layout of the property and any suitable locations for a DB.
Hello and thanks for your reply
the best place for the DB was in the house because of the layout of the garden hence the run.
no spare ways on existing board so fitted a garage unit at least that way outside was separated from the rest of the house.
The filter came fitted with a moulded 13amp plug
I guess may main concern was much of the cable has to be underground before it needs to be included in the calculation, because if it was all clipped direct then I could have used 4mm SWA
Ho and the other two double sockets were as you said just to feed phone chargers and a music system and maybe a portable heater.
 
It has not been mentioned as it ought to be automatic these days, but just checking it was fed from an RCD supply?
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Garage CU normally have it, but having seen some screw ups in the past I am always wary of any information not given clearly!
 
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It has not been mentioned as it ought to be automatic these days, but just checking it was fed from an RCD supply?
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Garage CU normally have it, but having seen some screw ups in the past I am always wary of any information not given clearly!
Sorry yes the unit has its own RCD
 

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