earth connecion for sub main

[terry451]

hi
Customer has had meter installed outside house in external box10 meters from consumer unit, cu is in kitchen at back of house.
Soooo need to install a consumer unit 10m from the servicehead/meter.
Plan to run tails from meter into house and connect to 100a isolator, then use 25mm swa from isolator back outside down side of house to kitchen where the consumer unit is fitted. ok so far,
Qustions are, is 2 core swa and use armour as earth sufficent, or if i use 3 core how do i terminate the 25mm earth on the consumer unit [and isolator end]
welcome sugestions.

 

[SirKit Breaker]

You will have to fit a switchfuse no more than 3meters from supplyhead to protect cutout fuse in the event your SWA gets damaged fit a 60 or 80a one, and drop your swa to 16mm 3 core, it will be a lot cheaper and easier to do, problem solved

Cheers..............Howard

 

[terry451]

Yep thats what i said tails to isolator [switchfuse] then to swa to new consumer unit in kitchen distance approx 10 m
,
This place also needs power to outbiulding from the consumer unit in kitchen hence 100 amp requirment As 16mm 2 core swa [xlpe] is on limit of 100 amp rating Im upgrading cable to 25mm swa.
comes back to question is 2 core using swa as earth sufficent or if i use 25mm 3 core how do i terminate a 25mm earth in a consumer unit. ? and on the isolator.[switch fuse]

 

[Amp David]

Why would there be a problem with using the armour for an earth, it would be if you had a tns supply. Only 16mm required then for your earth at CU.

Thats how I see it anyway.

 

[SirKit Breaker]

Yep thats what i said tails to isolator [switchfuse] then to swa to new consumer unit in kitchen distance approx 10 m
,
This place also needs power to outbiulding from the consumer unit in kitchen hence 100 amp requirment As 16mm 2 core swa [xlpe] is on limit of 100 amp rating Im upgrading cable to 25mm swa.
comes back to question is 2 core using swa as earth sufficent or if i use 25mm 3 core how do i terminate a 25mm earth in a consumer unit. ? and on the isolator.[switch fuse]

The only way i can see to terminate 25mm earth would be by using an earth block external to the consumer unit. I dont think you can get a 100a switchfuse because if you could it would be rated at or above the service fuse and so would be pointless as this is supposed to blow to protect the service fuse.

A 100a DP isolator is not a switchfuse.

Cheers..............Howard

 

[terry451]

For example Wylex 100A Switch fuse in metal, look it up. complies with isolator and fuse requirments, plenty of others out there.

Service head HRC BS1361 fuse has diffrent limits to other fuse so no problem

Not sure about terminating swa external to consumer unit as possible breach of regs. waiting for ruling from Governing body.

so back to question
can anybody suggest a method of reduceing 25 mm cable to fit 16mm terminal in consumer unit?

 

[Guest123]

Pin lugs.

25mm Copper Pin Terminal

 

[The Truth]

Why would there be a problem with using the armour for an earth, it would be if you had a tns supply. Only 16mm required then for your earth at CU.

Thats how I see it anyway.

steady boys...

remember that if its a PME TN-C-S supply ONLY COPPER EARTH CONDUCTORS ARE PERMTTED. these are part of the PME requirements and not in the regs book. So steel armor cant be used to as earth conductor in a sub main.

hi
Customer has had meter installed outside house in external box10 meters from consumer unit, cu is in kitchen at back of house.
Soooo need to install a consumer unit 10m from the servicehead/meter.
Plan to run tails from meter into house and connect to 100a isolator, then use 25mm swa from isolator back outside down side of house to kitchen where the consumer unit is fitted. ok so far,
Qustions are, is 2 core swa and use armour as earth sufficent, or if i use 3 core how do i terminate the 25mm earth on the consumer unit [and isolator end]
welcome sugestions.

just use 16mm 3 core SWA on an 80amp sw/fuse

remember with diversity that unless this is a major house with electric, shower, under floor heating etc your not going to hit the 80 amp mark

if your sure you need the full 100amps which is unlikely then use a 2 core 25mm SWA with separate 16mm earth run along side it.

there is no regulation stating that you cant terminate the SWA outside the consumer unit. as mentioned you could use a metal enclosure, terminate the CPC into an earth block and link betwen the earth block and consumer unit in 16mm.

 

[Spudnik]

If there is no requirement for RCD protection of the sub main (installation method) then why not use 25mm split con.

Gets over all the probs then.

 

[marksparky]

hello joe would i be wrong in saying that if using swa if u go bigger than 10mm the sheath is not deemed as an acceptable earth so you wud therefore need to use 3core or pull a seperate eath along wit it?

 

[terry451]

thanks guys but as i said extra needed for outbuilding so back to 25mm.
New service head being fited and round this way most are tncs [pme]hence requirment for 3 core swa.

Now getting advice may not need switch/fuse just isolator,cable is already covered by service head fuse. so isolator takes 25mm live's eth fed back through to service head

eitherway need to find way of connecting or reducing 25mm cable. pin connectors look intersting
T

 

[Spudnik]

You will need a switched fuse if the CU is further than 3 meters from the intake.

 

[pushrod]

You will need a switched fuse if the CU is further than 3 meters from the intake.

That's what we are being taught.

 

[terry451]

makes sense to switch fuse and i would be happier in myself doing it that way.

brain wave ....what if i take the 25mm earth back out the consumer unit and terminate on a henly block , either in or out of its insulator but fixed to the backing board next to the consumer unit, taking a 16mm back into the consumer unit, i could also run earth to banjo of swa, the idea is to use the henly block as an earth bar. Connection holes are good for 25 or 16mm cable maybe even 10mm for other bonding.
This avoids exposing inner insulation of cables of swa outside the consumer unit [thats a no no ] and avoids lots of joints.

Could do same at meter end with switch/fuse to service head.

see any problems ?

T

 

[The Truth]

just use 25mm 2 core SWA and run a separate 16mm earth!!

or

use an Eaton metal clad single phase dist. board who earth terminal will take 25. or any commercial metal clad single phase dist board. if your using big boy cable you have to wire it like the big boys otherwise you just wasting loads of time fannying around like a domestic sparky would