Joining and extending armoured cable outdoors

[andy2306]

Hi.

I'm in the process of a garden renovation, I've knocked down the old garage and I'm moving it approx 25m further away from the house. The old garage was fed by a 4mm 3 core SWA cable, this cable sticks out of a wall where the levels drop by about 6ft, I'm wanting to extend this connect above ground and then dig the cable in underground (finished depth will be 400 mm.)

My questions are.

1. If I just continue this old feed will I encounter a voltage drop to my new garage, that will make in unusable. The current cable is approx 15M from the main consumer unit so the overall length will be approx 40m from the main consumer unit.

2. What's the best connector to join the two SWA cables above ground? I want this to be as secure as possible.

3. I was thinking of running some 2.5mm cable back in the opposite direction while I have a trench dug to run a plug socket, does this need to be armoured? Which cable will I need? I may also put in some decking lights, what supply will I need for this

In the garage I will be running 2 or 3 sockets, a couple of fluorescent tube lights and an external PIR light.

Andy

 

[PrenticeBoyofDerry]

My questions are.

1. If I just continue this old feed will I encounter a voltage drop to my new garage, that will make in unusable. The current cable is approx 15M from the main consumer unit so the overall length will be approx 40m from the main consumer unit.

You will obviously encounter a voltage drop, whether it would make it unusable would depend on your loading requirements, but it not be completely unusable just a restriction on the load demand.

2. What's the best connector to join the two SWA cables above ground? I want this to be as secure as possible.

Encapsulated resin joint

3. I was thinking of running some 2.5mm cable back in the opposite direction while I have a trench dug to run a plug socket, does this need to be armoured? Which cable will I need? I may also put in some decking lights, what supply will I need for this

SWA cable would be recommended. As far as supply to lights, you need to calculate the requirements, factor in environmental influences and design the circuit accordingly.

In the garage I will be running 2 or 3 sockets, a couple of fluorescent tube lights and an external PIR light.

To be within the parameters of voltage drop on the existing circuit, plus the extra extended distance you will be looking at a 20A device on the 4mm SWA at the CU. This will accommodate most things, but if you intend to use any equipment that will produce an inrush current, you could be struggling to avoid start up overloads.

 

[JohnW2]

To be within the parameters of voltage drop on the existing circuit, plus the extra extended distance you will be looking at a 20A device on the 4mm SWA at the CU. This will accommodate most things, but if you intend to use any equipment that will produce an inrush current, you could be struggling to avoid start up overloads.

Why not a 32A MCB, then? I realise that a full 32A would be slightly OTT in terms of voltage drop (about 6.1%, by my calcs) but, assuming the OP didn't need that much 'running' current, it would help to reduce the risk of MB trips du to inrush/startup currents.

Kind Regards, John

 

[PrenticeBoyofDerry]

My calcs came to about 28A, and as 25A devices are a rarity for majority of boards. 20A it would be!

 

[JohnW2]

My calcs came to about 28A, and as 25A devices are a rarity for majority of boards. 20A it would be!

Do you mean calculations in terms of VD (in which case I make it about 26A for 5% VD and about 16A for 3%). If so, the MCB is surely there to protect the cable, not to limit the VD, isn't it - in which case (EFLI permitting) a 32A MCB would be fine, wouldn't it?

Kind Regards, John

 

[ban-all-sheds]

My questions are.

1. If I just continue this old feed will I encounter a voltage drop to my new garage, that will make in unusable. The current cable is approx 15M from the main consumer unit so the overall length will be approx 40m from the main consumer unit.

You will obviously encounter a voltage drop, whether it would make it unusable would depend on your loading requirements, but it not be completely unusable just a restriction on the load demand.

http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html <- Specify 2-core cable and PVC, even if that is not what you are using or it will make invalid assumptions.

2. What's the best connector to join the two SWA cables above ground? I want this to be as secure as possible.

Encapsulated resin joint

Excellent type of permanent joint.

If, on the wall where you could join the cables it would be useful to have a socket, you could use a twin MK Masterseal to kill 2 birds with 1 stone.

 

[andy2306]

The resin pack came with metal butt connectors.... I can't seem to get a good crimp using them, they seem too big. The cable is 4mm2 and the pack does upto 10mm2. Is it normal to double up the cable to get a better crimp or better still is there a connector I can use without crimping at all. Seems a bit daft buying a new crimping tool to join 3 cables.

Ideally one of these plastic choc box type, with the screw connector. but obviously not sure they deal with this kind of voltage? Do they do ones suitable? Rest of it is relatively straight forward.

 

[ban-all-sheds]

The resin pack came with metal butt connectors.... I can't seem to get a good crimp using them, they seem too big.

Which implies you've tried and now they are squashed, so you're going to need new crimps anyway.

The cable is 4mm2 and the pack does upto 10mm2.

"Up to 10mm²" means "From 1.5mm² to 10mm²". Which is a heck of a range for 1 crimp to cover. What does the product spec say? I thought that joint kits where cables are crimped come without the crimps, and you provide the right size yourself.

Is it normal to double up the cable to get a better crimp or better still is there a connector I can use without crimping at all.

You could have bought a jointing kit that doesn't use crimps.

Seems a bit daft buying a new crimping tool to join 3 cables.

Which implies you have a crimping tool already.

So you have a crimper, and you need new crimps - even if you don't have the right size you can get some. Don't see what the problem is.

Ideally one of these plastic choc box type, with the screw connector. but obviously not sure they deal with this kind of voltage?

Voltage isn't a problem, but I'd be wary of using that sort of connector in something as inaccessible as a resin joint. Will the resin properly encapsulate the screws to guarantee they never come loose? Compare the screwed connector in the photo above and you'll see the difference.

 

[andy2306]

I had a crimping tool that goes upto the yellow 6 mm crimps. The ones supplied are bigger. I would presume 10mm2. I can't get any crimps delivered in time, need them in the morning. So I'm a bit stuck. I've knackered one having a go with the yellow sized crimp. But it has 3 more, so I may be able to get away with them.

I say crimps. It's basically a metal tube connector? Can you get a crimping tool for this size? Ideally from screwfix so I can get it delivered tomorrow. Screwfix don't supply 6 mm butt connectors. I've already checked.

even if I get the crimping tool. Will the crimp be sufficient for the 4mm cable?or do I need to double the cores over?

 

[mfarrow]

I find ScrewFix crimps to be less than ideal, they're often too large and you'll prbably find the 2.5mm butt crimps they do will fit!

Not usual in my experience to find a resin joint kit without a range of red/blue/yellow crimps as well as uninsulated ones for the largest size. What do the instructions say, re what is supposed to be provided?

Maplin or toolstation would be your other option.

 

[leeco]

You can buy red blue or yellow crimps from motosave of halfords.

 

[ban-all-sheds]

I've knackered one having a go with the yellow sized crimp.

Different shaped jaws for insulated & uninsulated.

But it has 3 more, so I may be able to get away with them.

No - if you don't get a good connection things could go pear-shaped.

I say crimps. It's basically a metal tube connector?

Can you get a crimping tool for this size? Ideally from screwfix so I can get it delivered tomorrow.

Would it not make more sense to buy crimps for the tool which you have?

Screwfix don't supply 6 mm butt connectors. I've already checked.

Why does it have to be Screwfix?

even if I get the crimping tool. Will the crimp be sufficient for the 4mm cable?or do I need to double the cores over?

From http://www.thecrimpcompany.com/scpr...,75%20-%2010%20mm%B2&subproducts=3423&id=3423

sizes are 0.75, 1.5, 2.5, 4, 6 & 10mm². It really does seen very odd that the people who make this jointing kit think that one size fits all.

 

[andy2306]

It would make sense to buy new crimps, but the resin joint needs to be done and in the ground this morning. Before its covered over and then 12 tonne of type 1 poured ontop. Screwfix were the only ones to deliver next day when I was looking at night.

Anyway, a ratchet crimping tool and ill call at the motor parts place and hopefully get some yellow insulated connectors as back up.

The metal connector was the one you pictured. Obviously the 10mm version, can this be used with 4mm cable or do I need to use something a bit closer in terms of size?

 

[ban-all-sheds]

It would make sense to buy new crimps, but the resin joint needs to be done and in the ground this morning. Before its covered over and then 12 tonne of type 1 poured ontop.

Errr - I thought the actual joint was going to be above ground.

I'm in the process of a garden renovation, I've knocked down the old garage and I'm moving it approx 25m further away from the house. The old garage was fed by a 4mm 3 core SWA cable, this cable sticks out of a wall where the levels drop by about 6ft, I'm wanting to extend this connect above ground and then dig the cable in underground

The metal connector was the one you pictured. Obviously the 10mm version, can this be used with 4mm cable or do I need to use something a bit closer in terms of size?

If the joint is going to be buried as you now say, then it's clearly going to end up being utterly inaccessible. I cannot urge too strongly that you do not risk using the wrong sort of tool, or oversized crimps etc. You need the connections to be spot on, and to stay that way forever.

 

[Sureitsoff?]

andy, I think you should have taken B.A.S s advice and joined the SWA using a masterseal socket and as he said join the cables AND get the required socket