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I got the impression from the OP that this pipe is only buried in concrete for part of its run, it passes through concrete and the garden, but I may be wrong.
According to Doncaster cables, their split concentric is described as:

These cables are designed to be installed in air, or for burial in free draining soil conditions

So really the only issue is if they are at risk of physical damage. The presence of dampness, etc, is not a problem (other than waterlogged, I presume). If turn run under the existing house floor, or any sort of duct that is below a soil depth of realistic risk (e.g. under concrete), or are clipped out of harms way they should be fine.

Being a major step up doesn't negate the requirement to comply with the regulations.
Which regulation(s) do you believe it goes against?
 
If digging a new trench for a bigger duct (or two ducts) is feasible then you would be best to do that and get the cost and inconvenience over and done with in the one step!

Looking at your options you would not get even CAT-5 network cable and 2-core 6mm SWA down a 20mm ID pipe, but if you put in a new large duct you can do as you please.

If you are unsure of future demands then it is probably worth just going for 16mm cable instead of triming expectation to use 10mm. It will add a bit of cost at the start but probably no more than £50-100, and is far cheaper than finding you need more capacity later.

Same as the networking, your best solution would be a switch at the out building to have as many ports as you want, but running through at least 2 feed cables means you can deal with a fault on one (or even just swap to compare) without having any more work.

In duct you don't need SWA network cable (unless mice, etc, are potential visitors in an unsealed pipe) but you should use outdoor rated cable for the humidity resistance, etc.

To be honest If I'm digging and moling or drilling new holes, then I will increase the cable size to 16mm.

The network side of things would have been one outdoor rated cable if it went through the existing pipe, but since I know that isn't possible. The network cable is on the back burner unless I dig up.

If I dig up then I would be running double cables into switches at both ends most likely CAT6a or CAT7 to future proof.

It is a possibility! But they so say they need to be on the same circuit - not quite shore how much so, but it may be the magnetic trip coil of MCB/RCBO acts like a choke for the data signals.

In that case you might have to have 13A sockets for the two network thing hung off each end of the 50A-fused SWA, not terribly comfortable about that! Maybe a FCU feeding a 13A socket via a 3A fuse would be fine.

Also not clear how well SWA would carry the signal. If it were in place it would be worth a try, but depending on the decisions over cable routing if you can put in an Ethernet cable it would be far faster and more reliable.
I have one that sends the signal upstairs for the kids. This is on a different circuit to the downstairs.
People have also used them for data to their garage and not had a problem.
Worth considering then.

If the OP can live with less power then the option of getting 6mm through the pipe would work, but they need to check the VD over the whole length and to check the supplying fuse (presumably, or MCB) is going to clear OK and the 6mm section is not in danger over being damaged by that.
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20m of 6mm = 20 * 7.9 = 158 mOhm
30m of 10mm = 30 * 4.7 = 141 mOhm
Total = 0.3 Ohm, if acceptable drop 5% = 11.5V limit for current = 38A

Again, assuming 2 core SWA is used, then R1+R2 from Prysmian data sheet:
20m of 6mm = 20 * (3.08 + 7.0) = 202 mOhm
30m of 10mm = 30 * (1.83 + 6.0) = 235 mOhm
Total = 0.44 Ohm, if on TN-S then assume Zs = Ze + (R1 + R2) = 0.8 + 0.44 = 1.24 Ohm which appears to limit the fuse to no more than 32A and that is a bit worrying for selectivity.

Figures obviously should be checked by whoever is responsible for the design, and some of the above could be varied (measured Ze, try 3-core SWA, look at 16+6 options, etc) but it looks like the design is going to be limited to around half the desired power if a 6mm section like that is necessary.
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How about using split concentric if the route is physically protected by the existing pipe? 16mm is around 15 diameter so a sporting chance of getting through.

Power line adaptors are a non-starter. The lack of reliability and poor performance, makes them frustrating at best and at worst will lead to a very destructive meeting with a big mf hammer. :)

The existing pipe is MDPE water pipe so is not suitable protection for a buried cable which does not have a complete earthed metallic armour/sheath.
To be used for this purpose only the cable ducts complying with the specified standard in the regulations are allowed.
Firstly, as far as I am concerned, it is non-compliant.
I got the impression from the OP that this pipe is only buried in concrete for part of its run, it passes through concrete and the garden, but I may be wrong.

Being a major step up doesn't negate the requirement to comply with the regulations.
According to Doncaster cables, their split concentric is described as:

These cables are designed to be installed in air, or for burial in free draining soil conditions

So really the only issue is if they are at risk of physical damage. The presence of dampness, etc, is not a problem (other than waterlogged, I presume). If turn run under the existing house floor, or any sort of duct that is below a soil depth of realistic risk (e.g. under concrete), or are clipped out of harms way they should be fine.


Which regulation(s) do you believe it goes against?

Davesparks, you are correct in your assumption about the MDPE. The pipe goes into the house, and the cable then runs under the floorboards of the house a few metres (10 - 15) to the fuse board which will be updated. The breaker will be effectively a sub main to the garage at the appropritate amperage.

I don't know what split concentric is. I can live with less power if the cost of drilling is too prohibitive.

Thank you to everyone who is contributing to this question.
 
A check on cost shows it is not the cheapest option, but if cost of replacing pipe is included it might be worth considering:
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Data sheet:
[automerge]1589664832[/automerge]
Power line adaptors are a non-starter. The lack of reliability and poor performance, makes them frustrating at best and at worst will lead to a very destructive meeting with a big mf hammer. :)
That is my view of them...

I don't know what split concentric is. I can live with less power if the cost of drilling is too prohibitive.
The "split concentric" cable is what the DNO uses to power you property (most likely). If you look at the Doncaster data sheet you will see what it is like.

It quite likely possible that @davesparks is right and it is not OK due to a specific wiring regulation, but so far I don't see any justifiable reason for not using it here.
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The names comes from the construction where the centre is the live/phase conductor, and around that are concentric wires, and here they are "split" with a few earth and a few more insulated neutral. The N+insulation conductors have the same diameter as bare E, but they add up to essentially the same CAS as the live.
 
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Split con is a great cable, it is so much lighter and more flexible than the SWA, the OD is very small compared to the same conductor CSA of SWA.
 
I used powerline adaptors for years in my last house and never had any problems. They weren't even very "fast" ones, but fine for streaming TV and general internet use. The ones i had are discontinued now, superseded by faster units, and i have fibre here, so if anyone wants maybe 4 or 5 of these "old" ones, let me know!
 
The "split concentric" cable is what the DNO uses to power you property (most likely). If you look at the Doncaster data sheet you will see what it is like.

I would say it is the least likely to be used to supply a house, it is only used for new/altered TNS services which are rare these days.
Almost all new supplies will be TNCS using concentric cable, older supplies are likely to be one of a variety of paper insulated lead sheathed cables.
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According to Doncaster cables, their split concentric is described as:

These cables are designed to be installed in air, or for burial in free draining soil conditions

So really the only issue is if they are at risk of physical damage. The presence of dampness, etc, is not a problem (other than waterlogged, I presume). If turn run under the existing house floor, or any sort of duct that is below a soil depth of realistic risk (e.g. under concrete), or are clipped out of harms way they should be fine.


Which regulation(s) do you believe it goes against?

I don't doubt that is what Doncaster cables say, but then they aren't concerned with compliance with BS7671 specifically, they make the cable to its relevant standards and it is up to the specifier/installer to decide what is, or is not, compliant with the regulations they are working to.

Split concentric is suitable for direct burial from a physical point of view, and it is approved for such use by DNO's and the regulations they work to.

However in an installation complying with BS7671 then regulation 522.8.10 prevents its use for direct burial.
Under that regulation cables not protected by suitable duct or conduit must incorporate an earthed armour or metal sheath which is suitable for use as a protective conductor.
Split concentric has neither an earthed armour nor metal sheath.

If it is to be installed in ducting then the ducting must provide equivalent mechanical protection to an earthed armour or metal sheath.
BS EN 61386-24 is the standard for underground conduits.
 
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So I got in touch with a local company who do Moling and got a ballpark figure which is an eye watering £1400 - £2000 unfortunately. Add the cost of excavation and printed concrete, I'm at £8k before any electrical work is even undertaken, which is way out of budget.

That leaves me with 2 options:

Option 1: Use a 6mm SWA cable thread through the MDPE Pipe and ensure I keep the load below the maximum level.

Option 2: Keep the existing wire and add a proper consumer unit with breakers with a view to upgrade the cable in the future when budget allows.

What would be the concerns with option 2?
 
Option 1: Use a 6mm SWA cable thread through the MDPE Pipe and ensure I keep the load below the maximum level.

Do you know what the max level is?
Looking at 45 meters then its about 20A. About 4.6kW which is a lot less that your 13kW you originally said.
Your max Volt Drop is now 3%, as you have lighting.

Option 2: Keep the existing wire and add a proper consumer unit with breakers with a view to upgrade the cable in the future when budget allows.

What is the existing cable size? Have I messed this, as I can't see it?
 
Do you know what the max level is?
Looking at 45 meters then its about 20A. About 4.6kW which is a lot less that your 13kW you originally said.
Your max Volt Drop is now 3%, as you have lighting.



What is the existing cable size? Have I messed this, as I can't see it?

I'd have no choice but to keep it below the 4.6kw, which means not getting the machines I originally wanted to and going for considerably less powerful ones which is frustrating however necessary.

I have no idea what size cable the existing wire actually is, only that it is twin and earth. At best it's 4mm at worst it's 2.5mm. Installed over 20 years ago.

Essentially I'm asking is it possible for a spark to come out and simply upgrade the fuse box to a consumer unit in the garage, add a few outlets and the put in the lights. Or do the regs require them to replace the in feed because it's unlikely it's going to be sufficient size.
 
Essentially I'm asking is it possible for a spark to come out and simply upgrade the fuse box to a consumer unit in the garage, add a few outlets and the put in the lights. Or do the regs require them to replace the in feed because it's unlikely it's going to be sufficient size.

You say that the existing cable is wired back to your consumer unit.
Does it wire back to it's own breaker? (I'm presuming it is but it's not good to presume everything) If not then what circuit does it wire back to?
What size is the breaker?
Why add a consumer unit in the garage now?
I'm presuming the 'fuse box' which is in the garage, is a fused spur? (See.... presuming things again)
Why not stick with the fused spur until you upgrade the cable to the garage?
 
Option 2 is your cheapest option, but the spark would have to be satisfied the system was safe, and at the very least determine they cable type and condition before deciding if it can be safely reused, and if so what the load limit should be for it. However it might not be sufficient for your goals.

Option 1 with 6mm SWA certainly would meet the safety aspect, the issue is the total load limit you can get away with. To compare with what is already in, and based on 11.5V and 50m cable drop your limits are:

Vdrop​
11.5​
V​
Length​
50​
m​
CSA (mm^2)​
Dia (mm)​
R (mOhm/m)​
R (Ohm)​
Max on VD​
Max 4D4A (70C)​
Max I (A)​
1.5​
11.8​
31​
1.55​
7.4​
22​
7.4​
2.5​
13.2​
19​
0.95​
12.1​
29​
12.1​
4​
14​
12​
0.6​
19.2​
37​
19.2​
6​
14.4​
7.9​
0.395​
29.1​
46​
29.1​
10​
18​
4.7​
0.235​
48.9​
60​
48.9​
16​
19​
2.9​
0.145​
79.3​
78​
78.0​

Diameter is for 2 core SWA to BS5467 from Prysmian data sheet. The SWA resistance might also limit the current on breaker trip but you could get round that at modest expense with an up-front 100mA S-type RCD, or look at using 3-core SWA (slightly larger diameter) so you can disconnect in under 5s on a short.

Realistically 6mm is the max that you could expect to pull through at 20mm ID pipe, so 29A is your limit unless you play with adding a joint to 10mm or 16mm, etc.

Option 0 is using split concentric provided you can be satisfied it is sufficiently protected. If all of the buried duct section is under concrete already then it would be OK, otherwise as davesparks points out, it needs protection against damage if in the ground and anywhere it could be dug up in the future. It may be practical to put in duct to BS EN 61386-24 for those areas, but that would need to be factored in to the overall cost and the cable is not cheap, at £6.36/m for 16mm (first on-line figure I found), but is has more usable CSA per diameter than other cables (and is far better suited to outdoor use than T&E!)
 
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@pc1966 Just a reminder mate: The OP wants lighting in the garage, so the max volt drop is 3%, not 5%
 
@pc1966 Just a reminder mate: The OP wants lighting in the garage, so the max volt drop is 3%, not 5%
Ah, OK that is another thing to consider. It is a surprise it is still the 3% given most lights are now LED and not the voltage-sensitive filament lamps, but there you go!
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And by the miracle of a spread sheet:

Vdrop​
6.9​
V​
Length​
50​
m​
CSA (mm^2)​
Dia (mm)​
Res (mOhm/m)​
R (Ohm)​
Max on VD​
Max 4D4A (70C)​
Max I​
1.5​
11.8​
31​
1.55​
4.5​
22​
4.5​
2.5​
13.2​
19​
0.95​
7.3​
29​
7.3​
4​
14​
12​
0.6​
11.5​
37​
11.5​
6​
14.4​
7.9​
0.395​
17.5​
46​
17.5​
10​
18​
4.7​
0.235​
29.4​
60​
29.4​
16​
19​
2.9​
0.145​
47.6​
78​
47.6​
 
What sort of distance does the mole need to be , and could you post up some pictures of the run ?
That price was outright vicious !?
You can send me a PM if you like .
 
Option 0 is using split concentric provided you can be satisfied it is sufficiently protected.

The electrician doing the job also needs to be satisfied that the installation method is suitable.
I'm sure a lot of us would have different opinions on what would, or would not be suitable arrangements when using split concentric.
 
The electrician doing the job also needs to be satisfied that the installation method is suitable.
I'm sure a lot of us would have different opinions on what would, or would not be suitable arrangements when using split concentric.
I meant "you" in the broad sense of addressing the customer (OP) and the electrician they select who ultimately signs off on any design.

None of us have seen the site, or known more than a few descriptions posted here, so until they get someone in to look at the situation and options available all we can do is make suggestions of what might be an acceptable solution for various possible situations.
 
You say that the existing cable is wired back to your consumer unit.
Does it wire back to it's own breaker? (I'm presuming it is but it's not good to presume everything) If not then what circuit does it wire back to?
What size is the breaker?
Why add a consumer unit in the garage now?
I'm presuming the 'fuse box' which is in the garage, is a fused spur? (See.... presuming things again)
Why not stick with the fused spur until you upgrade the cable to the garage?

So the existing cable runs to a an old style consumer unit probably known as a fusebox with wired round fuses, that you would need to wrap new fuse wire round if it ever blew the black type casing. I don't know the size of the fuse breaker.

The current unit in the garage is a fuse box of some description and again I don't know the size. The reason for replacing it is one I don't believe it is safe and two I the circuits within the garage to be separated properly. I've attached images for reference.

Sticking with the current system, can lead to problems if I upgrade the lighting and start to use more equipment even if using the low power variety.

Option 2 is your cheapest option, but the spark would have to be satisfied the system was safe, and at the very least determine they cable type and condition before deciding if it can be safely reused, and if so what the load limit should be for it. However it might not be sufficient for your goals.

Option 1 with 6mm SWA certainly would meet the safety aspect, the issue is the total load limit you can get away with. To compare with what is already in, and based on 11.5V and 50m cable drop your limits are:

Vdrop​
11.5​
V​
Length​
50​
m​
CSA (mm^2)​
Dia (mm)​
R (mOhm/m)​
R (Ohm)​
Max on VD​
Max 4D4A (70C)​
Max I (A)​
1.5​
11.8​
31​
1.55​
7.4​
22​
7.4​
2.5​
13.2​
19​
0.95​
12.1​
29​
12.1​
4​
14​
12​
0.6​
19.2​
37​
19.2​
6​
14.4​
7.9​
0.395​
29.1​
46​
29.1​
10​
18​
4.7​
0.235​
48.9​
60​
48.9​
16​
19​
2.9​
0.145​
79.3​
78​
78.0​

Diameter is for 2 core SWA to BS5467 from Prysmian data sheet. The SWA resistance might also limit the current on breaker trip but you could get round that at modest expense with an up-front 100mA S-type RCD, or look at using 3-core SWA (slightly larger diameter) so you can disconnect in under 5s on a short.

Realistically 6mm is the max that you could expect to pull through at 20mm ID pipe, so 29A is your limit unless you play with adding a joint to 10mm or 16mm, etc.

Option 0 is using split concentric provided you can be satisfied it is sufficiently protected. If all of the buried duct section is under concrete already then it would be OK, otherwise as davesparks points out, it needs protection against damage if in the ground and anywhere it could be dug up in the future. It may be practical to put in duct to BS EN 61386-24 for those areas, but that would need to be factored in to the overall cost and the cable is not cheap, at £6.36/m for 16mm (first on-line figure I found), but is has more usable CSA per diameter than other cables (and is far better suited to outdoor use than T&E!)

@pc1966 Just a reminder mate: The OP wants lighting in the garage, so the max volt drop is 3%, not 5%

Ah, OK that is another thing to consider. It is a surprise it is still the 3% given most lights are now LED and not the voltage-sensitive filament lamps, but there you go!
[automerge]1589910604[/automerge]
And by the miracle of a spread sheet:

Vdrop​
6.9​
V​
Length​
50​
m​
CSA (mm^2)​
Dia (mm)​
Res (mOhm/m)​
R (Ohm)​
Max on VD​
Max 4D4A (70C)​
Max I​
1.5​
11.8​
31​
1.55​
4.5​
22​
4.5​
2.5​
13.2​
19​
0.95​
7.3​
29​
7.3​
4​
14​
12​
0.6​
11.5​
37​
11.5​
6​
14.4​
7.9​
0.395​
17.5​
46​
17.5​
10​
18​
4.7​
0.235​
29.4​
60​
29.4​
16​
19​
2.9​
0.145​
47.6​
78​
47.6​

Yeah I imagine option 2 is certainly the cheapest just incredibly limiting. Even the original plan of using 10mm was a compromise as I incorrectly believed it could be pulled through the existing pipe. At the very least the 6mm will be safer overall even if I have to compromise on the what I can use in the garage.

Those tables are very handy. Thanks.

You alluded to the VD for lighting at 3% being a surprise becaue of LED lights. I don't think I mentioned this earlier, however the lights I'm installing are going to be LED. Will that change anything?

What sort of distance does the mole need to be , and could you post up some pictures of the run ?
That price was outright vicious !?
You can send me a PM if you like .

I'm based in the North East, so it may be a trek. The company are the only ones in the area who do the work. I understand the pricing and as eye watering as it is, I can't fault them.

The mole needs to be no more than 6m long which will be under a conservatory. The area in front and behind would be clear and excavated.

I meant "you" in the broad sense of addressing the customer (OP) and the electrician they select who ultimately signs off on any design.

None of us have seen the site, or known more than a few descriptions posted here, so until they get someone in to look at the situation and options available all we can do is make suggestions of what might be an acceptable solution for various possible situations.

I appreciate everything being said here is purely hypothetical and do not take anything said here as gospel, unless it's a fact like pulling a 19mm cable through dubious 20mm pipe might be impossible. I understand the necessity to obtain professional advice from a registered sparky who has visited the site and made an assessment. I am simply arming myself with knowledge.
 

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So the existing cable runs to a an old style consumer unit probably known as a fusebox with wired round fuses, that you would need to wrap new fuse wire round if it ever blew the black type casing. I don't know the size of the fuse breaker.

The current unit in the garage is a fuse box of some description and again I don't know the size. The reason for replacing it is one I don't believe it is safe and two I the circuits within the garage to be separated properly. I've attached images for reference.
To say they are unsafe if in good condition is not quite right, they met the wiring regulations of many years ago.

But they are far less safe than a new CU would be for a couple of reasons and upgrading both is probably the single best thing you can do since a new CU offers:
  • RCD protection - a major reduction in shock risk (and to a smaller degree fire).
  • MCB trip on a lower overload and let through a lot less fault energy (at least up to the 1kA or so fault current) than fuses.
  • MCB can be reset easily by an unskilled (electrically speaking) person, and no risk of wrong fuse wire being used.
  • MCB can be used to isolate/restore a circuit without powering everything off (never ever change a rewirable fuse with the power on!).
  • It is also going to result in you house wiring being inspected/tested (done properly), either as an EICR before the CU change or as part of the deal. That can find faults that are not noticed in normal (no-fault) operations.
Also if you need any new circuits having a CU with spare slots allows better separation so faults are contained to less impact.

You alluded to the VD for lighting at 3% being a surprise because of LED lights. I don't think I mentioned this earlier, however the lights I'm installing are going to be LED. Will that change anything?
The reason for the wiring regulations having a maximum voltage drop of 3% on lighting circuits (compared to 5% on other) is to reduce the impact of load changes on the voltage, and resulting change in brightness.

Old filament lights are very sensitive to voltage, so a few percent has a noticeable effect, hence this concern. However LED lights have nowhere near the same change in brightness with voltage so they probably don't need the 3% rule.

But the regulations as they stand still say 3% for lights, and still advise on assuming 100W per light fitting when computing power use!

I appreciate everything being said here is purely hypothetical and do not take anything said here as gospel, unless it's a fact like pulling a 19mm cable through dubious 20mm pipe might be impossible. I understand the necessity to obtain professional advice from a registered sparky who has visited the site and made an assessment. I am simply arming myself with knowledge.
Some folk might think "arming yourself" sounds like it is a showdown with the electrician as many have had problems before with customers who think they know a lot more than they really do. But if you treat some of this discussion as points to go over with the sparky for ideas on how some of the issues could be solved it should be fine, and we don't know the details of your setup so none of us can do the job remotely. Whoever you do get will have to go over all of the calculations, etc, any way.

Good luck!
 
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No that is a vicious price .
Depending on the size of bore , ground type , if the pits have been prepared for us and distance to travel , we start at £250 plus vat upwards.
If you were local to Buckinghamshire your one would be £250 or £350 if we dig the pit .

I actually live near Skegness and commute each day at the moment to our yard in Buckinghamshire , my day tomorrow consists of a 7:30 am meeting in Milton Keynes then Thame then Southampton then Winchester then Lechlade then Lambourn , back to Oxford and finally home again to Lincolnshire , so you are not that far away to be honest if you wish to pm me some more Pacific information I could take a look and maybe price it for you .
 
If you can get a large enough duct put in then all your problems go away, you can put in whatever size of SWA power you want and a few networks cables to finish the job! :)

Well, maybe not total price...
 

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