Author Topic: Getting power to a shed  (Read 19087 times)

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Offline TBR

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Getting power to a shed
« on: August 07, 2014, 03:43 PM »
I have a small shed 80 ft from the house which id like to have a light and a power socket permenantly. I need 240V and probably the biggest load will be an electric heater e.g. 1-2kW

Is there a way of doing this myself safely without spending £500 on an electrician
« Last Edit: August 07, 2014, 03:47 PM by TBR »
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Offline Slartibartfass

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Re: Getting power to a shed
« Reply #1 on: August 07, 2014, 04:07 PM »
Safely doing this means you dig a trench yourself and save some money that way and let a qualified electrician do the connection. Otherwise you will potentially have no insurance if your house or shed burns down......

Offline jobsworth

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Re: Getting power to a shed
« Reply #2 on: August 07, 2014, 04:31 PM »
I would add a sub panel so you can run multiple circuits

Offline TBR

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Re: Getting power to a shed
« Reply #3 on: August 07, 2014, 04:43 PM »
Safely doing this means you dig a trench yourself and save some money that way and let a qualified electrician do the connection. Otherwise you will potentially have no insurance if your house or shed burns down......

Good idea.

Is steel conduit necessary if I use armed cable?

I can't seem to find sub panels in the UK, is it called something else? My friend said I need a consumer unit so I took a look at these> http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Crabtree_Starbreaker/index.html

My friend also said that the shed should be wired into the fuse box, not added to an existing ring. The house's fuse box is on an external wall but not sure if going under ground all the way is possible since at the house there is concrete for about 20 feet. Steel conduit along the outside wall might help get past half the concrete but I'd like to avoid that if possible.

I'd also like to run a CAT5e cable to the shed. I'll keep it well away from power lines to avoid crosstalk. Does this need to be any particular kind of cable if I want to bury it in the ground?
« Last Edit: August 07, 2014, 04:52 PM by TBR »
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Offline Davej

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Re: Getting power to a shed
« Reply #4 on: August 07, 2014, 05:33 PM »
When I did my detached garage I used 10mm cable in  scaffold pole , 18* deep , with warning tape across the top of it . My spark was impressed. I ran it through the first floor to the back of the house then down the wall and into the ground,  I wired it all myself then the electrician just tested it for me . I used a 6 way unit in the garage . 1 for 240v sockets , 1 for a 110v permanent transformer. 1 for heater. 1 for external socket .1 for lights and a spare way. .
Dave
« Last Edit: August 07, 2014, 05:37 PM by Davej »
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Offline GarryMartin

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Re: Getting power to a shed
« Reply #5 on: August 07, 2014, 05:38 PM »
Something like this would do inside a little shed no?!?

Generally, the search you're looking for for something simple like this is "Garage Consumer Unit".

This would be fine, and include a 40A RCD, and a 32A and 6A MCB (sockets and lights).

http://www.screwfix.com/p/bg-garage-kit-enclosure-5-module-ip55-40a-rcd-dual-6a-32a-mcb/68849

There are regulations associated with running power to an outbuilding, so it's probably best to get an electrician in to look at what would be required, and get him to advise what you can do, how to do it, what you can do to reduce the overall cost (dig the trench, run the cable, drill holes in walls etc.) and then what he'll charge to connect and test things for you.

Run more than one CAT5/5E/6, and enclose it in conduit so that you can replace/repair in the future if need be - something like blue MDPE water pipe would be ideal. Keep it at least 300mm away from the power cables. You can buy external quality CAT5/5E/6 but it's not absolutely necessary given you'll be running it in conduit and burying it.

Offline wow

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Re: Getting power to a shed
« Reply #6 on: August 07, 2014, 06:17 PM »
I can't speak to UK electrical codes, but I *can* make some universal observations. Some of them may not be valid depending on the size and intended use of your shed, but I'll tell you what I did for my shop (not a shed).

1. Put in a larger feed wire than you think you need or want. The price of copper (or aluminum) NOW is dirt cheap compared to wishing you had gone bigger later. I have never heard anyone say "I wish I didn't have so much power available to me!"

2. There is generally a 'sweet spot' that makes the most sense, i.e. best 'bang for the buck'. Here in the US it's either 60 or 100 Amps, so in the UK I'd guess it's around half of that since your voltage is double ours. (Same power level but half the current.)

3. If your feeder is in conduit or is otherwise shielded, drop in TWO runs of cat 6 underground cable and at least one RG6 ( or the metric equivalent [wink]) for television. If it's not metallically shielded, put some dirt over the power lines (do a little backfill first) to provide physical isolation between the power lines and the signal/low-voltage lines. I'm assuming that you can bury both in the same trench, but you'd need to verify that. (My electrical is 30-32" below the surface; low voltage stuff is ~6" above that).

4. Consider dropping in a PVC conduit (assuming that's legal and available in the UK) or a second run of whatever is legal. Pull in a nylon line to use for pulling wires later. Like your feeder line, make it bigger than you think you will need.

5. Assuming you do as much of the work as you can (trenching, laying conduit, backfilling, etc.) the cost from your electrician is not going to change much based on the size of the feeder or the size of the conduit. If you ever need to re-do it, however, the cost will be STAGGERING!

For reference, my shop is about 150 feet from my house. It has it's own 200 Amp electrical panel, as well as some direct buried video and control cables. It *also* has TWO 2" PVC conduits connecting it to the house, in which I have multiple Cat 6 and RG6 and low voltage control cables running. I feed TV signals TO the shop from the house, and security video FROM the shop to the house. I control my overhead door and HVAC over WiFi. I have heat sensing fire alarms (not smoke alarms, since I weld out there) in the shop that are connected to one in the house, so should a fire start out there I know about it right away. I am immediately alerted to motion or other activity in the shop via my alarm system over low voltage wiring. I can observe the security cameras over the internet, and - as a backup - through the buried cable which is not easy to cut or interrupt like WiFi could be.

None of this was insanely expensive, and your run is much shorter than mine. Sounds like your electrical contractor rates are MUCH higher, though?

BTW, I didn't get this all right the first time. I put in the 200 amp service initially, since I always intended to use lots of power tools in there. But I added the direct buried cables later, and the conduit even later than that. Both of those times required me to pretty much hand-dig the trench because I had other wires in the ground that prevented the use of earth-moving equipment. So learn from my mistakes and do it all now.

 [big grin]
« Last Edit: August 07, 2014, 06:23 PM by wow »
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Offline TBR

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Re: Getting power to a shed
« Reply #7 on: August 07, 2014, 06:41 PM »
Thanks for all the great advice.

I will get an electrician round for a quote and ask how I should best prepare for the connection.

How deep into the concrete is normally necessary? I have a sds drill for this so shouldn't be too much work if only 3 inches deep.

Is there anyway to prepare for the situation of getting a bigger shed in a slightly different position. It should be roughly the same place but may be 5 foot further away. Is it best to leave 5 ft slack underground?

This chap has minimised the amount of trench digging by fixing conduit to a fence But I think if fences only last only a few years is this a good idea
« Last Edit: August 07, 2014, 07:09 PM by TBR »
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Offline TBR

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Re: Getting power to a shed
« Reply #8 on: August 08, 2014, 04:24 AM »
This morning I found another hurdle to overcome. There is a drain and a manhole very close to the intended path for my buried power cable. See photo - the red line is my underground cable...



Is there a chance that I could damage the water pipes if I drill a trench near them?
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Offline jonny round boy

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Re: Getting power to a shed
« Reply #9 on: August 08, 2014, 04:50 AM »
There's always a chance, but lifting the manhole cover will soon solve that. I'd guess that the drain only runs the 12-15" into the manhole, so if you do damage that it's not a problem to replace. The key is where the outlet from the manhole runs. 5 seconds with the cover off & you'll know that. Hopefully it runs away from the side you want to run the cable.
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Offline TBR

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Re: Getting power to a shed
« Reply #10 on: August 08, 2014, 07:03 AM »
Can armoured cable be fixed to a brick wall without steel conduit? If so that would avoid digging a trench in concrete. I can't fit steel conduit because there is a down pipe in the way and only a small space behind it which might just fit a cable but not much else.
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Offline cliffp

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Re: Getting power to a shed
« Reply #11 on: August 08, 2014, 07:20 AM »
I am sure you can fix armoured cable to a brick wall.
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Offline carlb40

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Re: Getting power to a shed
« Reply #12 on: August 08, 2014, 08:10 AM »
As said uk regs state that armoured cable can be either burried (direct) or in pvc conduit. Our 4 inch soil pipe is fine. It can be clipped to a wall or sent overhead with supports. But clipped to timber fence posts is a no no.
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Offline Sparktrician

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Re: Getting power to a shed
« Reply #13 on: August 08, 2014, 08:23 AM »
I know nothing of UK regulations, but here in the Colonies, we can use LiquidTite flexible conduit both above ground and buried.  It certainly makes some things easier, plus it's a bunch of easier to fish wiring through, compared to hard conduit in most cases. 

« Last Edit: August 09, 2014, 01:57 PM by Sparktrician »
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Offline gkaiseril

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Re: Getting power to a shed
« Reply #14 on: August 09, 2014, 11:43 AM »
I would run at lest 2 conduits 3/4" each. Burry the conduits in sand and gravel, with an orange or yellow warning tape cover. The extra one could provide for more circuits or low a low voltage conduit for network or alarm systems.

 Have a cutoff panel at each end.

I would us UG wire specifically designed for in ground use and run with out splices in the ground. Metal armored cable will rust in the ground.
George Kaiser

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Offline E30Mark

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Re: Getting power to a shed
« Reply #15 on: August 09, 2014, 12:40 PM »
There are a few factors to be considered here!

All electrical installations should comply with BS7671:2008

What type of fuse-board do you already have in the house?... Does it have a spare way for another MCB? Do you have RCD protection on the existing fuse-board?

A 2kw load over 80' will produce a volt drop of around 6V with a 1.5mm2 SWA cable. Maximum cable load would be approx 16A

A 2.5mm2 SWA will have less volt drop and a max load of approx 21A

Without seeing the whole length of where you plan to run the cable it's hard to give a complete answer, but basically I'd run a 2.5mm2 SWA clipped to the house wall so you don't have to dig past the drains, and then bury it where necessary. The regs don't give an exact depth to bury the cable, but state it must be a 'suitable depth'.... rule of thumb is 18" down.

Your not allowed to clip to a fence, as it's not deemed a permanent structure, funnily enough, your allowed to leave the armoured cable laying on the surface un-buried...






Offline jobsworth

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Re: Getting power to a shed
« Reply #16 on: August 10, 2014, 06:31 AM »
When I did my detached garage I used 10mm cable in  scaffold pole , 18* deep , with warning tape across the top of it . My spark was impressed. I ran it through the first floor to the back of the house then down the wall and into the ground,  I wired it all myself then the electrician just tested it for me . I used a 6 way unit in the garage . 1 for 240v sockets , 1 for a 110v permanent transformer. 1 for heater. 1 for external socket .1 for lights and a spare way. .
Dave

Yup I believe you do call them consumer units over here.

Offline richy3333

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Re: Getting power to a shed
« Reply #17 on: August 14, 2014, 03:46 PM »
You should use a registered electrician for a number of reasons.

The existing demand in the house needs to be assessed as you might have no scope for adding additional loads. You need to asses the new load and then calculate the size of cable and voltage drop applicable. Earthing and bonding need to be considered. You also need to consider the existing main earthing type as this could have an effect on what is required - TNS/TNCS(PME)/TT etc. I'm not in England (in Scotland and our Building Standards are different) so can't say for sure but you may have a requirement to notify the local authority under building regs(LABC), plus you'll need an electrical installation certificate to prove the installation is safe. If you do the work yourself and notify LABC it will possibly cost several hundred pounds. If you use a registered spark their scheme membership will allow them to notify the job for you for a couple of pounds. Avoid sparks that are 'domestic installers'. look for someone that is an Approved Contractor or has a JIB gold card etc. Someone mentioned BS7671:2008 which are the Wiring Regulations. The current Standard is BS7671:2011 (and they're possibly going to be updated again next year).

SWA (armoured cable) can be clipped direct to the wall. Cables should not be fixed to fences and trenches should be at least 500 mm deep. There's always a way around things like protecting the cable with paving stones or possibly clipping to a 'kick board' if all else fails. If a trench needs digging, dig it yourself and save paying someone else to do it? If you use some form of conduit and run other cables in it with the supply cable you may have to consider derating factors on the supply cable.

A small consumer unit should be fitted in the shed for the shed circuits and they'll possibly need RCD/RCBO protection. The supply cable will not require RCD/RCBO protection but will need overload and short circuit protection from the house consumer unit. Proper electricians don't shop at screwed-fix but should use quality materials from a wholesaler.

Get several quotes, but a few hundred pounds to do the job right and safely is a small price to pay to avoid being killed!

Offline TBR

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Re: Getting power to a shed
« Reply #18 on: September 18, 2014, 04:55 AM »
I found a recommended electrician, but unfortunately he doesn't do any certificates. He's semi retired and used to be registered but its no longer worth him paying his membership because of the amount of work he does now. Is the certificate important?
Normal people... believe that if it ain't broke, don't fix it. Engineers believe that if it ain't broke, it doesn't have enough features yet.

Offline TBR

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Re: Getting power to a shed
« Reply #19 on: September 18, 2014, 05:04 AM »
There are a few factors to be considered here!

All electrical installations should comply with BS7671:2008

What type of fuse-board do you already have in the house?... Does it have a spare way for another MCB? Do you have RCD protection on the existing fuse-board?

A 2kw load over 80' will produce a volt drop of around 6V with a 1.5mm2 SWA cable. Maximum cable load would be approx 16A

A 2.5mm2 SWA will have less volt drop and a max load of approx 21A

Without seeing the whole length of where you plan to run the cable it's hard to give a complete answer, but basically I'd run a 2.5mm2 SWA clipped to the house wall so you don't have to dig past the drains, and then bury it where necessary. The regs don't give an exact depth to bury the cable, but state it must be a 'suitable depth'.... rule of thumb is 18" down.

Your not allowed to clip to a fence, as it's not deemed a permanent structure, funnily enough, your allowed to leave the armoured cable laying on the surface un-buried...


Yes there seems to be a spare switch on the consumer unit.
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Offline gkaiseril

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Re: Getting power to a shed
« Reply #20 on: September 18, 2014, 01:34 PM »
I found a recommended electrician, but unfortunately he doesn't do any certificates. He's semi retired and used to be registered but its no longer worth him paying his membership because of the amount of work he does now. Is the certificate important?
With building departments computerizing and power companies monitoring power consumption your chances of the work being found to be without a certificate are becoming more likely. You might not have a problem until you sell and the building inspector or buyer's house inspector find you did not get the certificate. You will then need to pay for a licensed electrician to inspect and possibly upgrade the work.

You might want to discuss this with your friend and see if he can do the work and if he has a friend that will get the required permit and inspect the work. You might not save that much.
George Kaiser

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Offline E30Mark

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Re: Getting power to a shed
« Reply #21 on: September 18, 2014, 03:58 PM »
If you were to sell the house, disconnect the wiring if it's not certified. Nowt anyone can complain about then!

There is no way on earth a power company can tell from the power consumption the condition of the installation, be it certified or not...

Offline CrazyLarry

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Re: Getting power to a shed
« Reply #22 on: September 18, 2014, 05:26 PM »
Someone mentioned BS7671:2008 which are the Wiring Regulations. The current Standard is BS7671:2011 (and they're possibly going to be updated again next year).

And they we're right.

It's BS7671:2008(2011) (the green one)

Where the (2011) refers to amendment 1 or Amd1:2011

Perhaps that's what you were thinking of?

Although we're now on Amd2 and soon to be Amd3:2015 - it's not terribly relevant unless you want to charge your g-wiz at home or in the shed! :)

L

Offline TBR

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Re: Getting power to a shed
« Reply #23 on: September 18, 2014, 06:24 PM »
If you were to sell the house, disconnect the wiring if it's not certified. Nowt anyone can complain about then!

There is no way on earth a power company can tell from the power consumption the condition of the installation, be it certified or not...

But I'm guessing that a not having a certificate might invalidate any insurance if anything should go wrong with the wiring.
Normal people... believe that if it ain't broke, don't fix it. Engineers believe that if it ain't broke, it doesn't have enough features yet.

Offline richy3333

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Re: Getting power to a shed
« Reply #24 on: September 19, 2014, 03:17 AM »
Someone mentioned BS7671:2008 which are the Wiring Regulations. The current Standard is BS7671:2011 (and they're possibly going to be updated again next year).

And they we're right.

It's BS7671:2008(2011) (the green one)

Where the (2011) refers to amendment 1 or Amd1:2011

Perhaps that's what you were thinking of?

Although we're now on Amd2 and soon to be Amd3:2015 - it's not terribly relevant unless you want to charge your g-wiz at home or in the shed! :)

L

Not really BS7671:2008 (using your definitions) is the red book and as you say after the subsequent amendments we are now on the green book. The amendments relate to more than charging electric cars.

Offline richy3333

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Re: Getting power to a shed
« Reply #25 on: September 19, 2014, 03:34 AM »
I found a recommended electrician, but unfortunately he doesn't do any certificates. He's semi retired and used to be registered but its no longer worth him paying his membership because of the amount of work he does now. Is the certificate important?

This is where the electrical industry is a nightmare. You don't have to be registered with a scheme to 'do' certificates. End of. You have to be competent to undertake electrical work. The inspection and testing once the work has been done allows the electrician to complete an Electrical Installation Certificate and prove the work is safe. Any proper spark should know that. If he doesn't have test equipment then he can't prove his work is safe. If he won't give you a certificate then that raises a number of considerations. Is this because he wants the ability to deny he ever did the work in the event it goes wrong - paper trail? Is he insured? PL and professional indemnity (he has to design the circuit(s)).

You also still need to check about LABC certification/approval. This is where scheme registration is applicable. If you need to notify to LABC and he is scheme registered he can do this for you. If he is not then you will have to contact the LABC yourself to get the work checked and signed off. Usually costs a few hundred pounds.

Offline richy3333

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Re: Getting power to a shed
« Reply #26 on: September 19, 2014, 03:35 AM »
If you were to sell the house, disconnect the wiring if it's not certified. Nowt anyone can complain about then!

There is no way on earth a power company can tell from the power consumption the condition of the installation, be it certified or not...

But I'm guessing that a not having a certificate might invalidate any insurance if anything should go wrong with the wiring.

Quite possibly, insurers will squirm out where they can.

We deducted £10K off our house purchase because the previous owner did his own wiring and couldn't prove it was safe. As it was some aspects were imminently dangerous!
« Last Edit: September 19, 2014, 03:39 AM by richy3333 »

Offline mattfc

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Re: Getting power to a shed
« Reply #27 on: September 19, 2014, 04:21 AM »

Quite possibly, insurers will squirm out where they can.

We deducted £10K off our house purchase because the previous owner did his own wiring and couldn't prove it was safe. As it was some aspects were imminently dangerous!

But I will bet it didn't cost you 10k to correct! Nice negotiating  [big grin]

Offline CrazyLarry

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Re: Getting power to a shed
« Reply #28 on: September 19, 2014, 04:50 AM »
Try the IET  http://electrical.theiet.org/wiring-regulations/
Hence BS7671:2008(2011)


SWA is the way to go, you have a spare way on a 17th ed CU, like Jonny round boy says pop the manhole cover to check the easiest path for an underground run and then decide how much will be underground v along the wall. If you're going to do the digging yourself. As stated 500mm is the minimum but there's a lot less fuss if you can bury a large pipe as a run. Direct burying SWA will involve sand above and below to prevent damage to the sheath from stones etc. Either way put warning tape about 300mm down for the entire length and take a photograph of the route for future reference.

Do have a small DB / CU placed in the shed, Schneider / MK / Hagar there are plenty of good brands. IMHO the quality of the brand / ease of installation matters most, personally I favour TLC as a supplier (service with a smile) but even Toolstation can supply a functional plastic conduit box!

A small CU with it's own RCD and 2 to 4 ways gives you one MCB for a socket or two another for lighting as well as 2 spares ways for the future.

As others have mentioned make sure your earthing is checked, with properly installed SWA there's a good likelyhood you'll be able to rely on the existing earth provision but make sure.

Do have someone who can legally issue you a cert and do make sure it's someone who actually tests what they say they do. Which applies regardless of what scheme or quals they have! This means they will have to do the cable installation / test / commisioning to sign for it. But you can still do much of the planning and preparation esp groundworks. Do overestimate your future needs a bit and build it in.

With your catV! run a separate plastic conduit make sure it's glue jointed to seal it and use gaskets / glands at covers / ends and either run 2 or 3 lengths straight away or make sure you can pull through if you need to, terminate both ends at shielded sockets and pay great care not to compromise the sheilding. One tip is to use grommets for entry holes even if the back box is plastic.

One last question: how far will you have to walk from your armchair to fill the kettle?

 

EDIT>  personal attack towards other forum member removed.

« Last Edit: September 20, 2014, 03:53 PM by SRSemenza »

Offline wow

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Re: Getting power to a shed
« Reply #29 on: September 19, 2014, 05:13 AM »
Not sure what the rules are over there, but in the U.S. your Cat5e would have to be underground rated even if it is contained in PVC / plastic pipe. It's probably a good idea even if it isn't required. The cost isn't that much more, BUT it can be a huge PITA to find it.

Underground rated Cat5e or Cat6 is easily identified over here as it has a bright orange sheath. Even a novice can identify it at a glance then.

Oh - the same is true of coax for the 'telly' (hey, I'm trying?!). It also need to be underground rated and it also has a bright orange sheath.

One other note about what we call low voltage (network) wire: Best practice dictates that it be around 12" (um...300mm) AWAY from your mains wires. This separation can be reduced a bit if it's surrounded by earth, and can be reduced even more if you use shielded network wire as suggested by CrazyLarry.

I offer my comments in hopes of helping you 'get it right the first time', based on my experience as a network guy who also wired his own home with multiple breaker panels (I think our equivalent of your CU's?) and was complimented by the electrical inspector at having 'done a better job than most of the licensed guys he sees'.

IMPORTANT - I want to be clear that do not know the regulations or code in the UK, so verify with the appropriate authority or contractor before you take anything I said as being valid for your situation, OK? I'm trying to help, and I'd feel terrible if something I suggested made it worse or harder for you...
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Offline jonny round boy

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Re: Getting power to a shed
« Reply #30 on: September 19, 2014, 12:53 PM »
Not sure what the rules are over there, but in the U.S. your Cat5e would have to be underground rated even if it is contained in PVC / plastic pipe.

Oh - the same is true of coax for the 'telly' (hey, I'm trying?!). It also need to be underground rated and it also has a bright orange sheath.

IMPORTANT - I want to be clear that do not know the regulations or code in the UK,

In the UK, there are, as far as I'm aware, zero regulations when it comes to cat-5/6, co-ax, etc. You can pretty much do what you like with it!
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Offline Brent Taylor

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Re: Getting power to a shed
« Reply #31 on: September 19, 2014, 01:33 PM »
I worked out of a site trailer with a 50 Amp hook-up that was tied to a RV style drop cord. The GC would provide the power outlet at the site. we were building schools ( 2 at once ) and were at the site for over a year. I have built Small houses (RV size)  that uses this same style hook-up. A hook-up like I am reading about in the other messages is the best way to go, get a sparky, have them do the brainy (read in stuff that can kill you) work and you do the bull work (stuff they don't want to do) and save a few pounds. The thing is if you need a temp set-up you might look at RV/ marine hook-ups. Brent

Offline richy3333

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Re: Getting power to a shed
« Reply #32 on: September 20, 2014, 10:47 AM »
Section 528 of the UK Regs deals with the proximity of wiring systems to other services.

Offline Pennywise

  • Posts: 2
Re: Getting power to a shed
« Reply #33 on: September 27, 2014, 06:42 PM »
We usually run a few lengths of this in

http://www.pipes-underground.com/cable-ducting.html

, you'd probably be looking at the 32mm stuff one for the SWA or HiTuff the other for your catV, it's smooth bore so cables glide in, and it pretty much future proofs you for any additions. Me personally I'd put a metal clad DB in the shed and do everything in high impact pvc conduit with metal clad socket outlets, or if you wanted to really push the boat out galv conduit :). Cable sizing as mentioned above needs calculation, 4mm to 6mm would be a good starting point.


Offline TBR

  • Posts: 109
Re: Getting power to a shed
« Reply #34 on: October 01, 2014, 04:02 AM »
I just started ringing around electricians yesterday. 1 chap said that it would take  one day and he would charge  £180 plus materials. Hopefully next week ill be able to get some of them to pay a visit so they can advise the best way to dig through the concrete or reroute around the house. I've ordered a catalogue from tlc so that when they are round we can build a shopping list.

 i found on youtube interesting video about how to get a pull cord through a pipe using a vacuum cleaner and some polystyrene on a hook to act as a piston. Very useful tip !
Normal people... believe that if it ain't broke, don't fix it. Engineers believe that if it ain't broke, it doesn't have enough features yet.

Offline TBR

  • Posts: 109
Re: Getting power to a shed
« Reply #35 on: October 01, 2014, 04:05 AM »
Here are some more detailed photos...
Normal people... believe that if it ain't broke, don't fix it. Engineers believe that if it ain't broke, it doesn't have enough features yet.

Offline TBR

  • Posts: 109
Re: Getting power to a shed
« Reply #36 on: October 11, 2014, 02:40 PM »
Finally, I got an electrician round last week and he's just quoted £1000 for the job. I asked for 2 security lights on the house, a light and 5 double sockets in the shed.

He looked at the concrete and i was worried that some of the underground pipes my crack, so we decided it would be best to run the armoured cable behind kitchen units, out through the back wall, under the doorstep and around the house to the other side of the garden and then down to the shed.

3 days labour at £240 per day. The rest is materials of which £140 for 50m of 6mm swa. £40 for a 2 way consumer unit.

Looking for ways to get this cost below £300.



Another recommended semi retired electrician quoted £30 an hour. But he couldn't do any certification work because he is no longer a member of necessary body. He used to be certified but nowadays he does less work and so is not worth it for him to pay his membership.
« Last Edit: October 11, 2014, 02:49 PM by TBR »
Normal people... believe that if it ain't broke, don't fix it. Engineers believe that if it ain't broke, it doesn't have enough features yet.

Offline richy3333

  • Posts: 198
Re: Getting power to a shed
« Reply #37 on: October 11, 2014, 03:00 PM »
£240 a day seems cheap to me for London, but 3 days is excessive for all that work. I'd say 2 tops. If breaking the concrete out is part of that time can you not dig the trench to save a few pounds? Else can he not use a catinery wire to save burying the cable?

£140 for 50m of 6mm doesn't sound bad

Offline TBR

  • Posts: 109
Re: Getting power to a shed
« Reply #38 on: October 11, 2014, 03:03 PM »
£240 a day seems cheap to me for London, but 3 days is excessive for all that work. I'd say 2 tops. If breaking the concrete out is part of that time can you not dig the trench to save a few pounds? Else can he not use a catinery wire to save burying the cable?

£140 for 50m of 6mm doesn't sound bad
No digging for that quote. We aggreed it might crack a pipe underground
Normal people... believe that if it ain't broke, don't fix it. Engineers believe that if it ain't broke, it doesn't have enough features yet.

Offline TBR

  • Posts: 109
Re: Getting power to a shed
« Reply #39 on: October 12, 2014, 11:50 AM »
There are a few factors to be considered here!

All electrical installations should comply with BS7671:2008

What type of fuse-board do you already have in the house?... Does it have a spare way for another MCB? Do you have RCD protection on the existing fuse-board?

A 2kw load over 80' will produce a volt drop of around 6V with a 1.5mm2 SWA cable. Maximum cable load would be approx 16A

A 2.5mm2 SWA will have less volt drop and a max load of approx 21A

Without seeing the whole length of where you plan to run the cable it's hard to give a complete answer, but basically I'd run a 2.5mm2 SWA clipped to the house wall so you don't have to dig past the drains, and then bury it where necessary. The regs don't give an exact depth to bury the cable, but state it must be a 'suitable depth'.... rule of thumb is 18" down.

Your not allowed to clip to a fence, as it's not deemed a permanent structure, funnily enough, your allowed to leave the armoured cable laying on the surface un-buried...

An electrician has quoted for 6mm2 SWA. It's almost twice the price of 2.5mm2. £110 as opposed to £60. Just wondering if there is a good reason for this?
Normal people... believe that if it ain't broke, don't fix it. Engineers believe that if it ain't broke, it doesn't have enough features yet.

Offline TBR

  • Posts: 109
Re: Getting power to a shed
« Reply #40 on: September 12, 2016, 08:41 AM »
Finally made the decision to put in the SWA cable to the shed. One of the electricians that has quoted me has recommended to install separate dual RCBO with enclosure to protect the circuit to the shed (materials required 25m tails x 2mm, 1 x Henley block and 16mm earth cable). He said that it would be best if the shed was on its own RCD because if the cable to the shed trips the RCD often then it will keep knocking out power to half the house.

Just wondering if this is really necessary.
Normal people... believe that if it ain't broke, don't fix it. Engineers believe that if it ain't broke, it doesn't have enough features yet.

Offline GarryMartin

  • Posts: 1671
Re: Getting power to a shed
« Reply #41 on: September 12, 2016, 01:31 PM »
You clearly work at the same speed as I do...  [big grin]

Assuming you mean 2m of 25mm [wink], it's actually a neat way of doing it and the way I've discussed doing mine with my electrician. As you've been told, it removes the issue of nuisance tripping of your main RCD in the house if there are issues in the external building.

I actually have a board in the house that's full of RCBOs so it didn't quite make the same difference for me, but getting the SWA to that board (on an inside wall) versus the Henley block from the main fuse entry point (on an external wall) was just much easier. It also means I can easily put in a 230V 16A socket in the garage where the entry point is too, so win win.

Factoring in voltage drop, and assuming 230V, 6mm SWA in PVC or XLPE will cope with a 7-8kW load over that 50m run.

Offline richy3333

  • Posts: 198
Re: Getting power to a shed
« Reply #42 on: October 23, 2016, 01:21 PM »
Finally made the decision to put in the SWA cable to the shed. One of the electricians that has quoted me has recommended to install separate dual RCBO with enclosure to protect the circuit to the shed (materials required 25m tails x 2mm, 1 x Henley block and 16mm earth cable). He said that it would be best if the shed was on its own RCD because if the cable to the shed trips the RCD often then it will keep knocking out power to half the house.

Just wondering if this is really necessary.

Hi.

If there is no spare capacity in your existing CU then the main tails can be split to supply 2 CU's. Tail size to the new board will be dependant on the type of earthing system you have at the property.

Re the use of RCBO's in the new board that supplies the shed - in simple terms there is no need for this if using SWA cable. An appropriately sized OCPD is all that's required. Then use an RCD or RCBOs in the board in the shed. If you use RCBOs on the supply circuit and in the shed an RCD, there will be no discrimination over which RCD/RCBO trips in the event of an Earth fault.

I assume the electrician is satisfied there are no extraneous conductive parts in the shed that require bonding?

BTW both new CU's will now need to be metal clad as of January 2016 so the ones previously discussed won't be suitable.

Also check if the work requires notification to BC as per part P of the English building Regs.

HTH


« Last Edit: October 23, 2016, 01:32 PM by richy3333 »