New electricity connection

[djcdan]

We are having a new connection installed in the next few weeks by SSEN - our local provider in Scotland. I want to run a few options by the Buildhub community so I can work out what is best in our situation. We will be living on site during the build in a static caravan so would like to install the connection for temporary and permanent use.

 

I've attached a diagram showing my thoughts right now:

 

- I'll excavate and lay ducting in all areas (red, green and burgundy colours).

- Initially, there would be a temp meter cabinet next to the garage.

- The supply will run through the ducting via a ducting coupler towards the temp meter cabinet.

- When we are ready to move the meter to the final position, I will reroute the cabling through the previously laid ducting going towards the house, attach the ducting coupler to the duct running towards the house and remove the temporary ducting previously used.

- I will build boxing around the coupler to allow ease of access later for this to be changed.

- We will pull through enough cabling to get us to the final meter position, so would likely mean extra cabling would sit beneath the temp meter cabinet.

- Until we move to the final position, the unused ducting lines will be capped off.

- Once the meter/CU has been moved, the cabling to the supply the garage will be laid through the prepared ducting.

 

We had considered both options - install the meter/CU in a temporary or permanent position outside - and we're leaning towards repositioning after the house has been built for aesthetics. Are there any other benefits to having this installed in a permanent position immediately other than the cost of repositioning (how much would we expect this to cost)?

 

On a separate note, SSEN have requested ducting meet ENAT 12-24 standards of at least Class 2. Many suppliers advertise their product as electric cable ducting, but do not advertise which class the product is. For example, would this or this suffice? I see some suppliers advertising Class 3 ducting. I presume Class 1 is the highest, and 3 the lowest and therefore not suitable?

 

Is this the best way to handle the ducting in this situation? Does anyone have any other solutions other than using a coupler to reattach the ducting to a different line? 

 

Thanks in advance!

[ProDave]

I would think out of the box.

 

Get the supply installed into the garage as a PERMANENT supply.

 

Run a sub main to the caravan, and when it is built, another sub main to the house.

 

 

[scottishjohn]

when Iasked about a supply they would not let me lasy the cable -all i could do was dig the thrench and htye lay it and last 20m cthey laya conduit and then want owatch use back fill it with suitable pea gravel etc.

So I would ask some more detailed questions ,but ilike @ProDave solution

[ProDave]

I got the cost of my electricity connection down a lot by doing all the digging and laying a continuous duct, with a draw string. from the connection pit to the meter box.  And I dug the connection pit and filled it afterwards.  SSEN were entirely happy with that.  all they did was pulled their cable through my duct and connected both ends of it.

[djcdan]

21 minutes ago, ProDave said:

Run a sub main to the caravan, and when it is built, another sub main to the house.

 

A sub main would include having the meter at one end and consumer unit at the other?

 

In the SSEN guide, it says 'The length of cable between your supplier’s meter and the consumer unit must not exceed 3m'. In another thread, I saw you answer this by saying installing our own switch fuse would allow us to increase this 3m distance (garage to final CU position is around 9m). https://forum.buildhub.org.uk/topic/3030-new-electric-supply/?do=findComment&comment=47128

So you'd propose installing the meter, temp CU and switch fuse to a backboard in the garage, run the supply to the caravan, and then also run a supply to the CU installed in the house when available? Then when moved out of the caravan, removing the temp supply and temp CU.

[ProDave]

Fit a consumer unit in the garage, that can feed the garage circuits and the static caravan.

 

Also fit a switch fuse to supply a SWA cable to the house when it is built.

 

Here is my remote meter and consumer units

 

 

I must take a new picture, that was before I connected the SWA to the house that now exits the bottom of the right hand meter box from the "main" switch fuse.

 

All that SSEN are saying, in common with ALL DNO's is you cannot rely on their fuse for anything longer than 3 metre long meter tails.  In this case the consumer unit feeds the caravan my shed and the site socket. the switch fuse feeds the house.  The off peak switch fuse is not currently in use but is future proofing should I want an off peak supply at some point.

 

In your case I would have a small permanent CU in the garage that will feed all garage circuits and can feed the static caravan and disconnect that when it goes. Remember the caravan must be on a TT earth not the probable PME supply you will be given.

 

And connect a switch fuse with an 80A fuse in it (to give discrimination from SSE's 100A fuse) to feed to the house.

[Jeremy Harris]

We have the meter in a box in a fence outside, with two sub-mains running from it, one to a weatherproof CU that has cables feeding the treatment plant, car charge point ,water pump shed, and garage about 35 metres away and one feeding the house CU about 15 metres away.

[djcdan]

17 minutes ago, ProDave said:

Fit a consumer unit in the garage, that can feed the garage circuits and the static caravan.

 

Also fit a switch fuse to supply a SWA cable to the house when it is built.

 

Here is my remote meter and consumer units

 

I must take a new picture, that was before I connected the SWA to the house that now exits the bottom of the right hand meter box from the "main" switch fuse.

 

All that SSEN are saying, in common with ALL DNO's is you cannot rely on their fuse for anything longer than 3 metre long meter tails.  In this case the consumer unit feeds the caravan my shed and the site socket. the switch fuse feeds the house.  The off peak switch fuse is not currently in use but is future proofing should I want an off peak supply at some point.

 

In your case I would have a small permanent CU in the garage that will feed all garage circuits and can feed the static caravan and disconnect that when it goes. Remember the caravan must be on a TT earth not the probable PME supply you will be given.

 

And connect a switch fuse with an 80A fuse in it (to give discrimination from SSE's 100A fuse) to feed to the house.

 

Thanks for that @ProDave. I can see this is going to be a great learning curve, looking forward to getting stuck in with it all.

 

So to review it to make sure I have understood each point:

 

- SSEN will take the connection from terminal to permanent position inside the garage and the supplier install the meter in this position. The meter connects to i) a permanent CU in the garage (next point) and the switch fuse.

- Connecting to the meter, we would install a permanent CU, which would feed 1) the garage circuits, 2) the caravan (which needs to be TT earthed instead of PME) until it leaves site and 3) any other site sockets positioned close by if desired.

- Also connected to the meter separately would be the switch fuse (fitted with an 80A fuse).

- The switch fuse would feed the house with a SWA cable running from the switch fuse to the finished property once built.

 

Once the SWA cable arrives in the property, I presume this would then go through a second CU positioned in the house to manage the individual circuits inside?

 

By installing inside the garage in a permanent position, would we still require the meter cabinet or can we install directly to a backboard/sheet of plywood considering it is positioned inside and undercover?

 

1 hour ago, djcdan said:

On a separate note, SSEN have requested ducting meet ENAT 12-24 standards of at least Class 2. Many suppliers advertise their product as electric cable ducting, but do not advertise which class the product is. For example, would this or this suffice? I see some suppliers advertising Class 3 ducting. I presume Class 1 is the highest, and 3 the lowest and therefore not suitable?

 

Going back to my OP, would either of the linked ducting be sufficient? I have noticed the second link states Class 3. It this better or worse than the required Class 2?

[ProDave]

The new connection process is all now a bit disjointed because you can (have to) choose your energy supplier.

 

So SSEN will connect the supply and the main fuse and walk away.

 

You have to choose an energy supplier.  You can do that before the actual connection is made as soon as they give you your MPAN (Meter Point Administration Number)

 

Some time days or weeks after the supply is connected your appointed energy supplier will turn up and connect a meter.

 

I think it simplifies the process if you choose SSE as your energy supplier.  Don't sign up to a fixed term tariff. You can then switch to your preferred supplier when it's all working.

 

If I were doing this now, I would have my garage consumer unit already installed and connected to a pair of Henley blocks so the meter installer just has to connect the meter output to the Henley blocks.  Then later on when you connect the house, you have the Henley blocks to join to for the switch fuse to the house.

 

When mine was connected, I chose SSE as the supplier because I know they generally fitted a meter that has a built in isolator switch.  I suspect however today you will be given a smart meter. If so that won't have the isolator.  Do please let us know if you are forced to have a smart meter or can still choose an ordinary one.

[jamieled]

Class 1 is the highest spec, class 3 is the lowest. The main difference between enats class 2 and 3 is the operating temperature. The compression strength is the same.

I also had a new connection from SSEN recently with the same spec as you and nobody batted an eyelid about me using class 3 ducting. I found jd pipes quite competitive for this sort of thing. 

[jamieled]

One other thing. They have a spec supposedly around backfilling the trench containing the duct with some sand to bed it in. It's not always necessary to do this and in our case was completely impractical. We agreed a variation with them on site.

[ProDave]

But don't forget the yellow warning tape to be burried just above the duct.

[Jeremy Harris]

SSEN initially requested that we install 150mm black Rigiduct for their underground cable, then, when the local chap came to have a look he told me he didn't see the point of using duct and asked if I'd mind just laying their cable in the trench if he dropped a reel off . . .

 

We did this, laid their cable for them directly, leaving connection pits for them at the ends.  Damned good job we hadn't already bought the duct!

[ProDave]

I used 70mm duct (or about that size) after SSEN also told us some ridiculous size like 150mm.  The guys on the ground are sensible.  But don't do as one builder I worked with did, and installed blue mdpe water pipe.  I can assure you SSEN WILL refuse to put a cable through that.

[scottishjohn]

3 minutes ago, ProDave said:

I used 70mm duct (or about that size) after SSEN also told us some ridiculous size like 150mm.  The guys on the ground are sensible.  But don't do as one builder I worked with did, and installed blue mdpe water pipe.  I can assure you SSEN WILL refuse to put a cable through that.

yes I got that problem when I run power down to my pump station at bottom of hill and water pipe up --needs to be seperate trenchs ,but as its not DNO that is doing that i will use minimum sensible distance -maybe one wider trench ?

400 m --so will need to have some joins in both pipe and cable

[joe90]

Bit late to this but yes we had a meter in the garage (external box) and CU in garage for its ccts  and temp caravan feed then cable to house CU . Saves paying for moving the meter later.  I did not want the meter box on our cottage to spoil its look but don’t mind it on the back of the garage. Utility co fitted meter with switched outlet to enable my sparky to connect the cable to house CU at a later date. No duct on my supply cable just opened the trench for them then I backfilled after they left.

[djcdan]

Thanks for all the advice! Appreciated. The connection is booked for 20th May, and now far more prepared.

[djcdan]

Hi all.

 

Connection went ahead successfully. They fitted us with a three phase rather than the single they originally priced and paid for, which was good of them. SSEN have therefore taken supply to the box and waiting for lockdown restrictions to ease for SSE to fit the meter.

 

Quote

SSEN initially requested that we install 150mm black Rigiduct for their underground cable, then, when the local chap came to have a look he told me he didn't see the point of using duct and asked if I'd mind just laying their cable in the trench if he dropped a reel off . . .

Exact same thing happened with us. We had prepared to the their official customer installation guide, the local engineer said it wasn't needed and we actually didn't use the ducting. We'll likely use it elsewhere though, so not too bothered.

Before meter installation, I'm looking to have all other infrastructure installed to the meter cabinet myself so when they arrive, SSE connect their installed meter directly to our Henley Blocks and we're good to go. I'm looking for the very helpful advise here to put me on my way (first time doing this stuff!).

 

I've attached to this post a drawing of the setup I am currently expecting to install. The meter backboard (not a cabinet) has been installed in a fixed and permanent position inside the garage and from there, I'm expecting to run a small permanent CU and two sub mains. The garage CU will operate garage lights, garage sockets (inc x1 external socket) and the waste treatment plant pump (situated about 30m away) and leave two for future garden related electric requirements. One sub main will run to the main CU in the house, and the second CU will run to the caravan, which has it's own CU. Both sub mains will be protected by a 80A switch fuse.

 

Question:
- Is it advisable to run a second sub main to the caravan, or could this supply be run from a suitably sized RCD (can you run CU to CU)?

- If two sub mains, can x1 Henley Block handle this or will two Henley's be required? How would two Henley's be configured? One with the garage CU and the other supplying the two sub mains?

- Would running the supply for the pump chamber for the treatment plant be ok to come from the CU or better as it's own sub main?

- The caravan would have it's own TT earthing. The garage CU would be earthed. However, other than this, does any other consideration need to be given to earthing?

 

In terms of the materials I need to purchase for this, am I correct in saying:

x1 Henley Block 25mm² connector (possible x2 based on the advice)
x1 Main switch consumer unit
x5 RCD's as shown in the diagram
Roll of 25mm² SWA three core cable
1m 25mm² 1-core live meter tail

1m 25mm² 1-core neutral meter tail

1m 16mm² earthing cable 
x2 Switch fuse (with 80A fuse)

x1 Four way earth block

 

The guidance and ideas received from here are always welcomed. Thanks!

Edited June 2, 2020 by djcdan
minor text correction

[PeterW]

Best using a Henley per tail so one live and one neutral as the stacked ones are crap and if they break then the bus bars become a very big welder...

 

Think you will also have to earth your SWA but one of the sparks will be along shortly...

[ProDave]

You WILL need to earth both SWA's at the origin.

 

At the CARAVAN you do NOT use the earth.  Use an insulated gland so the SWA does not terminate to anything, and the caravan will need it's own TT earth (earth rod)

 

Agreed do not use the 2 tier henley blocks.

[djcdan]

@PeterW @ProDave Thanks.

 

Attached an updated drawing.

 

Quote

Best using a Henley per tail so one live and one neutral as the stacked ones are crap and if they break then the bus bars become a very big welder..
 

Agreed do not use the 2 tier henley blocks.

I've updated the setup so one Henley Block to cover live and another to handle neutral.

 

Quote

 

Think you will also have to earth your SWA but one of the sparks will be along shortly...

 

You WILL need to earth both SWA's at the origin.

 

I now have earthing connected to the terminal from the switch fuse/origin of the SWA cable on the diagram. Is this correct?

 

Quote

At the CARAVAN you do NOT use the earth.  Use an insulated gland so the SWA does not terminate to anything, and the caravan will need it's own TT earth (earth rod)

I have attached a picture showing the current state of the electricity connection point on the caravan we've purchased.

 

To confirm what I will do; I'll remove this cabling up to the CU position and run the SWA cable in it's place. Upon entry of the SWA at the caravan CU, I would install with an insulated gland. I'd earth the insulated gland to the CPC in the caravan and then from the CPC (which would already be prewired to earth everything else in the caravan), I would install a TT earth, with the rod exiting the caravan and fitted securely in to the ground beneath the caravan. The SWA would still be earthed at origin as shown in the diagram. Because the caravan has a TT earth, would I need a three core SWA for that sub main or should I use two core? Since the earthing wire in this sub main - if we used a three core - wouldn't be needed as we are using TT.

 

Let me know if I've misunderstood anything.

 

[ProDave]

I would not connect to that cable.

 

Follow where it goes, it will almost certainly go to a small consumer uit inside the 'van.

 

Strip back the SWA and cut the armour back and insulate it so nothing can contact it, and take the inner cable of the SWA into the 'van and straight into the consumer unit.

 

Then drop an earth cable out from the consumer unit to an earth rod as close to the 'van as you can get it.

[djcdan]

Perfect. I think that's exactly how I had it:
 

Quote

I'll remove this cabling up to the CU position and run the SWA cable in it's place. Upon entry of the SWA at the caravan CU, I would install with an insulated gland. I'd earth the insulated gland to the CPC in the caravan and then from the CPC (which would already be prewired to earth everything else in the caravan), I would install a TT earth, with the rod exiting the caravan and fitted securely in to the ground beneath the caravan. The SWA would still be earthed at origin as shown in the diagram.

 

What do you reckon about the quote below? Is three core SWA needed for the caravan if we're TT earthing:
 

Quote

Because the caravan has a TT earth, would I need a three core SWA for that sub main or should I use two core? Since the earthing wire in this sub main - if we used a three core - wouldn't be needed as we are using TT.

 

Other than this, does all look ok with my plans? It's my first time doing electrics of this nature, and would prefer it not to go bang! But at the same time, determined to do it to learn some great skills.

From the garage CU, I'm planning on running another SWA cable for the treatment plant pump since the cable is going outside, but the garage circuits just PVC insulated cable.

[ProDave]

Just use 2 core SWA for the caravan.

 

For the treatment plant take it's own SWA straight from the garage CU

[djcdan]

Thanks @ProDave