SWA long run

[monkeyhanger]

A new build bungalow is 180m from the meter position (single phase meter in hut at the side of the road). There are 2x SWA from meter to a join next to the bungalow, where the supply then enters an external meter cupboard in 25mm SWA (new colours).

The two cables from the meter to the join are 1x 6mm 2C and 1x 16mm 2C (Red & black).

When I first entered site the building was already constructed, and that supply arrangement already present.
I have been to second fix, the builder was *sure* that the supply install had been done by a proper local firm (wont name here). After inspection it is evident that this isnt the case as there were no glands on any cable ends, no fused isolator or RCD or earth rod anywhere.

There is a static caravan and stables also on the site, which appear to be fed via the 6mm and 16mm SWAs from a join *somewhere* underground.

I have already been paid for 1st and 2nd fix, and stated that I wouldn't sign the job off unless the supply was adequate.

I have installed a 60A switch fused isolator and 100mA S type RCD & rod at the origin as a quick improvement to the situation and managed to gland the cables, however the cable run is obviously too far for 6 & 16 mm cables.

What would be the best way to proceed? To work out a suitable cabling arrangement from meter or to get the electric board to move the meter position to the bungalow?

 

[Engineer54]

This site's distribution system sounds like a complete Pig's Ear. It just has to be a DIY set-up. I can't see any Electrical Contractor installing such a system, Nor any qualified electrician come to that. I suppose i can't talk for some of these 17th only DI's, but even they should know better!! If our OP sticks to his guns and refuses issuing any cert's based on this potentially dangerous distribution sub-main, then something will get done about it. It's going to get a might expensive for someone down the line on this one!! lol!!

 

[Welchyboy]

so just doin a quick few calcs....35mm swa over 180m at 60A ib = 13.5V VD at end of cable
50mm = 10v VD
70mm = 6.8v VD
95mm = 4.9v VD

And thats just to the bungalow without the final circuits or the stables supplies, so the lighting circuits are never goin to comply with allowed voltage drop??

how would you overcome this situation??

surely only the distributor could resolve this issue?

 

[Engineer54]

so just doin a quick few calcs....35mm swa over 180m at 60A ib = 13.5V VD at end of cable
50mm = 10v VD
70mm = 6.8v VD
95mm = 4.9v VD

And thats just to the bungalow without the final circuits or the stables supplies, so the lighting circuits are never goin to comply with allowed voltage drop??

how would you overcome this situation??

surely only the distributor could resolve this issue?

Separately fused sub-main distribution circuits!!!

It doesn't comply in several areas, not just on the volt drop. As you say, this mixed size run of parallel cables is feeding at least 2 other installations on this site, so they won't comply either!!

 

[lamb]

Either way, the customer would have to run a larger cable. Either pay the DNO or an electrical contractor to do the work.
Alternatively the DNO could alter the medium voltage network and provide a pole mounted sub adjacent to the property, though for a run of only 180m this would probably not be cost effective.
I have done one of these jobs before, with a large property, driveway was a few hundred meters long. DNO installed supply to a kiosk on property boundary, and we ran 185mm SWA in a trench along the driveway. Either end was terminated in a poured resin joint underground and spliced onto 25mm SWA for ease of termination in house/kiosk.

 

[Welchyboy]

Either way, the customer would have to run a larger cable. Either pay the DNO or an electrical contractor to do the work.
Alternatively the DNO could alter the medium voltage network and provide a pole mounted sub adjacent to the property, though for a run of only 180m this would probably not be cost effective.
I have done one of these jobs before, with a large property, driveway was a few hundred meters long. DNO installed supply to a kiosk on property boundary, and we ran 185mm SWA in a trench along the driveway. Either end was terminated in a poured resin joint underground and spliced onto 25mm SWA for ease of termination in house/kiosk.

185mmm SWA in trench 200m ££££££££££££££££££££££££££££££££££!

 

[Engineer54]

Either way, the customer would have to run a larger cable. Either pay the DNO or an electrical contractor to do the work.
Alternatively the DNO could alter the medium voltage network and provide a pole mounted sub adjacent to the property, though for a run of only 180m this would probably not be cost effective.
I have done one of these jobs before, with a large property, driveway was a few hundred meters long. DNO installed supply to a kiosk on property boundary, and we ran 185mm SWA in a trench along the driveway. Either end was terminated in a poured resin joint underground and spliced onto 25mm SWA for ease of termination in house/kiosk.

2 X 95mm SWA cables would have been a cheaper option, and a dammed sight easier to handle too!! lol!!

 

[lamb]

E54:
Expense was not a major issue to the client, however dimmed or flickering lights when large loads turned on/off would have been very unacceptable.

185mm is easy to handle when its off the drum (on screw type cable jacks), onto rollers every few meters, then chucked into trench with a team of a few lads. It's when you have to lift it off the floor (eg onto ladder racking) that you will require a cable gang from the north east with arms like gorrillas.

2 x 95mm would have presented a bit of a jointing problem underground to change to 25mm (would probably require to terminated in a large feeder pillar above ground or in an underground link box)

Regards, lamb

 

[Engineer54]

E54:
Expense was not a major issue to the client, however dimmed or flickering lights when large loads turned on/off would have been very unacceptable.

185mm is easy to handle when its off the drum (on screw type cable jacks), onto rollers every few meters, then chucked into trench with a team of a few lads. It's when you have to lift it off the floor (eg onto ladder racking) that you will require a cable gang from the north east with arms like gorrillas.

2 x 95mm would have presented a bit of a jointing problem underground to change to 25mm (would probably require to terminated in a large feeder pillar above ground or in an underground link box)

Regards, lamb

WOW!! Glad to hear that your cable was installed using all the right gear!! lol!!

No jointing problem there with the 95's , they make resin joint cases for just about every configuration you can think of. If anything easier to line up the cores too, especially if you had to make joints in that 185 cable over that long a distance...

I think you'll find you that the 2 X 95's would surpass what the 185mm gave you, in just about every area. Not sure why, but Paralleling cables and it's advantages doesn't seem to have caught on in the UK. You seem to like humping the bigger cables about for some reason...lol!!!

 

[Rockingit]

Hump? Are we back on the rash thing again??

 

[lamb]

WOW!! Glad to hear that your cable was installed using all the right gear!! lol!!

No jointing problem there with the 95's , they make resin joint cases for just about every configuration you can think of. If anything easier to line up the cores too, especially if you had to make joints in that 185 cable over that long a distance...

I think you'll find you that the 2 X 95's would surpass what the 185mm gave you, in just about every area. Not sure why, but Paralleling cables and it's advantages doesn't seem to have caught on in the UK. You seem to like humping the bigger cables about for some reason...lol!!!

Makes you feel like a real man!
95mm, my bootlaces are thicker than that, LOL.
I also use to do electrofusion work on large underground PE pipelines, now some of those joints were a real wrestling match, hehe.

 

[Knobhead]

Got to admit I would have gone for 2 X 95. A breach joint is easy enough using epoxy joints and mechanical connections.

Thinking about it I think the last breach I did was 95mm PVC SWA in to a 37/072 PILC DWA, enjoyed doing it. It was old meets the new, the PILC was 70 years old.

 

[Geordie Spark]

E54:
Expense was not a major issue to the client, however dimmed or flickering lights when large loads turned on/off would have been very unacceptable.

185mm is easy to handle when its off the drum (on screw type cable jacks), onto rollers every few meters, then chucked into trench with a team of a few lads. It's when you have to lift it off the floor (eg onto ladder racking) that you will require a cable gang from the north east with arms like gorrillas.

2 x 95mm would have presented a bit of a jointing problem underground to change to 25mm (would probably require to terminated in a large feeder pillar above ground or in an underground link box)

Regards, lamb

Wheyayeyerbuggerman !!! we may not be very bright up here, but we can all lift heavy weights !!!!

 

[richy3333]

Either-way when that existing, wrong SWA comes out of the ground think of the £'s you'll get for the scrap

 

[Welchyboy]

So 2x 95mm 2/3core SWA in parallel instead of say a single 185mm SWA?


this would be an acceptable/preferable method of supplying an installations sub main given the circumstances?

not judging or commenting, just for my own interest and information for future reference, i havent heard of this method really used before, but then again ive never been involved in such an extreme situation, im assuming that this is acceptable because even if one 95mm core became disconnected the CCC would still be miles within limits of the fuse

and just to clarify, for example, supplying the run in 185mm swa then underground resin joint at either end reducing down to 25mm swa to terminate into switchgear

resulting in a nice low value for VD and ZE?

 

[Engineer54]

Of course it's acceptable and in the right situations very much preferable!!!

Do a comparison, between the two methods, and see for yourself.

It's not really rocket science to use 2 smaller cables to achieve what a far larger cable can. The lager the CSA of a cable gets, the lower the increase in Current carrying ability it has. What i mean by that is, ... if you look at a 70mm cable then compare with 2 x 35mm, you will see the 2 X 35mm cables will carry far more current than the 70mm cable, and will also have a better volt drop figure too....