2 x portable work cabin

[baazab]

Hi everyone need help pls

I need to power 2 x portable work cabin

The meter people came today installed new supply with one meter 25 meters away from the 2 cabin

Each cabin have 3 heaters sockets lights

My question is what size Swa cable can I use

Cable length 35 meters from meter box

 

[westward10]

Is this a construction site and are you an electrician.

 

[LukeD]

Is this a construction site and are you an electrician.

This 100%

 

[westward10]

Are you going to embellish us with more information?

 

[baazab]

Is this a construction site and are you an electrician.

Good morning sorry for the late reply

Yes it construction site
Yes I'm approved niceic electrician

 

[James]

It seemed to be a very simple question and because of that I suspect that many people wondered if you were undertaking something outside of your knowledge base And experience.

work cabins in my experience tend to have an appliance inlet on the side and this can vary between 16A and 63A generally.

to be on the cautious side, I would assume the rating of the inlet is the maximum demand.
pick your cable type, probably swa? Have a look at the cable rating tables in the back of the book and post your results here for a double check.

don’t forget to consider earthing type and arrangements or possibly the need for an rcd or 2 of differing types maybe.

 

[timhoward]

It's not really any different from any other circuit design, you need to arrive at what current each unit will draw after some diversity (as the heaters will presumably be thermostatically controlled), then consider how cable is run, and volt drop and fault protection.

(I would suspect these will not be allowed to be connected to TN earthing but I haven't read section 7 and checked. Certainly the mobile/transportable units section would prohibit it, but I'm not familiar with the Construction Sites section)

 

[baazab]

It seemed to be a very simple question and because of that I suspect that many people wondered if you were undertaking something outside of your knowledge base And experience.

work cabins in my experience tend to have an appliance inlet on the side and this can vary between 16A and 63A generally.

to be on the cautious side, I would assume the rating of the inlet is the maximum demand.
pick your cable type, probably swa? Have a look at the cable rating tables in the back of the book and post your results here for a double check.

don’t forget to consider earthing type and arrangements or possibly the need for an rcd or 2 of differing types maybe.

Thank you
Will have to wait and see what the big electricians going to advice me

For example if they say use 2 x 16mm swa to each one this mean I need second electrical box next to the meter with small fusebox to glan the 2x Swa .

I'm confused

It seemed to be a very simple question and because of that I suspect that many people wondered if you were undertaking something outside of your knowledge base And experience.

work cabins in my experience tend to have an appliance inlet on the side and this can vary between 16A and 63A generally.

to be on the cautious side, I would assume the rating of the inlet is the maximum demand.
pick your cable type, probably swa? Have a look at the cable rating tables in the back of the book and post your results here for a double check.

don’t forget to consider earthing type and arrangements or possibly the need for an rcd or 2 of differing types maybe.

 

[baazab]

It seemed to be a very simple question and because of that I suspect that many people wondered if you were undertaking something outside of your knowledge base And experience.

work cabins in my experience tend to have an appliance inlet on the side and this can vary between 16A and 63A generally.

to be on the cautious side, I would assume the rating of the inlet is the maximum demand.
pick your cable type, probably swa? Have a look at the cable rating tables in the back of the book and post your results here for a double check.

don’t forget to consider earthing type and arrangements or possibly the need for an rcd or 2 of differing types maybe.

I agree with you this new to me

To be honest I don't want to do it ,
But if I do it I can have the 14 house later which I love to do empty house rewire that's what I been doing for the last 8 years

 

[westward10]

You need to know the nature of the cabins, office, wc, welfare etc...
The most they will have is a couple of 2kw heaters, lighting and mostly low load appliances apart from a kettle or a few kettles. 16.0 is likely to be overkill.

 

[baazab]

Yes I agree with you few 2 kW heaters and mainly the kettle

its snall cabin mainly use for breaktime

You need to know the nature of the cabins, office, wc, welfare etc...
The most they will have is a couple of 2kw heaters, lighting and mostly low load appliances apart from a kettle or a few kettles. 16.0 is likely to be overkill.

 

[baazab]

16mm swa is way to much but if I decided to use it the system is tnc-s

Reading few minutes ago say cant use the earthing if it Tn system ,I'm confused pls pls
Does this mean I need to install a Earth rod

 

[westward10]

The cabins do not fall under Section 704 so TN-C-S can be used however the supplier may not have provided an earth so it may be TT anyway.

 

[baazab]

The cabins do not fall under Section 704 so TN-C-S can be used however the supplier may not have provided an earth so it may be TT anyway.

Thanks again
It' is tnc-s
100% I checked

 

[timhoward]

The cabins do not fall under Section 704 so TN-C-S can be used however the supplier may not have provided an earth so it may be TT anyway.

I realise it's rarely complied with but would the cabins themselves they not fall under Section 717 wherever they are?
"Unless these installations are under continuous supervision by a skilled or instructed person and the effectiveness of the means of earth has been confirmed prior to connection, TN-C-S systems are prohibited."

 

[westward10]

TN-C-S is not prohibited on a construction site, see 704.411.3.1.
As for the cabins I view Section 717 as cabins which are constantly on the move, cabins on construction sites can stay there for years.

 

[loz2754]

I agree that a cabin used as a canteen does not fall under 704 Construction Sites.

I also agree that under Section 717, Mobile Or Transportable Units, a PME supply may used, if the installation is continuously under the supervision of a skilled or instructed person. It could easily be argued that, as the cabin is associated with a construction site, it is therefore under such supervision.

 

[baazab]

We going to far on this job I need experience electrician to say run the cable put another rod if I have to and get powered
Even if I have to pay him for his correct advice I don't want see section numbers ,

If it can't be done then I just going to pull out

Im sure someone will come and give the correct way

 

[loz2754]

I would suggest in that case that you go ahead pull out, if you're in over your head.
Unless it's possible for a more senior electrician to mentor you on site?

 

[goasis]

I dread to think what the wiring in the 14 houses would look.like if this is such a tricky concept for him to get his head round....

You don't want to see section numbers?!! So what your actually saying is you can't be bothered to educate yourself on this, you just want someone else to do the thinking for you and give you free advise?

 

[davesparks]

TN-C-S is not prohibited on a construction site, see 704.411.3.1.
As for the cabins I view Section 717 as cabins which are constantly on the move, cabins on construction sites can stay there for years.

I thought ESQCR prohibited TNCS on construction site?

 

[westward10]

I thought ESQCR prohibited TNCS on construction site?

Without looking I'm pretty sure it's just caravans and boats.

 

[Rockingit]

I thought ESQCR prohibited TNCS on construction site?

Nope. Although as Westward just said, it does specifically mention caravans and boats (9.4)

 

[davesparks]

Without looking I'm pretty sure it's just caravans and boats.

Nope. Although as Westward just said, it does specifically mention caravans and boats (9.4)

Ah OK, I must be thinking of UKPNs internal specs.

 

[baazab]

I dread to think what the wiring in the 14 houses would look.like if this is such a tricky concept for him to get his head round....

You don't want to see section numbers?!! So what your actually saying is you can't be bothered to educate yourself on this, you just want someone else to do the thinking for you and give you free advise?

Hi everyone I don't want to you to understand wrong off course I want to follow and respect the Bs7671 all I'm asking is help from the boys who's doing this all day long
I all ready put my hands up and said I'm domestic never worked in this field ,if I knew all this I wouldn't ask for help

House rewire is easy for me I do it all day long

We all have to respect each other and work forward

 

[baazab]

Goasis pls pls if you can help and you want money for helping tell me I will forward to you
If you just want to talk bad pls don't as we not going to achieve anything
Manythanks

 

[nicebutdim]

Thank you
Will have to wait and see what the big electricians going to advice me

For example if they say use 2 x 16mm swa to each one this mean I need second electrical box next to the meter with small fusebox to glan the 2x Swa .

I'm confused

That would be the easiest way, enclosed in some sort of weatherproof structure which the builders will probably be happy to make. Then run appropriate circuit to each cabin.

 

[Aaron b]

I can't see how section 717 can't apply it lists transportable as containers and cabins and lists welfare units. They are designed to be transported.

If it's pme TT it. If it's a 32 amp plug or under it needs a rcd anyway.

Prysmian do a free cable app that may help start you off with the right size cable.

 

[UNG]

Goasis pls pls if you can help and you want money for helping tell me I will forward to you
If you just want to talk bad pls don't as we not going to achieve anything
Manythanks

If you post your location there may be a member who is local that can help you out

 

[timhoward]

I can't see how section 717 can't apply it lists transportable as containers and cabins and lists welfare units. They are designed to be transported.

I don't want to start a huge diversion on this topic but this does seem to be an area where different sparks have different interpretations both as to what's in scope, and what constitutes continuous supervision by skilled or instructed people. If you look back at previous threads it's been discussed before on this forum and the iet forum.

I have some sympathy for the argument that the more structures move, the more relevant section 717 is. For example an outside broadcast unit (in a past life I drove one and was the resident engineer) could move every day and be connected to a different supply daily. That is a good example of something being under continuous supervision too. Which is handy as banging an earth rod in at every venue for the antiques roadshow isn't really practical!

Even if this section was in scope, it's been pointed out there is likely to be someone skilled supervising things on a construction site. So PME would be allowed.

 

[baazab]

16mm swa 3core 30 metre
Cleat
60amp metal kmf switch
Glans

 

[nicebutdim]

Are the cabin DBs to be supplied directly or via an external connector?

 

[baazab]

Are the cabin DBs to be supplied directly or via an external connector?

Cabin Dbs are metal I would glan straight in to db

 

[nicebutdim]

Cabin Dbs are metal I would glan straight in to db

I see. As @James mentioned earlier, such cabins are often supplied via an external connector, in which case supply directly from switchfuse may far exceed its rating.

 

[Aaron b]

I don't want to start a huge diversion on this topic but this does seem to be an area where different sparks have different interpretations both as to what's in scope, and what constitutes continuous supervision by skilled or instructed people. If you look back at previous threads it's been discussed before on this forum and the iet forum.

I have some sympathy for the argument that the more structures move, the more relevant section 717 is. For example an outside broadcast unit (in a past life I drove one and was the resident engineer) could move every day and be connected to a different supply daily. That is a good example of something being under continuous supervision too. Which is handy as banging an earth rod in at every venue for the antiques roadshow isn't really practical!

Even if this section was in scope, it's been pointed out there is likely to be someone skilled supervising things on a construction site. So PME would be allowed.

Thanks I appreciate your opinion on this. I understand the exception of the broadcast unit and where for instance a socket in a technicians office could be used for one particular piece of equipment or an instruction given not to drill a wall but the risk of losing the neutral is going to be difficult to monitor.

I suppose it's up to the electrician to complete a designers risk assessment and make there own judgement.

 

[baazab]

I see. As @James mentioned earlier, such cabins are often supplied via an external connector, in which case supply directly from switchfuse may far exceed its rating.

Thanks for that
What I will do first thing in the morning will try to call the cabin people and ask if they have any special requirements for there cabin

 

[westward10]

The norm is to have a distribution board at source as the site will require other power you connect into this. 16.0 to me is overkill I would use 10.0 straight into the board with 40 or 50A protection.

 

[baazab]

The norm is to have a distribution board at source as the site will require other power you connect into this. 16.0 to me is overkill I would use 10.0 straight into the board with 40 or 50A protection.

Good idea respects to you ,
10mm 3 core cheap to buy
You think 10mm 3 core enough for the job from your experience

 

[Aaron b]

Assuming that the load would be under 32amp 10mm would be fine for VD.

 

[goasis]

Goasis pls pls if you can help and you want money for helping tell me I will forward to you
If you just want to talk bad pls don't as we not going to achieve anything
Manythanks

Fair enough, I'm good ta. No problem asking for help on something, def worth having a look through the regs book and seeing what you can come up with. If you figure out the what why and how then its an extra skill for next time and you won't have to think about offering someone else money to do it for you.

 

[baazab]

Thank you everyone thanks westward10