TT Earthing

[Lost-in-space]

Guys, hope you can help.

First thing, i am a spark but need some advise. i've been looking at a job today for a farmer friend. he's just built a new plant shed which is about 5-6000 sq ft and about 30ft to the apex. the plant shed is the outskirts of the yard about 150mtrs from the incomer. The supply to the farm is 100amps TP&N TT. He wants a 45amp TP&N supply to the new barn which should be fine with a 16mm 4core. i'm going to up-grade his incoming switch gear and split off some of the sheds as follows

100amp 100mA DT RCCD feeding 3no 63amp 100mA RCCD's for other loacl submains, including the new shed

in the new shed i was going to install a 6way TPN MCB dis board to serve the lights, general power and some small plant.

is it best to make the new shed TT and put a new rod down, or use the existing earth at the intake and take it to the shed. The other problem is the new shed has an electric roller shutter so i dont want to feed this via an RCCD located in the shed because if it trips, there is no other way in.

I know as its a farm the lower value of 25v applys for RCD's calcs but i'm not sure about not having an RCD on the incomer in the shed

I hpe this make's sence

 

[ban-all-sheds]

dont want to feed this via an RCCD located in the shed because if it trips, there is no other way in.

Put it on the outside then?

Also - does he have a standby generator? How would he get in if there was a power cut?

Sorry I can't answer the rest, but if I were forced to guess I'd say local TT, given the likelihood of local e-c-ps being present. But this is not my area of expertise.

 

[Cork]

One would want to be daft to build even a shed with only a roller door for access and egress, What is the plan if something goes wrong when he is in there with the door down, roller doors are slow to open. In my experience they can give trouble. Usually have a manual wind to cover problems with the motor, limit switch etc. With no other door how do you get to use this manual winder

No other way in ... no other way out.

 

[Lost-in-space]

Thanks mate, putting it outside is one option. he does have a standby set which feeds the hole yard via a really old amf panel im no spring chicken but this panel, it's well before me and should be changed.

if i feed it TT and earth the swa at the incomer end only could i use DP rcbo's for other circuits and rely on the 100mA rcd back at the supply for the roller shutter?

 

[Lost-in-space]

I know what your saying Cork, but he's just had his JCB pinched so he wants fort nox

 

[Cork]

I know what your saying Cork, but he's just had his JCB pinched so he wants fort nox

Thats possibly the best arguement to use with him then. I'm sure he will have some tools etc. in the shed along with the heavy machines. On the day the motor doesn't work is he going to just leave the whole place open?

 

[Lost-in-space]

you do have a point. i don't wire to may roller shutters and when i do i never go back once it's done so i don't know how reliable they are. do they fail often, its got a good sized 3 phase motor

 

[Steve]

in my experience of using shop front shutters (similar sort of motor / structure as a big door thing i guess), the motors are very reliable. Never been let down by one. Never tripped an MCB (type C's).

I dont know about these "garage door" type ones, but i would think they have a similar motor to the shop front shutters, all the ones i have used are single phase motors.

And make sure he has a winding rod, and bullet locks in the sides of the shutter. (our shop has 3 winding rods, kept inside the shop. very handy when we stuck outside at 5am )

 

[Cork]

I have 9 of them in the plant. Probably have someone at one of them every other month. To be fair they get a lot of use. Problem is often that some muppet has hit off one. Or hit a track. All single phase motors. However the point is, as the saying goes " As sure as the jug goes to the well some day it will break" We need as far as possible to only be associated with safe work. If there were a bad accident and the question asked who helped him build that set up? I would not like my name associated with the job.

 

[Lost-in-space]

i will check if its got a winder because if it has, problem solved. There is a lot brian power on here, whats the setup, have you got shares?

 

[Steve]

i will check if its got a winder because if it has, problem solved. There is a lot brian power on here, whats the setup, have you got shares?

1. whos brian?
2. no shares, just like helping

 

[Lost-in-space]

lol, been out in the cold all day, my fingers are only just getting back to normal, could never spell anyway. i can type invoices all right though!