Circuit design for new extension

[skamuk]

Got to go back to install a PIR flood so will test again then. Obviously I did something wrong when testing. Thanks

 

[Amp David]

Problem with this is the price of weatherproof RCD's is extortion!

Blimey, is 25 quid deemed as extortionate nowadays!

 

[Octopus]

Blimey, is 25 quid deemed as extortionate nowadays!

Well, if you are winning business on trying to be the cheapest then anything is expensive!!

 

[whichone'slive?]

Every time I ask a question on here I get mixed messages, some wanting to help, others just want to harass you about your qualifications. I do appreciate the help.

I guess it's because considering the potential for harm, some people get perturbed when they feel an unqualified (or not yet competent) person asks questions about work they want to undertake. It's not like your being advised on what kind of pointing you feel a particular wall needs...this stuff'll kill yer...or someone else.

I doubt it's personal. It doesn't seem that way, anyway.

 

[Amp David]

I was under the impression it was all a skam, thats all

 

[Ronyg]

You sure you haven't fitted a non passive spur, which means when the power is turned off it automatically trips.
If so you will need a passive one.

 

[skamuk]

Here's a link to the exact spur I've installed: Toolstation > Electrical > Extension Leads & RCDs > SafetySure RCD Spur Metalclad

I went back today and disconnected everything from the RCD spur except the feed in. It just trips, it will stay in the on position when the power is off, as soon as power is restored, with nothing at all connected to it, it trips instantly and then is impossible to switch back on. I have tested the SWA cable and all is ok. I'm really lost! Don't want to leave it un-protected really. The thing that is also leading me to believe that it's the wiring in the house is that the RCD socket in the kitchen also does not work?

 

[skamuk]

I understand, really I do. It just seems some people are reluctant to help at all, because I lack experience, qualifications and knowledge in some place or another. Id help anyone with anything if I knew the answers to their questions. I don't take it personally, it just confuses me!

 

[Octopus]

If a RCD trips without any thing connected to it, I'd be back down the wholesalers for a replacement.

 

[skamuk]

If a RCD trips without any thing connected to it, I'd be back down the wholesalers for a replacement.

I'll be doing exactly that tomorrow, I thought I was loosing the plot!

I was going to wire it up at home to see if the same thing happens but as you say it shouldn't trip without anything connected anyway...

 

[skamuk]

Are you sure this is a good idea?

Just realised you highlighted where I mentioned clipping SWA to fence. I figured it would be ok as you only have to bury SWA if damage is likely to occur for instance on a driveway or main road, or where 'pedestrians' could damage it. Most of it is concealed under decking and the rest is clipped to fence above flower bed.

 

[skamuk]

Resurrecting this one purely to inform you all that a fault on the 'feed' side of RCD spur can cause it to trip! I went back to the wholesalers a good few weeks back and got a replacement RCD spur. Wired it up this week and it still instantaneously trips. I decided to test my installation AGAIN! By disconnecting it at the socket I spurred from in the house and disconnected all loads in the shed. Carried out Continuity L-N L-E N-E, none present. Continuity of earth neutral line all around 0.4ohms... IR all good...

Cut a long story short there was voltage present in the cpc of downstairs ring, which if RCD's were present in CU would not be allowed to run under normal operating conditions. Therefore tripping the RCD in the shed that I'm trying to install!

I've told him to get the council round to test and inspect, judging by the age of the consumer unit he will probably end up with a rewire as he is now receiving electric shocks when he stands on the grass outside the door of his shed whilst reaching for the metal clad socket I have installed next to what would be an rcd (but is just a junction box atm). Obviously due to the potential difference between the socket and the ground outside.

Was quite funny watching him demonstrate how he gets the shock (standing on the grass with no shoes on and even funnier watching him try to get one (after explaining the science) when standing in the shed itself (insulated from the ground)!

 

[HandySparks]

...as he is now receiving electric shocks when he stands on the grass outside the door of his shed whilst reaching for the metal clad socket I have installed next to what would be an rcd (but is just a junction box atm). Obviously due to the potential difference between the socket and the ground outside.

Hope your public liability insurance is up to date.

Seriously though, why did you leave this new work in a dangerous condition?

 

[electric will]

Resurrecting this one purely to inform you all that a fault on the 'feed' side of RCD spur can cause it to trip! I went back to the wholesalers a good few weeks back and got a replacement RCD spur. Wired it up this week and it still instantaneously trips. I decided to test my installation AGAIN! By disconnecting it at the socket I spurred from in the house and disconnected all loads in the shed. Carried out Continuity L-N L-E N-E, none present. Continuity of earth neutral line all around 0.4ohms... IR all good...

Cut a long story short there was voltage present in the cpc of downstairs ring, which if RCD's were present in CU would not be allowed to run under normal operating conditions. Therefore tripping the RCD in the shed that I'm trying to install!

I've told him to get the council round to test and inspect, judging by the age of the consumer unit he will probably end up with a rewire as he is now receiving electric shocks when he stands on the grass outside the door of his shed whilst reaching for the metal clad socket I have installed next to what would be an rcd (but is just a junction box atm). Obviously due to the potential difference between the socket and the ground outside.

Was quite funny watching him demonstrate how he gets the shock (standing on the grass with no shoes on and even funnier watching him try to get one (after explaining the science) when standing in the shed itself (insulated from the ground)!

and you've really left it like this?
Sure this isn't a wind up?

 

[ackbarthestar]

Resurrecting this one purely to inform you all that a fault on the 'feed' side of RCD spur can cause it to trip! I went back to the wholesalers a good few weeks back and got a replacement RCD spur. Wired it up this week and it still instantaneously trips. I decided to test my installation AGAIN! By disconnecting it at the socket I spurred from in the house and disconnected all loads in the shed. Carried out Continuity L-N L-E N-E, none present. Continuity of earth neutral line all around 0.4ohms... IR all good...

Cut a long story short there was voltage present in the cpc of downstairs ring, which if RCD's were present in CU would not be allowed to run under normal operating conditions. Therefore tripping the RCD in the shed that I'm trying to install!

I've told him to get the council round to test and inspect, judging by the age of the consumer unit he will probably end up with a rewire as he is now receiving electric shocks when he stands on the grass outside the door of his shed whilst reaching for the metal clad socket I have installed next to what would be an rcd (but is just a junction box atm). Obviously due to the potential difference between the socket and the ground outside.

Was quite funny watching him demonstrate how he gets the shock (standing on the grass with no shoes on and even funnier watching him try to get one (after explaining the science) when standing in the shed itself (insulated from the ground)!

I just popped in so that I could just pop out. There is definitely the sniff of ex-military about this.....

One of my ex students was grabbed by a couple of blokes in a helicopter and hoisted into the air just for fun !

 

[Octopus]

Resurrecting this one purely to inform you all that a fault on the 'feed' side of RCD spur can cause it to trip! I went back to the wholesalers a good few weeks back and got a replacement RCD spur. Wired it up this week and it still instantaneously trips. I decided to test my installation AGAIN! By disconnecting it at the socket I spurred from in the house and disconnected all loads in the shed. Carried out Continuity L-N L-E N-E, none present. Continuity of earth neutral line all around 0.4ohms... IR all good...

Cut a long story short there was voltage present in the cpc of downstairs ring, which if RCD's were present in CU would not be allowed to run under normal operating conditions. Therefore tripping the RCD in the shed that I'm trying to install!

I've told him to get the council round to test and inspect, judging by the age of the consumer unit he will probably end up with a rewire as he is now receiving electric shocks when he stands on the grass outside the door of his shed whilst reaching for the metal clad socket I have installed next to what would be an rcd (but is just a junction box atm). Obviously due to the potential difference between the socket and the ground outside.

Was quite funny watching him demonstrate how he gets the shock (standing on the grass with no shoes on and even funnier watching him try to get one (after explaining the science) when standing in the shed itself (insulated from the ground)!

And you aren't willing to sort this out? Madness.

And I'm guessing that you are simply lacking in competence and shouldn't be goingt round, installing in peoples houses and running away

 

[kingeri]

to Skamuk - I fail to see anything funny in what you've described. If I were you I'd be feeling something more like shame.

 

[ackbarthestar]

Just to add. It is unwise to install M/C equipment outside the EPBZ particularly on a PME system. Mind you it doesn't appear to make much difference as you're all having fun getting poked by the suppliers floating neutral voltage.
As it is going to be hot today, why not get the hose pipes out and spread a bit of water

 

[skamuk]

I told him to get the council out as it is their responsibility. I'm not going to start re-wiring his house! Council are due round on monday, they can test and inspect and deal with the problem as it's their job. I'm not a registered electrician I have just completed my 2365 L2 at college. I only did the job as he is a relative. He tells me hes had electric shock from a socket and light switch within the house before and the rcd socket in the kitchen has never worked, he has always been aware of dodgy wiring but didn't think to tell me before I installed the garden stuff.

My additional circuit/spur has been isolated for the time being until the council sort out the problem.

I realize now that I should have tested the house wiring first. My mistake!

Can I ask why it is un-wise to install metal clad in shed outside? I figured it would be better mechanical protection and stronger connection of SWA without need for metal JB to terminate SWA into. If I had used plastic he wouldn't have called me informing me of a problem as he wouldn't of got a shock!

Its funny that everyone here criticizes me for being in the wrong but you were all convinced that an RCD spur can't be tripped on the FEED side, leading me to believe that the RCD was FKD not the system in the house! I came here for advice, no-one advised me to test the house before installing.

I didn't come here for a debate, just wanted to inform you that RCD spurs can be tripped by supply.. I'm staying away from electrical work until the day I start my apprenticeship as its not worth getting things wrong! You live and learn. Thanks for your feedback

 

[ackbarthestar]

Was quite funny watching him demonstrate how he gets the shock (standing on the grass with no shoes on and even funnier watching him try to get one (after explaining the science) when standing in the shed itself (insulated from the ground)!

So was he able to stand on the ground while touching the M/C RCD socket/FCU or was this some fictional anecdote?

Can I ask why it is un-wise to install metal clad in shed outside? I figured it would be better mechanical protection and stronger connection of SWA without need for metal JB to terminate SWA into. If I had used plastic he wouldn't have called me informing me of a problem as he wouldn't of got a shock!

A 2.5mm2 SWA will terminate perfectly well into something like a masterseal IP rated box and it means you are not exporting an exposed conductive part where you are very likely to get microshocks.

Of course, the more insulation there is between you and the ground the less of a shock you will experience.

So for a PME installation the MET earths will be connected to the supply neutral where the voltage will float depending upon the neutral length and loading downstream

 

[skamuk]

So was he able to stand on the ground while touching the M/C RCD socket/FCU or was this some fictional anecdote?



A 2.5mm2 SWA will terminate perfectly well into something like a masterseal IP rated box and it means you are not exporting an exposed conductive part where you are very likely to get microshocks.

Of course, the more insulation there is between you and the ground the less of a shock you will experience.

So for a PME installation the MET earths will be connected to the supply neutral where the voltage will float depending upon the neutral length and loading downstream

When he touched any of the M/C in the shed whilst stood on the grass, with just socks on, he got a shock. My uncle is a nut case and demonstrated more than once that he receives electric shock!! When he stepped into the shed which happened to have an insulation board laying on the floor, he received no shock at all, no matter how hard he tried.

I need to do some more research on PME as i find it hard to understand. I still don't understand why the E is taken from the same point as the N... I expect more lessons on this in 2365 L3.

Have just found this but have had a few beers and am now off to the pub garden for some more as the sun is beating but will have a sober read tomorrow.

the plastic masterseal box makes sense but to me is just hiding the problem that exists in the first place.

Thanks for the help and information.

 

[markjenks]

Hi, after abit of advice.

Wanting to install a new aditional circuit for a lathe. Technical info on label says this lathe runs at 3 phase, 2500 rpm 54A. There are already Lathes installed with same spec but circuits installed to run these are currently BSEN 60898 type b breakers, using 4mm single core PVC, with cable run length approx 10-15M. Rather than just installing what's already in, I wanted to check all sizes, breakers, cable etc. My calculations come back much higher than what's already installed although everything is working and tested out/certified ok?
Any ideas what I could be missing when following cable calc procedure through BS7671?

Cheers. Mark

 

[Knobhead]

54A for a lathe? What the hell is it? A quick calculation gives a motor of 40HP!

I’ve worked on an 18’ X 30’ lathe, that only had a 25HP motor.

(It’s not a typo, 18 foot face plate and a 30 foot bedway.)

 

[telectrix]

maybe the 54A is total current of the 3 phases? or is there a decimal point missing? 5.4A?

 

[markjenks]

maybe the 54A is total current of the 3 phases? or is there a decimal point missing? 5.4A?

hi, thanks for your quick response. Maybe it is meant to be 5.4A rather than 54 as this is quite an old machine. I'll try putting the figures in for 5.4 see if they become any closer.

Thanks again.

 

[markjenks]

54A for a lathe? What the hell is it? A quick calculation gives a motor of 40HP!

I’ve worked on an 18’ X 30’ lathe, that only had a 25HP motor.

(It’s not a typo, 18 foot face plate and a 30 foot bedway.)

as this machine seems to be substantially smaller than the one you quoted, I'm going to presume there was a decimal point missing and try using them figures.

many thanks. Mark

 

[telectrix]

does the rating plate have a kW or HP figure?

 

[markjenks]

does the rating plate have a kW or HP figure?

Not on that lathe. There is a milling machine that also needs to go in. This has more info - 4.8A 2.475KW with rpm @ 4200
Is this any good as I'm having the same problems with this.

thanks, mark

 

[davidcaulfield]

Hi guys I have always been told by my boss which cable size to install. He doesn't work out why size cable to use.

I went to a job yesterday and it was a garage board being fed by a 2.5 T&E off a socket.

The garage is being made into a little office with 4 double sockets and 2 convector heaters and a kettle.

I recommended a 6mm T&E through the roof of the bungalow an throughout the metal conduit going to garage over head.

Does every1 calculate which cable size should be installed or do they use a rule of thumb so to speak.

Appreciate any help with this

 

[ackbarthestar]

54A 3-phase probably equates to 18A per phase giving 12.6kW rating (16-17HP). A 4.0mm2 SWA/SY should be able to cope with that sort of loading but it does, as stated before, seems a rather large machine to me.

What about the PF?

If it was as stated 5.4A then you'd be looking at 4kW or 5 HP - still a powerful machine....

 

[Engineer54]

To determine the size of cable to be used, without calculation comes only from long experience, taking into consideration what length, installation method, and load that cable is likely to carry.


It's easy to just say i'll install a 6mm cable as a cover all for arguments sake, but doing this type of assessment, will in some cases, cost you very dearly!! ...lol!!

 

[ackbarthestar]

Does every1 calculate which cable size should be installed or do they use a rule of thumb so to speak.

It would be wise to particularly as it is a sub-main. Other factors will include not just maximum demand and diversity but also volt drop, future additions, fault protection in its various disguises....

 

[GLENNSPARK]

6mm will be OK...i hazard..lol..
how long is the length of run?

whats the earthing arrangements and are we talking an armoured sub....or twin or summat?

 

[Guest55]

6mm will be OK...i hazard..lol..
how long is the length of run?

4 miles :-D

 

[ackbarthestar]

4 miles :-D

Lol...... This garage must be installed at the end of his private airport. Will need a 11kV TX link then ?

But that's ridiculous no garage can be installed that far away from a private supply. Better contact the DNO to put in a 23kVA service head.......

We could go on but E54 has given sound advice.
Remember if you signing this installation off then do your homework.....

 

[Guest55]

Lol...... This garage must be installed at the end of his private airport. Will need a 11kV TX link then ?

But that's ridiculous no garage can be installed that far away from a private supply. Better contact the DNO to put in a 23kVA service head.......

We could go on but E54 has given sound advice.
Remember if you signing this installation off then do your homework.....

23kva ??? you think too small , i'd go for the uranuim fuel cell in the greenhouse -
half life of 27 years , volt drop not a problem

 

[GLENNSPARK]

just park this thing up and run it all off that....

 

[shanky887614]

just park this thing up and run it all off that....

View attachment 19881

worse case you can go and see biff in his prime :biggrin5:

 

[Guest55]

cheeky monkey , i'm a young & trendy 41 year old ;-)

 

[Knobhead]

You are talking complete and utter garbage.

A note to every one, look at the RPM!