PIR on a farm house.

[Lectrician]

Work this one out...

4mm split concentric from generator to change over switch.
16mm tails from DNO meter to this switch gear mess.
10mm tails out of RCD to run a submain in a barn (jointed to 16mm split in loft).
16mm tails out of RCD to house CU.

Can you work out what they have done with the changeover?!

Not good.

 

[electronicsuk]

I'm not familiar with the layout of that particular C/O switch, but it doesn't look as if there are enough wires in there. It seems as if the changeover is only switching the line conductors, and there's a DP switch next to it to tie the generator and DNO supply neutrals.

 

[ricicle]

Mr DNO wouldn't be happy to see that, especially up the pole in wet conditions

Also SWA with only a single conductor (Mr Eddy Current)

 

[Lectrician]

Yep - not sure why they didn't switch the neutrals. The CO switch is three pole.

They tied the gen and DNO neutrals via the 30amp switch, which I guess they turned on and off with the CO switch - however, it was on when I got there.

 

[ColJack]

Mr DNO wouldn't be happy to see that, especially up the pole in wet conditions

Also SWA with only a single conductor (Mr Eddy Current)

you mean the split con cable as mentioned? not SWA?

 

[ricicle]

Oops, missed the bit about it being split con......

 

[studentspark]

I looked up what a change over switch was, and I gather its something that switches over the power from one piece of equipment to another.
What sort of reasons would you have one.

Also that switch, (Isolator?) if you follow the red cable. it appears to go to the right hand side of that Wylex box, (Is it an RCD of some type) however the left hand side has a red cable which makes me think the red cable from the switch has gone to the neutral side.

Any enlightenment on what is going on here would be appreciated

 

[Steve]

I looked up what a change over switch was, and I gather its something that switches over the power from one piece of equipment to another.
What sort of reasons would you have one.

Also that switch, (Isolator?) if you follow the red cable. it appears to go to the right hand side of that Wylex box, (Is it an RCD of some type) however the left hand side has a red cable which makes me think the red cable from the switch has gone to the neutral side.

Any enlightenment on what is going on here would be appreciated

Its all cack, isnt it?



Basically the C/O switch is set up so it switches the live between the generator and the mains. It is also supposed to switch the neutrals too. But whoever has fitted it has run the neutrals through that bottom switch, relying on the user to switch it with the changeover switch. This is bad - the connection must be failsafe. Or else a lineman could be up a pole fixing a fault and the neutral will give him a nasty belt if its not grounded.

A changeover switch can also be used to switch between two appliances which must not be used together.

 

[studentspark]

Thanks
I don't really get it though.

I under stand the principle I think, but I an unsure about how the circuit will work if the neutral is not switched over, and how the lineman will get a belt.

 

[1john]

when there is a load the neutral becomes 'live' as it is taking the returning current, this is where the linesman gets a tad upset.

 

[RF Lighting]

Not forgetting step down transformers in substations also work the other way.

Back feed it with LV and you could 'liven up' part of the HV network

 

[davelx]

Thanks
I don't really get it though.

I under stand the principle I think, but I an unsure about how the circuit will work if the neutral is not switched over, and how the lineman will get a belt.

Get yourself some paper and a pencil, draw out the circuits and try to work it out for yourself then. That way you might actually understand what is happening.

 

[NamelessRob]

Not forgetting step down transformers in substations also work the other way.

Back feed it with LV and you could 'liven up' part of the HV network

Not doubting you, but I'm genuinely interested why; surely with the live switched over, there's no current flow, so even if the LV neutral is high the HV side won't be affected?

 

[ricicle]

Any sort of voltage managing to find it's way across L and N would manifest itself onto the HV side of the Tx by a factor of approx 47.5. Although this might not be enough to provide much current, the voltage would still be enough to test the nerves of even the most sturdy of linesmen/substation repairmen !!

 

[ColJack]

don't these substation switchgear have earthing isolators?