Guess the fault

P

p11jor

Had a call out late last night, everytime the shower comes in it's blows the whole house.

The set up of the board is duel rcd. 2 mcb either side.

Cooker/shower on left

Lights/sockets on right



So the power to the shower switch is fine, again this can function fine and send power to the shower, bit as soon as the shower is pressed is wipes both rcds straight out after 2seconds.

I did a insulation resistance test, was getting 0.25megohms.
Removed tge switch and was getting 459megohms. So thought new switch, put new switch on and still wiping the whole board out, but obviously were not getting a dead short as the power to the shower is fine untill pressed.

Quite interesting this one. But such a obvious one which I will always look out for on my future PIRs
 
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If it's taking out both RCD's then there cannot be any discrimination between them, ie. there is a common point between them. Are the circuits correctly fitted to correct sides of board, more to the point the nuetrals as this would not trip until power runs through the appliance. i know this seems like a daft suggestion but to take out both RCD's there has to be some kind of connection between them.... And the number of customers that try to do their own work without the faintest idea is gobsmacking, always remember they may have been in the board before you..!!
 
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miner69er said:
If it's taking out both RCD's then there cannot be any discrimination between them, ie. there is a common point between them. Are the circuits correctly fitted to correct sides of board, more to the point the nuetrals as this would not trip until power runs through the appliance. i know this seems like a daft suggestion but to take out both RCD's there has to be some kind of connection between them.... And the number of customers that try to do their own work without the faintest idea is gobsmacking, always remember they may have been in the board before you..!!
Click to expand...

Agree. Shower neutral connected to wrong neutral bar in CU.
 
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It's was guys, the bus bar there was only a 6mm separation between them and as soon as my mate pressed the shower the Lecky jumped from one bus bar to another, And wiped the whole board out.

Snipped it back....jobs a gooden!
 
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Can't quite see how that would suddenly become an issue.

Out of interest did you put the sockets and lights on different RCD's while you were there?
 
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Don't take that 6mm as a set in stone measurement (as you know diy and poor sparks put them in and they angle slightly, again I taken a measurement from the bottom of the bus bar so it may of been 2mm at the top) I didn't care it was late, dark I found the fault so was made up to fix it and go home without measureing the degree of angle it was on......but whatever it was they were not touching and with it being dark I could see tge jump of 230/240 to the next bar.

I don't kno why all of a sudden this has happened but he had been away and he bought a cooker that was fitted when he was away, there is a 6mm supply for this but the new cooker was just gas range with a ignition, so apparently they swapped the cooker plate behind the over for a fuse spare and ut a 3amp fuse and wired the 1mm flex in the fuse spare.....don't see any reason for them to be in the board though???

Also as tge house is a 2 up 2 down there is only 1 circuit for sockets and one circuit for lights, 12 sockets, 6 lights, I didn't see tge need in swapping these over, as 1 I didn't install it and two it was dark, late, and not my install.
 
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Me too, this wipe the whole lot out, rcds & mcbs, bridge you bus bars on a install and see for yourself.

Tony, due you think moist air that another member mentioned could contribute to this?
 
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There was no continuity between neutral & earth and untill the shower is switched on from the body of the shower not the iso switch then we are all good and no tripping. But when the shower was activated both rcds and all 4 mcbs blew.
 
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A residual-current device (RCD) is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor.

In a pme system the neutral will be at the same potential
 
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Obviously it's not jumping that If no one is taking a shower, but as soon as the button is press it will drawn power from that board....(same as sometimes you see a flash in a light switch when pressed) how far can that jump at the very moment the shower draws power?
 
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p11jor said:
Obviously it's not jumping that If no one is taking a shower, but as soon as the button is press it will drawn power from that board....(same as sometimes you see a flash in a light switch when pressed) how far can that jump at the very moment the shower draws power?
Click to expand...


That is an arc that's being drawn across two contacts, normally when being switched Off. Not the same thing as two static bars and an arc jumping across them....
 
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Ian it's my phone, it's ment to be "the" but the "h" & "g" are so close on
The touch screen and it dosnt auto correct for a few seconds by that time i have pressed post!
 
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To be fair I had bought one for £60 a protek one and that seemed ok, are they anygood?

Also just installed a Chint one which was apparently "ip" rated so could take top entry without sealing "according to wholesaler"

But your right screwfix (elecfix) have mk ones on offer at mo £50 + vat and that's with the breakers.
 
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topquark said:
Not necessarily, if there's a route back via another circuits neutral (under fault conditions) the rcd will trip if the imbalance L->N is in excess of the rating (nominal 30mA).
Click to expand...
Someone was also postulating about the posibility of an induced current from one RCBO to an adjacent RCBO causing a trip (must be very poorly designed if that's the case though).
 
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Local well known wholesalers sell wylex/mem/mk cheap enough, i find these cheap ones are horrible to work with too, fall apart/clips snap/cant get lid back on correctly etc...
 
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Lol, but soon as that shower draws it's power then surely this would be able to cause say a 2nm jump to the next bus bar? Or would it! I don't kno, I bin at it for only 7 years, but my mate i work with has been at it 49 years and he gas never saw this, he couldn't even explain why.
 
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Guess the fault
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