RCDs tripping

[wrighty]

hey, i was rung today by my dad to come and look at a glasswasher that is causing the main RCD incomer to trip every time it trys to cycle.
This glasswasher is in a pub, over the last 2 days the landlady said every time she tried to cycle the dishwasher it tripped all her pumps out. The glass washer powers up fine and fills with water everytime it tried to run a cycle tho it tripped the RCD on the fuseboard, its a really old fuse board didnt catch the name but im going bk tomorrow after work to investigate more. my thoughts was could it be the element that is nakard and causing this tripping? if not any ideas?

also the shower in the flat above the pub is causing tripping aswell. The fuseboard in the flat is a dual RCD split board, the shower switch has recently been changed and so has the shower as the last 1 was nakard. now this is the interesting part. when the shower switch is turned on it powers the shower no problem, then when you push the power button on the shower it causes the opposite rcd to trip not the 1 feeding the shower side. Ive not had any experience with split rcd boards being in the commercial side of things. and this 1 is baffling me a touch. now i havnt had the cover of the board off to see whats going on inside ill be doing that tomorrow on my return visit. i just thought id post on here to see if any of you have had similar situations of this. also to maybe save myself some time when going back tomorrow. i dont have full test equipment available either this is a favor for some1 so just trying to help out without it costing them a fortune.

is it a coincidence these are tripping together or could it be something further down the line?

 

[telectrix]

you could wel, be right on the dishwasher. as for the shower, check that the neutral is in the correct neutral bar in the CU. and you really need an IR tester to proceed any further.

edit. paul.m is close to you if you get stuck.

 

[i=p/u]

id say very likely for shower in wrong neutral bar, cost a fortune we cant go ny cheaper

 

[wrighty]

that was my thoughts on the neutral but will have to check tomorrow. The board hasnt been installed too long and i know of the company that installed it, ill see what tomorrow brings though just after some possible pointers before i waste loads of time

 

[i=p/u]

as for the dishwasher, would be good if you get a pat tester to test the earth leakage or el clamp meter

 

[murphyosama]

hey put the shower on its own 40a rcbo

 

[Dan the spark]

hey put the shower on its own 40a rcbo

What good would that do in a split board??

 

[ringer]

What good would that do in a split board??

It would mean that only the shower would trip, and not half the circuits in the house.

To the OP, if you haven't taken the cover off then you can't be sure the shower is on that side. It won't be the first time someone has moved a circuit from one side to the other and not updated the schedule on the front of the board! Or is it obvious by the MCB size where the shower is?

 

[GLENNSPARK]

neutral on the wrong side for the shower.....IR issue on the glasswasher......

 

[GLENNSPARK]

could also be a loose neutral on the shower...

 

[GLENNSPARK]

actually no....it isn`t a loose neutral.....its in the wrong side of the C/U i would say.......

 

[ringer]

If the neutral is on the wrong side, wouldn't that cause an imbalance on both RCDs and therefore they both would trip?

 

[GLENNSPARK]

depends on which side a load is applied thats connected to the wrong neutral bar.....

 

[Dan the spark]

It would mean that only the shower would trip, and not half the circuits in the house.

Wouldn't really tho would it, if both rated at30mA it would be pot luck which one went out first

 

[ringer]

Surely with a split load board, you would expect there to be a load almost constantly on each side of the board, with each side being monitored by a separate RCD. So if the N for the shower is put in the wrong side, then side A (with the shower MCB) would have less neutral current than Line current and side B would have more Neutral current than Line current. I thought RCDs detect an imbalance, regardless of whether it is the Line or Neutral has more current flowing than the other. If they only detect when there is less Neutral current than Line current (because the shower N is in the wrong side), then I would expect the shower side to trip, not the other one.

Or is this a split load board with RCD on one side only? Shower MCB on non-RCD side?

 

[ringer]

It would mean that only the shower would trip, and not half the circuits in the house.

Wouldn't really tho would it, if both rated at30mA it would be pot luck which one went out first

Even if the other side pops and the shower keeps running, then the shower side will exhibit a difference in current between L and N on that side, and should therefore trip as well.

 

[Dan the spark]

Lost me there ringer, still don't get what ur gonna gain from putting it on a rcbo on a split board?

 

[Paul.M]

edit. paul.m is close to you if you get stuck.

"He's off to have a look at it after work" and "its in a pub." Count me in but your driving .

I'll pm you my number if you need a hand.

First place to look at is that new switch, it worked ok before that was changed? Next step the cu, visual first then an IR test as above, if that's not the problem then clamp meter cpc at the cu as it could be accumulated earth leakage.

You say it trips when the shower on/off button is pushed. Let's have a look at the element, probably the same problem as the dishwasher in the pub.