MCB Tripping.. Help !!

[Darkwood]

Just a quick one on this, please excuse my ignorance, but surely if there was a L - N fault, then any discrepency between the two would trip the RCD. Again please excuse me if I'm talking bulls**t

L/N fault intermittent, short or low insulation is exactly that L-N, rcd look for earth leakage and as this isnt down to earth the rcd wont see it.
To note though in a L/N short circuit can sometimes trips the rcd but this is from my own assumption due to magnetic saturation of the device when the ampage can be in the 1000+ range for a split second until mcb trips and due to rcd looking at mA magnetic fields in normal use its plausable to me it will get saturated and activate.

 

[Guitarist]

Just a thought, are the mcbs type B or C? Most mcbs/rcbos I have fit for a shower are type C. It may not be the problem but I just wanted to give you another angle to look from.

Jay

As darkwood said, no inrush so type B for showers

 

[cakey]

Be nice to hear what was actually the problem?

 

[wallyanker]

Update.....

Been back over the weekend and can not find anything wrong with any terminations, connections, etc. IR test >1999Mohm. Split load board with 1 x 40a mcb on each side. Also tested RCD to make sure and all is good. So I turned to the shower unit itself....

Very very low water pressure at the shower head concerned me, especially when I raised the shower head above the unit and the water nearly stopped before going red hot and then the shower cut out (thermal cut out for element I think). MCB was still "on".

I told her to call the plumber back and do a pressure test at the shower end, then have the shower checked. It turns out that the pressure was indeed a little low but is not the main cause, the shower element is causing the MCB to trip so the plumber has replaced the shower and all is good so far.

Brand new gear causing all the problems, they dont make stuff like they used to!!!

 

[Darkwood]

Thx for update and as you said the thermal cutout was their to protect element but its continuous overheating and tripping will be the cause of the element failing and tripping mcb .... All down to the low water pressure, i suspect the shower lacks a pressure valve something missing on cheaper shower brands.