Shower Tripping Out help

[Ash4eva12]

Hi, I have a recently installed a 9.5kw shower on a 50a mcb wired in 10mm twin and earth...cable run is 2metres to a 45a switch then from that ...2metres to a dual rcd fuseboard 100a main switch with 63amp rcd x 2 ... The shower works ok on low settings but as soon as you turn it up to Eco or high it trips both the RCD's. However if you turn just one RCD on ...it will run fine on any setting low Eco or high and won't trip. As soon as you put both RCDs on and it's on Eco or high setting it trips both out. It doesn't matter wether it's on hot or cold setting either still get the same outcome as above. It's a brand new shower also. I have checked for cable damage all cables seem fine and also checked there are no crossed cables or that the neutrals are crossed on the board and are under the correct RCD bar. I'm baffled now as to why? Any help much appreciated. Thank you.

 

[Leesparkykent]

What are the IR results?

 

[Ash4eva12]

Hi,

Thanks for the reply,

as far as I know the results from another electrician were

live to live +200Mohms
live to earth +200Mohms

They couldn't find anything wrong with insulation resistance...

 

[Richard Burns]

Tripping both RCDs on high current draw is standard for a highish (10s of ohms) resistance joint between neutrals or between neutral and earth so you must have missed something.

 

[assegayer]

I dont want to sound stupid but why would two of the rcds trips? surely the shower is only protected by one of the RCDs and not two???

 

[Deleted member 9648]

Hi,

Thanks for the reply,

as far as I know the results from another electrician were

live to live +200Mohms
live to earth +200Mohms

They couldn't find anything wrong with insulation resistance...

There will be a fault to earth on the neutral,try testing for that. When a high current is drawn some of that current can divert down a fault to earth,causing an imbalance which will trip RCD(s). You'll need to test the entire installation as the fault may well be on another exisisting circuit which was not apparent untill the high current of the shower enabled the fault current to reach a level to cause tripping.

 

[nickblake]

As Richard and wire puller have said if you have a high resistance connection N to Earth then this will cause both RCD's to trip and this fault may not necessarily be with the shower it could be on another circuit so im afraid to say its get the tester out

 

[telectrix]

hahaha, so anglesey hasn't drifted off into the atlantic after all.

 

[nickblake]

No mate im still here got a tad fed up with all the threads ending up a slagging match , so thought i'd pop back and have a look at whats going on

 

[Darkwood]

I find it can be quicker to take each circuit (excluding the shower) and fully disconnect it (L/N & E) then test shower in your case, if you have a crushed cable or even a socket screw partly into a N then the issue will disappear when you get the correct circuit (circuits if 2 crushed together).

 

[telectrix]

No mate im still here got a tad fed up with all the threads ending up a slagging match , so thought i'd pop back and have a look at whats going on

it's calmed down now. mods have clamped down on aggressive posts.

 

[nickblake]

it's calmed down now. mods have clamped down on aggressive posts.

Oh good , was getting a tad silly I'll have to come on more often then

and back to the original thread think Darkwood has answered the question perfectly

 

[Darkwood]

Oh good , was getting a tad silly I'll have to come on more often then

and back to the original thread think Darkwood has answered the question perfectly

Hopefully the waters are way calmer now and good to see you back, don't be afraid to hit the report option at the bottom left of the post if you spot other doing it again although we are keeping a tight watch ourselves, we prefer that abusive members had a break rather than the positive input of members like yourself.

 

[Ash4eva12]

Right, thank you for all the comments I shall take on board what you've all said and go in search... at least I now know what I'm looking for. Test meter at the ready. Shall see what I find...unk:

 

[DPG]

Hopefully the waters are way calmer now and good to see you back, don't be afraid to hit the report option at the bottom left of the post if you spot other doing it again although we are keeping a tight watch ourselves, we prefer that abusive members had a break rather than the positive input of members like yourself.

It's definitely better on here now. Daz

 

[Ash4eva12]

Sound a slight idiot saying it but 2nd time round looking at it...it took me all of 5 minutes to find. Whoever replaced the fuseboard had left the buzz rail uncut so both RCDs were connected together via the buzz bar. Schoolboy error and I can't believe I didn't spot it in the first place! Thanks all for help and advice anyway

 

[DPG]

Thanks for letting us know. We normally never find out! Daz