Shower / Memera 2000 fuse box trip

[glynm15]

Hi all,

Help needed with annoying problem.

My shower is hooked up to a memera 2000 box situated in the loft. It is connected to a 45amp fuse. There is a seperate extractor fan on a 6 amp fuse.

The shower is activated by a red switch on the wall outside the bathroom.

Now the problem is - if I ever switch this red switch off 50% of the time it will trip the box off in the loft.

If the red switch is left on (like it used to be until I hooked the extractor up in the loft) the box never ever trips.

It only ever trips after I flick the red switch (not all the time - 50%).

I can go in the loft and immediately trip it back on.

Any suggestions on what this could be and is it easily solved by a medium level Diy er!

Any help would be appreciated.

Regards.

 

[electronicsuk]

What exactly is tripping in the loft? And what kind of box do you have in the loft? Have you taken the original shower supply and split it inside a mini distribution board with 45A supply to shower and 6A to extractor, all back to a single MCB/fuse at your main consumer unit?

 

[glynm15]

Thanks for the prompt reply.

The box in the loft is a Memera 2000 100amp 240v.

It has three seperate inputs

shower on a 45amp
extractor on a 6 amp
and a bath pump on 6amp.

The main swich trips. This only happens when I turn the red switch outside the bathroom off.

I have recently added the extractor fan to the box, but this problem has always occured even before I added the extractor fan. I got round this by leaving the switch on and the box never tripped. I now cannt leave it on because that would mean the extractor on all the time.

Thanks again for your reply and I hope this info helps further.

Regards.

 

[Lectrician]

I suspect the incomer to the board in the loft is an RCD?

MEM RCDs will trip if they loose the supply neutral. You DP switch may be breaking the neutral before the live every so often...

Change the RCD to a standard passive type or remove the RCD and replace with a main switch, providing RCD protection BEFORE the switch.

You could try changing the switch first.

 

[electronicsuk]

Wouldn't it make more sense to have the switch dedicated to the shower only, and then have the fan either come on with the light or a separate pullcord switch? Perhaps a humidity sensor may be an alternative? That way, you wont need to switch the supply side of the RCD.

 

[glynm15]

Again thanks for the reply.

Lectrician - the earth cable from the DP switch (which i assume is the red switch outside the bathroom, i keep talking about) is exposed out of its casing as it goes into the Memera 2000 box - could that be the problem?

The other parts of your post go way over my under qualified head, so i assume i'd get a sparky for that, unless a untrained monkey like me could do it.

electronicsuk - this was my first plan, but couldn't quite figure it out. Fitted the extractor and light - hooked up the light to the cable that was there for the original light and then wasn't sure where to hook up the extractor.

Ended up doing it the way i did because i tried it and it worked.

Am i to assume if instead of hooking straight up to the box in the loft i added the pull cord in between and then hook to the box this would work?

Again thanks for your advice and if you can advise further please do.

Regards

 

[electronicsuk]

Lectrician - the earth cable from the DP switch (which i assume is the red switch outside the bathroom, i keep talking about) is exposed out of its casing as it goes into the Memera 2000 box - could that be the problem?

Very unlikely that this is the cause.

electronicsuk - this was my first plan, but couldn't quite figure it out. Fitted the extractor and light - hooked up the light to the cable that was there for the original light and then wasn't sure where to hook up the extractor.

Ended up doing it the way i did because i tried it and it worked.

Am i to assume if instead of hooking straight up to the box in the loft i added the pull cord in between and then hook to the box this would work?

Well, if you consider never turning off the DP isolator outside the bathroom and using a pullcord to control the fan to be a proper solution. What I actually intended was that you would re-route the shower supply such that the Memera distribution board isn't fed from the DP shower isolator, but rather is used to feed said isolator by pulling back the supply from the isolator and feeding straight into the distribution board.

If you were to then run only the shower through the isolator, you wouldn't be cutting the supply to the RCD all the time. An additional consequence is that you'd need to find an alternative means of controlling the fan, hence the suggestion of a pullcord.

 

[glynm15]

Thanks again for your reply.

Does this mean if i remove the cables of the DP isolater out of the Memera distribution board and just have the shower cables connected straight into the distribution board then this would solve the solution and is safe.

I would then need to add the pull cord to activate the extractor fan.

If you mean anything else, as you can probably can tell it will be beyond my limited capabilities unless its is explained very basically.

Again thanks for your time.

Regards

 

[electronicsuk]

Thanks again for your reply.

Does this mean if i remove the cables of the DP isolater out of the Memera distribution board and just have the shower cables connected straight into the distribution board then this would solve the solution and is safe.

You've lost me now. My understanding from what you've told us is that things are currently wired like this:

[code:1]Main supply - DP isolator - Memera 2000 + - 45A - Shower
+ - 6A - Fan
| - 6A - Whirlpool bath
[/code:1]

Whereas this may be more sensible:

[code:1]Main supply - Memera 2000 + - 45A - DP isolator - Shower
+ - 6A - Pullcord - Fan
| - 6A - Whirlpool bath
[/code:1]

That way, the DP isolator is for the shower only, and under normal conditions the supply to the Memera CU is never interrupted.