RCD / LED problem

[Emkey]

Hi,

I'm new to this forum and I would like to get some advice.

I was asked to install a 6 way DB feeding four 3ph tanning beds. I installed the board (Hager 100A 30mA RCD as incomer, C32 MCBs )and isolators, tested the system and left. The sun beds installers team arrived this morning. After connecting the beds they rang me and said that three of the beds trip an RCD when on standby. They also said that they are sure the beds are fine. Every time they tried to start any of those three beds an RCD tripped.

The rest of the electrics in the unit are fed from a single phase (L1) CU which was already there. One of the circuit in this CU is B6 MCB feeding about ten cheap ebay LED drivers for LED light strips. There is no switch on the circuit so those LEDs are being switched on and off by operating an MCB.

The bed installers noticed that with this LED lights circuit being OFF, the RCD incomer on DB trips when they turn the beds on. With the same light circuit ON, the beds seem to work fine.

DB and CU are two separate units. Have any of you ever came across anything like this? I'm going there early next week to give it a good check and I'm trying to build some plan of action.

Any ideas?

 

[Octopus]

Not sure the upfront RCD was a good idea.

Borrowed neutral?

Have you got an earth leakage clamp metre?

 

[Dillb]

Why have you put the whole DB on one RCD?

 

[Toneyz]

Why do the circuits have to be RCD protected?

 

[buzzlightyear]

CU is B6 MCB feeding about ten cheap ebay LED drivers for LED light strips. There is no switch on the circuit so those LEDs are being switched on and off by operating an MCB.

b6 not c6 then or 10amps?

The bed installers noticed that with this LED lights circuit being OFF, the RCD incomer on DB trips when they turn the beds on. With the same light circuit ON, the beds seem to work fine

wired up wrong !

 

[Octopus]

So the op has just been reviewing the thread ....... and no updates .......

 

[Emkey]

Don't have earth leakage clamp metre but might get one.

RCD required by the customer, apparently something to do with insurance or council.

RCD incomer feeds only the four sun beds. There are no other circuits in DB.

 

[Emkey]

And thanks for such a quick reply. I wasn't expecting it.

 

[Octopus]

RCD incomer feeds only the four sun beds. There are no other circuits in DB.

Hum. ... did you not think this was a bad idea

“Only” .... hum

 

[Dillb]

Don't have earth leakage clamp metre but might get one.

RCD required by the customer, apparently something to do with insurance or council.

RCD incomer feeds only the four sun beds. There are no other circuits in DB.

What are the sunbeds connected too? (eg socket)
Why have the council stipulated RCD protection?
Are you a electrician?

 

[Emkey]

It could be a bad idea but I have seen five beds running on a single RCD without any problems.

But why a light circuit in a separate consumer unit affects an RCD which it isn't wired to (without tripping "its own" RCD inside CU)?

 

[Octopus]

It could be a bad idea but I have seen five beds running on a single RCD without any problems.

Have you got a copy of the BYB?

 

[Emkey]

The sunbeds are connected to 5-pin interlocked sockets.

RCD is required by the customer and the installers.

Yes. I am an electrician.

 

[Dillb]

Hang on is the RCD required by
1) insurance
2) council
3) customer
4) installer

You have told us 4 different things in the space of 5 minutes

 

[Toneyz]

Can we rule out that these LED lights are nothing to do with the sunbeds? Edit these are just doing lighting in the shop.

 

[UKMeterman]

The sunbeds will have lots of filters in them each leak to earth. Fit rcbos, and if the customer wonders about the extra cost then explain if a bed goes faulty then he will only have an issue with 1/4 of his beds not all 4.

 

[Dillb]

The sunbeds will have lots of filters in them each leak to earth. Fit rcbos, and if the customer wonders about the extra cost then explain if a bed goes faulty then he will only have an issue with 1/4 of his beds not all 4.

You’d think the OP would of thought about that rather than closing a whole shop down because of one faulty device.

 

[Emkey]

That is the whole point of this thread. The LEDs don't suppose to have anything to do with the sunbeds but they DO.

EVERY time the LEDs are off, the beds trip an incomer RCD.
EVERY time the LEDs are on, the beds work fine.

LEDs are in the separate consumer unit and are not connected to the distribution board incomer.

Yes. I do have a copy of the regs.

 

[Emkey]

Sorry. Sent it twice.

 

[Emkey]

I did want to fit separate RCDs for each bed and explained to the customer why. He wasn't happy with an extra cost.