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.

 

[Octopus]

Next time don't give the customer the option.

They are running as business ... Hours lost cost far more than a couple of rcbo's

Best get back on site and use your tester

 

[Dillb]

Costing you now though isn’t it.

 

[Emkey]

You are absolutely right about not giving a customer an option in this case.

I will be there next week and try to get an earth leakage metre too. They are not cheap but seem very useful.

 

[Emkey]

It's costing me a lot cause the place is 100 miles away. Only agreed to do it because the owner is a friend of a friend. Big mistake.

 

[PEG]

The clamp is a must,on issues such as this,but if the only thing i had was a screwdriver,i would be pulling the neutral on that mcb switched lighting circuit,and seeing what happened...

 

[Toneyz]

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

So the LED lights are only in the shop ceiling are they?

 

[Emkey]

That's right. LEDs are on the walls and don't suppose to have anything to do with the Beds.

 

[buzzlightyear]

the plot thickens

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

the only persons who is missing from the that is the candle stick maker ,now cluedo comes to mind

 

[Midwest]

Seems a less than helpful night on the forum.

 

[Octopus]

Seems a less than helpful night on the forum.

posted at 10.56 pm on a Saturday night!

Could have been a lot worse.................

 

[Richard Burns]

Theoretically the LEDs cannot be affecting the RCD on a different supply as the RCD is only monitoring the outgoing circuits.
Possibly, but I am not sure how, the LED dimmer is introducing a DC component that is masking the RCD operation; alternatively if there is a Neutral Earth fault on the sunbed side of such resistance that is just tripping the RCD and there is also a neutral earth fault on the LEDs once switched on then this would give parallel paths for the neutral current and so reduce the current seen by the RCD below its tripping threshold.
If the sunbeds are switched on by a double pole switch then it is possible that there is a difference in arcing across the poles so that the RCD occasionally thinks there is an imbalance and the LEDs just happen to coincide with the trip times. This could be tested by connecting the "working" sunbed to one of the other sockets.

 

[johnduffell]

So when the LEDs are on, the RCD doesn't trip? All one one RCD?
If so it could simply be the sun beds are leaking inductively to earth and the LEDs are leaking capacitively. So they cancel out enough to stop a trip. Not sure how well RCD trip if you leak imaginary power, but either way the above suggestions about one 3p RCD per bed make sense.

 

[Deleted member 26818]

So when the LEDs are on, the RCD doesn't trip? All one one RCD?
If so it could simply be the sun beds are leaking inductively to earth and the LEDs are leaking capacitively. So they cancel out enough to stop a trip. Not sure how well RCD trip if you leak imaginary power, but either way the above suggestions about one 3p RCD per bed make sense.

Did you test the RCD?
Did you test the RCD with the LEDs on or off?

 

[johnduffell]

Did you test the RCD?
Did you test the RCD with the LEDs on or off?

I guess that was aimed at the op, not to me

 

[Deleted member 26818]

I guess that was aimed at the op, not to me

Sorry, thought you were the OP.
You need a picture.

 

[johnduffell]

You need a picture.

Good point, never intended to hang around here long enough to need one, but turns out you lot are more welcoming then i expected

 

[Wilko]

Hi - The shop's LED lights with no functional switch caught my eye - an indicator perhaps the rest of the place isn't wired as we might expect?

 

[Octopus]

Hi - The shop's LED lights with no functional switch caught my eye - an indicator perhaps the rest of the place isn't wired as we might expect?

I was wondering this but he has stated the new rcd board is wired independently of the existing cu which supplies the led light circuit ......

Very odd

Hope we get feedback once he’s been back on site ..

 

[marconi]

http://www.solansunbeds.co.uk/How_to_Set_up_a_Successful_Tanning_Salonv1.2.pdf

See page 16 of 17 of the reference which is quite clear that if RCD protection is provided for Solan sunbeds then the trip current difference must be 100mA and not 30mA to take into account the accumulated leakage from the many ballasts and hot humid ambient air inside the equipment. What do the technical installation instructions say for the make and model of tanning machine for which you have provided electrical supplies?

 

[Wilko]

Gives a good insight as to why RCBO should be used for each one. Hopefully 30mA rating will be ok, as I'm not overjoyed at the idea of stepping in and out of a metal box with 100mA ... (is it just me?) Still no clue as to the LED role in all this .

 

[johnduffell]

overjoyed at the idea of stepping in and out of a metal box with 100mA

True but as long as you trust the earthing (and any supplementary bonding if you like) you should be disconnected within a few seconds if there's a fault, and the touchouch voltage shouldn't be too high.
I'd be more worried about all that 17kw of uv coming from the tubes tbh, it'd be factor 50 for me!

 

[Wilko]

Being born in a sunny place (and seen the results) I think these things are just plain crazy .

 

[marconi]

See #13 - The OP says each bed is connected to its supply by a 5 pin interlocked plug and socket. Is this acceptable if a 100mA RCD is used? I don't know if it is and whether instead each bed must be 'hard-wired' in.

 

[Deleted member 26818]

Would be acceptable if the plug and socket is rated above 20A or if the sockets are labled up.

 

[Chris1234]

As above, power circuits with sockets of 16A and below require a 30mA RCD.

Presumably if he has 32A MCB’s then he is using 32A sockets.