Fairy lights, and lots of them

[TommyBoy]

Hi all, another year and another problem with Christmas decorations.

I have a project with a large number of fairy lights - 230v through rectifiers, strapped to a metal grid. I am getting a pretty sizeable earth leakage per frame - around 8-10mA which increases to 15 when wet. The lights are from a high quality manufacturer, ip67 rated and tied on with cable ties. Other than the cable ties being too tight reducing the effectiveness of the insulation is there anything else that could be causing the earth leakage? Would induction have an impact as there's quite a bit of that going on.
I have multiple frames and the earth leakage is very similar frame to frame so it makes me think there is no proper short to ground happening and there is something else i have no knowledge of.

Now my real question is whether this really is an issue, does it need to be covered by an RCD? The location is way out of reach of the public and the 32A outlet could be considered as for specific use, is there anything in the regs that make it so all outside sockets require RCD protection regardless of application? One outlet is feeding two frames and when wet the leakage rises just enough to trip the 30mA RCBO, if you plug one in on its own - no issues.

Any thoughts appreciated.

 

[HandySparks]

Just to get a better picture, how and why is the current rectified, and how are the metal frames earthed?

 

[PEG]

Hi,tell us more about these rectifiers,and how they are supplied.

 

[TommyBoy]

The frames are earthed with a nut and bolt with crimped bond back to the junction box where the rectifiers split from the main feed. LEDs require DC so cheap (I assume bridge type) rectifiers are used to stop the LEDs from flickering from AC.

 

[TommyBoy]

The rectifiers do not have an earth connection due to double insulated construction.

 

[dmxtothemax]

Probably just mutual induction !
Earth the metal frame with an earth stake.

 

[TommyBoy]

Probably just mutual induction !

Do you think that would be enough to imbalance the load? I guess it's only mA were looking at and with the amount of cables on there...

Unfortunately the frames are hung between buildings and the only way to earth it is through the supplying cable

 

[dmxtothemax]

Are they hung with wire cable (metal) ?

 

[marconi]

Can you measure the leakage current:

a. To the frame with the lights connected to the transformer on the frame.

b. To the frame with the lights disconnected from the transformer on the frame.

c. To the frame with the lights of the frame connected temporarily to another transformer hung in the air by a length of insulated flex or plastic rope.

d. Of the transformer at para c disconnected from the lights on the frame. Do this test even if the transformer has a plastic casing - just touch the casing with the test probe.

e. Also for paras a, b, c and d measure the voltage between the frame or transformer casing (if metal) and a metal rod or other metal structure driven into the ground.

Do these measurements outside away from other electrical equipment and wiring.

Please provide details of your test equipment, fairy lights and the transformer rectifier.

 

[marconi]

If you find no fault yet the RCD protecting the 32A socket trips when both displays are connected to it purchase a 240v-240v isolating transformer with suitable IP and VA rating and 240V single phase blue c form socket to isolate your displays from the mains. eg:

| RS Pro, 750VA Isolation Transformer, 230V | - https://uk.rs-online.com/web/p/products/1237381/?grossPrice=Y&cm_mmc=UK-PLA-DS3A-_-google-_-PLA_UK_EN_Power_Supplies_And_Transformers-_-Transformers-_-PRODUCT+GROUP&matchtype=&gclid=EAIaIQobChMI1uepo-zg1wIVrrztCh2miwC_EAYYAyABEgK56fD_BwE&gclsrc=aw.ds

 

[TommyBoy]

Many thanks for your reply Dom, it'll be tricky getting back up to do some more measurements as I'll have to wait for a road closure to be put in place. Usually takes a few days but I'll likely be forced to find a solution before I get the chance to return if the client has anything to do with it. I should have come here first before fault finding but as always, hindsight is a marvellous thing.
From the measurements I did take it seemed that per set of lights (two per frame) we were getting around 6-8mA and this was relatively uniform across the 4 frames that were accessible.
The idea of an isolating transformer is a very good one, this will definitely go on the list. Thanks again!

 

[marconi]

Remember to buy the correct blue c form plugs and sockets and splitters/connectors including on the isotran and to size the isotran (the VA or VoltAmps) to suit the load plus some extra so its not on its limit - say 30-50% more - you don't want its thermal cutout operating on overcurrent.

Are the displays in London?

 

[elsparko]

ruddy xmas lights...

 

[elsparko]

i gave sunty a red glowing nose a few years ago