US Surge Protector trips RCD

[NorthernLights]

Hi everyone, I need some advice please.

I have a number of 110v equipment from the US that I need to supply power to.

When using a step down 240 to 110 transformer when I plug in the 110v power Strip with built in Surge protection it trips the RCD on my consumer unit.

I read up on this a little and it seems this is a potentially dangerous situation.

Can someone explain how I can solve this other than having to buy all new 240v equipment?

Best wishes,

Nathan

 

[NorthernLights]

I would have to agree with you. Good luck

So is just getting a non surge protected power strip going to work and be safe given the fact U have RCD protection on the circuit?

 

[Megawatt]

So is just getting a non surge protected power strip going to work and be safe given the fact U have RCD protection on the circuit?

I would have to say yes since it’s already RCD Protected

 

[NorthernLights]

That is an autotransformer, as it clearly says on it! But it is a good one to have, so there is nothing wrong with it as such.

The obvious things to check are the wiring of the UK 13A plug to it (making sure the L & N are the right way) if it is not a moulded plug. Also have you got a socket tester to make sure your 13A outlet(s) are wired the right way round? That is rare, but can be very dangerous as it puts the fuse in the neutral line.

Ok so it is a moulded plug on the transformer. I've checked the socket using my socket tester, all good.

I think I've discovered the issue. If the power strip is connected to the transformer when I plug it in then it trips the RCD.

However if I plug the transformer in, give it 10 seconds and then plug in the power strip, it then works fine.

Is this to do with inrush current on startup perhaps?

 

[pc1966]

However if I plug the transformer in, give it 10 seconds and then plug in the power strip, it then works fine.

Is this to do with inrush current on startup perhaps?

Good to hear there are no serious wiring issues.

It sounds like on switch on the transformer is kicking out a short high voltage spike that is enough to exceed the power strip's L-E voltage protection, so in a sense it is doing its job, but equally it is not convenient for you!

Good to know you have a work-around for the problem!

 

[pc1966]

If you want a better long-term solution you could get a non-protected US distribution strip and add a UK style surge protector to the autotransformer input.

With the 18th edition of the IET wiring regulations surge protection devices (SPD) at the supply to a home became a factor to consider but I suspect very few home will have that for years to come.

 

[UKMeterman]

Ah, if it is a double pole switch and it closes live first then the whole lot will be at 230V above earth and the surge protector will then provide a path live to earth. Also the transformer will take a while to settle down and could provide some interesting spikes.

 

[Megawatt]

If you want a better long-term solution you could get a non-protected US distribution strip and add a UK style surge protector to the autotransformer input.

With the 18th edition of the IET wiring regulations surge protection devices (SPD) at the supply to a home became a factor to consider but I suspect very few home will have that for years to come.

All new homes built or service changes will have to have SPD’s located at the main panel starting this year according to the 2020 edition of the NEC

 

[pc1966]

All new homes built or service changes will have to have SPD’s located at the main panel starting this year according to the 2020 edition of the NEC

That is good to hear, basically same ethos as our regulations!

While most mains stuff should be OK with 4kV spikes a lot of consumer electronics is crap and so it not

 

[Lucien Nunes]

I like the DP switch explanation, and given your observation that it only trips at switch-on, either that or the inrush transient is almost certainly the cause.

RCD's dont like capacitors to ground.

In the absence of any reference to the size of capacitors, I think that's too broad a generalisation. Many appliances and electronic goods have capacitors to ground and are intended to operate from an RCD. Looking at my bench equipment, I probably have 40 separate devices with Y-caps to ground all running from the one RCD, IIRC the leakage is around 8-10mA. A standard power strip made for the USA market would be intended to run from a 6mA GFCI which may trip from 4mA upwards, so would only be permitted to leak a fraction of that current.

However, you may well have a point that in this case the presence of the capacitors is increasing the leakage pulse due to the transient.