Effect of DC on AC RCDs with JW (John Ward joins the e5 Group youtube channel)

Me and John Ward look at what happens when DC is applied to a Type AC RCD.
Comparing with a Blakley Earth Leakage Sensor which is designed to operate correctly even when DC is present.
There will be more detailed reviews on AC RCDs coming from Paul in time. Consider this a rig demo
e5 Group: e5group.org.uk/
Blakley Electrics: www.blakley.co...

[@DanstheEngineer]

The world of RCD's is far more complex than many of us have been led to believe for many years. Great video John and Paul #e5

[@Marcel_Germann]

In most countries. Here in Germany the AC type RCDs were already banned in 1984 for new installations, the standard here is the type A RCDs which detects AC and pulsating current faults. Pulsating current is unsmoothed DC directly from the rectifier, mostly found in switch-type power supplies. The RCDs look absolutely identical, they're connected the same way, but the symbols on them are different: www.elektrotechnik-hager.at/pics/Typ.jpg In 1984 the VDE, which releases the regulations for electrical installations in Germany, also introduced that "electrical installations in locations which contain a bath tub and/or a shower must be protected by RCD". The german VDE 0100 is comparable to the british BS7671, even some parts are absolutely identical. Section 701 for example is the same in the VDE 0100 and the BS7671, the numbering and the content is identical.

[@cumberland1234]

Back in the 1990s there were some EFLI testers which utilised DC to lock RCDs while the EFLI test was being carried out. I think the function was called DLOK and was on some of the Robin testers

[@dsesuk]

Top stuff chaps!

[@richardwilliamson3624]

Great video and a really interesting area of ‘our’ trade. Thank you.

[@e5Group]

Richard Williamson your welcome, lots more to come on RCDs and their history and also more available on the impact of DC in the links at the end. Thanks for watching

[@PJB71]

Excellent informative video John as usual. More information on this subject is required for all contractors. I’m not concerned with PV or car charging as most sparks were aware of this effect. I think it has shocked the industry, the average electrician. I’m particularly concerned with TT earthing systems in domestic & commercial premises. Also during periodic inspections (EICR) i & other electricians I know have actually attached to the report, information for the client relating to the effects of DC in AC type RCD’s. Not scaremongering, but informing the client, that it should be given due consideration, taking into account modern domestic premises are usually overwhelmed with electronic devices, LED lighting, usb sockets etc; it would be interesting to see what these devices actually leak to earth during normal operation. 👍🏼

[@e5Group]

patrick brannan earth leakage will be covered in our RCD mop up video. There are formulas for this. Give us time as we are working on this now. But thanks for watching. Lots more to come on RCDs

[@dennisfowler7873]

Hi can use a clamp meter to measure the DC current that might affect an RCD

[@rossmurdoch7870]

Well explained Mr Ward, many thanks

[@Beasto180]

Great video gents

[@Sarcastix7]

Excellent videos guys. Big JW fan

[@markhorton8578]

Excellent Video John. I know its not strictly about electrical installations But please could you explain how DC gets back into the neutral. Almost all PSU's in all equipment begin with an isolating transformer. So getting a significant pulsed "dc" signal back that way is not impossible but tricky. (Pulses only occurring on one side of the cycle). Beyond the PSU there is often a capacitor and very high resistance resistor to the chassis to prevent charges building between dc circuit and chassis, and that would provide a very small current to earth. (In fact this used to be the cause of quite high earth currents in large office buildings.) Please could you direct me to, or give examples of how DC gets into the neutral? I just asked at another E5 video, but then figured with all those low voltage PSU's etc, that you seem more likely to be into the electronics side of things and to be able to give some explanation. ...Oops I edited a word and lost 9 upvotes.

[@Marcel_Germann]

That's the reason the AC type RCDs are banned here in Germany for new installations since 1984. Type A is the standard here for households since then.

[@e5Group]

Marcel Germann 🤭🤐 we talk about in the next video #spoiler

[@mortenwinslw2785]

Same in Denmark

[@markevans2294]

Why, given 35 years, did this not become the standard throughout Europe? At that time switched mode PSUs were uncommon. Whereas now they are ubiquitous. Including in the likes of LED lamps used as a direct replacement for incandescent ones.

[@Marcel_Germann]

@@markevans2294 The first ones came over here during that time. At first the VDE considered them as beeing potentially dangerous. And they demanded that the power supplies had to be in a housing touch-proof up to 500V.

[@Mandolorian9379]

Another great video very informative.👍

[@wallbouncer9655]

Brilliant video 👍🏻

[@david_pilling]

DC devices usually have full wave rectifiers - they have been around for a long time (before RCDs) - how many incidents when the RCD failed to trip.

[@e5Group]

Agree, but issues are on the rise as you will soon see. The older 4293 were more mechanical than electronic biased so it’s a complex debate. Given the huge variety of switch mode power and co start DC that can appear it’s challenging to compare to RCDs of many years ago, especially given their history of which we will cover in a video coming soon. Thanks for watching

[@gavinquin1913]

Please could you give us schematic I would like build a rig to teach or local sparks about this phenomenon, as we have started to run into the DC problems on RCD's as we are all using the AC type here in South Africa. PV Systems are becoming very popular at the moment. e5 and JW are really up my street as I have a passion for the electrical industry.

[@shaunsparky5354]

Just a brief insight! Without much understanding of what real world installs inject such DC currents to our lovely RCD (Life savers!). What do we actually know? Perhaps a minimum of A Type RCD's being provided by industry for us to use, is this too much to ask of those who profit from us and our customers??

[@rossmurdoch7870]

When installing an EV charger this must be a major consideration. Maybe a little additional DB installed before the rcd is an option?

[@squakkers]

Shouldn't there be some sort of accountability with the manufacturers? Basically, we have to consider changing AC rcd's because of shoddy equipment. Wouldn't it be better if there was a mechanism or electronic trip within DC producing equipment to stop the RCD coil becoming saturated? The manufacturers are aware that their equipment produces DC power so they should take steps to mitigate the effect on a domestic installation instead of just shrugging their shoulders. Any death or injury that occurs from DC blinding on an AC RCD is avoidable if the DC is prevented from entering the live conductors in the 1st place. It all seems a bit backward to me in that the electrical industry has to change because that is considered easier than getting manufacturers to be a little more proactive. Why aren't British Standards (or even Trading Standards) stepping in? Maybe we have to wait for a few more deaths from DC blinding before someone has the guts to challenge the manufacturing industry. Actually getting quite annoyed about this

[@rossmurdoch7870]

Well said , big tech firms should have more responsibility for their impact. As everyone is now being forced to consider the environment ,less focus on possible health and safety.

[@Richardincancale]

Does the Blakey device actually have some specific circuitry to compensate for DC or is it just that the current transformer is visibly much larger than the one in an RCD so less likely that the core will be magnetically saturated by the DC?

[@e5Group]

Richard Deasington it has two current transformers in parallels with a circuit to monitor them. Faults will rise potential with a lead lag and as such that indifference will lead to trip. More content will come in coming months. Lots more! Thanks for watching

[@ef7480]

Just wondering how ‘51 ms’ is within the requirements?

[@charliechimples]

Great vid again John. 🐵

[@muzikman2008]

Great informative video.. Cheers. I can see everyone getting their RCDs changed quite soon... ££££s 😉

[@reggiewac]

I ❤ JW :)

[@e5Group]

reggiewac so do we lots more to come!

[@scottijones40]

Hi Guys, did you make this but if kit or is it available to purchase through a 3rd party. This is a great visual aid that I could use for training I provide

[@e5Group]

The test rig was made specially, it's not a product that you can buy.

[@rich1051414]

I have a battery charger for a golf cart that charges 6 lead acid batteries in series, so it produces over 86 volts DC. That is significant.

[@tarassu]

I'm not sure EV can inject DC back to grid. EV's have their own safety devices onboard. Though I don't know is it mandatory on EV-s (to not inject DC back into grid..above 5mA or similar)