All RCBOs?

[ericmark]

If I am reading it correct the residual direct current detecting device (RDC-DD) trips the supply, so not talking about normal operation but fault conditions. I know some RCD's don't actually switch the supply, they send or remove a supply to for example a moulded breaker. So would think the RDC-DD could do the same, it may detect the current but not do the actual switching. An ELCB is clearly a circuit breaker, but an RCD is just a device, it may not do the breaking of the supply.

I have not got the 18th Edition, so don't know what an EV is defined as, one would think "Electric Vehicle" I have worked a lot on fork lifts, and the chargers would not cause any DC on the line, it would not pass through the transformer, the same applies to Milk Floats, I suppose both the Mobility scooter and the ebike are also electric vehicles, even a golf trolley, and there were no instructions with the Mobility Scooter or the ebike as to what type of RCD should be used, and clearly there is no RDC-DD built into the charger, both are switch mode so may be a case for not using a type AC, but I would have thought the main point is where the electric vehicle is charged, a caravan in a show room can be supplied with a TN-C-S supply, only when on a
caravan / camping parks and similar locations does it need a TT or TN-S supply.

The problem with the electric powered car was it is often charged to close to premises with a TN-C-S supply to be able to make it a TT supply with an acceptable gradient. I do not charge the ebike battery or mobility scooter battery outside, and I don't have a RDC-DD or type B RCD are you saying my home would fail an EICR because I have a mobility scooter? I am sure it would not, so must be a different definition to EV to being simply an electric vehicle.

 

[JohnW2]

If I am reading it correct the residual direct current detecting device (RDC-DD) trips the supply, so not talking about normal operation but fault conditions.

Exactly - that is the very point I was making.

As you say, it seems that what is being talked about is a device (a "RDC-DD") that will operate under fault conditions that result in a residual (i.e. L-N imbalance) DC current due to a fault to earth.

However, as I said, I thought the main issue was that a constant DC component of current, equally in the and N, during normal operation could potentially impair the ability of the device to operate in response to a residual current (usually AC, but possibly with a DC component) due to a fault to earth. If so, it sounds as if a RDC-DD" would not detect that ...but maybe they are relying ion the Type B or Type F device being used "in conjunction with the RDC-DD" to deal with that?

Kind Regards, John

 

[winston1]

A DC component on the mains is nothing new. I have a 1939 radio that belonged to my late mother. The HT is derived from a half wave rectifier straight from the mains.
Virtually all TVs from the end of the war till the 80's also half wave rectified the mains.

 

[ericmark]

A DC component on the mains is nothing new. I have a 1939 radio that belonged to my late mother. The HT is derived from a half wave rectifier straight from the mains.
Virtually all TVs from the end of the war till the 80's also half wave rectified the mains.

This is the point I have being trying to make, the DC component has been there well before we had ELCB, RCCD, RCD never mind type AC, A, F, or B, so why is there a requirement now for type A, F, or B when there was not a requirement before? Seems to be another got it wrong again dad?

 

[JohnW2]

A DC component on the mains is nothing new. I have a 1939 radio that belonged to my late mother. The HT is derived from a half wave rectifier straight from the mains. Virtually all TVs from the end of the war till the 80's also half wave rectified the mains.

Very true, and I probably still have some things like that lying about. In fact, there might not actually have been all that much of an 'AC component' to the current, given the smoothing after the half-way rectifier.

However, in those days we certainly didn't have to worry about the possible effect of those DC components on the functioning of RCDs!

 

[JohnW2]

This is the point I have being trying to make, the DC component has been there well before we had ELCB, RCCD, RCD never mind type AC, A, F, or B, so why is there a requirement now for type A, F, or B when there was not a requirement before? Seems to be another got it wrong again dad?

The DC component was obviously not relevant (at least, not in the sense we are discussing) before we had protective devices (of any Type/type) whose functioning might have been impaired by those DC components.

Kind Regards, John

 

[winston1]

The DC component was obviously not relevant (at least, not in the sense we are discussing) before we had protective devices (of any Type/type) whose functioning might have been impaired by those DC components.

Kind Regards, John

Indeed but those devices were still in use into the RCD era so why were type AC RCDs allowed. In some countries they are not allowed.

 

[ericmark]

Indeed but those devices were still in use into the RCD era so why were type AC RCDs allowed. In some countries they are not allowed.

You make a good point, which was what I was trying to say, since when RCD's were first required we have had DC components, so what has changed, if a type AC was OK in 1990 why not today?

 

[JohnW2]

Indeed but those devices were still in use into the RCD era so why were type AC RCDs allowed.

I suspect at least partially because it was, at least initially, technologically difficult to produce anything other than what we now call 'Type AC' (I don't think this concept of 'Type', in this sense, even existed in the early days).

The other possible issue (which, as I've said, I've been trying very hard to learn about) is the question of the true magnitude, in practice, (particularly in domestic installations) of the 'problem' with Type AC ones. Until I can find some facts, it remains a possibility in my mind that, in domestic installations, it is perhaps not much of 'a problem' at all.

In some countries they are not allowed.

I think one needs to be careful not to over-interpret that. Germany is often cited in this context - but maybe they have taken the same approach to RCDs as they recently have with the matter of Covid-19 vaccines in older people - i.e. by assuming that the lack of strong evidence that there 'is not a problem' means that there 'is a problem'.

 

[Swwils]

As a reminder in some EU countries type AC is already effectively banned and the other RCD types see more use because for example it's far more common to have say, air conditioner that requires a type F or solar that requires type B.

I can only guess they predicted upwards trends in those items here aswell!

 

[JohnW2]

You make a good point, which was what I was trying to say, since when RCD's were first required we have had DC components, so what has changed, if a type AC was OK in 1990 why not today?

Maybe it usually is ("OK today)?

Don't forget that, as I illustrated, Amendment 1 of BS7671:2018 (published in February 2020, and effective from July 2020 - so hardly 'out-of-date') says:

For general purposes, Type AC RCDs may be used.

Kind Regards, John

 

[JohnW2]

As a reminder in some EU countries type AC is already effectively banned and the other RCD types see more use because for example it's far more common to have say, air conditioner that requires a type F or solar that requires type B.

As I keep saying, I've been struggling to find any definitive information about the magnitude of the perceived 'problem'.

I can accept that EV charging and solar generation raise particular issues (air conditioning, even if it is a special case, is not all that big an issue in the UK) - but what (pending the learning of some facts) I'm far less sure about is whether (as some people are asserting) there is a strong case for all RCDs in UK domestic installations being required to be 'at least Type A'.

Kind Regards, John

 

[RF Lighting]

Most circuits in a modern home can reasonably be expected to feed some sort of electronic power supply so the use of an AC type device may not work properly.

 

[He who knows]

But in real terms until we are required to test RCD's with a DC component

You may be sure that as the prevalence of Type F & B RCCBs increases, then as soon as the test equipment manufacturers are in a position to produce testers they'll be lobbying the regulators to require their use. And making them is probaby not hard - no trip loop testers stop RCDs tripping by saturating the core with a DC component.

Anybody experienced their loop tester tripping F or B RCCBs?

 

[JohnW2]

Most circuits in a modern home can reasonably be expected to feed some sort of electronic power supply so the use of an AC type device may not work properly.

You may be right - but, as I keep asking, where are the 'facts and figures'? I can find lots of 'theory', and lots of unsupported assertions, but where are 'the facts'?

I have a vested interest. Far from merely having circuits which can "reasonably be expected to feed some sort of electronic power supply", I have, and have had for many years, circuits protected by Type AC RCDs which definitely do (simultaneously) feed several 'electronic power supplies', and I would really love to have some proper understanding of the possible implications of this!

Kind Regards, John