Correct selection of RCD with regards to EICRs

[GBDamo]

The picture is a section of text from the October edition of Professionals Electrician, NAPIT Codebreakers.

I have an issue with coding 'incorrect RCD type selected'.

1, is it now expected that all permanently connected equipment is assessed and MIs consulted to determine if the correct type of RCD has been used?

2, in general purpose circuits are we now to assess what DC leakage is likely?

3, are we expected to test DC leakage with the installation at full normal usage.

The selectively of RCDs is easy to spot and is most likely to be no more than a C3.

As far as installations this is all easily covered in the design and the correct RCD type can be selected but when it comes to EICRs how does it work in practice?

 

[HappyHippyDad]

That's interesting. Using the correct type of RCD is now something that is being examined more closely than before, so it's a relevant discussion. They have clearly said it is 'potentially dangerous' which is a C2. However, they then go go to talk about scenario's which indicates it could be any code depending on what you find. Perhaps we do need to give it a little thought when carrying out an EICR.

I have just fitted a type B RCD for a tesla EVCP. A type AC RCD would not have detected any DC leakage so 'could' be deemed as potentially dangerous and therefore a C2.

Ps.. I haven't answered any of your questions, sorry

 

[GBDamo]

That's interesting. Using the correct type of RCD is now something that is being examined more closely than before, so it's a relevant discussion. They have clearly said it is 'potentially dangerous' which is a C2. However, they then go go to talk about scenario's which indicates it could be any code depending on what you find. Perhaps we do need to give it a little thought when carrying out an EICR.

I have just fitted a type B RCD for a tesla EVCP. A type AC RCD would not have detected any DC leakage so 'could' be deemed as potentially dangerous and therefore a C2.

Ps.. I haven't answered any of your questions, sorry

No, but you've illustrated my point.

If your fixed installation was inspected as part of an EICR and it had AC type RCD you could safely code it C2.

Likewise you could go and give the socket ring a visual and find a USB socket outlet on an AC type. It is not inconceivable that this device could fail in such a way as to saturate the AC type device, is this a C2? Maybe.

Then we have a look in the kitchen and they have a fancy inverted washing machine, again DC saturation is not inconceivable so is this also C2? Again, maybe.

But now we are coding the installation on what is plugged in, not the fixed wiring.

If we are coding on what IS plugged in then does it then not follow that we should code on what MAY be plugged in?

Have I jumped the shark here or are we now in the situation where type AC Devices should be coded C2 in domestic EICRs.

Thoughts please.

 

[Pretty Mouth]

Would a C3 code not be more appropriate, with a C2 if DC leakage was found to be preventing it from operating under test?

 

[Dartlec]

The picture is a section of text from the October edition of Professionals Electrician, NAPIT Codebreakers.

I have an issue with coding 'incorrect RCD type selected'.

1, is it now expected that all permanently connected equipment is assessed and MIs consulted to determine if the correct type of RCD has been used?

2, in general purpose circuits are we now to assess what DC leakage is likely?

3, are we expected to test DC leakage with the installation at full normal usage.

The selectively of RCDs is easy to spot and is most likely to be no more than a C3.

As far as installations this is all easily covered in the design and the correct RCD type can be selected but when it comes to EICRs how does it work in practice?

This sounds like rather a can of worms, especially when there are so few type A RCDs out in installations yet.

According to the ESF guide, sockets without RCD protection would usually be a Code 3 (assuming RCD not needed for fault protection and socket not likely to be used to supply outdoor equipment)

Most of the 2000s flats I've inspected have grid switches to appliances under cabinets, with flex outlet plate and no RCD protection as it wasn't needed.

So assuming a socket or flex outlet set aside for a washing machine that isn't likely to be used for outdoor equipment and has a low Zs - Code 3 if no RCD, and Code 2 if there is an type AC RCD?

If they want us to go down that road, surely they will have to start publishing tables of the 'guilty' appliances.

Not to mention the fact that EICRs are often done with the flat empty between tenants, so it's impossible to know what will be plugged in where...

 

[Dartlec]

Would a C3 code not be more appropriate, with a C2 if DC leakage was found to be preventing it from operating under test?

Trouble is that unless the tenant is doing a wash cycle while you EICR, it probably won't show up anyway?

Of course, one solution might be to ask appliance manufacturers to find a way to stop injecting DC into the supply, but presumably they would be against such madness! (I don't actually know if there is a way to stop it, to be fair)

 

[Lister1987]

I'd go C3 with an FI to examine the RCD for DC leakage with an appropriate clamp meter. If the investigation doesn't show DC leakage then C3 (with a note on how DC leakage can have a negative effect on Type AC RCDs and how the client should consider RCD type when making future purchases (EV charger, DC heavy white goods), but if it does show a sizable amount of DC leakage (potentially enough to blind the RCD and prevent proper operation) then I'd C2 then I'd look to replace the RCD for a more suited type.

 

[GBDamo]

This sounds like rather a can of worms, especially when there are so few type A RCDs out in installations yet.

According to the ESF guide, sockets without RCD protection would usually be a Code 3 (assuming RCD not needed for fault protection and socket not likely to be used to supply outdoor equipment)

Most of the 2000s flats I've inspected have grid switches to appliances under cabinets, with flex outlet plate and no RCD protection as it wasn't needed.

So assuming a socket or flex outlet set aside for a washing machine that isn't likely to be used for outdoor equipment and has a low Zs - Code 3 if no RCD, and Code 2 if there is an type AC RCD?

If they want us to go down that road, surely they will have to start publishing tables of the 'guilty' appliances.

Not to mention the fact that EICRs are often done with the flat empty between tenants, so it's impossible to know what will be plugged in where...

Another problem is manufacturers are specifying type AC RCD protection for plug in items, like washing machines.

Simply inserting a statement in the War and peace that has become the modern instruction manual is not good enough.

The consumer buys it, plugs it in and if it works that it. Many don't know what an RCD is let alone what type it is, it simply isn't consumer level knowledge.

Retailers need to be forced to point this out at point of purchase.

 

[GBDamo]

I'd go C3 with an FI to examine the RCD for DC leakage with an appropriate clamp meter. If the investigation doesn't show DC leakage then C3 (with a note on how DC leakage can have a negative effect on Type AC RCDs and how the client should consider RCD type when making future purchases (EV charger, DC heavy white goods), but if it does show a sizable amount of DC leakage (potentially enough to blind the RCD and prevent proper operation) then I'd C2 then I'd look to replace the RCD for a more suited type.

An EICR is a snapshot in time, similar to an MOT for car.

You simply cannot certify DC leakage as it is dependant on factors not within the remit of an EICR.

It can also be influenced by simple and expected actions by the uneducated.

We, as electricians, have a duty to keep abreast of these changes and take all reasonable steps to ensure our installations reflect changes in the regulations.

The general public do not, we should know to put the correct protective device in where required, and know to look to see if a special requirement is needed.

As said above, can of worms.

 

[Dartlec]

Another problem is manufacturers are specifying type AC RCD protection for plug in items, like washing machines.

Simply inserting a statement in the War and peace that has become the modern instruction manual is not good enough.

The consumer buys it, plugs it in and if it works that it. Many don't know what an RCD is let alone what type it is, it simply isn't consumer level knowledge.

Retailers need to be forced to point this out at point of purchase.

Retailers can barely get the measurements right in my experience, let alone much else.

Though did see a pump the other day that comes with a plug, but states in the manual that a Part P installer can cut it off and wire to a spur without it affecting the warranty.... I'm sure that will please all the highly qualified electricians who aren't a member of a scheme

 

[GBDamo]

I'd go C3 with an FI to examine the RCD for DC leakage with an appropriate clamp meter. If the investigation doesn't show DC leakage then C3 (with a note on how DC leakage can have a negative effect on Type AC RCDs and how the client should consider RCD type when making future purchases (EV charger, DC heavy white goods), but if it does show a sizable amount of DC leakage (potentially enough to blind the RCD and prevent proper operation) then I'd C2 then I'd look to replace the RCD for a more suited type.

Think of it as half a dozen sockets on an unused spur off a 32A ring.

You wouldn't, on inspection, say there was no overload at point of inspection, or even evidence of previous overloading, therefore C3.

You would say there is potential to overload an insufficiently protected circuit, therefore C2.

Its about what can reasonably be expected.

 

[Lister1987]

Think of it as half a dozen sockets on an unused spur off a 32A ring.

You wouldn't, on inspection, say there was no overload at point of inspection, or even evidence of previous overloading, therefore C3.

You would say there is potential to overload an insufficiently protected circuit, therefore C2.

Its about what can reasonably be expected.

As you say, an EICR is a snapshot in time and we can only code by what we can see.

If we get an idea of present DC saturation (based on what is installed) then we are in a position to C2 (if saturation is present) or C3 (if none present). We can only code what we can see. Obviously if MIs state an RCD type and they aren't being followed then you could code as a C2 citing 134.1 and 510.3 - By not following instructions them there is the potential for danger, and the C2 then forces that MIs to be followed, whereas a C3 can be 'ignored'

If we are coding on what IS plugged in then does it then not follow that we should code on what MAY be plugged in?

No, because we don't know what the client is likely to buy, all we can do is educate or future proof by changing the RCD (which may need changing as a result of the C2 for 134.1 and 510.3

 

[Pretty Mouth]

Think of it as half a dozen sockets on an unused spur off a 32A ring.

You wouldn't, on inspection, say there was no overload at point of inspection, or even evidence of previous overloading, therefore C3.

You would say there is potential to overload an insufficiently protected circuit, therefore C2.

Its about what can reasonably be expected.

Subtly different to your example IMO.

A cable unprotected from overload could be dangerous in normal use - there are no additional failures required, just equipment drawing a heavy load.

An incorrect RCD has 2 points of failure before it becomes a dangerous situation - DC leakage from faulty equipment, and an AC earth fault. Hence why I'd code C3.

 

[GBDamo]

Subtly different to your example IMO.

A cable unprotected from overload could be dangerous in normal use - there are no additional failures required, just equipment drawing a heavy load.

An incorrect RCD has 2 points of failure before it becomes a dangerous situation - DC leakage from faulty equipment, and an AC earth fault. Hence why I'd code C3.

Fair point, but some equipment produces DC leakage current during normal operation it is not necessarily a fault that caused the RCD saturation. C2 now?

I'm not saying I have the answer and will be having a word with NAPIT before my next EICR, when ever that is.

 

[GBDamo]

As you say, an EICR is a snapshot in time and we can only code by what we can see.

If we get an idea of present DC saturation (based on what is installed) then we are in a position to C2 (if saturation is present) or C3 (if none present). We can only code what we can see. Obviously if MIs state an RCD type and they aren't being followed then you could code as a C2 citing 134.1 and 510.3 - By not following instructions them there is the potential for danger, and the C2 then forces that MIs to be followed, whereas a C3 can be 'ignored'




No, because we don't know what the client is likely to buy, all we can do is educate or future proof by changing the RCD (which may need changing as a result of the C2 for 134.1 and 510.3

I don't disagree with any of that.

However 513.3.3 states "Where DC leakage current is confirmed to be present or may be produced by equipment....."

Now, on fixed equipment, we have a known unknown a case of finding out if DC current leakage is likely under normal operation or a likely fault product.

With socket circuits we have an unknown unknown. That is, we know there is potential for appliances to be used but we don't know what they are and how they could affect DC current levels.

Also many appliances work in cycles so you could have the situation where it is only when appliances are at the correct point in their cycle that they leak DC current. How do you measure this? How do you account for the cumulative effects of various appliances?

To me this doesn't pass the reasonableness test, which is, could it reasonably be expected that a normal person ,acting normally, is highly unlikely to introduce a saturating DC current to a circuit?

When any person can go out and buy an appliance with a plug on it that can satuate an AC type RCD then the answer has to be, no.

 

[Dartlec]

If as it seems, Type A RCDs will become the standard in the next BS7671 which won't be fully in force till 2023, then that would seem the time to introduce this level of consideration for RCD types.

If we can still get a satisfactory EICR on properties without RCD protection at all, then I don't see how we can give an unsatisfactory to one that does - unless there is a clear case like a car charger, PV, etc. where a Type A is mandated.

I'm also a little wary of manufacturers of 'end user' white goods specifying things when it is often to avoid them having to make improvements to their products. As far as the end user is concerned, if it comes with a 1363 Plug, then it fits into a 1363 socket - and is either rated at 3A or 13A.

What would happen if a washing machine manufacturer makes a deal with Wylex and states that only a specific Wylex model RCD must be fitted?

Have there been any real world incidents of injuries caused by this situation as yet? It's hard to grasp how much of a practical risk it is, even though the theoretical risk is clear enough. If there is actually a significant risk out there now, then more should be done than expecting EICRs to always pick up the issue.

 

[GBDamo]

If as it seems, Type A RCDs will become the standard in the next BS7671 which won't be fully in force till 2023, then that would seem the time to introduce this level of consideration for RCD types.

If we can still get a satisfactory EICR on properties without RCD protection at all, then I don't see how we can give an unsatisfactory to one that does - unless there is a clear case like a car charger, PV, etc. where a Type A is mandated.

I'm also a little wary of manufacturers of 'end user' white goods specifying things when it is often to avoid them having to make improvements to their products. As far as the end user is concerned, if it comes with a 1363 Plug, then it fits into a 1363 socket - and is either rated at 3A or 13A.

What would happen if a washing machine manufacturer makes a deal with Wylex and states that only a specific Wylex model RCD must be fitted?

Have there been any real world incidents of injuries caused by this situation as yet? It's hard to grasp how much of a practical risk it is, even though the theoretical risk is clear enough. If there is actually a significant risk out there now, then more should be done than expecting EICRs to always pick up the issue.

It seems to be the latest fad to have an inverted motor on washing machines, certainly the high end ones, with EV chargers, home batteries and PV.

It certainly looks like we are heading this way.

 

[Dartlec]

It seems to be the latest fad to have an inverted motor on washing machines, certainly the high end ones, with EV chargers, home batteries and PV.

It certainly looks like we are heading this way.

Sure - and Type A don't have any disadvantages that I know of, so makes sense to make the change.

But with EV chargers, home batteries and PV there is usually (hopefully) a competent installer who will be certifying that work and can either upgrade the whole installation, or install new consumer unit for that bit with the correct RCD.

Washing machines are the tricky one, since they are almost never supplied or fitted by an electrician, but sold to the customer directly who will just plug it in.

I wonder if the "installation services" that Currys, AO etc offer, check whether the installation is correct for the appliance and notify the customer if there are issues. (hint: I doubt it).

I had to attend a flat earlier in the year where the people "installing" the washing machine wouldn't do so because there was a flex outlet plate under the worktop, not a socket.

 

[Pretty Mouth]

Fair point, but some equipment produces DC leakage current during normal operation it is not necessarily a fault that caused the RCD saturation. C2 now?

I'm not saying I have the answer and will be having a word with NAPIT before my next EICR, when ever that is.

I didn't know that. Yeah, could be a C2 then. What sorts of equipment does produce DC leakage in normal operation?

 

[Pretty Mouth]

What sorts of equipment does produce DC leakage in normal operation?

terrible misuse of the English language