Amendment 3 2024, BS7671 2018.

[HappyHippyDad]

I can't see any thread started on the amendment, this is because. ..
A) I've had one strong beer and haven't looked hard enough.
B) It's not terribly important.
C) No one has thought about it yet.

Is this going to have much of an effect on us?
Personally, I don't fit PV or battery installs. I do install the odd EVCP though.

Will the manufactures update there MI to include the need (or not) for bidirectional devices?

 

[suffolkspark]

Lewden did a vid on their bi directional rcbos, i did ask if they actually differed internally or if it was simply re labelled, got a kinda generic reply, would be interested to see a teardown of uni directional and bi directional devices to see if they actually differ inside.

Presumably were now giving C2 to uni directional rcbos or rcds with downstream solar on an eicr if there is a very genuine risk it might scupper them?

 

[oscar21]

Can you imagine the conversations in the IEE office,

"look man we need to get a new book out ASAP I need a new Rolls Royce. But sir we cant release a new book until we've had 3 amendments to the current book. Well what are you waiting for, get an amendment out now. What on sir. Anything, I don't care there must be something you can think of."

 

[UNG]

Lewden did a vid on their bi directional rcbos, i did ask if they actually differed internally or if it was simply re labelled, got a kinda generic reply, would be interested to see a teardown of uni directional and bi directional devices to see if they actually differ inside.

Presumably were now giving C2 to uni directional rcbos or rcds with downstream solar on an eicr if there is a very genuine risk it might scupper them?

Why only solar it could also affect EV's where they are used as an energy store and back feed when required

 

[suffolkspark]

Why only solar it could also affect EV's where they are used as an energy store and back feed when required

Yea those too i guess if present, would be interested to know what actually happens or doesnt happen when a unidirectional device is subjected to this, and with that info what the coding consensus is.

 

[UNG]

Can you imagine the conversations in the IEE office,

"look man we need to get a new book out ASAP I need a new Rolls Royce. But sir we cant release a new book until we've had 3 amendments to the current book. Well what are you waiting for, get an amendment out now. What on sir. Anything, I don't care there must be something you can think of."

There is going to be an amendment 4 the Draft for Public Consultation is published on the 7th of this month with comments going till November

 

[SparkySy]

There is going to be an amendment 4 the Draft for Public Consultation is published on the 7th of this month with comments going till November

This is getting out of hand!
In all my years I cannot remember any previous amendments being this close together!!
Or is it just me getting old and time feeling like it's going faster?

 

[HappyHippyDad]

This is getting out of hand!
In all my years I cannot remember any previous amendments being this close together!!
Or is it just me getting old and time feeling like it's going faster?

Probably a bit of both
2026 is a fair way away, so your £80 is safe for a while.

 

[SparkySy]

Probably a bit of both
2026 is a fair way away, so your £80 is safe for a while.

Yeah your probably right there!

Still another exam to go and sit and another new book or 3 at least!
My loft is starting to bulge with the amount of former regs books, guidance notes and onsite guides I have amassed since 1995.

 

[Julie.]

I can't see any thread started on the amendment, this is because. ..
A) I've had one strong beer and haven't looked hard enough.
B) It's not terribly important.
C) No one has thought about it yet.

Is this going to have much of an effect on us?
Personally, I don't fit PV or battery installs. I do install the odd EVCP though.

Will the manufactures update there MI to include the need (or not) for bidirectional devices?

I think it's probably B)

It amounts to "where a RCD may be fed from either direction, it must be suitable for feeding in either direction"

Or perhaps even more succinctly "equipment has to be suitable for the application "

I know they're both a bit brief for inclusion in a modern standard (probably why I haven't been involved in writing/amending standards since the late '80s) but that is effectively it.

I think most good electricians would have been aware of this (along with "open the door before you try to walk through the doorway" sort of thing) so to the people on here - the likelihood is it isn't really adding anything.

My only thought is dismay that it has to be specifically included in a standard.

That means effectively that there are people out there (professionals?!) who are not selecting equipment suitable for purpose or perhaps even thinking about if the equipment they supply/install is actually suitable for the application.

How wide does this go, do they fit 5A switches on 13A immersion heaters? (because they then only need to carry one switch type for all lighting and everything else?)

The standard was clear before that equipment has to be suitable for the application, now it has to be "suitable for purpose PLUS don't forget, it really has to be suitable for purpose!"

 

[Simon47]

Has anyone actually come up with a scenario where an RCD might not work with reverse power flows ? Assuming the designer didn't add extra complexity just to make it unidirectional.

 

[Julie.]

Has anyone actually come up with a scenario where an RCD might not work,
with reverse power flows ? Assuming the designer didn't add extra complexity just to make it unidirectional.

It's to do with the detection/test circuit if they're tied specifically to one side, then they may not work with the wrong direction, and would still be energised when off. The manufacturer is the only one who knows if this is a problem or not.

 

[littlespark]

What happens if you put in 2 RCDs in “series” but one of them is put in backwards?


I’m sure this doesn’t need yet another amendment… just a note in the manufacturers instructions that we are supposed to be reading anyway

 

[Simon47]

It's to do with the detection/test circuit if they're tied specifically to one side, then they may not work with the wrong direction

Do you have a mechanism in mind where it wouldn't detect an imbalance between the line and neutral lines which are AC ?
Unless it specifically calculated the phase angle (why do that ?) then it would see the same imbalance whichever way the device is inserted.

and would still be energised when off.

So ?
The detection circuit is normally energised 100% of the time. If you mean the trip circuit, when it's tripped, the fault will disappear. The only exception might be a N-E fault with a single pole device that doesn't switch the neutral, but who fits those ?

 

[ipf]

Downloaded, but I'm not printing off 10 pages with hardly anything on them and stapling to the brown book (as told by latest assessor). Could print off pages required only, or just get the biro out.
A numbered Amendment containing two definitions and reg change regarding operational direction of devices...what a waste of time, paper and Amendment number.
Why not just send out one sheet as an update, as we used to get for changes/printing mistakes?

 

[Julie.]

Do you have a mechanism in mind where it wouldn't detect an imbalance between the line and neutral lines which are AC ?
Unless it specifically calculated the phase angle (why do that ?) then it would see the same imbalance whichever way the device is inserted.

So ?
The detection circuit is normally energised 100% of the time. If you mean the trip circuit, when it's tripped, the fault will disappear. The only exception might be a N-E fault with a single pole device that doesn't switch the neutral, but who fits those ?

The problem is that the electronic circuit is, say energised and has a detection feed from the output, when it's the correct way round and it trips or is switched off, the detection circuit is dead, but the main circuit is still energised. All good.

However if the wrong way round, when it trips, the detection circuit remains live, but the main circuit is disconnected! This can cause a reverse supply to the circuit. If it wasn't designed for this condition, it can damage the electronics.

Once damaged the rcd may not work - yet outwardly all you did was switch it off and back on again.

Only the manufacturer would know if keeping the detection circuit energised whilst the main control circuit is not causes a problem or not.

It isn't just RCDs BTW, RCBOs and especially combined AFDDs may be especially susceptible to this issue.

In reality if a manufacturer dictates their device is not suitable for bidirectional applications, they don't have to explain why; we need to follow their recommendations.

 

[SparkySy]

The problem is that the electronic circuit is, say energised and has a detection feed from the output, when it's the correct way round and it trips or is switched off, the detection circuit is dead,

Sorry @Julie.
I have not looked in depth at how bi-directional RCD's overcome this issue, as the detection circuit would surely have to come from one or other side of the device.
Do you have any knowledge of how this is achieved?

Thanks
Sy

 

[Julie.]

Sorry @Julie.
I have not looked in depth at how bi-directional RCD's overcome this issue, as the detection circuit would surely have to come from one or other side of the device.
Do you have any knowledge of how this is achieved?

Thanks
Sy

Well it's a pretty common issue with the cheaper microprocessors out there.

If there is no supply to the main controller, but there is to one of the i/o ports the current can flow into the controller and destroy it. If the supply is there the relative voltage across the protection diodes is not a problem.

If however you can limit the current to a much lower value, although the current backfeeds it isn't enough to cause damage.

So a redesign of the detection circuit may be sufficient, or changing to a microcontroller which doesn't suffer from this problem may be required.

In effect it's merely an electronic design flaw/feature the solution of which comes down to the actual implementation itself.

As a hobby I do design stuff using microcontrollers (often better ones like atmega4808 or atmega328, or stm32... but i have use things like the attiny range which are "cheap and cheerful".)

When I use an i/o port I tend to use a potential divider into a zener diode, then into the i/o port. The zener limits the voltage (usually to 4V9) and given the voltage a 10k resistance limits the current into the controller to 0.49mA. Of course this adds a zener and a resistor in addition to any potential divider on every i/o port - which for me is not a problem, and probably overkill for the better devices, but adds up for every production device.

 

[SparkySy]

thanks @Julie
That is an incredibly detailed answer.

I have forgotten a lot of electronics from my college days through lack of use unfortunately, but that makes sense!