AFDD and Ring Circuits

[mort2376]

Morning peeps.

I attended the ECA Project18 technical briefing yesterday and asked the question do these work on ring circuits.

The answer..... Yes and No !

They will work on parallel arcs L-N, L-E.
But won't work on serial arcs L-L as in a broken ring conductor.

I asked then if that means rings will be removed in the future ?

His answer was he would think so.

There was also the caveat that AFDD will only operate if the conditions are right !

And there is currently no standard so each manufacturer programs them with their own settings. Some have red indicator lights, some Amber, some green.

Also these devices are not updateable in the field. So they find an issue and you have to buy a new unit if your having issues.

While Amd2 doesn't say you have to install these in a normal domestic environment I think it will come.

Interesting surge protection note as well. No longer have to use that calculation that was so easy. Only have to be fitted to meet any one of 3 criteria.

However one of them is to protect safety circuits and at the moment a smoke detector circuit or on a circuit means its a safety circuit !

 

[Murdoch]

Re AFDDs unless you’re considering a job on the list where they have to be used don’t fret about them

As for rings, can’t see that changing as few people read the 18th and apply it , so they will carry on for more years IMHO

As for AFDDs , None of the wholesalers I use think they are going to be selling many

 

[SPECIAL LOCATION]

Re AFDDs unless you’re considering a job on the list where they have to be used don’t fret about them

As for rings, can’t see that changing as few people read the 18th and apply it , so they will carry on for more years IMHO

As for AFDDs , None of the wholesalers I use think they are going to be selling many

You missed off..

And all DIYers, and 5WW's think anything with a socket MUST be on a ring!!!

(lost count of the number of 2socket rings I have seen in DIY garden sheds & workshops!)

 

[Murdoch]

You missed off..

And all DIYers, and 5WW's think anything with a socket MUST be on a ring!!!

(lost count of the number of 2socket rings I have seen in DIY garden sheds & workshops!)

The more the regs get complicated, the less people understand them, and the more non compliant installations get done.

I cite the fiasco about EV chargers ……

 

[Sidewinder]

Morning peeps.

I attended the ECA Project18 technical briefing yesterday and asked the question do these work on ring circuits.

The answer..... Yes and No !

They will work on parallel arcs L-N, L-E.
But won't work on serial arcs L-L as in a broken ring conductor.

I asked then if that means rings will be removed in the future ?

His answer was he would think so.

There was also the caveat that AFDD will only operate if the conditions are right !

And there is currently no standard so each manufacturer programs them with their own settings. Some have red indicator lights, some Amber, some green.

Also these devices are not updateable in the field. So they find an issue and you have to buy a new unit if your having issues.

While Amd2 doesn't say you have to install these in a normal domestic environment I think it will come.

Interesting surge protection note as well. No longer have to use that calculation that was so easy. Only have to be fitted to meet any one of 3 criteria.

However one of them is to protect safety circuits and at the moment a smoke detector circuit or on a circuit means its a safety circuit !

The product standard is IEC 62606, for AFDD’s so the ECA person is wrong with his statement.

 

[Murdoch]

The product standard is IEC 62606, for AFDD’s so the ECA person is wrong with his statement.

There's absolutely no surprise about that

 

[Andy™]

just wait til the incompetent 'installers' find out they dont work with rings, every EICR will have them as C2 regardless of an AFDD being fitted or not

 

[Sidewinder]

They do work with ring circuits.
They just cannot detect a series arc in line or neutral.
All arcs in spurs & connected devices and parallel arcs in the ring are detected.

 

[binky]

All arcs in spurs & connected devices and parallel arcs in the ring are detected.

surely shorts would be detected by the MCB?

 

[Fleeting]

surely shorts would be detected by the MCB?

Arc faults differ to dead shorts between conductors. Arc faults occur where there is damage to the insulation and other influences ecourage tracking between the conductors, this tracking creates heat which can create carbon on the insulation and carbon being conductive just compounds the situation.

 

[Sidewinder]

surely shorts would be detected by the MCB?

An arc isn’t a fault of “negligible impedance” though.

 

[Murdoch]

Arcs can be detected by RCD's too

 

[Fleeting]

The fact it may not disconnect on a single point series fault on a ring final circuit is irrelevant, there is not likely to be an arc therefore it is does not matter except in terms of overcurrent protection for which it is not there to detect.

 

[binky]

An arc isn’t a fault of “negligible impedance” though.

I'm trying to think of any cable damage I've encountered whereby you may get an arc without a screw or nail through the cable, squirrel damage maybe?

 

[Fleeting]

I'm trying to think of any cable damage I've encountered whereby you may get an arc without a screw or nail through the cable, squirrel damage maybe?

If you have two bare conductors with a sterile space separating them then nothing is likely to occur. Introduce a contaminate which produces a marginal conductive path then an arc across them may take place which can be compounded by carbonation of the insulating materials of the conductors.

 

[Murdoch]

If you have two bare conductors with a sterile space separating them then nothing is likely to occur. Introduce a contaminate which produces a marginal conductive path then an arc across them may take place which can be compounded by carbonation of the insulating materials of the conductors.

saw this a few years ago and yes it sparked- which is why the rcd was tripping. The local mice had chewed right through the insulation and copper

 

[Fleeting]

saw this a few years ago and yes it sparked- which is why the rcd was tripping. The local mice had chewed right through the insulation and copper

An rcd may well trip if sufficient power is introduced between live conductors and earth but this is not an arc fault, rcds do not detect arc fault.

 

[Murdoch]

An rcd may well trip if sufficient power is introduced between live conductors and earth but this is not an arc fault, rcds do not detect arc fault.

did I say it was an arc fault?

 

[Fleeting]

did I say it was an arc fault?

The thread is referring to arc fault detection devices, in #12 you state arcs can be detected by rcds this is not the case. In #15 I was referring to arc faults, in #16 you commented you had seen this as to a reason an rcd was tripping. What am I missing.

 

[Murdoch]

You are missing first hand experience of seeing an arc tripping a rcd