Ring or spur, no, it's a debate about AFDD's

John Burns · Aug 29, 2024

Taking the garage supply back to the main consumer unit with its own MCB/RCBO/AFDD is the best approach for sure. Fit a proper new garage CU unit.

Split from a DIY post. (John Burns will not be replying)

SPECIAL LOCATION · Aug 29, 2024

John Burns said:
Taking the garage supply back to the main consumer unit with its own MCB/RCBO/AFDD is the best approach for sure. Fit a proper new garage CU unit.

AFDD's are not required for basic domestic dwellings.

Providing suitable cable types/installation methods are used RCBO (RCD) is not required for sub-mains.
If fitting a CU in the garage with local RCD / RCBO's, discrimination is more easily achieved with an MCB protecting the sub-main.

However a CU in a garage is optional if only feeding a small number of sockets plus a light..
So an RCBO radial direct from the house CU, plus a 3A FCU in the garage for the light is also a suitable approach.

Fleeting · Aug 29, 2024

Spur is the interesting word, is it spurred from a ring final because if so you may have problems or has the term spur been used to describe a separate supply to the fuse box.

John Burns · Aug 29, 2024

SPECIAL LOCATION said:
AFDD's are not required for basic domestic dwellings.

Providing suitable cable types/installation methods are used RCBO (RCD) is not required for sub-mains.
If fitting a CU in the garage with local RCD / RCBO's, discrimination is more easily achieved with an MCB protecting the sub-main.

However a CU in a garage is optional if only feeding a small number of sockets plus a light..
So an RCBO radial direct from the house CU, plus a 3A FCU in the garage for the light is also a suitable approach.

If you are going to do it, do it properly to the best available. BTW, AFDDs are 'recommended' on all socket circuits, mandatory on many high-rises, HMOs, etc. Also it is best to fit AFDDs on showers as they are problematic using high currents. Or any high current drawing circuit really. BTW, I have an AFDD on my socket circuit. I view them as essential, not something nice to have.

SPECIAL LOCATION · Aug 29, 2024

John Burns said:
If you are going to do it, do it properly to the best available. BTW, AFDDs are 'recommended' on all socket circuits, mandatory on many high-rises, HMOs, etc. Also it is best to fit AFDDs on showers as they are problematic using high currents. Or any high current drawing circuit really. BTW, I have an AFDD on my socket circuit. I view them as essential, not something nice to have.

It is not a High Risk Residential Building, or a House in Multiple Occupancy, or a Purpose built student accommodation or a Care home.. so as I said previously they are NOT 'required' in this situation..
e.g. for a garage wiring alteration in a private domestic dwelling.

(The OP can refer to Regulation 421.1.7 for clarification.)

The OP can still do the job properly, by complying with requirements of BS7671, without following your preferences about what you consider essential, rather than what is just recommended.

So the majority of your above post, (I have quoted), has minimal relevance to the OP's question about a few extra sockets in a garage.

Historic statistics suggest that the lack of AFDD's in UK domestic dwellings, has so far not presented any major immediate, or potential, dangers to people, property or livestock.

Murdoch · Aug 29, 2024

AFDDs are an expensive con

John Burns · Aug 29, 2024

You are just going by what the regs say, which do say they recommend AFDDs on all socket circuits.

The original poster has a garage off a ring. He was asking if it better to take it from the CU. Of course it is. He has an old setup, so best put in new garage CU which is not an expensive item. And while at it I would say go to the highest safety levels fitting a RCBOs or better still an AFDD for sockets.

Best not have a race to the bottom.

John Burns · Aug 29, 2024

Murdoch said:
AFDDs are an expensive con

On what do you base this article faith?

Murdoch · Aug 29, 2024

John Burns said:
Best not have race to the bottom.

Hum. Best not sell something that isn’t required either. AFDDs are far too expensive at the moment and likely to stay that way for quite a while

I have only quoted once for a board with AFDDs for a HMO - I gave the owner a rough price face to face, to gauge her reaction - she was shocked to say the very least

Murdoch · Aug 29, 2024

John Burns said:
On what do you base this article faith?

There is no proof that they make things safer ….

John Burns · Aug 29, 2024

Murdoch said:
There is no proof that they make things safer ….

A wild statement. They do catch arcs, which can cause fires, then trip.

John Burns · Aug 29, 2024

Murdoch said:
Hum. Best not sell something that isn’t required either. AFDDs are far too expensive at the moment and likely to stay that way for quite a while

I have only quoted once for a board with AFDDs for a HMO - I gave the owner a rough price face to face, to gauge her reaction - she was shocked to say the very least

I bought an AFDD for around £80. If it saves a fire it is £80 well spent. I just did a Google. Saw one for £45 and another for £23 on Ebay.

kerching · Aug 29, 2024

AFDDs…has anyone watched Mr Savery,s YouTube post on these?

Fleeting · Aug 29, 2024

John Burns said:
You are just going by what the regs say, which do say they recommend AFDDs on all socket circuits.

The original poster has a garage off a ring. He was asking if it better to take it from the CU. Of course it is. He has an old setup, so best put in new garage CU which is not an expensive item. And while at it I would say go to the highest safety levels fitting a RCBOs or better still an AFDD for sockets.

Best not have a race to the bottom.

It is not clear if it is off a ring final they do not say this and the fact a fuse box is involved it is not certain, the use of the term spur maybe misplaced who knows without more info.

John Burns · Aug 29, 2024

Yes a Heath Robinson testing affair. Makers all say there is a difference between an arc and spark.

UNG · Aug 29, 2024

John Burns said:
I bought an AFDD for around £80. If it saves a fire it is £80 well spent. I just did a Google. Saw one for £45 and another for £23 on Ebay.

And what do you do if it doesn't save that fire

UNG · Aug 29, 2024

John Burns said:
A wild statement. They do catch arcs, which can cause fires, then trip.

And a wild statement back from you
They only catch the arcs that meet the right arc signature

AFDD's can be prone to nuisance tripping due to noise on the mains but how do you positively identify the cause
To rectify the problem, Do you replace the AFDD or do you rewire the circuit or do you do both as talking to a few test equipment manufacturers it is unlikely to be picked up by any of the test equipment currently in use

Phoenix · Aug 29, 2024

kerching said:
AFDDs…has anyone watched Mr Savery,s YouTube post on these?

The one with the Hager AFDDs failing to trip because they were designed to pass against a different trip method?

The problem with My Savery, is while he quite often has something worthwhile to say and can be funny with it too - he drags it out for for too long that I'm starting to fall alseep by the time he has made the point!

John Burns · Aug 29, 2024

UNG said:
And a wild statement back from you
They only catch the arcs that meet the right arc signature

AFDD's can be prone to nuisance tripping due to noise on the mains but how do you positively identify the cause
To rectify the problem, Do you replace the AFDD or do you rewire the circuit or do you do both as talking to a few test equipment manufacturers it is unlikely to be picked up by any of the test equipment currently in use

My AFDD has not done no such things. They are not useless and actually do what they say they do.

John Burns · Aug 29, 2024

Phoenix said:
The one with the Hager AFDDs failing to trip because they were designed to pass against a different trip method?

The problem with My Savery, is while he quite often has something worthwhile to say and can be funny with it too - he drags it out for for too long that I'm starting to fall alseep by the time he has made the point!

He tested the Siemens which appeared to work on his Heath Robinson test setup.

Ring or spur, no, it's a debate about AFDD's

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