AFDD in 18th 2nd Amendment

[UNG]

Indeed.

In fact the regulation goes on to say in Note 1:

"Higher risk residential buildings are ASSUMED to be....etc";

"It is ANTICIPATED that in many areas higher risk residential buildings will be defined in legislation which can be subject to change over time..."

About as clear as mud.

Just to stir the mud a bit

Does "in many areas" mean that in diiferent locations around the country there is a higher risk of arc faults or is it many areas of a building depending on it's residential status may be more at risk

 

[loz2754]

Just to stir the mud a bit

Does "in many areas" mean that in diiferent locations around the country there is a higher risk of arc faults or is it many areas of a building depending on it's residential status may be more at risk

Or perhaps local councils will be allowed to make up their own definition of a higher risk residential building?
Just as they do with the definition of an HMO.

 

[timhoward]

Just as they do with the definition of an HMO.

I tried to discuss this with Napit - they said there is a national definition of a HMO on gov.uk and what varies regionally is which of them require a license.
Ok, I said, so the does the regulation mean any HMO or any licensed HMO's? "Any HMO, we think" was the answer.

 

[UNG]

I tried to discuss this with Napit - they said there is a national definition of a HMO on gov.uk and what varies regionally is which of them require a license.
Ok, I said, so the does the regulation mean any HMO or any licensed HMO's? "Any HMO, we think" was the answer.

When I last looked the gov.uk HMO definition was somewhat vague and every LA has it's own set of rules as to how many unrelated people / bedrooms constitutes a HMO also the number of floors can throw extra requirements in

 

[John-SJW]

Blocks of flat over 6 floors, inc' ground, come into the focus of AFDDs. But the regs do not state must have AFDDs, saying shall. Shall does not mean you have to fit AFDDs.
So, in a new installation, or new socket circuits up to 32A, it is not mandatory to install AFDDs. If it was the word must would be used.

The regs recommend fitting AFDDs on 32A, or less, socket circuits. This can be totally ignored on new installs or new circuits.

Side note. A shower circuit is not mentioned in AFDDs. These cause most of the arcing in domestic premises that I have seen, especially the pull cords. AFDDs IMO must be fitted on shower circuits.

About metal CU cases. It all makes sense, but they have plastic glands, which makes the installation less safe than metal glands. If the case is to be metal so should the glands.

 

[davesparks]

Blocks of flat over 6 floors, inc' ground, come into the focus of AFDDs. But the regs do not state must have AFDDs, saying shall. Shall does not mean you have to fit AFDDs.
So, in a new installation, or new socket circuits up to 32A, it is not mandatory to install AFDDs. If it was the word must would be used.

The regs recommend fitting AFDDs on 32A, or less, socket circuits. This can be totally ignored on new installs or new circuits.

Side note. A shower circuit is not mentioned in AFDDs. These cause most of the arcing in domestic premises that I have seen, especially the pull cords. AFDDs IMO must be fitted on shower circuits.

About metal CU cases. It all makes sense, but they have plastic glands, which makes the installation less safe than metal glands. If the case is to be metal so should the glands.

Shall does mean you have to fit AFDD's as 'Shall' is used to indicate a requirement. See page 18 of the regulations for the clarification of this.

How does a plastic gland make an installation less safe?

 

[John-SJW]

Will look at page 18.
A fire inside the CU has more chance of spreading out of a steel CU with plastic glands.

 

[davesparks]

Will look at page 18.
A fire inside the CU has more chance of spreading out of a steel CU with plastic glands.

A fire will spread out of a steel CU regardless of what glands are installed.

CUs are not required to be any sort of fire containment, they are merely required to be made of a non-combustible material.

 

[John-SJW]

CUs are not required to be any sort of fire containment
Then not mandatory, as some have hinted at.

 

[John-SJW]

Prompted by a thought from @UNG on another thread.
Today I have been mostly eating thinking about cooker circuits...

If one of the AFDD-required building types has a 32A cooker circuit and an isolator with a socket on it.....do we interpret regs to say that an AFDD is required because of the socket on the cooker plate?
Or does the fact the regs says "final circuits supplying socket outlets" (plural) imply an exception ?!?!
It does seem clear that if you swap to an isolator without socket, or run a 40A rated circuit, you are back to no mandatory AFDD again.

Irrespective of the cooker plate, many ovens now have a plug on them and it's become quite common to find a double socket fed from the cooker circuit for hob ignition and plug-in-oven in certain new-builds.
So I guess cooker circuits are often going to need AFDD's anyway.

Hopefully this won't lead to plugs being chopped off things simply to cut costs.

So a dedicated radial to say a washing machine with one socket needs an AFDD. £130 each. Gulp!

I can see these AFDDs promoting large rings with some 4mm cable to the 1st socket on each leg of the ring to prevent overheating cable on an unbalanced ring - to save costs. As much as possible will be put onto the one ring. One ring for a whole house, with hard-wired dedicated radials on: Oven, Hob, Immersion.

 

[mainline]

Years ago it was the theft of lead off church buildings etc, then came the theft of alarm systems/cameras, in more recent times it's been copper cable, catalytic converters.
I wonder if before too long that people are going to come home to find their Afdds have been stolen.

 

[John-SJW]

You have a point. CUs may be prised off walls, as boilers were swiped in new builds before handover.

421.1.7
"AC final circuits supplying socket-outlets with a rated current not exceeding 32 A".

As they say recommend, AFDDs will be the defacto norm, as RCD became. It was not mandatory to fit RCDs but all were fitting them. New builds all had them in.

So any circuit with a socket on it will be fitted with an AFDD. So back to the 1940s and 50s with one ring in a largish house. In my place I have two rings, and four dedicated radials with sockets on them. So six Wylex AFDDs needed, which I have seen online for £126 each. So on a new installation deduct the cost of an RCBO which I have seen for £28. That is £98 for each AFSS circuit, which is a total of £588. Just swapping out existing RCBOs for AFDDs will be £756.
So, to cut costs I could join the two rings into one ring, then hard wire all the appliances on dedicated radials removing the sockets - washing machine, dishwasher, etc. Then a renew cost of one AFDD (£126) and four cable outlets @ approx £4 each, giving £142, plus some Wagos to join the two rings.

So, a saving of around £612. I see us going back to the 1940/50s.

 

[nicebutdim]

At this point there is no suggestion of their being required in the average domestic dwelling. By the time that becomes mandatory I would expect their relative cost to be significantly lower than it is at the present time.

As for new builds, the cost of AFDDs would be fairly trivial where overall build cost is concerned. The main issue of cost, at this time, would be borne by those who find that upgrades now include their addition.

Furthermore, the idea of saving money through the use of fewer circuits would be incredibly poor design and I can't imagine many self-respecting electricians would consider such an idea as it directly contravenes instructions contained within BS7671.

 

[John-SJW]

There is clear a suggestion AFDDs be fitted (not required but fitted) in the average dwelling.
In 421.1.7 it is clear saying "For all other premises", it recommends AFDDs in final circuits of 32A or less.

We will follow the USA it seems.

 

[nicebutdim]

There is clear a suggestion AFDDs be required in the average dwelling.
In 421.1.7 it is clear saying "For all other premises", it recommends AFDDs in final circuits of 32A or less.

We will follow the USA.

As I stated; no suggestion of requirement.

A recommendation is just that and until they become more affordable, it's likely that their adoption will mostly be limited to installations where regs tell us they shall be fitted. Language matters.

 

[John-SJW]

You never got my point. RCDs were not required, but were fitted wholescale way before being mandatory, because they were recommended.

 

[nicebutdim]

You never got my point. RCDs were not required, but were fitted wholescale way before being mandatory, because they were recommended.

There was exceptionally strong reasoning behind the move to RCD protection, whereas the argument in favour of arc fault protection is less compelling. Furthermore, early use of earth leakage protection involved a single device, which involved significantly less relative cost for the end user.

While I'm not convinced of the need for arc fault protection in many circumstances, I'm certainly not opposed to it and simply wish to present an alternative position. One which I feel is not far from reality.

 

[John-SJW]

I am with you. But it seems AFDDs will be on all circuits in the near future, going the way of RCDs. Which is back to 1940/50s wiring. AFDDs, don't detect a fault on line to line on rings because it's at the same potential. AFDDs only protect against screw-in faults, line to neutral or faults with appliances plugged in.

AFDDs being made mandatory in some installations has highlighted an overlooked advantage of a final ring. If there is an arc, the arc creates a resistance, so the current will go around the ring from the other direction, reducing any dangerous arcing, an arc which would say cause a fire in a radial. That is before AFDDs are fitted, so a level of safety is an integrated part of the final ring's design.

 

[John-SJW]

As I stated; no suggestion of requirement.

A recommendation is just that and until they become more affordable, it's likely that their adoption will mostly be limited to installations where regs tell us they shall be fitted. Language matters.

I have not looked at page 18 yet. But in normal English shall is not must. Need to get this clear.

 

[nicebutdim]

I have not looked at page 18 yet. But in normal English shall is not must. Need to get this clear.

I'm sorry, but there is no ambiguity where the meaning of shall is concerned

It is a statement 'You shall do this', rather than a question 'shall we do this? '.

The wording clearly states what is to be done and doesn't ask for opinion.