Cheap AFDD implementation in flats.

[John-SJW]

So, a flat 6 floors and above needs an AFDD on each socket circuit. At up to £150 each it is going to be an expensive undertaking if there are a number of socket circuits.
But! ... A 40A AFDD can be fitted in the CU. It can supply the socket circuits which will have their own DIN rail mounted fuses carriers fitted on the same DIN rail in the CU. The 40A AFDD is the master, the fused circuits slaves. Then fused circuits:

• a kitchen (heavy appliances);
• living room;
• bedroom;
• etc

All can have their own circuit, radial or ring, off their own fuse for over-current protection. Fuse are for selectivity conflicts with AFDD/RSCO/MCB's in series. But still have the protection of AFDD and RCD. Each fuse holder with a 4mm or 6mm conductors into the AFDDs terminal. The lights and and cooker can have their own RCBOs. In a typical flat that would be:

1) 40A AFDD;
1a) 32A fuse supplying kitchen sockets on ring final circuit;
1b) 20A fuse supplying sockets on the rest of the flat.
2) 40A RCBO supplying a cooker;
3) 6A RCBO for lighting.

Three circuits.
Two sub circuits.
Cost are now way down.

 

[SparkyChick]

My personal take is you'd need to consider the possibility that you would become the designer of a type tested enclosure/assembly. I have a feeling that you would be using the AFDDs outside the bounds of their specifications which could open up a whole world of hurt if something went wrong.

The board would no doubt look amazing with all your hand crafted bodgery and you'd also be going against the regs as far as minimising inconvenience in the event of a fault, possibly to the point where (based on your circuit schedule) the flat would have no heating/hot water (I'm assuming it's gas, powered by 1b) due to a fault on 1a).

How easy is it going to be for people to fix a blown fuse (here I'm thinking specifically about availability of said fuses - you can't typically get these at B&Q or ScrewFix)?

To be fair, with the excessive faffing around you'd be doing in the consumer unit just to construct this solution, I think simply installing two appropriately sized AFDDs would work out to be a more economic solution once you factor in everything.

As much as I don't like the price, unfortunately they are now a requirement in specific situations, so get over it, pay the price and do the job properly... don't be a plank trying to use the letter of the regs to defeat the spirit of the regs.

 

[littlespark]

The cost of the AFDDs are passed onto the customer and will eventually go down.
Trying to do it cheap now will end up being the same as when mainswitch RCDs came out with any number of mcbs coming off it.

Hence why certain regulations came in…. Eg, being left in the dark when you plugged in a faulty hoover

 

[loz2754]

AFDDs are designed to be installed one per circuit.
421.1.7 ...to be placed at the origin of the circuit to be protected.

 

[pc1966]

If its a flat and cost is critical then have one standard 32A RFC to rule them all from the AFDD, just route cable so kitchen stuff is very approx mid-way.

Cooker on RCBO radial without socket. Lights, etc, same as usual RCBOs.

Job done, nothing needing special design or certification as outwith "standard circuits".

 

[Dustydazzler]

As above over the next 2 or 3 years the unit cost of AFFDDDs will come down as sparks start buying more of them.
I remember when individual Rcbos were £35-40 a pop now you can get them for a £15

 

[pc1966]

Thinking about it again, it is quite simple:

• If they need more than one RFC due to electrical demand, then they can afford more than one AFDD.
• If not, they can't afford to use those appliances!

 

[John-SJW]

If its a flat and cost is critical then have one standard 32A RFC to rule them all from the AFDD, just route cable so kitchen stuff is very approx mid-way.

Cooker on RCBO radial without socket. Lights, etc, same as usual RCBOs.

Job done, nothing needing special design or certification as outwith "standard circuits".

One RFC can be done for sure. 4mm cable can be run to heavy current appliances in kitchen, to ensure a 2.5mm cable does not fry.

What I outlined in post 1 can be one 40A AFDD on a radial with two or three sub radials off it. There happens to be a fuse to the sub radials. The DIN fuse holders are in the CU for convenience. They can be outside in a separate enclose, but why when all can be in one enclosure. The CU.

Another angle is all the heavy appliances, say three of them, off a 6mm radial cable, with 2.5mm from 2nd to 3rd socket to reduce cable costs. One sub radial off the 6mm after AFDD serving other sockets, off their own fuse, say 25A. Fuse holder is in CU for convenience.
Lighting and cooker off their own RCBOs..

 

[John-SJW]

My personal take is you'd need to consider the possibility that you would become the designer of a type tested enclosure/assembly. I have a feeling that you would be using the AFDDs outside the bounds of their specifications which could open up a whole world of hurt if something went wrong.

The board would no doubt look amazing with all your hand crafted bodgery and you'd also be going against the regs as far as minimising inconvenience in the event of a fault, possibly to the point where (based on your circuit schedule) the flat would have no heating/hot water (I'm assuming it's gas, powered by 1b) due to a fault on 1a).

How easy is it going to be for people to fix a blown fuse (here I'm thinking specifically about availability of said fuses - you can't typically get these at B&Q or ScrewFix)?

To be fair, with the excessive faffing around you'd be doing in the consumer unit just to construct this solution, I think simply installing two appropriately sized AFDDs would work out to be a more economic solution once you factor in everything.

As much as I don't like the price, unfortunately they are now a requirement in specific situations, so get over it, pay the price and do the job properly... don't be a plank trying to use the letter of the regs to defeat the spirit of the regs.

The AFDD can serve a radial with sub radials off it. Within bounds of AFDD.

The sub radials just have fuses on them. Nothing wrong with that.

DIN fuse carriers in the CU is for convenience. A professional working in the CU would not bodge the job.

 

[UNG]

One RFC can be done for sure. 4mm cable can be run to heavy current appliances in kitchen, to ensure a 2.5mm cable does not fry.

Why do some people unnecessarily oversize cables as someone pointed out in another deceased thread

What I outlined in post 1 can be one 40A AFDD on a radial with two or three sub radials off it. There happens to be fuse to the sub radials.The DIN fuse holders are in the CU for convenience.

Why create unnecessary work the amount of time messing around and the material costs plus the added complications encountered if a fault occurs in the future you may as well just ............................................ install another AFDD and have done with it and bask in the long term savings

Another angle is all the heavy appliances, say three of them, off a 6mm radisl cable, with 2.5mm from 2nd to 3rd socket to reduce cable costs. One sub radial off the 6mm after AFDD serving other sockets, off their own fuse, say 25A. Fuse holder is in CU for convenience.
Lighting and cooker off their own RCBOs..

Why bodge an installation before it has even been used this is the sort of bodge you find after an installation has been in service for a decade or two not a new unused one

 

[John-SJW]

Thinking about it again, it is quite simple:

• If they need more than one RFC due to electrical demand, then they can afford more than one AFDD.
• If not, they can't afford to use those appliances!

Say a block of 60 flats in a 6 floor old block renovation like seen in London mansion blocks. All flats have gas heating. Costs are then dramatically cut for the electrical installations giving full protection.

AFDDs may drop dramatically in price, but far from that yet. The drop in the price is only opinion.

 

[JBW175]

Division of installation, or rather lack of it.

 

[westward10]

I doubt anyone renovating a mansion block in London will be considering the savings from omitting a few AFDDs in fact the wiring in such an installation is likely to be complex, no expense spared.

 

[John-SJW]

Adding another AFDD at £150, is not an option, as costs spiral.

The exercise is to get full AFDD protection in a flat meeting regs at minimal cost.

 

[John-SJW]

I doubt anyone renovating a mansion block in London will be considering the savings from omitting a few AFDDs in fact the wiring in such an installation is likely to be complex, no expense spared.

I see no complexity in the wiring.

1. Heavy appliance sockets cable back to CU.
2. General sockets cable back to CU.
3. Lighting cable back to CU.
4. Cooker cable back to CU.

 

[westward10]

I see no complexity in the wiring.

Understand what I put. These dwellings being in London are likely to have complex wiring money would not be an issue. I am not referring to your suggestion.

 

[John-SJW]

Understand what I put. These dwellings being in London are likely to have complex wiring money would not be an issue. I am not referring to your suggestion.

You are guessing.
The aim is an AFDD installation to regs at minimum cost.

 

[westward10]

You are guessing.
The aim an AFDD installation to regs at minimum cost.

Guessing, you are making unfounded assumptions I know what I am talking about.

 

[John-SJW]

You are guessing that money would not be an issue. Money being an issue or not, the aim is an AFDD protected installation to regs at "minimal" cost. If you can suggest a cheaper method please do.

 

[davesparks]

No matter how foolproof you make something there will always be someone more foolish waiting in the wings.

 

[davesparks]

Say a block of 60 flats in a 6 floor old block renovation like seen in London mansion blocks. All flats have gas heating. Costs are then dramatically cut for the electrical installations giving full protection.

A job like that will be designed and specified by someone in a design office. They won't have any concerns over the cost as they will just be getting paid to do the design so it can be put out to tender. They will design it along standard lines and specify an AFDD for each circuit that the regs require them for, they may even go further and specify an AFDD for every circuit just because they can and it covers their backside.

The job will go out to tender and whoever wins the job will follow the design spec, if they don't and decide to cut costs following your method they will get called back and have to change it to meet the spec at their own cost.

 

[SparkyChick]

Yet another thread that appears to be arguing for the sake of arguing.

Closing.