New circuit in plastic consumer unit. Yes or no?

[swaRRR]

I work with someone who really isn't happy installing new circuits into plastic consumer units.

Sometimes he refuses to do it if the board in question isn't in a great state or if the existing wiring is spaghetti junction.

Obviously the regs state that it's fine to add if the board conforms to the regs at time of installation, but he argues that they're not law they're guidelines and that if he's not happy doing it then he doesn't have to and has every right to refuse.

My take is, if site told me to install a cable without RCD protection and said it was fine because the cable was >50mm in a wall, i still wouldn't do it even though allowed in regs. A similar although not identical scenario.

What do you all think?

 

[swaRRR]

Outside domestic which is where I work I avoid rcds at all costs.

Why? Is there a disadvantage to having them in industrial/commercial settings? Something to do with leakage i presume?

 

[westward10]

Why? Is there a disadvantage to having them in industrial/commercial settings? Something to do with leakage i presume?

To avoid nuisance tripping they are a pain, a 'normal' protective device provides adequate circuit protection providing all criteria is met.

 

[westward10]

But in a domestic setting what stops humans from dying if circuits aren't on RCD's? (Sorry i should have mentioned that i'm talking about domestic since that's where we work.)

Never assume a rcd will save your life.

 

[pc1966]

Why? Is there a disadvantage to having them in industrial/commercial settings? Something to do with leakage i presume?

As @westward10 has said, you might have random trips due to leakage or noise (e.g. welder, large motors switching) and if the DB is locked (normal outside of domestic) then you get even more grief.

For most industrial equipment with proper earth bonding the traditional ADS disconnection requirements are sufficient to protect personnel from electric shock danger. Also most commercial/industrial sites have better PAT testing regimes than domestic, and you rarely have wet or outside areas where the risk of shock is highest.

Where RCD really do offer an advantage is outdoors or other areas where DIY modifications can result in cable damage. But I would never test one with my life! The trip curve should protect you, but it is not guaranteed, it is very painful, and occasionally an RCD fails. I don't know if the RCD failure rate is higher or lower than parachutes for recreational jumping, but I would guess parachutes are tested more often!

 

[swaRRR]

Never assume a rcd will save your life.

I don't, but compared to not having one at all the chances of living are significantly higher, no?

 

[timhoward]

I don't, but compared to not having one at all the chances of living are significantly higher, no?

That rather depends on the chances of live parts being exposed.
Leaving installations with TT earthing aside, they would only die if something else is already wrong or they do something rather special like stick the fork in the toaster....
If the regs are met regarding basic and fault protection, and everything exposed and conductive is correctly held at earth potential, then a fault shouldn't result in a death.
(That's why RCDs are classed as "additional protection" in the regs)

Let's also remember that the vast majority of them are not used in accordance with manufacturers instructions, and the test button is never ever pressed. I've encountered a fair few older main-switch RCD consumer units where I turn it off and it won't turn on again due to a leakage fault that's been there all along but the RCD was stuck and didn't trip. In those situations it wouldn't have saved a life as it wasn't functional!

RCD's are certainly a good idea as an extra back-stop against the unknown, and early warning of leakage faults / faulty equipment. But according to my view of the world they aren't quite as transformative as can be made out sometimes.

 

[swaRRR]

That rather depends on the chances of live parts being exposed.
Leaving installations with TT earthing aside, they would only die if something else is already wrong or they do something rather special like stick the fork in the toaster....
If the regs are met regarding basic and fault protection, and everything exposed and conductive is correctly held at earth potential, then a fault shouldn't result in a death.
(That's why RCDs are classed as "additional protection" in the regs)

Let's also remember that the vast majority of them are not used in accordance with manufacturers instructions, and the test button is never ever pressed. I've encountered a fair few older main-switch RCD consumer units where I turn it off and it won't turn on again due to a leakage fault that's been there all along but the RCD was stuck and didn't trip. In those situations it wouldn't have saved a life as it wasn't functional!

RCD's are certainly a good idea as an extra back-stop against the unknown, and early warning of leakage faults / faulty equipment. But according to my view of the world they aren't quite as transformative as can be made out sometimes.

But as a father i want to know that an RCD protection is in place should one of my dingle children decide to stick a fork in the toaster..in a domestic setting i just don't see a reason not to install one. If you can prevent idiotic events occurring in death then imo RCD protection should be a given.

Going back to the original point, I wouldn't install say a 2.5mm radial and not put RCD protection on it because it's buried 50mm deep for example. Even if someone said it was allowed i wouldn't do it.

 

[timhoward]

But as a father i want to know that an RCD protection is in place should one of my dingle children decide to stick a fork in the toaster..

Completely understood! As a father when we moved house and found the electric shower was on a 30 amp fuse I did a board change pretty quickly too, so I think we agree on this point!
I've also just advised a church that having a 3036 board in a hall that is used by children's groups isn't really on these days.

I'm not saying we shouldn't install RCDs. Maybe I misinterpreted your point, it looked as though you were suggesting not having one was dangerous in itself.
My point is that in the risk management game RCD's only come into play when the low-likelihood events happen, and then as you point out they can make a big difference (if they actually work).

 

[timhoward]

Going back to the original point, I wouldn't install say a 2.5mm radial and not put RCD protection on it because it's buried 50mm deep for example. Even if someone said it was allowed i wouldn't do it.

There's the odd exception. If we are sticking to domestic, I might possibly do this for a smoke alarm circuit in some circumstances. If it was a split load board and all required regs were met I'd happily favour the non-protected side over a shared RCD.
Every day is different and everything is weighed up!

 

[telectrix]

Dont want to say too much else I would be a hypocrite, but thats like me would never fit a light switch inside a bathroom no matter what.

whyever why not?

 

[DPG]

whyever why not?

See the thread from yesterday for one example.

 

[UNG]

But as a father i want to know that an RCD protection is in place should one of my dingle children decide to stick a fork in the toaster..in a domestic setting i just don't see a reason not to install one.

Would it not be prudent to teach your kids the dangers of sticking a fork in the toaster rather than relying on something that can fail

If you can prevent idiotic events occurring in death then imo RCD protection should be a given.

And the big problem is we left common sense behind many years ago. the reduction in testing of RCD's in the latest 18th edition amendment will IMO end up with a lot of potentially faulty RCD's remaining in service which may have an outcome of more idiots dying

 

[Lister1987]

One person's engineering judgement may differ from the next and that's fine, as long as the fundamentals are met. It could be an excessive application of 132.16 BUT equally it could be a valid application depending on the points put forward.

Another way to look at is its been considerable time since plastic boards were first allowed (16th? I don't know but I'm guessing close to 20 years?) and plastic does, over time degrade, even on a molecular level, so the drive to change to metal is a valid one (product life expiration).

Some would say its using a sledgehammer to crack a nut but if the end result is a safer installation, is that not the end goal?

 

[brianmoooore]

Another way to look at is its been considerable time since plastic boards were first allowed (16th? I don't know but I'm guessing close to 20 years?) and plastic does, over time degrade, even on a molecular level, so the drive to change to metal is a valid one (product life expiration).

Some would say its using a sledgehammer to crack a nut but if the end result is a safer installation, is that not the end goal?

Definitely not 20 years. I only ever fitted one domestic metal CU, and I've not been out of the game that long.
I'm yet to be convinced that a metal CU is inherently safer than a plastic one, with the possibility of incomers shorting to the steel, and outgoing cables passing through sharp edged holes that may or may not still have a grommet fitted, even if one was fitted on installation.
The only heat damaged plastic CUs I've ever seen have been down to poor workmanship, coupled with poor terminal design on the components in the CU.

 

[UNG]

Another way to look at is its been considerable time since plastic boards were first allowed (16th? I don't know but I'm guessing close to 20 years?)

16th edition was circa 1992

and plastic does, over time degrade, even on a molecular level, so the drive to change to metal is a valid one (product life expiration).

So when do you expect the manufacturers to introduce metal MCB's / RCBO's as using your argument they must have a similar degradation rate on the plastic