How common is total RCD protection?

[ericmark]

I will include 100 mA and 100 mA delayed as well as 30 mA in the question as although today we should use 30 mA in real terms 100 mA will normally trip before anyone gets hurt.

Start with my family.
Father-in-law - No RCD at all.
Mother - RCD in kitchen and for wet room and supply to garage but most of house no RCD protection.
My house - 2 x 30mA RCD's covering all circuits installed around 1992.
Daughter 1 - All RCD fitted about 6 months after buying house around 2009.
Son - One of the first things he did after buying both his houses so around 2010.
Daughter 2 - Within one month after buying house so 2015.

So all RCD protection for my family 2/3rds. Is this above or below normal?

 

[RF Lighting]

My house has a 16th ed split load board. It's MEM so will be cheaper to replace the whole lot rather than upgrade it.

My brother has RCBO protection to lights and sockets. The rest of his circuits are in steel tube so do not require RCD protection.

My sisters is all RCBO. I upgraded both installations when they bought their houses. Both since 2008.

 

[davelx]

I'm all RCBO, installed 2 years ago. Next door neighbor still has the old 4-way backelite Wylex 3036 fuseboard with the wooden base - not an RCD in sight (which is what I had until 2 years ago)

 

[EFLImpudence]

Interesting question and answer from RF.

Do I deduce correctly that RCDs are only installed because of the regulations and neither of you consider that they be installed for personal protection?

 

[Jackrae]

100mA won't necessarily protect against fatality

The following is an extract from http://en.wikipedia.org/wiki/Residual-current_device#Sensitivity

Sensitivity[edit]
RCD sensitivity is expressed as the rated residual operating current, noted IΔn. Preferred values have been defined by the IEC, thus making it possible to divide RCDs into three groups according to their IΔn value.
High sensitivity (HS): 6 – 10 – 30 mA (for direct-contact / life injury protection)
Medium sensitivity (MS): 100 – 300 – 500 – 1,000 mA (for fire protection)
Low sensitivity (LS): 3 – 10 – 30 A (typically for protection of machine)
Note that the nominal value of residual current indicated above is not an absolute value........


When I bought my house some 35 years ago the first thing installed was a 30mA RCD main isolator. The house was wired 3-phase and used old MEM fuse boards. I got my supplier to fit the RCD (in the days when they offered real service) and the old boy who fitted it said I'd have nothing but trouble. It did take me 2 days to resolve existing electrical faults, the main ones of which were earth and neutrals being mixed up. A couple of years ago the MEM boards were ripped out, the RCD isolator removed and replacement boards installed with RCDs and MCBs. All circuits are 30mA RCD protected and I have never had a nuisance tripping problem. Lighting circuits (a separate sub-board) use individual RCBOs. So those who argue "they are a nuisance" are dismissing the problems of existing system faults.

 

[Iggifer]

All RCBO's for me.

I can't ever forsee putting a board in for myself that wasn't all RCBO

 

[JohnW2]

I will include 100 mA and 100 mA delayed as well as 30 mA in the question as although today we should use 30 mA in real terms 100 mA will normally trip before anyone gets hurt.

That's all very well if the fault current is due to some electrical fault - in which case, as you say, unless someone's timing is incredibly unlucky, the fault will be cleared before anyone has a chance to be harmed by it. However, if the 'fault current' is flowing through a human being (which is the main thing people think about in terms of RCD protection in a TN installation), then a 100mA RCD will provide virtually no protection at all.

Kind Regards, John

 

[RF Lighting]

Interesting question and answer from RF.

Do I deduce correctly that RCDs are only installed because of the regulations and neither of you consider that they be installed for personal protection?

I think they're important for sockets and would always protect them, especially as my brother has two little boys running round!

I think the blanket requirement for all circuits to be RCD protected is overkill, but often what the regs prescribe.

 

[JohnW2]

So all RCD protection for my family 2/3rds. Is this above or below normal?

My house - lots of RCDs and a few RCBOs (all 30mA) - all final circuits protected.
Daughter 1 - single 30mA RCD protecting entire installation
Daughter 2 (rented flat) - split load dual 30mA RCDs - all circuits protected
In-laws (now deceased) - 1980s Wylex Standard - single 30mA RCD installed in front of that at some point
Immediate neighbour (1) - dual 30mA RCDs - all circuits protected
Immediate neighbour (2) - re-wire 2-3 years ago - all RCBOs
Almost immediate neighbour (3) - dual 30mA RCDs - all circuits protected

... so that's 100% for those 'close to me'.

Kind Regards, John

 

[JohnW2]

I think they're important for sockets and would always protect them,

Yes, even though we haven't a clue as to how many deaths or serious injuries have been prevented by RCDs, there presumably must be at least a few cases, so I think that makes sense. However, every time I ask the question, people seem to have experienced, or heard of, very few cases in which an electric shock (which may not have had serious consequences even without an RCD) caused an RCD to operate.

especially as my brother has two little boys running round!

Again, that makes good sense, since an RCD presumably affords at least some potential protection to individuals of any age/size. However, as I've pointed out before, a 30mA RCD gives increasingly less protection as a child gets younger/smaller, so we might not always be achieving quite what we think!

I think the blanket requirement for all circuits to be RCD protected is overkill, but often what the regs prescribe.

I would generally say that RCD protection of most domestic lighting circuits is probably 'overkill', but I can see that there is an argument for most other types of circuit.

Kind Regards, John

 

[AndyPRK]

I'm amazed how little people care about protecting lighting circuits with RCD's when you have two prongs sticking out a bulb holder.

If its 2 way switching your not sure its off.
If your a cocky electrican you might not bother switching it off.

And if its hard to reach your fingers could slip.

 

[JohnW2]

I'm amazed how little people care about protecting lighting circuits with RCD's when you have two prongs sticking out a bulb holder. ...

In a few cases, yes - but the great majority of lamp/bulb holders are plastic with no earth in sight - so if you stick your fingers into a live (non-'safety') one, you'll get a L-N shock which no RCD would or could notice.

... but, yes, I do concede that if there were earthed metal lampholders or light fittings around, then there would be a reasonable case for having RCD protection.

Anyway, I don't think you need worry too much. The way 'we' are going, I doubt that it will be all that long before all circuits (with just a few specific exceptions) will have to be RCD protected.

Kind Regards, John

 

[OwainDIYer]

I'm amazed how little people care about protecting lighting circuits with RCD's when you have two prongs sticking out a bulb holder.

If its 2 way switching your not sure its off.

Well I am, because I always wire mine so that all up = off.

My main CU is split load with 2 x RCD; my heating CU is 1 x RCD.

 

[sparkwright]

6 way board, no RCD at all,
apart from,
second board for shower served by stand alone 30 mA RCD.

40+ year old wiring in concealed imperial round tube, can be re-wired any time I like. Any recent additions done in PVC PVC which won't need re-wiring for a very long time.

 

[ericmark]

Far better than I expected to this point 16 all RCD, 4 part RCD, 1 no RCD and that last one is my father-in-law who was electrical project director for Liverpool Hospital board before be retired so well aware of the dangers.

As to trips I have found they come in batches it may trip once a week for 6 weeks then with no internal change can go two years to next one. I think mainly as RCD's in my house are so old pre-electronics.

I have installed emergency lights for stairs.

I struck me how we with nearly every post talk about RCD protection just wondered how common.

As to 100 mA read the Wylex data sheet page 5 which shows 100 mA in the main will protect. Hence included.

I wanted to list sparkwright as no RCD but can't really as shower is covered. As to OwainDIYer up is off then CU must be upside down. All industrial switches are down for off so anything falling on the switch can only switch it off. Only domestic switches are up for off.

As to RCD saving lives my son when he tripped the RCD would hold up his hands to tripping it and as a licensed radio ham at 14 years I had to expect it. I have had shocks but with RCD and without. The worst of recent years was with a RCD at 30 mA and tested to trip within the 40 mS required. I was installing a new fridge freezer this was about 15 years ago or more which required a water supply. Lucky the toilet was right above it so I tapped two hacksaw blades together with a spacer and was cutting a duel cut ready to remove the plaster and fit pipe. What I had not expected was when the extension had been built the electrician had run the lighting two way switch wire horizontally between the two switches. The belt even with RCD protection put me on the floor. Hard to say if it knocked me out no one else was there.

So that calls to question how good RCD protection is for direct contact? But also answers question as to RCD protection on the lights as that is the only belt I have got at home. I did not call the ambulance and also not silly enough to drive directly after a shock like that so don't know if it did any harm.

I am dam sure I got more than 100 mA so the only difference between a 30 mA and 100 mA RCD would have been time.