RCBOs and lighting?

pauldavis123

I am getting a commercial unit wired and was wondering if I could ask the electrician if it was possible to wire in all the lamps off the 2.5mm sockets as the entire board is RCBOs.

Each room has its own circuit.

Only one lamp in one room should go if the is a fault.

All lamps are LED bulkheads.

Help with maintenance, energy usage metering and reconfigurability.

2011

Very bad practice, I would be surprised if the electrician agrees to this.
Why would you want this?

tomplate

I presume he wants to monitor the energy on a single circuit

It's better to keep the lighting separate

pauldavis123

2011 wrote: »

Very bad practice, I would be surprised if the electrician agrees to this.
Why would you want this?

From what I have read the lighting is kept on (several) seperate circuts to allow only certain areas to fail and leave lighting still available in the building for escape / faultfinding.

If each lamp is on one RCBO is this not a better solution? Only one room will go dark.

Apoligies if missing something basic

My reasons are maintenance, energy usage metering and reconfigurability.

ted1

pauldavis123 wrote: »

From what I have read the lighting is kept on (several) seperate circuts to allow only certain areas to fail and leave lighting still available in the building for escape / faultfinding.

If each lamp is on one RCBO is this not a better solution? Only one room will go dark.

Apoligies if missing something basic

My reasons are maintenance, energy usage metering and reconfigurability.

Emergency lighting will work of batteries.
What type lamps are being fitted , I can’t see much benefit measuring individual lighting loads

tomplate

It's not the normal practice

Will a fault plunge a room into darkness creating a hazard for workers in the room?

2011

pauldavis123 wrote: »

From what I have read the lighting is kept on (several) seperate circuts to allow only certain areas to fail and leave lighting still available in the building for escape / faultfinding.

Correct.

If each lamp is on one RCBO is this not a better solution? Only one room will go dark.

For a start RCDs / RCBOs can suffer from nuisance tripping. Not something desirable on a lighting circuit.

Also a faulty appliance is far more likely to cause a loss of lighting.

Remember loss of lighting can make an accident more likely. This is an important consideration in this claims culture we live in. Your insurance company may also use this unapproved deviation from the norm to avoid paying out in the event of a claim.

As this is a commercial premesis you should also consider emergency lighting.


Deviation from electrical norms without good reason is not recommended.

My reasons are maintenance

How would this help? If your electrician can’t understand a lighting circuit the he/she is incompetent.

energy usage metering

This can still be metered.

reconfigurability.

pauldavis123

ted1 wrote: »

I can’t see much benefit measuring individual lighting loads

While super small it is easier to any prospective tennant that all the usage is on one metered circut. I know this can still be done , just 6 more MCB or RCBOs.

tomplate

If the unit is being subdivided what you'd do is fit a sub-board at each room with separate circuits for lighting and power and provide isolation for the unit.

Energy monitoring can be done on the distribution circuit at the main board or the sub board

What you're describing is a bodge kind of job

pauldavis123

tomplate wrote: »

It's not the normal practice

Will a fault plunge a room into darkness creating a hazard for workers in the room?

True

pauldavis123

2011 wrote: »

Correct.



For a start RCDs / RCBOs can suffer from nuisance tripping. Not something desirable on a lighting circuit.

Also a faulty appliance is far more likely to cause a loss of lighting.

Remember loss of lighting can make an accident more likely. This is an important consideration in this claims culture we live in. Your insurance company may also use this unapproved deviation from the norm to avoid paying out in the event of a claim.

As this is a commercial premesis you should also consider emergency lighting.


Deviation from electrical norms without good reason is not recommended.



How would this help? If your electrician can’t understand a lighting circuit the he/she is incompetent.



This can still be metered.

OK, I'll go with the norm, thanks for all the info

pauldavis123

tomplate wrote: »

If the unit is being subdivided what you'd do is fit a sub-board at each room with separate circuits for lighting and power and provide isolation for the unit.

Energy monitoring can be done on the distribution circuit at the main board or the sub board

What you're describing is a bodge kind of job

Probably the best way to go about it thanks :rolleyes:

2011

tomplate wrote: »

If the unit is being subdivided what you'd do is fit a sub-board at each room with separate circuits for lighting and power and provide isolation for the unit.

Energy monitoring can be done on the distribution circuit at the main board or the sub board

What you're describing is a bodge kind of job

Exactly.
Depending on a number of factors it may be possible to use the socket circuit supply cable to supply the sub board in each case. I would be reluctant to have just one light per room.

What sort of commercial premesis is it?

pauldavis123

2011 wrote: »

Exactly.
Depending on a number of factors it may be possible to use the socket circuit supply cable to supply the sub board in each case. I would be reluctant to have just one light per room.

What sort of commercial premesis is it?

1. Room is only 3m x 3m,
2. Workspaces.

I'll go with the sub board.

Risteard81

2011 wrote: »

For a start RCDs / RCBOs can suffer from nuisance tripping. Not something desirable on a lighting circuit.

I'd have to disagree that RCD protection is undesirable on a lighting circuit generally as tripping is indicative of an earth fault. Particularly with a neutral/Earth fault on a lighting circuit this could be useful for safety reasons.

That said the generally accepted practice here is to segregate lighting and small power circuits and I wouldn't advocate not doing that without very good reason. But I don't see an issue with lighting circuits having an RCBO. (In fact, for bathroom lighting circuits it's a rule.)

tomplate

Risteard81 wrote: »

I'd have to disagree that RCD protection is undesirable on a lighting circuit generally as tripping is indicative of an earth fault. Particularly with a neutral/Earth fault on a lighting circuit this could be useful for safety reasons.

That said the generally accepted practice here is to segregate lighting and small power circuits and I wouldn't advocate not doing that without very good reason. But I don't see an issue with lighting circuits having an RCBO. (In fact, for bathroom lighting circuits it's a rule.)

Can't see any advantage in general having lights on RCDs

Bruthal

tomplate wrote: »

Can't see any advantage in general having lights on RCDs

Even this bathroom thing. Just because its a rule doesnt mean its better having them on an RCD.

I would say there is more risk of falling in a dark bathroom than being electrocuted by a ceiling light.

Risteard81

tomplate wrote: »

Can't see any advantage in general having lights on RCDs

Again, consider neutral/Earth faults coupled with loss of connection of the neutral tail to the PEN conductor and the consequences of this. I've seen it and it's not pretty. As I pointed out operation of the RCD (RCCB/RCBO) will almost certainly be due to an earth fault.

Bruthal

Risteard81 wrote: »

Again, consider neutral/Earth faults coupled with loss of connection of the neutral tail to the PEN conductor and the consequences of this. I've seen it and it's not pretty. As I pointed out operation of the RCD (RCCB/RCBO) will almost certainly be due to an earth fault.

What was the nature of that fault?

Risteard81

Bruthal wrote: »

What was the nature of that fault?

There was a neutral/Earth fault on an outside light. A homeowner had a non-REC in to rewire downlights because the cable had melted to them. After they were rewired the cables were burned again and the non-REC didn't want to know. At this point I was called and discovered that the entire installation load was returning through the neutral/Earth fault in the 1.5mm^2 T&E as the neutral tail had no continuity between the ESB meter and the DB. (Now I do all of his electrical work.)

I'm not trying to push RCDs for lighting but just pointing out why they may not be a bad thing. In fact the 18th Edition of the IET/IEE Wiring Regulations in the north and Britain (which comes into effect on 1st January) will require any circuit supplying luminaires in a domestic dwelling to be RCD protected.

Who knows what will happen with the 5th Edition of the Wiring Rules?

2011

Risteard81 wrote: »

I'd have to disagree that RCD protection is undesirable on a lighting circuit generally

You are entitled to your opinion. It is my view that this would result in a net increase of risk for the reasons given.

as tripping is indicative of an earth fault. Particularly with a neutral/Earth fault on a lighting circuit this could be useful for safety reasons.

Would you apply this logic to all fixed appliances? The cooker too?

That said the generally accepted practice here is to segregate lighting and small power circuits and I wouldn't advocate not doing that without very good reason.

That is exactly what I said.

But I don't see an issue with lighting circuits having an RCBO. (In fact, for bathroom lighting circuits it's a rule.)

I think the this rule is a bad idea.

I'm open to correction here but I don't believe that this is a requirement if the lighting in the bathroom is ELV. If that is the case I would deal with it that way.

2011

Risteard81 wrote: »

There was a neutral/Earth fault on an outside light. A homeowner had a non-REC in to rewire downlights because the cable had melted to them.

So you are saying that despite the lights being rewired the neutral to earth fault was not fixed?

After they were rewired the cables were burned again and the non-REC didn't want to know.

.......because the entire neutral current for the house was passing through the neutral of the outside light, through the short, back along the earth wire to the main earth bar, to the (10 mm sq.?) earth rod neutralising link [Edit].

If that was the case the volt drop must have been colossal when larger loads were switched on as the impedance of the return path could be so high.

At this point I was called and discovered that the entire installation load was returning through the neutral/Earth fault in the 1.5mm^2 T&E as the neutral tail had no continuity between the ESB meter and the DB. (Now I do all of his electrical work.)

So what did the customer say his electrical issues were? I would imagine that he had a lot of under voltage issues that became very noticeable when things like the hob were switched on.

What caused the issue? Did the REC just not connect the tails properly at the meter? I saw this before.

In fact the 18th Edition of the IET/IEE Wiring Regulations in the north and Britain (which comes into effect on 1st January) will require any circuit supplying luminaires in a domestic dwelling to be RCD protected.

Yeah, different country and they will be even further removed post Brexit.

Who knows what will happen with the 5th Edition of the Wiring Rules?

I will ask and see what I can find out.
I doubt it to be honest.

Risteard81

2011 wrote: »

Would you apply this logic to all fixed appliances? The cooker too?

I'm certainly not opposed to it.

In a new domestic installation in the north typically every circuit would be RCD protected. The reality is that this doesn't generally lead to any issues (even with cookers).

For a southern installation I don't make a habit of putting RCD protection where it's not required, but just wanted to point out that there can be benefits to such an approach.

tomplate

Bruthal wrote: »

Even this bathroom thing. Just because its a rule doesnt mean its better having them on an RCD.

I would say there is more risk of falling in a dark bathroom than being electrocuted by a ceiling light.

in time the rules will surely be EFL protection on all domestic circuits


they just need to get it right and not create additional hazards with the rule changes

Risteard81

2011 wrote: »

So you are saying that despite the lights being rewired the neutral to earth fault was not fixed?

.......because the entire neutral current for the house was passing through the neutral of the outside light, through the short, back along the earth wire to the main earth bar, to the (10 mm sq.?) earth rod neutralising link [Edit].

The fault wasn't fixed presumably because no testing was done and the non-REC was unaware of it.

The entire load current was not returning through the Earth electrode but through the main protective conductor (neutralising link) to the PEN conductor. (Obviously as a parallel path some would flow through the electrode but this would be a tiny proportion.)

There were volt drop issues such as dimming with the electric shower running but still none of them clicked what was going on.

tomplate

Bruthal wrote: »

Even this bathroom thing. Just because its a rule doesnt mean its better having them on an RCD.

I would say there is more risk of falling in a dark bathroom than being electrocuted by a ceiling light.

you could be having a bath though and the light falls off the ceiling


you decide to tidy up the wires while having your bath and get electrocuted

Bruthal

tomplate wrote: »

you could be having a bath though and the light falls off the ceiling


you decide to tidy up the wires while having your bath and get electrocuted

I always wondered is it possible to survive being electrocuted

2011

Risteard81 wrote: »

The fault wasn't fixed presumably because no testing was done and the non-REC was unaware of it.

I can’t help but notice the persistent use of the term “non-REC”. Is this strange beast an electrician or not? Surly that is more relevant?

There is no “REC qualification”. Besides the overwhelming majority of electricians work for RECs so they are entitled to do unsupervised electrical work.

tomplate

Bruthal wrote: »

I always wondered is it possible to survive being electrocuted

it is



you have to be electrocuted to death to die

Risteard81

tomplate wrote: »

it is



you have to be electrocuted to death to die

Technically electrocution means that it is a fatal electric shock. It was originally a contraction of "electrical execution" when the electric chair was invented.

Risteard81

2011 wrote: »

I can’t help but notice the persistent use of the term “non-REC”. Is this strange beast an electrician or not? Surly that is more relevant?

I used the term because that was how the person was described to me. He thought that he was a registered contractor but later found out that he wasn't. As I don't know who that person was I can't offer an opinion as to whether he was an Electrician or not.

Non-REC was not being used in a derogatory sense - simply the only factual way to describe the person unknown.

Bruthal

Risteard81 wrote: »

Technically electrocution means that it is a fatal electric shock. It was originally a contraction of "electrical execution" when the electric chair was invented.

Invented by a non-REC no doubt

Bruthal

Risteard81 wrote: »

Non-REC was not being used in a derogatory sense - simply the only factual way to describe the person unknown.

Would you say it is more likely it would be a superior installation if it was a REC as opposed to a non REC qualified electrician?

2011

Risteard81 wrote: »

Technically electrocution means that it is a fatal electric shock.

Correct.
This applies whether it is by REC or non-REC

Bruthal

Would an electric chair be on an RCD?

Risteard81

Bruthal wrote: »

Would an electric chair be on an RCD?

It would be irrelevant if no pole of the supply was Earthed.

Fordcspri23

Does 2011 not know that to comply with regulations lighting in certain locations, outdoor at certain heights etc have to go through an rcbo. Also they do not nuisance trip.

2011

Fordcspri23 wrote: »

Does 2011 not know that to comply with regulations lighting in certain locations, outdoor at certain heights etc have to go through an rcbo.

If you were to read this thread you would have the answer.

Also they do not nuisance trip.

Are you actually stating that no RCD has ever nuisance tripped?
So its just an urban myth?

2011

@ Fordcspri23, a little bit of light reading for you:
ABB seem to think that nuisance tripping exists. See link

Bruthal

Risteard81 wrote: »

It would be irrelevant if no pole of the supply was Earthed.

To help reduce the chance of electrocution though
Joking here, just in case you think im serious

2011

Risteard81 wrote: »

The fault wasn't fixed presumably because no testing was done and the non-REC was unaware of it.

I doubt that testing would have been necessary to know that something was seriously wrong.

There were volt drop issues such as dimming with the electric shower running but still none of them clicked what was going on.

It is amazing that the short survived so long. What caused it? Was it the enclosure?

I agree that an RCBO would have tripped for this specific fault but so would a double pole MCB which are required by the regulations in some situations. I just feel that although RCDs solve one issue they introduce a different problem.

What caused the issue with the neutral between the ESB meter and the DB in the first place?

2011

Bruthal wrote: »

To help reduce the chance of electrocution though
Joking here, just in case you think im serious

Not if it was desensitised first, this could happen if you were electrocuting someone upstream on the same circuit :pac:
I'm joking too

Fordcspri23

2011 wrote: »

@ Fordcspri23, a little bit of light reading for you:
ABB seem to think that nuisance tripping exists.

In low percentage terms, I will choose not to read the light reading thanks.

Bruthal

2011 wrote: »

Not if it was desensitised first, this could happen if you were electrocuting someone upstream on the same circuit :pac:
I'm joking too

The executioner is probably desensitized anyway.

2011

Fordcspri23 wrote: »

In low percentage terms, I will choose not to read the light reading thanks.

Yes, nobody suggested otherwise.

In fact RCDs are actually are very rarely needed too when you think about it. The number of times we actually want them to trip (due to a fault) is probably an even a lower percentage.

Risteard81

2011 wrote: »

What caused the issue with the neutral between the ESB meter and the DB in the first place?

The DB was so full and a bit of a rat's nest that it was difficult to see where it was going. Had floorboards up above that initially with the intention of replacing the meter tails but then managed to get the end of the neutral. Not sure how long it had been like that but there seemed to have been a number of additions and alterations including a supply to a garage (which was now a granny flat with a tenant in it) so I would guess that it happened when that was being done. (The granny flat had its own issues such as a low-level northern-style DB hidden at the back of a press in the kitchen units. Needless to say I was less than impressed with this setup.

Just a lot of poor work done over probably a substantial period of time. (I think the house was a repossession.) It would be within a mile or so of the border so I suspect had work done on it by people with little or no knowledge of the southern Wiring Rules.

In the border areas it's not unusual to come across installations in the north butchered with southern components and installations in the south butchered with northern components. It can be quite frustrating and can often lead to dangerous situations.

Tuco88

I'd be on the side of dedicated RCBOs for all, thats just my opinion. An RCD covering several circuits its only hassle. Are farms/milking palours all rcds protection now anyway.

I would think all rcd protection and arc fault protection is the road in the future?

2011

Tuco88 wrote: »

I'd be on the side of dedicated RCBOs for all, thats just my opinion.

I would only have this view if a risk assessment justified it. Do you know of anyone that got a shock from a light? If they did was it of sufficient magnitude to trip an RCD? Probably not.

What about critical stuff such as comms cabinets, servers, PLCs?
What about double insulated fixed appliances?

Also some devices such as nonlinear loads can nuisance trip RCDs even when healthy.

An RCD covering several circuits its only hassle.

Agreed.

Risteard81

2011 wrote: »

Do you know of anyone that got a shock from a light? If they did was it of sufficient magnitude to trip an RCD? Probably not.

Whilst it may not be of sufficient magnitude to trip a 30mA RCD, this is also the case for anything else protected by it. The fact that it's a lighting circuit rather than a socket circuit does not reduce the magnitude of the shock, which is instead to do with Ohm's Law and the impedance through the human body. So a shock from a lighting circuit is every bit as likely or unlikely to trip the RCD as a shock through another type of circuit.

Tuco88

2011 wrote: »

I would only have this view if a risk assessment justified it. Do you know of anyone that got a shock from a light? If they did was it of sufficient magnitude to trip an RCD? Probably not.

What about critical stuff such as comms cabinets, servers, PLCs?
What about double insulated fixed appliances?

Also some devices such as nonlinear loads can nuisance trip RCDs even when healthy.


I agree, the same for a fire alarm panel, remote i/o panels, BMS, so on.

I was looking at a domestic view. But a modern milking parlour id imagine would have interesting load characteristics.I cant honestly say whats in a new one. So suppose design and location?

You could argue the rcd offers a degree of fire protection, which I like the idea in a domestic lighting setup. In a modern house at minimum have dedicated RCBOs on the sockets circuits.

Fordcspri23

Risteard81 wrote: »

Whilst it may not be of sufficient magnitude to trip a 30mA RCD, this is also the case for anything else protected by it. The fact that it's a lighting circuit rather than a socket circuit does not reduce the magnitude of the shock, which is instead to do with Ohm's Law and the impedance through the human body. So a shock from a lighting circuit is every bit as likely or unlikely to trip the RCD as a shock through another type of circuit.

+1