Electrician upped lighting MCB to 20A

joebre

Have decorative light fitting with 20 No. 10W G04 bulbs. Would often trip as I switched on the light, forcing me to go downstairs in the dark to reset the MCB.
Called back the electrician and he changed the MCB from 10A to 20A. He was back the other day, as part of my snag list. He refused to change the MCB back to 10A, saying the light would trip again.
I am under the impression that what he done is a potential fire hazard. Can someone point me in the right direction ?

Thanks,

Joe

Dotsie~tmp

joebre wrote: »

Have decorative light fitting with 20 No. 10W G04 bulbs. Would often trip as I switched on the light, forcing me to go downstairs in the dark to reset the MCB.
Called back the electrician and he changed the MCB from 10A to 20A. He was back the other day, as part of my snag list. He refused to change the MCB back to 10A, saying the light would trip again.
I am under the impression that what he done is a potential fire hazard. Can someone point me in the right direction ?

Thanks,

Joe

The circuit in question is almost certainly wired in 1.5mm sq PVC/PVC cable. No need to consult the regs, we can safely say if done properly the circuit should able to carry at least 10 Amps. The light fitting you have sounds like the ball shaped star fitting i have with 20 or so 10W 12V bulbs. Generously allowing for losses at 300W you could have 7 of these fittings on one circuit and there should be a problem.

One things for sure. If wired in 1.5mm sq the circuit is no longer protected from over-current and overheating with 20A breaker. Here what I suggest you do.

-Check old 10A breaker was B-Type. It will say B10 on it, not any other letter.
-Turn off 20A breaker.
-Count amount of fittings no longer working. (Shouldn't be much more than 10 and you can count 2 50W spots as 1).
-Add up their wattage.
-Calculate current. (Wattage/Voltage)=Current

If all seems well and under 10A calculated look further and measure.

-Check so see if anything else isn't working, even stuff that shouldn't be on a lighting circuit.
-Get a clamp meter and measure the current on the circuit. Do not ask the electrician. In my opinion his willingness to put 20A breaker on 1.5mm sq means his dedication to safety can not be trusted.

If over 10A you must find the cause. If under then maybe the fitting in question is faulty causing a large inrush of current.

BTW if you have the clamp meter handy just do that first. If you can no longer proceed from here call a competant electrician. Like me

fishdog

As a qualified electrician I would agree with Dotsie~tmp

The 10A MCB should be a just fine. I would not accept a 20A MCB

I would tell the electrician that either he puts a 10A MCB on the circuit and fixes the problem or you will be forced to call an inspector. Both the ECSSA and RECI have inspectors and if your electrician is registered he is with one or the other.

I am under the impression that what he done is a potential fire hazard

The way I would put it is that the MCB should operate (trip) before the cable carries too large a current and a potentially dangerous situation arises. When currents rise to a certain level something has to give. This should be the protective device, in your case an MCB. If this does not operate, and the current is high enough for long enough something will fail! If it is the cable that fails it can actually glow red and melt, as you can imagine this could cause a fire.

If you were to put a 20A MCB on a 1.5 PVC/PVC cable (the type of cable your lights most probably have) the cable could become dangerously overloaded for hours on end without the MCB operating. A 20A MCB B type MCB can take 30A for hours without operating. The tables in the wireing regulations show this. A 1.5 cable can not safley take a current of this magnitude for very long!

On the other hand if the cable was protected by a 10A MCB (this would be standard practice for a lighting circuit) the cable should not be able to carry a current that exceeds the rating of the cable.

Also if the 10A MCB will not stay on this would indicate that there is a problem!! This problem could be due to several different things such as:

1) An earth fault. This means that something metal in your house may be live and touching it could cause electrocution!
2) There may simply be too many lights on the same cable which may mean it is carrying an unsafe level of current to flow in the cable.
3) There could be a fault between live and neutral, causing an unsafe level of current to flow in the cable.
4) It could be a faulty MCB!

One thing is for sure, a 20A MCB is not a normal way to solve this problem and you should not accept it as a solution!!

Clearly your electrician expected the 10A MCB to work!

If you can no longer proceed from here call a competant electrician

Perhaps that is the best bit of advice and the safest option.

joebre

Thanks Dotsie for the detailed reply.


I posted my problem on an UK forum as I did not realise this sub-forum was here. I did not say I was in Ireland. They were saying that what he has done is not permitted, quoting 17th Edition of the Regs. I do not know what applies here.

I will get somebody with me, to check what is on the circuit, particularly if there is something other than lighting on it.
House is fairly large and has 8 lighting MCBs on it. All rated B10.
Will update later.

Joe

fishdog

Has the house been completley rewired??

17th Edition of the Regs

English reulations, similar to ours but a slightly lower standard.

joebre

Thanks Fishdog for your reply as well. I was replying to Dotsie when you were posting. I will check the loading later.
I was not here when he was at snag light the other day.
I put it in writing last week to my builder that I believed that I had a fire hazard. The electrician is subbed to the builder.
I see that he is registered with RECI. Could be be with the other organisation as well ? There is a sticker on his van.
A neighbour of mine had problems with the same guy as well. He will not allow him back into his house at this stage.
He was then quoted €1,000 by a new electrician to correct some work that was left faulty by the original electrician.
He rang RECI to inquire but did not get much info.
What does the RECI inspection, costing arounf €380, involve ?
Or it is enough for him or I to lodge a written complaint with RECI and let them investigate the matter.

Joe

joebre

The house was a showhouse for about 12 months.

I bought it , as first owner, about 18 months ago !

Joe

fishdog

I see that he is registered with RECI. Could be be with the other organisation as well ?

No

What does the RECI inspection, costing arounf €380, involve ?

It is free. There is a different type of inspection RECI do that they charge for.

1st get a good independent electrician to inspect the work, but not to alter it. Get him to write down what is wrong. If the electrician does not fix it or you are not happy ring RECI and tell them you want an inspection.

I did this before! The inspector arrived for free and made the electrician fix stuff that the electrician refused to fix. But the inspector expected me point out what was wrong. Pity for him I am an electrician! That is why you need an independent electrician to look at it first.

joebre

Found him on RECI site.
But I thought a saw a sticker for ECSSA on another of his vans the other day !

I will speak to my neighbour and we should both get the same independent electrician to check us over !

Joe

fishdog

Good luck with it Joe! Let us know how you get on.

Dotsie~tmp

You would be better off if he was in ECSSA as a customer IMO. I'm in it. Just remember you cannot use this as an excuse to withhold an unreasonable amount of money. Also there are guidelines in ECSSA that prohibits a member from taking up somebody elses unfinished work until they have ascetained the reason for the previous contractor not finishing the job. You are doing the right thing going to them and will be ale to make a clean cut in the event he wont do the right thing.

joebre

Dotsie,

He is on the RECI so he cannot be with the ECSSA ?
I do not owe him any money. He is working for the developer that I bought the house off and the builder is fully paid.
I consider this to be part of my snag list.

Is the documentation somewhere that says you cannot use a 20A MCB on a light circuit 1.5mm circuit. I would just like to sjhow him something in writing.
He said that if it was put back to the 10A, it would trip again.
I checked quickly the other night and there are no more than 2 rooms on each MCB. I have eight covering the lights.

Joe

Steve

Just my tuppence on the matter:

If the B10 only ever tripped at switch-on then could it be caused by inrush due to the amount of lamps on the circuit?

i.e. what I'm asking is, once the lights are on, do they stay on?

If so then it would be worth trying a C10 breaker. The thermal protection would remain but it should cope with inrush better.

fishdog

Is the documentation somewhere that says you cannot use a 20A MCB on a light circuit 1.5mm circuit

By reading the current wiring regulations it can be clearly shown that this is not allowed.

I would just like to sjhow him something in writing.

This will not work because you do not have the technical training to be able to win this argument. That is the job of the inspector!

I consider this to be part of my snag list.

Exactly!

He said that if it was put back to the 10A, it would trip again.

Then there is a fault! This means that the cert issued for your installation has been falsified! There is a something wrong and it could potentially be very dangerous. This could result in a serious accident occurring. If your home insurance company was aware of this your policy would be null and void.

I do not owe him any money. He is working for the developer that I bought the house off and the builder is fully paid.

Irrelevant!

This is simple and free to fix. Simply ring RECI and get the inspector in.

The electrician is responsible for his work for years after he installed it, once you don’t have someone else altering it.

Stoner

fishdog wrote: »

The electrician is responsible for his work for years after he installed it, once you don’t have someone else altering it.

+1

Don't get anyone else in to alter/check it, go down the certified body route IMHO.

Solair

fishdog wrote: »

Has the house been completley rewired??



English reulations, similar to ours but a slightly lower standard.

They're different, but I wouldn't necessarily says ours are a slightly lower standard. There are aspects of our regulations that are tighter than the UK and aspects of theirs that are tighter than ours. It's not very fair to say ours are 'lower'.

Irish regulations have always been a bit of a mixture of UK and continental (particularly German) practice for historical reasons. i.e. ESB was heavily influenced by Siemens in the past and this carried through to things like the use of 220V (rather than 240V), the use of diazed fuses, the use of continental 'schuko' 10/16 amp sockets in some old installations etc. The UK influence was there for pretty obvious reasons too given it's our nearest big neighbour.

Both systems are pretty decent and very safe if you implement them fully and properly. Usually, in either country issues arise where someone's failing to comply with the regulations or where there's a DIY or cowboy 'hack job'.

Sadly, both the UK and Ireland have lacked decent regulation of electrical work, most of it is dependent on self-regulation by the electrical contractor industry and an assumption that people will take the regulations seriously. On the continent and in the USA there's a much great emphasis on inspection.

joebre

Slight update on the situation.

The light that was causing the trip had a transformer with 20 No. 10W 12V bulbs.
Spoke to the electrician last week and he suggests putting in a 10A C-rated MCB, as he said it would handle in initial surge without tripping

Joe

fishdog

They're different, but I wouldn't necessarily says ours are a slightly lower standard.

I didn't! I said ours are a higher standard. Perhaps I worded it badly, sorry!

There are aspects of our regulations that are tighter than the UK

Yes we must have a main fuse for a domestic installation and we must have RCDs fitted to all socket circuits, unlkie the UK.

Irish regulations have always been a bit of a mixture of UK and continental (particularly German) practice for historical reasons

I know I worked in Germany and I studied the IEE rules when I sat C & G course B and C exams.

Both systems are pretty decent and very safe if you implement them fully and properly

Yes, you are correct.

But rewirable fuses are often abused. They still allow them in the UK for some crazy reason!

aspects of theirs that are tighter than ours.

They give a good guide as to how to apply diversity factors, that is true. I cant think of much else!

Sadly, both the UK and Ireland have lacked decent regulation of electrical work, most of it is dependent on self-regulation by the electrical contractor industry and an assumption that people will take the regulations seriously.

I could not agree more!

fishdog

The light that was causing the trip had a transformer with 20 No. 10W 12V bulbs.
Spoke to the electrician last week and he suggests putting in a 10A C-rated MCB, as he said it would handle in initial surge without tripping

A C type is allowed, but should not be required. If a C type is used a minimum lower earth fault impedance is required than for a B type to ensure that the MCB operates within the correct time (5 seconds). This is not normally a problem.

There is something funny going on with your wiring.

20 x 10 = 200watts

This should not be a problem even if all 20 are on the same switch.

Like many others that post here I have connected 500watt halogen sensor lights to a 10A B type MCB without any issues.

I think you should get the wiring inspected!!! Better to be safe than sorry. The remarks your electrician made earlier would worry me.

joebre

There are 8 MCB's in total. The fancy light is on the stairs/landing and I would usually turn it on going up to bed. The only other lights on the same MCB were in the main bedroom and en-suite. These would not be on at the time. I would have to go back down and reset the MCB before I could go to bed !

joebre

Meant to say 8 lighting MCB's !

fishdog

Joe, there is something wrong with your wiring!
You should get it checked

Steve

fishdog wrote: »

Joe, there is something wrong with your wiring!
You should get it checked

As you previously said though, it could just be a dodgy breaker, it's not unheard of.
My first action would be to swap the circuit onto another breaker and see does the fault follow the circuit or does the same breaker still trip, this would at least narrow down the source.

If the traffo can be disconnected, it would be worth doing a hipot on the wiring to be sure.

fishdog

As you previously said though, it could just be a dodgy breaker, it's not unheard of.

Yes, but that would still fall under the category of "something wrong with your wiring". If the "electrician's solution" to fix the problem is replace the 10A MCB with a 20A MCB alarm bells should start to ring!

This alone is enough for me to want to have the place checked over!

My first action would be to swap the circuit onto another breaker and see does the fault follow the circuit or does the same breaker still trip, this would at least narrow down the source.

If you touch the wiring the sparks that wired it is no longer responsible, so the best thing todo is to get him to fix it.

If the traffo can be disconnected, it would be worth doing a hipot on the wiring to be sure.

I think you mean insulation resistance test. This can be done regardless and should be done anyway as part of the cerfication process.

Steve

fishdog wrote: »

If you touch the wiring the sparks that wired it is no longer responsible, so the best thing todo is to get him to fix it.

Ok, fair point, maybe suggest is as the next course of action by the sparks then.

I think you mean insulation resistance test. This can be done regardless and should be done anyway as part of the cerfication process.

Can this be done with a 12V lighting traffo connected? would it not fry it?

My background is control panels / LV switchgear so please excuse my ignorance of domestic testing procedures. Random breaker tripping and finding the cause of it is something I know a bit about though.

fishdog

Can this be done with a 12V lighting traffo connected? would it not fry it?

It would fry a 12 volt traffo, you are correct.

I thought you were talking about the ESB traffo as opposed to a temporary generator supply

An insulation resistance test would require disconnection the traffos.

The chances are the insulation resistance is too low between phase and earth or phase and neutral.

Solair

(Sorry Fishdog if I misinterpreted a bit - I'm off sick with flu, I think it must be impacting on my brain!)

There's definitely something strange going on with the wiring described there. A normal lighting transformer will not cause a surge capable of tripping a 10A type B breaker. If anything, low voltage lighting tends to come on with much less of a surge than normal 230V halogen fittings.

Assuming it's just some kind of surge when the lights go on is a little risky.

The entire circuit needs to be inspected carefully for faults. It sounds to me like you've got some kind of a loose connection or an insulation problem along the line, or that the fitting itself is faulty.

Also, ensure that there isn't anything else connected to that circuit that you are unaware of. I have come across things like TV distribution amps, fans, even central heating boilers and pumps inappropriately wired into lighting circuits because they were easily accessible in the attic and someone decided to just add a branch via a junction box. Something like this could be drawing a lot of power and the extra lighting load may have been tripping the breaker.

If there are any outdoor lights on the circuit, it's quite possible that something's become waterlogged or that there's a dodgy connection too.

The only thing that I've come across in lighting that will legitimately trip a B10 MCB is a large halogen light blowing. It can cause quite a bang.

Replacing the MCB with a slower tripping higher rated version is a little foolhardy in my opinion. You're treating the symptoms of a fault, not the fault itself.

----

Check the rating of each light on the circuit and calculate the total load and see if it's close to 10amps.

If you've exceeded the total rating for the circuit, you really should have had a new lighting circuit installed. It's not acceptable to just replace the MCB with one of a higher rating as you are over-loading the circuit.

Also, it should be noted that light switches, dimmers and most fittings are designed to cope with a 10A fault. It's not just a case of protecting the 1.5mm2 house wiring. You could end up with a fire in a fitting due to thinner wire or pendant wire overloading.

If you are unhappy with the electricians work, I would suggest that you contact his licensing body i.e. RECI etc

fishdog

Sorry Fishdog if I misinterpreted a bit - I'm off sick with flu, I think it must be impacting on my brain!

No problem

There's definitely something strange going on with the wiring described there.

+1

an insulation problem along the line, or that the fitting itself is faulty.

That is what I would guess too. But I have never seen the job.

Also, ensure that there isn't anything else connected to that circuit that you are unaware of.

I would check for this a with a grip on ammeter with everything switched on and measure the current if I was fault finding.
(I assume you know I have never seen this installation)

I have come across things like TV distribution amps, fans, even central heating boilers and pumps inappropriately wired into lighting circuits because they were easily accessible in the attic and someone decided to just add a branch via a junction box.

So have I come across this kind of thing but the OP says it is a new house and he is the first owner! So I dont think the above applies.

If there are any outdoor lights on the circuit, it's quite possible that something's become waterlogged or that there's a dodgy connection too.

That is a good point!

Replacing the MCB with a slower tripping higher rated version is a little foolhardy in my opinion. You're treating the symptoms of a fault, not the fault itself.

I 100% agree. That is why I would be worried about what else this "electrician" may have done!

It's not acceptable to just replace the MCB with one of a higher rating as you are over-loading the circuit.

Exactly

You could end up with a fire

That is why the OP should touch nothing and phone RECI and get it inspected! If he touches anything the sparks is no longer responsible.

fishdog

The light that was causing the trip had a transformer with 20 No. 10W 12V bulbs.

I just read the OP's post again! I think I would start with this light. I would remove it from circuit. It might just be a faulty light fitting or something simple like a nicked live wire touching an earth, could happen to anyone. It is the proposed solution that would worry me!

joebre

Thanks to everybody for their input. Some of it over my head but we are getting there.

The load is as follows
20 No. 10W 12V on traffo on landing

10 No. 10W 12V on separate traff in bedroom
2 No. 240V 40W side lights.
3 No. 12V 50W downlights on separate traffos.

2 No. 240V 40W side lights in en-suite
2 No. waterproof downlights en-suite. Can't check them.

Some outside lights on temp. lead. Not connected to lighting circuit.

If he comes back during week, should I just ask him to switch the light onto a different MCB rather than changing to a C10.

Steve

Are those all on the same circuit joebre?

It could well be that there is just too much on it.

joebre

Yes they are.

It's just that I did not know how to convert to Amps.

When it used trip, there would be nothing on circuit as I would not have gone up to bedroom.

Joe

fishdog

It's just that I did not know how to convert to Amps.

Devide total watts by 230 = Amps

I dont think it is over loaded. I would bet it is a fault to earth or between earth and neutral.

It could well be that there is just too much on it.

I would not think so, remember:
1000 watts = 4.35 amps

Steve

Ok, sort of a scientific approach...

20 No. 10W 12V on traffo on landing = 200W = 0.909A = 7.2A inrush
10 No. 10W 12V = 100W = 0.45/a = 3.6A inrush
2 No. 240V 40W = 0.36A
3 No. 12V 50W = 0.68A
2 No. 240V 40W = 0.36A

so.. if all other lights except the landing were on it would be 1.85A which is nothing in the grand scheme of things, adding a 7.2A inrush should definitely not trip a B10 breaker. This would again point me towards a dodgy mcb...
OK, I know I'll get slated for this but it's worth a try... turn everything on and give the breaker a rap of your knuckle and see does this cause it to trip... if it does then maybe my theory is correct and the breaker is just too sensitive and needs replacing...

joebre

Could try that, but at the moment there is a B20 fitted!!

fishdog

0.909A = 7.2A inrush

I dont know how you are arriving at 7.2 A (other than multiplying by 7.92 !).
But I see your point is that there is an initial surge, which is correct. This is normal for many electrical loads and the load here is very small. A 10B type should have no problem dealing with small transients such as this as you correctly stated.

This would again point me towards a dodgy mcb...

This is possible, but I would not think so. Just from over 20 years experience this has never been a problem for me. However it is easy to rule out and there is no harm trying it out.

turn everything on and give the breaker a rap of your knuckle and see does this cause it to trip...

This will tell you nothing. Measure the current with a grip on ammeter and swap it for another 10A B type MCB and you will quickly know a lot more!

JOHNPT

How do u calculate the inrush current? In what circumstances would you have to take account of this in normal domestic lighting situations i.e in what situations may it cause a problem of tripping?

Thanks in advance

fishdog

In what circumstances would you have to take account of this in normal domestic lighting situations

In normal domestic, none so dont worry about it. That is not the problem here. Large inductive loads can have a large transient currnet for an instant when first switched on that quickly reduces.

in what situations may it cause a problem of tripping?

For example if you were to plug a 2kVA 230/100V transformer (site type traffo) into a normal socket it will sometimes trip the MCB.

You may also suffer from this if you had say 10 twin fluorescents on one switch, the current may be less than 6A with all of the lights turned on, but at the instant of turning on the switch a 10A MCB may well trip. Solution: Simple, dont put all 10 on the same switch, but they can stay on ther same circuit.

DK47

its this simple, the mcb protects the circuit not the fitting. a 1.5 t+e requires a B10. this is why. the B20 would only trip when more than 20 amps flows. if lets say the fitting is drawing 18 amps over a period of time the insulation would degrade and fire would be a concern. if the fitting is tripping the B10, you have to change the fitting or upgrade the circuit no the mcb. it is cheaper and easer to replace the fitting. your electrician is a cowboy, if he dosent understand why is he uses what mcb where, he needs a new job.

Solair

dkhill47 wrote: »

its this simple, the mcb protects the circuit not the fitting. a 1.5 t+e requires a B10. this is why. the B20 would only trip when more than 20 amps flows. if lets say the fitting is drawing 18 amps over a period of time the insulation would degrade and fire would be a concern. if the fitting is tripping the B10, you have to change the fitting or upgrade the circuit no the mcb. it is cheaper and easer to replace the fitting. your electrician is a cowboy, if he dosent understand why is he uses what mcb where, he needs a new job.

100% agree with you there! The 'electrician' sounds clueless!. It's basic laws of physics i.e. ohms law. If you exceed the maximum load carrying capacity of the wire it will get hot, the insulation will melt off and your house will go on fire. Pretty much as simple as that!

Good luck claiming against your insurance too!

You cannot just change an MCB for a bigger one, they're designed to protect you being able to overload a circuit. If the MCB is tripping, it simply means you're drawing more power than the circuit can provide.

Your options are, re-wire the circuit with higher capacity cable, or, run a new circuit for some of the fittings on the circuit (a lot more easily done!)

joebre

Yes, I agree with you that the electrician sounds clueless!

I was not around the last time he called to do some snags.

I had it tested with a meter by a separate electrician recently.
I have 8 lighting MCBs in the house.
The lighting circuit drew 4.5A when I turned on a fancy light fitting with transformer and 20 G04 10W bulbs. It then settled at slightly over 3 amps.
Definitely no need to go from 10A to 20A !

Could it be that the original 10A was faulty and that I should get him back to put in a 10A again ?


Joe