Questions About Breakers

[curtklay]

Hi All,

Attached are some pictures of the inside of my home’s breaker box with the front cover removed. My questions are about that one oddball 10 amp breaker on the lower right side, second from the bottom. The circuits from 2 bedrooms are on this breaker; nothing heavy duty, just ceiling lights and wall sockets. During the four years since the house was built, this breaker will occasionally trip for no apparent reason. Oddly, it usually happens late at night when there is no load on it at all. It resets normally, and will not trip again for several days or even weeks. It’s very sporadic. I have turned on every appliance in both rooms simultaneously to see if it could be an overload issue, but it stays on, and as I said, it usually trips when there is little or nothing on.

What strikes me as strange is the fact that it is the only 10 amp breaker in the box. All others are 16, 20, or 40. It looks like the so called “electrician” ran out of 16 amp breakers, and just threw this one in. So, my thought was to replace it with a 16 amp breaker. But after looking closely at the wiring, I see that there is one, and only one, red wire coming into the box, and it is attached to that breaker. Now I am puzzled.

My questions are, 1. Does replacing the 10 amp with a 16 amp seem logical to solve the tripping? (the wire size looks the same to all the breakers) 2. Is there any reason they used a 10 amp breaker in that spot? (other than TIT) 3. Why would they use a red wire for that breaker. (the close up shows the red wire attached to the front screw post, a white wire on the center screw post, and a black wire going into the back.

Any assistance from the TV experts will be greatly appreciated!

[thaibeachlovers]

Lights should be on a 10 amp breaker but plugs on 16 ( I think- certainly higher than 10 ), so if both lights and plugs on it, that's wrong for a start.

BTW, you should not up the breaker if lights are on it.

In my house ( previously had everything on two 10 amp breakers ), I ran new wires to all the plugs and put them on a 16 amp breaker, but left the lights on the old 10 amp breaker.

I'd turn off all the other breakers, and make sure nothing was working in the 2 bedrooms, then look at the meter to see if there was still current being drawn. I'm no expert, but it sounds to me as if there is something else connected that you don't know about.

[Crossy]

Those three bottom breakers are RCBOs, the 10A one is 10mA leakage trip, I can't see what the others are, maybe 30mA. Is the bathroom outlet on that breaker perchance? That would explain it being a 10mA unit. If there is no bathroom outlet on that breaker upping it to a 30mA 10A may (or may not) solve the issue.

I would NOT replace it with a normal breaker until we know exactly what it controls, the sparks put RCBOs on those circuits for a reason.

A possible reason for an RCBO (or RCD) tripping for no apparent reason is an N-E fault somewhere (not necessarily on the circuit controlled by the breaker) enjoy finding that one.

Nothing wrong with lights and outlets on the same breaker, it's common in Europe and many other parts of the world including Thailand.

[thaibeachlovers]

Those three bottom breakers are RCBOs, the 10A one is 10mA leakage trip, I can't see what the others are, maybe 30mA. Is the bathroom outlet on that breaker perchance? That would explain it being a 10mA unit. If there is no bathroom outlet on that breaker upping it to a 30mA 10A may (or may not) solve the issue.

I would NOT replace it with a normal breaker until we know exactly what it controls, the sparks put RCBOs on those circuits for a reason.

A possible reason for an RCBO (or RCD) tripping for no apparent reason is an N-E fault somewhere (not necessarily on the circuit controlled by the breaker) enjoy finding that one.

Nothing wrong with lights and outlets on the same breaker, it's common in Europe and many other parts of the world including Thailand.

I stand corrected, but why then do they say that lights should be 10 amp and plugs 16 if they can all be on 10? Why bother selling different amp breakers?

[Crossy]

It's all down to wiring styles. In the UK we have separate lighting and outlet circuits but in Italy it's not uncommon to find a whole house on a single 15A breaker.

Small homes here have two or three circuits separated by room with both lights and outlets on the one breaker, often the outlets are next to the light switches (with the associated trailing leads).

One reason to split outlets and lights is that you can then use thinner wire (and a smaller breaker) on the lighting and save on the cost of having to run power sized wire everywhere.

[curtklay]

Thank you, Crossy. I was hoping you would reply. You are correct; the bathrooms are on that breaker along with the bedroom lights and sockets. You have put my mind at ease knowing that the breakers are correctly installed. I assume that the occasional tripping source is elsewhere as you suggest. I am not going to search for it, knowing I am over my head. My confidence is restored, and I take back my sarcasm regarding Thai electricians.

[bankruatsteve]

One thing you can check/try for the occasional trip: use the test button on the RCBO to trip the breaker, then use your vacuum to clean out receptacles and light boxes (you can probably get by just taking off the cover plates and light bulbs). Dust webs, spider webs, bug nests, etc. and humid weather can easily trip 10ma RCD.

[Crossy]

One thing you can check/try for the occasional trip: use the test button on the RCBO to trip the breaker, then use your vacuum to clean out receptacles and light boxes (you can probably get by just taking off the cover plates and light bulbs). Dust webs, spider webs, bug nests, etc. and humid weather can easily trip 10ma RCD.

Good point Steve and it's always wise to test with the 'test' button occasionally.

One thing I've noticed. We have those microscopic ants, they get in all the outlets and light switches. Ants do conduct electricity (so will trip the RCD), until they've been squashed between switch contacts when they do not, at which point the light stops working. I've had to dismantle and clean out several light switches and the water pump pressure switch.

If you have similar visitors after cleaning everything out put some of that ant powder in the back box, hopefully they won't be back.

[Pib]

RCBO's can be frustrating sometimes, in terms of nuisance trips, as long as it don't occur too often. But if it occurs too often while it could be actual an earth leakage problem causing the RCBO to do its job and protect you, it could also just be a defective RCBO.

If you go to this 2012 archived ThaiVisa thread on Square D RCBOs consisting of 51 posts from various folks with a lot from me, you'll see that T_Dog and me had some real issues with our new Square D RCBOs.

I can't provide an update to that thread since it's now archived but in my post #39 in the thread where I basically summarized my posts, but it appears one of the two new Square D 10ma RCBO I bought and I personally installed for my two dedicated circuits shower heaters that one of the RCBOs was indeed defective (i.e., frequent nuisance tripping) from the factory. And "exercising" the RCBOs, or at least one of them, may have helped minimize further nuisance tripping. A person would really need to read the whole thread of 51 posts for the full story....and I think there is some very good RCBO info in general on this thread besides just the problems T_Dog and I experienced with our Square D 10ma RCBOs. I would have preferred to get 30ma Square D RCBOs but 10ma Square D RCBOs is all I could find in Thai hardware stores like HomePro, Global, Thaiwatsuda, etc

Anyway, in that post #39 I said my last tripped RCBO occurred on 16 Apr 12. Well, another one did occur on 28 Jul 12 for apparently no determinable reason like the shower heater had been used in my guest bathroom, etc. Anyway, I reset it, Pushed the Test button few times, and then Reset it to wait for the next trip of either this RCBO or the other identical Square D 10ma RCBO on the other shower heater. Knock on wood, as of today/21 Jul 13/almost been a year, there have been no more trips...and I do press the Test button on both every few months to test the RCBOs. Just FYI.

[curtklay]

Thanks for that link, Pib. But after reading all 3 pages, my head hurts. A defective breaker was my first thought, and there is some question about Square D quality control in other discussions. But because my tripping issue is only occasional, and I am not an electrician, I'm going to let it be for now. I think the most likely cause is either leakage, "overambitious" RCBOs, or Thai ghosts. I will clean up the switches and sockets to eliminate the possibility of bugs, and also will "exercise" the test button, which does work. If the situation worsens, I'll call in some pros. But I'm happy to live with the knowledge that it's offering more protection than less.

My thanks to all who replied. If I find a definitive explanation, I will post it.

[Forkinhades]

A possible reason for an RCBO (or RCD) tripping for no apparent reason is an N-E fault somewhere (not necessarily on the circuit controlled by the breaker) enjoy finding that one

Disagree!

If you have an RCBO then any fault occurring before the RCBO will not be detected as it is only measuring the supplying circuit and does not care what happens upstream of it. It is similar to saying will an MCB trip if there is a high current in another circuit, and yet your lights do not trip when you turn the oven on!

Your RCBO is TELLING you that you have a fault on THAT circuit, it is indeed protecting you! Of course a skilled electrical tester can find these faults quite quickly with the correct (expensive) equipment.

[bankruatsteve]

delete dup

[bankruatsteve]

I think Crossy is referring to the situation when a "borrowed neutral" will trip an RCD. IE: RCD thinks a leak on it's circuit b/c the neutral is on a different one. Your diagram correct when RCD is in the main CB but not when individual RCBO.

[Forkinhades]

^ That kind of fault is instant (as long as there is a load on the circuit) and not intermittent as the OP states.

[Forkinhades]

Your diagram correct when RCD is in the main CB but not when individual

My diagram is showing a individual RCBO, my diagram does not show the mainswitch which would be to the left. If it was a main RCD then the phase (live) conductor would be feeding the other MCB's from the load side of the RCBO, not the live side as I have shown.

multiple edits to correct poor grammer

[Crossy]

I'm not going to argue with Forky as he (and his diagram) are 100% correct, at least in theory.

Practice is sometimes different, you don't have to search far in the forums frequented by sparkies to find odd behaviour of RCDs and RCBOs which turns out to be a seemingly unrelated fault.

Case in point, my own home. When we moved in, operating the en-suite water heater on full power would occasionally trip the RCD protecting the upstairs outlets, low or medium power did not, nor did it ever trip its own RCD.

Evidently something odd was going on but a cursory check of the shower circuit revealed nothing, and since it only did it on full power there was no issue, take cooler showers.

I 'fixed' it some time later when I discovered a N-E short in the power circuit to the small (and very rarely used) bedroom. This circuit shares nothing (or should I say is supposed to share nothing but TiT) with the water heater, it's even on a different RCD.

I have no idea of the mechanism that caused the tripping of the outlet RCD, and I'm not totally sure that the cause was the N-E fault, but it's not tripped since said fault was cleared.

[Forkinhades]

^ Would you agree that if a full electrical installation test was conducted, before the supply was energised that these faults would have been highlighted?

Thus giving a full explanation of what the 'little gremlins' were?

Just highlights yet again how important it is to have your installations tested thoroughly, and competently!

Open neutral faults on three phase systems can fry all your electrical appliances! Which can lead to fires starting very quickly.

Sent from my GT-I9300 using Thaivisa Connect Thailand mobile app

[Crossy]

Yup agree 100% Forky, the concept of installation testing seems (at least for domestic sparks) totally alien, none of our sparkies possessed any test gear above a neon screwdriver.

Apply power, if it doesn't go bang it's OK, test passed.

I did a lot of rudimentary tests using a bulb and battery, I'm 100% certain our sparks (we used up four) thought I was out of my tree.

I'm confident our installation is safe although there are still multiple borrowed neutrals on the lighting.

As I write this our supply is down to 150V, the AVR is earning its crust today

[Forkinhades]

In my vocation as an Electrical Inspector, and Qualifying Manager I have come across many situations which has made me/people think 'why did that happen'. It always comes to light after investigation and IME theory wins everytime.

Not taking nothing away from crossy's experience, which I would have loved to inspect and test as to find out exactly why his problem happened., but indeed blaming the smiley sparks of there inept practices here in LOS, I am sure there would have been a logical expalnation, but since his problem has now been fixed, we will not know, unless it raises its head in near future.

Problem being is that anybody can claim to be an electrician in LOS, and indeed anybody can run a cable form a to b, or from x to y as the case seems to be, which IMO makes sparking the easiet of all trades to do, but the most complex in theory and regulations. In reality the LOS sparks really do not have a clue.

Having said all that I would like to show a picture of a single phase DB that I am testing at the moment for one of the top hotels in the world, and indeed need to sign off.

There are only 8 circuits via RCBOs/MCBs, but they in turn control 48 fuses and relays which will turn each light /power or other accessory point on. If one of them neutrals are in the wrong terminal then the system fails!

Peace to all, and good luck to the OP