Fried Circuit Breakers.... Help

[ozbanglamung]

Can somebody please advise me on what may have caused this (seer attached pics).. It was attached to a HW Heater.  I have another with the same issue but I am not sure what it was attached too, I think probably the other water heater. There are three that have been destroyed, one of them was burned by the one that  burned out below it. Its a bloody miracle the house didn't burn down. Now the circuit breakers are a mix of Shneider as you can see in the panel pic. I am not  sure what the difference is between C16, C20 and C32 and what should be attached to what, but I assumed that C32 was the strongest so I had a spare and attached the HW heater to it and tested it. I let the hot water run for ten minutes then pulled the breaker out. It was warm to the touch but onlu just warm,  but by no mean   anywhere near what would be required to melt it. So I am at loss to know what caused it. I was just about to go down and buy a couple more when i noticed these different numbers so I thought I should better ask. Thanks for your help in advance.  

 

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[ozbanglamung]

I just remembered something I should probably add, The house was hit (literally and it frightened the crap out of me)  twice by lightning during a storm about six months ago. Some strange things happened to the circuit breakers then, Nothing was tripped but I lost power to all the power points in the master bedroom. The next day I had a look at the breakers and there was a spare with nothing attached to it and it had this red light on it. So being the electrician that I am, (not) I went and bought a new one and plugged it in then the bedroom was ok. Now remember this breaker had nothing attached to it so the short answer is NFI what happened there but I guess the strikes could have been the beginning of the end for the two water heater breakers and they took a while to burn out because they only cook up when somebody has a shower. Anyway, back to the main program 

[Crossy]

That looks like it was a loose connection that's been fizzing for a while. You should be able to replace with the same type with no issues.

 

Check all the other connections are tight (power off of course).

 

[Crossy]

ALSO.

 

Since they are water heaters it would be wise to replace them with RCBOs unless you have a Safe-T-Cut device that's out of the photos.

[sometimewoodworker]

2 hours ago, ozbanglamung said:

I am not  sure what the difference is between C16, C20 and C32 and what should be attached to what,

The C is the rating for the maximum trip current (you will find getting other letter ratings difficult here) 

the 16 20 and 32 are the ratings in Amps 

 

They are designed to protect the cables that are attached to them, so a 16A breaker should have thinner wire than a 32A breaker.

 

Do not put in a bigger breaker than you take out unless you really understand what you are doing. You could create the conditions for a fire if you do.

[xylophone]

1 hour ago, Crossy said:

That looks like it was a loose connection that's been fizzing for a while. You should be able to replace with the same type with no issues.

 

Check all the other connections are tight (power off of course).

 

Agree with Crossy; also..............what size are the water heaters, in watts? These breakers MAY be a little light if the heaters are hefty buggers!!

[Crossy]

Just now, xylophone said:

Also..............what size are the water heaters, in watts? These breakers MAY be a little light if the heaters are hefty buggers!!

 

Indeed, but as STWW notes, the breakers are there to protect the cable, so a bigger cable may also be on the cards. 

[xylophone]

13 minutes ago, Crossy said:

 

Indeed, but as STWW notes, the breakers are there to protect the cable, so a bigger cable may also be on the cards. 

Could be the case, but from what I could see on the pic the cable size for that breaker looked bigger than 2.5mm and was poss 4mm, so whilst the cable could be ok, the breaker could be 'light" for a high rated heater???

 

Whereas the cable could stand operating near its capacity for short durations, quite easily?

[ozbanglamung]

Thanks for the replies guys. The water heaters are 6000W. The cables for the water heaters are the fatest black ones. now the fact is i could well be responsible for this cock up as I did  not know that the number protects the cable. In fact until i looked at that pic today I did not know there was more than one number and I could well have moved a water heater to the twenty when it may well have been attached to the 32 few months ago when I replaced a whole bunch of light switches.  Today i made sure both water heaters were on 32's because I thought bigger is better ( I know i'm a dumb ass) and then tested it for ten minutes as stated !!! Simply amazing I am still alive to be honest. It all seems to be ok now although one of the air conditioners would not turn off either with the remote or by pressing the power button on the unit, I had to turn the breaker off to shut it down but that is probably another issue and muddying the waters. So the 32's would be for water heaters and aircons ? I have a shit load of stuff going through that board, my bill averages 8000 baht a month and no that is not a mis type !!

[stud858]

If cable is rated for the current, as another poster said, good idea to check connections.

Breakers should not melt.

They should break before they melt if it's been a matter of high current demands. 

Lightning strikes can blow things apart but seems like poor dirty connections is the culprit this time or a bodgy breaker or 3.

Try a different brand of breaker for replacements.

[ozbanglamung]

thanks stud ???? well i managed to burn pretty big holes in two of them. and as far as poo/dirty connections goes the idiot that wired my house has used red, white, black and blue wires wherever he felt like it and there is not an earth wire within miles of any powerpoint in this house. I will pull all the breakers off and have a good look at them. One of the pics of the board in close up shows they are in pretty poor condition i think, and the house is only three years old

[stud858]

8 minutes ago, ozbanglamung said:

thanks stud ???? well i managed to burn pretty big holes in two of them. and as far as poo/dirty connections goes the idiot that wired my house has used red, white, black and blue wires wherever he felt like it and there is not an earth wire within miles of any powerpoint in this house. I will pull all the breakers off and have a good look at them. One of the pics of the board in close up shows they are in pretty poor condition i think, and the house is only three years old

Take it slow. Make sure you are not playing with live wires. Be certain and work with a friend along side who is not distracting you but enforcing safety.

Should be a main breaker and check with a multimeter for voltage to make sure Meter is working and then without voltage to show 0 reading. 

I hate the higher voltage stuff cause my brain is like a zombie these days.

B safe.

 

[Crossy]

Can you see any markings on the fat water heater cables? For a 6kW heater (27A or so) they should be at least 4mm² and on a 32A breaker.

 

I would also urge you to install some form of earth-leakage breaker (RCD or RCBO) either an over-all Safe-T-Cut device (could be expensive for a 3-phase supply) or individual RCBOs (which you can get to replace the current breakers) on risky circuits. Particularly the water heaters, pool pump and any outside power outlets.

 

[sometimewoodworker]

10 hours ago, ozbanglamung said:

Thanks for the replies guys. The water heaters are 6000W. The cables for the water heaters are the fatest black ones. now the fact is i could well be responsible for this cock up as I did  not know that the number protects the cable. In fact until i looked at that pic today I did not know there was more than one number and I could well have moved a water heater to the twenty when it may well have been attached to the 32 few months ago when I replaced a whole bunch of light switches.  Today i made sure both water heaters were on 32's because I thought bigger is better ( I know i'm a dumb ass) and then tested it for ten minutes as stated !!! Simply amazing I am still alive to be honest. It all seems to be ok now although one of the air conditioners would not turn off either with the remote or by pressing the power button on the unit, I had to turn the breaker off to shut it down but that is probably another issue and muddying the waters. So the 32's would be for water heaters and aircons ? I have a shit load of stuff going through that board, my bill averages 8000 baht a month and no that is not a mis type !!

There is a page that is helpful in understanding which size breakers go with which size cables here Simple guide. 

A single 6000W water heater (6000w/220v = 27A) should be on a dedicated circuit that is on 4mm or greater cable and a C20 or C25 (not commonly used) or C32 breaker. The reason that 4mm cable and a C20A breaker is OK is that they virtually never use the maximum power they are rated for and even if they do the breaker is not going to trip with a 30% overload that will be for a short (20 minutes) period.

 

You will easily be able to confirm which circuits are used by which appliances just by switching off the breaker and seeing what doesn't work. 

Then it's quite easy to see if the wire and breaker is the correct size by adding up all the Wattages of the items that are on that circuit and dividing that by 220  that will give you the Maximum Amps (breaker size) that can be used by that circuit. 

 

If you get very high numbers for a single circuit then you need professional advice.

 

As you are using over 1,800 kWh a month you are probably going to have a high total.

 

Also the bottom left hand C32 breaker looks as if the cable running to it is 2.5mm so the breaker is definitely in the wrong place

 

it also looks as if you have 4 connections to the breaker above that one while you have space on the right. That probably isn't a good idea either.

[Stevey]

I don't think anyone has caught on that the breaker shouldn't be a C32 it should be a B32 and be sure the cable connected is rated for 6 kw =4mm minimum. C breakers are for motors and take a lot more amps to blow . Also the voltage if low will cause higher amps so factor that so may need 10mm cable 

[atyclb]

15 hours ago, stud858 said:

If cable is rated for the current, as another poster said, good idea to check connections.

Breakers should not melt.

They should break before they melt if it's been a matter of high current demands. 

Lightning strikes can blow things apart but seems like poor dirty connections is the culprit this time or a bodgy breaker or 3.

Try a different brand of breaker for replacements.

 

 

could it be a faulty breaker and thats why it melted?  

[bankruatsteve]

3 minutes ago, atyclb said:

 

 

could it be a faulty breaker and thats why it melted?  

As Crossy said in early post, the melting almost certainly caused by a loose connection which caused arcing.  

[sometimewoodworker]

37 minutes ago, Stevey said:

I don't think anyone has caught on that the breaker shouldn't be a C32 it should be a B32 and be sure the cable connected is rated for 6 kw =4mm minimum. C breakers are for motors and take a lot more amps to blow . Also the voltage if low will cause higher amps so factor that so may need 10mm cable 

"C" breakers are available everywhere, "B" breakers are difficult if not impossible to find.

 

The letter rating governs the instantaneous current that will trip the breaker and has nothing to do with the continuous current ratings 

 

A 6000W shower will commonly draw about 10A unless your water temperature is low and you have it set on boil then it's going to be around 20A. So a dedicated 4mm circuit with a C20 breaker is perfectly adequate. 

 

A 10mm cable is a ridiculous suggestion for that usage.

[stud858]

1 hour ago, atyclb said:

 

 

could it be a faulty breaker and thats why it melted?  

Metal switching contacts inside breaker may arc like tiny mini lightning strikes due to poor mechanism,connections and metal degredation.

Much like when you plug in to the el cheapo power boards and sparks fly.

 

 

 

 

 

[Sumarianson]

To understand what size breaker

Look for the wattage on the appliance. Ie 3Kw is 3000 Watts

Devide by the voltage 240Volts

3000÷240 = 12.5 Amps. 

The nearest breaker is 16 amp.

A C type breaker is normally only used in a circumstance where there is a heavy starting current, like on a motor. Type B is the normal. It will take longer for a C to react to the over current which may cause damage to most common appliances especially electronic. 

I agree that there maybe a loose connection on the breaker to cause that burn out. 

Good luck. 

[bankruatsteve]

2 minutes ago, Sumarianson said:

To understand what size breaker

Look for the wattage on the appliance. Ie 3Kw is 3000 Watts

Devide by the voltage 240Volts

3000÷240 = 12.5 Amps. 

The nearest breaker is 16 amp.

A C type breaker is normally only used in a circumstance where there is a heavy starting current, like on a motor. Type B is the normal. It will take longer for a C to react to the over current which may cause damage to most common appliances especially electronic. 

I agree that there maybe a loose connection on the breaker to cause that burn out. 

Good luck. 

No issues with your math but IMO the breaker size should be determined by the size of wire in the circuit.  The tables are conservative for that.  Use a smaller breaker if you think it helps something but never more than the wire is rated.

[Sumarianson]

12 minutes ago, bankruatsteve said:

No issues with your math but IMO the breaker size should be determined by the size of wire in the circuit.  The tables are conservative for that.  Use a smaller breaker if you think it helps something but never more than the wire is rated.

One would hope that the electrician that installed the appliance ensured the correct size cable for the current drawn. However this is thailand and you are correct. One should always ensure that the cable is capable of carrying the current drawn. Thank you for noticing that, breaker protects the cable breaker size is not determined by the size of the cable the breaker is set to the load. The cable is also determined by the size of the load. You could have a 4mm cable but on a 10Amp breaker with no worries.

[stud858]

8 minutes ago, bankruatsteve said:

No issues with your math but IMO the breaker size should be determined by the size of wire in the circuit.  The tables are conservative for that.  Use a smaller breaker if you think it helps something but never more than the wire is rated.

Especially when wires are buried in concrete.

If wires burn out like they did at my condo ugly conduit needs to be run along walls to lay new cable.

[xtrnuno41]

19 hours ago, ozbanglamung said:

Thanks for the replies guys. The water heaters are 6000W. The cables for the water heaters are the fatest black ones. now the fact is i could well be responsible for this cock up as I did  not know that the number protects the cable. In fact until i looked at that pic today I did not know there was more than one number and I could well have moved a water heater to the twenty when it may well have been attached to the 32 few months ago when I replaced a whole bunch of light switches.  Today i made sure both water heaters were on 32's because I thought bigger is better ( I know i'm a dumb ass) and then tested it for ten minutes as stated !!! Simply amazing I am still alive to be honest. It all seems to be ok now although one of the air conditioners would not turn off either with the remote or by pressing the power button on the unit, I had to turn the breaker off to shut it down but that is probably another issue and muddying the waters. So the 32's would be for water heaters and aircons ? I have a shit load of stuff going through that board, my bill averages 8000 baht a month and no that is not a mis type !!

Ah there you go.  6000 watts per heater formula: P=U(volts) times I (current). 

so in this case you have 6000/230= 26 amps running when heating.

You have an C20 , which means it shuts down in a value 1.5 -2 times indicated I value.

You also have fuses with a  B number, like B20 that will shut off at 0-1,5 times the I value.

They all work best on a spike in power, which exceed the switching value.

 

IN this case 30-40 amps and you are running 26 amps, so the fuse will remain in and keeps running then for long time, as long as you need hot water and it will not shut off.

I see it really got hot on your fuse connection, so could be a loose connection, you will have sparks and then burns. You really have to tighten the connections. This case you didnt.

 

I do see your wires are all about the same, so guess just 2.5 mm2 ?.

For your water heaters of 6000 watts you need 4 mm2. IF too thin, you can have your wires melt down. Your insulation of the wires get hot and burn, it can start a fire and eventually then the fuse will shut off, but only when it reaches a current of 30-40 amps. Yes the fuse is for protecting the wires and if you choose wrong, you still are in trouble some time.

 

Now you put it on a C32, which means 48-64 amps for shut down, your wires cant handle and you could have serious problems, you changed the protection of the wires. 

So put it back on the C20 ! Check your wiring, what is it? 2.5 or 4 mm2 

You cant have both heaters on the same fuse, unless you only use one heater or combine it with your airco and use it at the same time, then also it runs on higher amps.

 

Such big spenders in power should have their own fuse. IF you do then we are not talking about your safety and you can easily just put a C50 or higher in it, it will never shut off and you could have your fire. Its all about protecting you wires and if something goes wrong in your heater or whatever is connected at the end. If too big, the high power can start a fire and you ll have your house burned down or what ever else. 

Also very wise to bring a RCBO in your box, thats real safety for you and your family in case of touching a troubled instrument. But thats another story.

Your trouble with the airco not shutting down by remote or switch is due to a failure in the printboard of the airco.

[sometimewoodworker]

5 hours ago, xtrnuno41 said:

Ah there you go.  6000 watts per heater formula: P=U(volts) times I (current). 

so in this case you have 6000/230= 26 amps running when heating.

Not quite. Standard power here is 220v.

 

It is extremely unlikely that the shower will ever be drawing full power. I have just run a real world test and on normal load my 6000 W shower is drawing 10A if I set the heat to 44 degrees C then it draws 20A I can't get it higher than that.

 

I agree on the C20 being the correct breaker for a single 6000W shower though a 2.5mm cable would be sufficient if it's a dedicated circuit.

 

5 hours ago, xtrnuno41 said:

I do see your wires are all about the same, so guess just 2.5 mm2 ?.

There are at least 3 different sizes of cable tha I can see, though the resolution is too low to read the sizes

[xtrnuno41]

18 hours ago, sometimewoodworker said:

Not quite. Standard power here is 220v.

 

It is extremely unlikely that the shower will ever be drawing full power. I have just run a real world test and on normal load my 6000 W shower is drawing 10A if I set the heat to 44 degrees C then it draws 20A I can't get it higher than that.

 

I agree on the C20 being the correct breaker for a single 6000W shower though a 2.5mm cable would be sufficient if it's a dedicated circuit.

 

There are at least 3 different sizes of cable tha I can see, though the resolution is too low to read the sizes

I see its 220 volts, only then the current would slightly be higher.

However you did a test ! Test is always the best

Only 10 A in low section of temp and 20 A on higher, so no 6000 watts heater, just  20 X 220= 4400 watts.

Depending on what heater you have, I think,maybe could be more. But older/cheaper models have 2 heating elements and are switched on/off. 

In case you have an electronic model, it could be thyristor controlled.

As i see, in your case , first 1 element is heating using 10 A and when you turn it up , a second comes in and current is controlled only by the use of the 2 element(s). 20 A

About the cables. I was in january with my gf who bought cable. When i checked it , there was 2.5 on the cable.

When i looked at the wiring, i couldnt imagine anyhow that would be 2.5. I sincerely doubted what is on the cable and what the cable is in Thailand.

Or it was a cable misprint or she got cheated by impropiate delivery. TO be real sure i had to measure, but didnt had the means. But by experience, i would say it was NOT 2.5. I will have a micrometer next time ever in question of diameter.

[sometimewoodworker]

36 minutes ago, xtrnuno41 said:

However you did a test ! Test is always the best

Only 10 A in low section of temp and 20 A on higher, so no 6000 watts heater, just  20 X 220= 4400 watts.

Depending on what heater you have, I think,maybe could be more. But older/cheaper models have 2 heating elements and are switched on/off. 

In case you have an electronic model, it could be thyristor controlled.

As i see, in your case , first 1 element is heating using 10 A and when you turn it up , a second comes in and current is controlled only by the use of the 2 element(s). 20 A

 

Sorry few of you assumptions are correct. It/they are both new 6000W units the power draw is variable from the low I've seen of about 1~3A all the way up to the maximum that I've seen of 20A. It Depends on the temperature that I have set which goes in 1 degree increments from 32C to a maximum of 48C

 

So while there could be a couple of elements they certainly can't just be switched in to control temperature. 

[RocketDog]

On 3/6/2019 at 1:59 PM, sometimewoodworker said:

"C" breakers are available everywhere, "B" breakers are difficult if not impossible to find.

 

The letter rating governs the instantaneous current that will trip the breaker and has nothing to do with the continuous current ratings 

 

A 6000W shower will commonly draw about 10A unless your water temperature is low and you have it set on boil then it's going to be around 20A. So a dedicated 4mm circuit with a C20 breaker is perfectly adequate. 

 

A 10mm cable is a ridiculous suggestion for that usage.

At 10A you must be assuming the internal triac temperature control circuit is in regulation mode. 

If it's on full tilt boogey it will draw closer to 30A for a 6kw heater at 220V. This should be OK indefinitely for a 32A breaker. No? 

 

Unlike motors and other inductive loads, heaters are resistive devices and don't cause instantaneous current charges other than the off to on state. As you probably know temperature controllers work by switching the full load on and off rapidly to modulate the average power to the heater, hence the water temperature. 

As a general tidbit of information, one shouldn't use lamp dimmers to control motors and other inductive loads like welders! 

 

Good info on the B vs C breakers Sometime. News to me. Thanks. 

 

Also good note on the breakers actually being there to prevent the wiring from going into torch mode. People tend to think in terms of the breaker and the load only. Bigger load? Just install a higher current breaker and all is well? NOT! 

 

Also note that long extension cords with lighter wires (higher resistance) will cause a voltage drop to the load. This will cause some loads like motors to draw higher currents which will overheat and possibly damage the motor (overheat the winding insulation) and the cable. I see a lot of water pumps being connected to small wire extension cords.

 

In general, heavier wire is a small cost when doing new work so I use the largest wire readily available such as 8-12AWG or the mm equivalents. Certainly 16AWG at a minimum for extension cords. I fully understand that these are the norms for wire gauge in America with 120VAC wiring (higher currents fur the same load power) but still like the safety factor that insures for new construction.  Good wire is relatively cheap in the big picture, lasts forever, and let's you sleep better at night. 

 

Lots of ways to go wrong here. 

 

Electric wiring, plumbing, masonry, concrete work, welding, and a few other obscure trade crafts are not strong skills in this country. 

 

Someone building a house here should spend a few months first pursuing knowledge in these areas. The people doing the work certainly won't. Ample evidence of this fact abounds on every Soi here. 

 

My comments are not targeted at patronizing you Sometime. Your post just seemed a good lead in to add these additional comments. I'm not pretending to educate you Sometime. In fact you educated me on breaker classes. Thanks. 

[stud858]

1 hour ago, RocketDog said:

This will cause some loads like motors to draw higher currents which will

A voltage drop causing more current through the load? Doesn't sound right.

The motor would just reduce in torque or speed right?

Or the heater would be lower in temperature or take longer to heat to desired temp, right?

There would just be more  loss as heat in the higher resistance wire. I.e. less efficient. 

 

 

 

[RocketDog]

2 hours ago, stud858 said:

A voltage drop causing more current through the load? Doesn't sound right.

The motor would just reduce in torque or speed right?

Or the heater would be lower in temperature or take longer to heat to desired temp, right?

There would just be more  loss as heat in the higher resistance wire. I.e. less efficient. 

 

 

 

What you said is true of resistive loads. 

 

Many AC small motors are permanent split capacitor motors using a cap to phase shift one winding to produce starting torque. So the rotor is always chasing the field winding. As supply voltage drops the rotor slows and effectively lowers the inductance of the field winding. This lowers the inductive impedance causing higher current draw from the motor. The resultant heat lowers the resistance of the copper wire field winding as well, further exacerbating the current draw. The net result is usually a thermal breaker near the motor core opening up and needing reset. 

 

You see these motors in cooling compressors, air con fans, water pumps, larger power tools, etc. You'll spot the cap very close to the motor usually, typically around the size of an egg and generally black cylinders. 

Notably, many motor 'failures ' are actually a result of the phase shift cap failing, a cheap part, not the actual motor. Disreputable repair folks will try to sell you a new unit instead of just replacing the cheap 2-terminal capacitor. I call this the Air Con !