Circuit Breaker Problem

[lujanit]

First some background.  When this house was built about twelve years ago the electrical contractor did a reasonable job. An extension was built two years later, carport, indoor and outdoor kitchen.  During the 2011 floods I had to do some temporary, lets say innovative adjustments as the circuit suppling power to the kitchen/outside was flooded.  No water in the house but the pump and another low outlet were under water.

 

After the flood I decided to find out what circuit supplied what.  To my utter amazement one circuit was supplying nearly all the lights and power outlets downstairs and outside. Twenty one outlets in fact, lights, power outlets and the water pump. Obviously the electrician was too lazy to run an extra circuit for the extension and just daisy chained onto an existing one. The breaker is 15 amp.

 

Every so often, more and more lately the main breaker trips if the air-con is running and we try to use the. washing machine.  As soon as the washing machine is switched on the main breaker trips.  The only solution is to turn off the air-con.  There is a newish, maybe three years old Safe T Cutout that a sparky put in saying that should fix the problem.  It didn’t.

 

So should I change the CB from 15 amp to 20 or 32 amp?  Or is the answer more complicated?

 

TIA

[Metropolitian]

It would be better if you connect the aircon to its own CB in the consumer unit if possible.

Consider do the same for the washing machine (and that group) if it is an modern western washing machine with heater element.

[daveAustin]

Your house needs to be rewired by the sounds, with sockets, lights and showers etc having dedicated circuits. Simply upping the MCB could potentially lead to a fire should there by a fault with a light, for example. 

[Crossy]

Yup ^^^. I agree with the above sentiments, you need to do some re-thinking / re-wiring.

 

When you say "main breaker" do you mean the breaker on the incoming supply? What rating is it? What rating is your meter - it will be marked as 5/15, 15/45 or 30/100?

 

Post some photos so we know what we are dealing with.

 

Note - IF the wiring on the "big" circuit is all 2.5mm² you could up the breaker to 20A but this really would be a temporary fix.

[thaibeachlovers]

2 hours ago, lujanit said:

There is a newish, maybe three years old Safe T Cutout that a sparky put in saying that should fix the problem.  It didn’t.

Sounds like a typical Thai "electrician" that doesn't actually know much about the technical aspects. I had one that thought a single 1 foot earth rod was sufficient, and another ( in the village ) that didn't understand that it's not a good idea to cause a link from the outside mains directly to neutral ( no circuit breaker ).

 

When I was in the village house I discovered that when they built an extension they ran all the power to the new extension through a single 1.5 mm wire from a single circuit breaker.

[lujanit]

Thanks for the replies. I have included a photo of most of the breaker box.

 

 

 

The CB on the far RHS was installed by a HomePro contractor when we purchased a 28k btu unit for downstairs.  There is another breaker located near the unit. This one doesn’t cause any known problems. Why it bypasses the Safe-T- Cut breaker is unknown to me yet there was  heated discussion between the HomePro installers and the electrical contractor at the time of installation.

 

The Safe-T- Cut is the breaker that always trips.

 

To the left of the Safe-T-Cut are two 50 amp CB’s (or one dual?) which appear to be the main line incoming breakers although these never trip.  If I turn them off all the power in the house stops.

 

The CB, 15 amp with the piece of tape on it is the circuit with all the lights and power outlets on it, including the washing machine.  The washing machine has a breaker at the outlet which must be turned on before it will operate.

 

All the air-cons (4) have a dedicated CB in both the box or beside it and near the unit.  So two breakers per unit.

 

Any Q’s please ask.

[Metropolitian]

Does the tripping occur if you set the STC sensitivity to say 30mA instead of the 5mA on which it is set now?

 

(It is the grey dial with yellow/red markings under the Safe-T-Cut transparent lid)

[Metropolitian]

17 minutes ago, lujanit said:

Any Q’s please ask.

Another question, do you see an indicator in the square maybe reddisch colored after a trip has occured?

This will help us wheter it was an overcurrent or an imbalance (earth leak) error.

 

Check the picture:

 

[Crossy]

12 hours ago, Metropolitian said:

This will help us wheter it was an overcurrent or an imbalance (earth leak) error.

 

Since the Safe-T-Cut MCB portion is 63A and the MEM main breaker is 50A it's a good chance we have an earth leakage trip. But let's wait for confirmation.

 

Because this would be a load related (but not overload) trip I suspect a N-E fault, not a short but relatively high resistance. Time to look for damp or wildlife living in an outlet or light switch methinks.

 

[maxpower]

3 hours ago, Crossy said:

 

Since the Safe-T-Cut MCB portion is 63A and the MEM main breaker is 50A it's a good chance we have an earth leakage trip. But let's wait for confirmation.

 

Because this would be a load related (but not overload) trip I suspect a N-E fault, not a short but relatively high resistance. Time to look for damp or wildlife living in an outlet or light switch methinks.

 

Considering only excess load, if the old MEM 50A is type 2 then I'll have $20 on the Safety Cut B63 going first. 

 

Having said that, I agree with the earth fault theory especially as the cheat dial is set down at low death rate 5.

[lujanit]

On 8/1/2020 at 6:08 PM, Metropolitian said:

Does the tripping occur if you set the STC sensitivity to say 30mA instead of the 5mA on which it is set now?

 

(It is the grey dial with yellow/red markings under the Safe-T-Cut transparent lid)

Sorry for the delay in replying.  I was hoping the system would trip over the weekend.  It didn’t even though this morning the air-con was on and the washing machine was going.

 

Adjusting the sensitivity rating is a hit and miss affair, more often miss.  I have tried this many times in the past.  I’ve never noticed a light on the Safe-T-Cut when it has tripped and you think it would be noticeable in the dark as that is when it trips the most.

 

We have a maid who comes over, usually weekends and she will have the WM going when the bedroom air-con is going. This is most often when the system trips. She is scared of ghosts and every light is on as well.

 

I have noticed a slight correlation between heavy rainfall and the system tripping.  Sometimes but not always.

 

I can find no earth pole buried in the ground.

[sometimewoodworker]

14 minutes ago, lujanit said:

I’ve never noticed a light on the Safe-T-Cut when it has tripped and you think it would be noticeable in the dark as that is when it trips the most.

Well you would not have noticed a light as there is no light.

 

The plastic in the opening moves if there has been an earth leak trip so it will be red, to see it you need a torch to shine on the opening before you reset it. If it trips from over current the plastic does not move.

[Crossy]

7 hours ago, lujanit said:

I have noticed a slight correlation between heavy rainfall and the system tripping.  Sometimes but not always.

 

It's sounding more and more like a N-E leakage issue.

 

Time to pop off all your outlets and light switches (start with the outside ones) and look for and remove any infiltators, spiders (webs) and ants are the favourite instigators. 

[thaibeachlovers]

On 8/1/2020 at 10:56 PM, lujanit said:

To the left of the Safe-T-Cut are two 50 amp CB’s (or one dual?) which appear to be the main line incoming breakers although these never trip.  If I turn them off all the power in the house stops.

Certainly the mains switch, IMO, as the big wires go in, and the two switches are joined together. However, just being curious, are they in fact breakers that would trip in the event of overload, or like every other mains switch I've ever seen which only switch mains power on and off, and have no overload function?

 

I must point out that my 240v experience is limited to a bit of DIY in Thailand with help from the experts on here, but that specific issue never came up.

Edited August 5, 2020 by thaibeachlovers

[sometimewoodworker]

4 hours ago, thaibeachlovers said:

Certainly the mains switch, IMO, as the big wires go in, and the two switches are joined together. However, just being curious, are they in fact breakers that would trip in the event of overload, or like every other mains switch I've ever seen which only switch mains power on and off, and have no overload function?

It (not they) is a dual MCB as is extremely common now. Virtually every incoming switch in Thailand is fused or an MCB even the knife switches.

 

The number 50 on it is a giveaway.

Edited August 6, 2020 by sometimewoodworker

[lujanit]

Thanks for the replies.  I have spent the last couple of days trying to rectify the problem.  Firstly the power to the lights on the gateposts have not worked since the 2011 flood so I just taped over the light switch so no one could turn it on.  The apparent problem is plain to see, yet was not the case in 2011.  No bees nest at that time.

 

I removed the two gatepost lights and replaced them with solar powered lights thereby bypassing the wired electrical system.

 

I also found an outside power outlet which showed signs of a short,  burnt across the points.  I replaced it with a new one.

 

The CB on the WM is 20 amp although the CB in the box is 15 amp. I tried to find a 20 amp CB yet couldn’t find one.  The box is filled with MEM breakers yet I could find only Schnider (?) ones which are not compatible.  Where can I buy MEM CB’s?  Not at Homepro, Baan n Beyond or many independent construction shops.  I spent yesterday looking..

 

I swapped the 20 amp CB for three power points upstairs with the 15 amp supplying the line which includes the WM.  I noticed the wire coming out of the 15 amp is not as large as the wire on the 20 amp CB.  Did I do the wrong thing?

 

To add insult I had the WM and the toaster oven both going at the same time and the whole system tripped.  No air-con going.

 

I am at a total loss at what to do next.  Should I replace the 50 amp dual MEM breakers?  If so I don’t where to find them.

 

 

[Crossy]

1 hour ago, lujanit said:

I am at a total loss at what to do next.  Should I replace the 50 amp dual MEM breakers?  If so I don’t where to find them.

 

Was it the MEM that tripped?

 

On other trips did you identify whether the Safe-T-Cut  was opening on leakage (red indicator window) or overload?

 

[natway09]

If the Safety cut out only occurs when aircon on with WM good chance just overloaded. If you had a leakage it would pop all the time if set correctly.

I would rewire the aircon on a dedicated circuit first before any other expense but if you can find a good sparke he can test in 5 minutes if have a leakage

[xtrnuno41]

You say the T safety is every time breaking. It has nothing to do with the 15 A rail breaker. You can leave that one alone.

It is the safety breaker. You have an electronic device monitoring the in and outlet wiring, combined with the left switch

on the breaker B63 . That B63 is your main breaker circuit, it has B characteristic, so that s good.

 

But the B63 is switched off when the T safety is responding. It is set on 5 mA, real low. You can and are allowed to set that one

higher. Max of the safety is 30 mA, as shown on the pic. A normal mechanical T-safety is made with just one setting, mostly 30 mA.

Higher could be, but only used in industries. Never go higher, i would say so, as it is your live. I know it "tickles" but could still kill you.   

You do have a problem with the machines and could be moist, water. Maybe even both machines and when it passes more then 5 ma leakage, it shuts down

on the main breaker B63.  My guess would be the washing machine, maybe leaking water and comes into the electronics. 

 i cant see any ground as you already said you couldnt find. Happily you do have the T-safety. 

 

The 50 A breakers are mechanically connected to each other, you can see on top. They are used as a mechanical switch to switch off the power on the board.

It also says so on the cover plate of the box.

As they are breakers, they also switch off when way more then 50 A is passed, one of them. Somewhere in the box they split it and had 2 wires (fase) to both breakers. You have a rail system and when it's getting older, the breakers are harder to find. Normally it can last for decades, but never the less...

I cant make up which characteristic they are, but ill guess it will be C50.

In Asia the C-characteristic breakers are commonly used. I also think the other breakers are the same. If one passes more then 50 A, peak amps, it will shut down then. A B-type switches between 5-10 X value of breaker, a C -type higher 10-15 X value. So in your case if you have a spike of 500-750 A in (milliseconds) short time. 

Nowadays you see B-types coming up in Thailand and they are "saver" current limit is less. Prove is your mainbreaker, as this one is a B63, 3 years old.

Im though amazed they have B63 or C63 breakers in a house hold.

 

With your new airco, they took one of the breakers and fixed a wire under it, which lead to your extra breaker on the wall for the new airco.

So your wiring is protected again, not needed, but they do so in Thailand. Then you have an electric switch (probably the reason) to shut off the airco.

Switch and extra safety, though 20 A? Dont be surprised once a breaker trips in the box and the other breaker is still on. 

 

 

[Crossy]

24 minutes ago, natway09 said:

If the Safety cut out only occurs when aircon on with WM good chance just overloaded

 

It's a 63A Safe-T-Cut, that's not going to think about opening before 70A or so. So that's 15kW!!!

 

Big A/C maybe a couple of kW, washer maybe 3kW so there's 10kW (45A) going somewhere.

 

Our OP still hasn't responded if the Safe-T-Cut is showing that it tripped on leakage.

 

[DUNROAMIN]

1.  Every air con should have own breaker.

2. Every hot water unit should have own breaker.

3. lighting should be on separate breaker ( maybe split into two depending on size of house).

4. Each room can have a separate breaker for power only, depending on usage in each room.. (Exception for kitchen if you have electric stove /oven) then this needs separate breaker. Sorted my electrics years ago with up to date with RCBO/ circuit breakers boards. All important here in Thailand that you have all power outlets and lighting earthed and a earth ground rod.

[sometimewoodworker]

49 minutes ago, xtrnuno41 said:

As they are breakers, they also switch off when way more then 50 A is passed, one of them. Somewhere in the box they split it and had 2 wires (fase) to both breakers.

Correction it is line and neutral going to the incoming breaker. You are describing a USA system where there could be just 2 phases, also the current is going to be well over 50A for a period before the dual breaker trips.

[rwill]

On 7/31/2020 at 1:44 PM, lujanit said:

So should I change the CB from 15 amp to 20 or 32 amp?  Or is the answer more complicated?

It depends on the size of the wiring used.  It is not safe to just randomly change the breaker to a higher amperage.  It could cause the wiring to overheat and possibly start a fire.

[rwill]

What is your electric meter rated for?  If you have a 5/15 one you might need it changed to a 15/45.  

[ifmu]

my god   ..  if its as bad as u say then get a pro to rewire everything to us or brit standards .. and that means ground everything and move it out of water 

 

dont use thai for any electrical .. they take too many shortcuts and it is dangerous as hell 

[xtrnuno41]

22 hours ago, sometimewoodworker said:

Correction it is line and neutral going to the incoming breaker. You are describing a USA system where there could be just 2 phases, also the current is going to be well over 50A for a period before the dual breaker trips.

I go with the pic and i see 2 black wires going out T-cut. According code they should be black and grey again then. Would be logical.

So the system has 2 railings on which one has a connection at the end of the board for neutral leading towards neutral bus? ok.

The system is only fase switching action.

I saw two blacks, so thought maybe they spread power over two cables, but then i dont see any gray going to somewhere.

It has a different route? I dont know only see pic. i dont know what the Thai electrician was thinking. You cant see it by pic.

A single core wire 4 mm2 can have max 32 A, so not protected by the big B63. As this one will switch 5-10 value peak.

And even in normal operation lower then 63 A or even over it, the wiring will be cooked. The wiring is now a breaker, even the C50 A breaker wouldnt do a thing.

So they used the C50's for switches, as you can switch more then 50 A with them.

And when ever will the B63 switch, probably never, only when T- cut jumps in.

I cant see, as i can see a black on the neutral bus, where it is going to and then the wiring code is wrong again?, or changed to English then? As i see many red and black. When do you change then and how consistent is the electrician?

I also wonder if there are insulated in/outputs in the METAL box. As long as the insulation of the cables is good no problem,

but when damage happens the box could be powered.

There are also other colored wiring in the box, making no sense. Blue wires used for fase, brown for neutral, (European style or not?)? Wrong again.

White, grey for what? All random, no code what so ever. Just easy add ons without keeping code(s). Everything is possible in this installation.

[sometimewoodworker]

14 hours ago, xtrnuno41 said:

I go with the pic and i see 2 black wires going out T-cut. According code they should be black and grey again then. Would be logical.

So the system has 2 railings on which one has a connection at the end of the board for neutral leading towards neutral bus? ok.

The system is only fase switching action.

I saw two blacks, so thought maybe they spread power over two cables, but then i dont see any gray going to somewhere.

It has a different route? I dont know only see pic. i dont know what the Thai electrician was thinking. You cant see it by pic.

A single core wire 4 mm2 can have max 32 A, so not protected by the big B63. As this one will switch 5-10 value peak.

And even in normal operation lower then 63 A or even over it, the wiring will be cooked. The wiring is now a breaker, even the C50 A breaker wouldnt do a thing.

So they used the C50's for switches, as you can switch more then 50 A with them.

And when ever will the B63 switch, probably never, only when T- cut jumps in.

I cant see, as i can see a black on the neutral bus, where it is going to and then the wiring code is wrong again?, or changed to English then? As i see many red and black. When do you change then and how consistent is the electrician?

I also wonder if there are insulated in/outputs in the METAL box. As long as the insulation of the cables is good no problem,

but when damage happens the box could be powered.

There are also other colored wiring in the box, making no sense. Blue wires used for fase, brown for neutral, (European style or not?)? Wrong again.

White, grey for what? All random, no code what so ever. Just easy add ons without keeping code(s). Everything is possible in this installation.

You are making a classic western viewpoint mistake, thinking that wire colour used in Thailand by many Thai “electrical fitters” has a logical meaning. 
 

you can see a black feed to the exposed neutral bar, it looks to be at least 6mm², but probably 10mm² .

 

your comment is a little difficult to read as there is no English word “fase” I am assuming you mean phase which is only relevant in a 3 phase system or in the USA. AFIK virtually no other country supplies 2 of the 3 phases to a domestic installation as that can be rather dangerous.

[bankruatsteve]

5 minutes ago, sometimewoodworker said:

AFIK virtually no other country supplies 2 of the 3 phases to a domestic installation as that can be rather dangerous.

The US is not 2-phase.  It is a split single phase supplying 120v from N to each side of the split and 240v between the split L which are 180^o phase different.

[lujanit]

Some answers.

 

All four air-cons and both water heaters have their own dedicated breaker in the board as well as a breaker near the unit.

 

I have never seen a MEM breaker trip, it is always the Safe-T-Cut.  Altering the resistance from 5mA to 30mA sometimes works but not most of the time.

 

We contacted a Siemens service rep to look at the WM and he quoted 10k baht with no guarantees.  So we today installed a new Hitachi WM.  Hopefully that will fix the problem.

 

I'm sorry but I don't follow all the technical talk, I am no electrician.  However I do appreciate all the advice.

[Crossy]

@lujanit did you determine if the Safe-T-Cut is opening on leakage (coloured indicator in the small window on the left hand unit)?