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lujanit

Circuit Breaker Problem

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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

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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.

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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.

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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.

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Thanks for the replies. I have included a photo of most of the breaker box.AD988483-7991-47E7-AA55-1CA7D4DA40D5.thumb.jpeg.9c14f84eae146992bd36d3718532cda1.jpeg

 

 

 

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.

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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)

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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:

359684000_jstclujanit.jpg.e6ddaeb643efebb72baae50673164542.jpg

 

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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.

 

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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.

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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.

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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.

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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. 

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Posted (edited)
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 by thaibeachlovers

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Posted (edited)
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 by sometimewoodworker
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