Circuit Breaker Problem

[rvaviator]

My money is on a intermittent ground fault - causing the 'Leakage current' trip to go.  As Crossy is saying.   It could even be that the Safe-T-Cut circuit that measures the imbalance is faulty. 

 

Did you leave it on the 5mA or 30mA setting ?  Earlier the OP mentioned about 'happens more if its raining'  High humidity is typical driver for causing issues with this type of circuit.

 

I would set it to 30mA  - Then I would pull some of the individual breakers (to isolate part of the circuit) and then see if it happens less (or not at all) ..

 

[rvaviator]

 

Do I understand this as - If left on 30mA the trip will not trip as often .. but still does trip ? 

[lujanit]

On 8/11/2020 at 6:31 AM, rvaviator said:

Do I understand this as - If left on 30mA the trip will not trip as often .. but still does trip ? 

That is correct. Shifting the level between 5mA to 30mA sometimes helps however usually not.

[lujanit]

On 8/11/2020 at 5:16 AM, Crossy said:

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

I have never noticed a light, then again I never looked for it.  If/when the next time it trips I will pay close attention to this detail.

[Crossy]

4 minutes ago, lujanit said:

I have never noticed a light, then again I never looked for it.  If/when the next time it trips I will pay close attention to this detail.

 

It isn't a light, as noted earlier there's a small window in the laft-hand "switch" with a coloured (red/brown) marker that drops down when it trips on earth leakage. You may need a torch/flashlight to actually see it.

 

 

[lujanit]

1 hour ago, Crossy said:

It isn't a light, as noted earlier there's a small window in the laft-hand "switch" with a coloured (red/brown) marker that drops down when it trips on earth leakage. You may need a torch/flashlight to actually see it.

You are, of course right.  I needed a torch now I can see the grey plastic in the small window turns red after tripping.

 

Something else has become noticeable.  I turned off the Safe-T-Cut to replace the 15 amp and the 20 amp CB's to their original position after advice from another poster (fire hazard due to insufficient wire thickness).

 

I switched the system back on and tried to adjust the resistance mA from 6 (not 5 as I originally thought, torch again). Immediately the Safe-T-Cut tripped. I hadn't even managed to alter the level to 10mA.  So with the system off I switched the resistance to 10mA, then 20mA and finally 30mA.  After every alteration the system immediately tripped.  The Safe-T-Cut will only remain on if the resistance is set to 5mA.

 

Is this a faulty Safe-T-Cut (only three years old) or do I need to get a ground rod installed?  

 

Thanks.

[Crossy]

8 minutes ago, lujanit said:

I switched the system back on and tried to adjust the resistance mA from 6 (not 5 as I originally thought, torch again). Immediately the Safe-T-Cut tripped. I hadn't even managed to alter the level to 10mA.  So with the system off I switched the resistance to 10mA, then 20mA and finally 30mA.  After every alteration the system immediately tripped.  The Safe-T-Cut will only remain on if the resistance is set to 5mA.

 

Is this a faulty Safe-T-Cut (only three years old) or do I need to get a ground rod installed?  

 

This is worrying and it could indeed be a faulty Safe-T-Cut device. Unfortunately testing these needs specialist knowledge and test gear.

 

Try this:-

Turn off all your breakers except the 50A incomer. Does the Safe-T-Cut trip on 30mA? If not try turning the breakers on on at a time until it trips.

 

If it does trip with everything off try turning off the 50A incomer as well. Trip?

 

[ifmu]

On 8/10/2020 at 3:40 PM, lujanit said:

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.

so you are diy .. ?  stating that you do not know what it all means ..also i am worried about the Siemens tech that said he would not guarantee anything 

i would have contacted another tech till i found someone that had confidence in his work 

[bankruatsteve]

5 hours ago, lujanit said:

The Safe-T-Cut will only remain on if the resistance is set to 5mA.

You say you also have a 6mA setting?  Seems strange.  Are you sure the setting that does not trip is 5mA?  Does it have a "Direct" setting?

[Metropolitian]

 

2 hours ago, bankruatsteve said:

You say you also have a 6mA setting?  Seems strange.  Are you sure the setting that does not trip is 5mA?  Does it have a "Direct" setting?

There are a few different versions of the dial settings. His is indeed 6mA and not 5mA.

 

 

 

 

[RichCor]

9 hours ago, Crossy said:

 

This is worrying and it could indeed be a faulty Safe-T-Cut device. Unfortunately testing these needs specialist knowledge and test gear.

 

Try this:-

Turn off all your breakers except the 50A incomer. Does the Safe-T-Cut trip on 30mA? If not try turning the breakers on on at a time until it trips.

 

If it does trip with everything off try turning off the 50A incomer as well. Trip?

 

I just noticed that the installation doesn't seem to be following the recommendation of bonding N-G prior to the Safe-T-Cut input.

 

Safe-T-Cut end user manual (link)

 

[Metropolitian]

 

 

3 hours ago, RichCor said:

I just noticed that the installation doesn't seem to be following the recommendation of bonding N-G prior to the Safe-T-Cut input.

Bonding of N-G is bad practice and only left to the earth busbar by grounding the neutral with the earth.

This is called MEN, and I called it in the Netherlands ''PEN = Earth is Nulled; Neutral and Earth connected''

 

It's the terminology used, bonding means a link between two conductors that doesn't carry any current to eliminate  potentials difference between conductors, which can be copper pipes and metal frames.

Earthing is also using an ground rod to earth a device, for example an outdoor pump.

In electricity Ground is the zero, the difference between ground and live is the voltage that you get, but doesn't mean that it is zero with respect to earth.  With AC we get from the utility we call ground the Neutral.

 

There are some difference with use of the words grounding and earthing, especially between the USA's IEEE and Europe IEC. I'm IEC (NEN). ???? 

 

About your comment regarding the recommendation from the Safe-T-Cut, you are right according the manual.

And the Safe-T-Cut is indeed placed between the main incoming wires and the CU.

If only we know what the heated discussion between the installer of that extra breaker for the air con and the other fellow was all about..

 

With the OP consumer unit there are more things playing.

* i dont see a MEN situation. The Live and Neutral from the STC goes directly to the MEM  Main breaker and the Neutral out from the main breaker goes to the Neutral Bar.

 

The neutral wire to the CU should go directly to this point and from there to the main breaker.. Nothing to see.

 

 

The breaker is directly connected to the incoming mains, I can see a subject of the heated discussion between the guys.

Also, that is something that should be checked if the connection is still good and not loose, but the OP can't do that as it is LIVE parts there.

(There was a thread before about a  failing STC due to an loose screw/connection.)

 

 

 

To the OP, Lujanit. This situation of your CU would only ''''acceptable''' like that IF the CU is a sub panel and feed from another bigger panel (where eventually the neutral and earth are linked). 

Are you getting your mains as private with your own meter and wired directly to this CU or from a shared connection with a non-utility-company(PEA/MEA..) meter?

 

 

[RichCor]

@lujanit,

 

I'm also having a problem following the wiring in your Consumer Unit.

Can you take another photo, with better lighting, of the entire box so we can see all the wiring properly. I'm following RED, BLUE, WHITE, BLACK ...but no Green?

 

I'd like to see how the Neutral and Earth Ground cabling is connected.

[Metropolitian]

7 minutes ago, Metropolitian said:

Bonding of N-G is bad practice

Years ago when I visited the USA, I had a few looks in the consumer units used here as well reading their codes. Learned about wiring in home and the split phase system.

There actually -is- an bonding cable between N and G in some of their CU's, called bonding jumper, as the neutral bar is one long bus and the ground rod was directly connected to this.

Between the bonding block and the outdoor meter was also a bonding cable.

 

Somewhat different then used here in Thailand which mostly follows the European model.

 

[RichCor]

I find it interesting that the MAINS INCOMER into the S-T-C is White/Black (L/N color flipped)   ...but as electricity is color blind this only matters to the people playing with the wires.

Edited August 13, 2020 by RichCor

[Crossy]

Way back in Post #9 I suggested checking outlets and switches for wildlife infiltration and damp.

 

If not already done it wouldn't hurt to check.

[bankruatsteve]

12 hours ago, Metropolitian said:

His is indeed 6mA and not 5mA.

 

20 hours ago, lujanit said:

The Safe-T-Cut will only remain on if the resistance is set to 5mA.

I thought he is saying he has both - which doesn't seem likely.  Wonder if he is somehow reading a direct setting as 5mA.  (?)

[Crossy]

27 minutes ago, bankruatsteve said:

I thought he is saying he has both - which doesn't seem likely.  Wonder if he is somehow reading a direct setting as 5mA.  (?)

 

From his photos he has 5(could be 6), 10, 20, 30 mA, this unit does not appear to have a "direct" setting (it was removed from the later production).

 

Either way, it should not be more "enthusiastic" on the higher mA settings. Something is amiss.

[Metropolitian]

4 hours ago, Crossy said:

 

From his photos he has 5(could be 6), 10, 20, 30 mA, this unit does not appear to have a "direct" setting (it was removed from the later production).

He has the Safe-T-Cut Gold , type S from CS International (Currently NANO - S series, so he has the older version).

Model PR20

 

I-Delta-n : 6 , 10 , 20 and 30 mA.

 

Safe T Cut is not one brand in Thailand, I know there are two (at least). The one being STC Smart and the other STC Gold.

 

STC Golds never had the 'direct' setting as far as I know, never seen them.

 

Both 'brands' do have their own history and production plants.

 

'Registered Trademark' is like ice here, it melts in front of you.

 

Quote

 

Either way, it should not be more "enthusiastic" on the higher mA settings. Something is amiss.

Absolutely agree with this.

 

 

EDIT:

OP, Lujanit. I do see another 'safe t cut' in your picture. Was it replaced? What was the issue?

Edited August 14, 2020 by Metropolitian

[lujanit]

6 hours ago, Metropolitian said:

He has the Safe-T-Cut Gold , type S from CS International (Currently NANO - S series, so he has the older version).

Model PR20

 

I-Delta-n : 6 , 10 , 20 and 30 mA.

 

Safe T Cut is not one brand in Thailand, I know there are two (at least). The one being STC Smart and the other STC Gold.

 

STC Golds never had the 'direct' setting as far as I know, never seen them.

 

Both 'brands' do have their own history and production plants.

 

'Registered Trademark' is like ice here, it melts in front of you.

 

Absolutely agree with this.

 

 

EDIT:

OP, Lujanit. I do see another 'safe t cut' in your picture. Was it replaced? What was the issue?

When we were having problems the electrician (not qualified, just a lot of experience) said it was  a Safe T Cut problem so we purchased a new one from Baan n Beyond.  That seemed to sort out the problem for a while.

 

Sorry about the lowest resistance, it is 6mA.  My eyesight is not too good in the half light.  Even touching the resistance adjuster will trip the Safe T Cut.

 

Overnight we had heavy rainfall.  Early this morning I got the WM going and it tripped the Safe T Cut (no air-con going).  Changing the resistance makes no difference as previously noted.

 

About 1300 with no rain for about 8 hours the offending breaker held.  I isolated the circuit by turning that CB off.  About 1500 we had heavy rain and the system tripped.  I used extension cords to make sure the fridge and the water pump had supply.

 

 My better half contacted her friend whose niece employs an electrician.  Maybe next week, but Thai time.

 

I can, in my ignorance, can only conclude that one of the outlets or lights is contaminated with water and after a period of no rain it drys out.

[Crossy]

10 hours ago, lujanit said:

I can, in my ignorance, can only conclude that one of the outlets or lights is contaminated with water and after a period of no rain it drys out.

 

Well it has been mentioned a couple of times in this thread too ????

 

There are also some simple checks you could carry out noted in earlier posts to try and isolate the fault.

 

[Metropolitian]

It very much looks like the combination of two:  

A failing (too enthusiast) Safe-T-Cut and damp/debris in some electrical outlets outside (lamp, sockets,..)

 

Quotes.

 

Lujanit (OP) : "So with the system off I switched the resistance to 10mA, then 20mA and finally 30mA.  After every alteration the system immediately tripped.  The Safe-T-Cut will only remain on if the resistance is set to 5mA. "

Crossy: "Either way, it should not be more "enthusiastic" on the higher mA settings. Something is amiss. "

 

Lujanit (OP): " Overnight we had heavy rainfall.  Early this morning I got the WM going and it tripped the Safe T Cut (no air-con going).  Changing the resistance makes no difference as previously noted. "

         " I isolated the circuit by turning that CB off.  About 1500 we had heavy rain and the system tripped. "

 

To the OP, Lujanit, with regard to Crossy's post #37 , are there another outdoor fixtures connected to other CB's maybe ? Have you 'eliminated' them as the culprit?

[rvaviator]

If you feel 100% sure that you have LESS trips when the adjustment is set to 5mA than when its set to 30mA then I would say that the safety trip measuring circuit (RCCB) is faulty and you need to change the unit.

5mA or 30mA is not measuring resistance – it is measuring the imbalance between N and L.  In other words if you have 5mA difference .. it will trip .. if you have 30mA it will trip.

What is causing this imbalance ?  It will happen if you have a ground fault. One of the ‘wires’ have a short to ground.

As 30mA is a higher value than 5mA .. it should trip more easily at 5mA than at 30mA  - You will always have some imbalance .. a few mA ....  Typical 30mA is a for a complete installation 5 or 6mA  .. for just the electric shower ...   On a side note .. Desktop PC power Supplies  can be notorious for having some leakage current - especially if a few years old.

[bankruatsteve]

1 hour ago, rvaviator said:

Desktop PC power Supplies  can be notorious for having some leakage current - especially if a few years old.

And usually well below 5mA.

[lujanit]

We had an electrician over yesterday.  He checked ever light and outlet.  He found two outlets beside each other contaminated with water/moisture.  No idea where the leak is.  He is coming back on Wednesday to see if he can fix it.

 

Would an option be to install waterproof outlets like the one below?

 

[bankruatsteve]

8 minutes ago, lujanit said:

Would an option be to install waterproof outlets like the one below?

Sure.  Unless the problem is inside.  In that case, finding the source is the goal.

[RichCor]

4 hours ago, bankruatsteve said:

4 hours ago, lujanit said:

Would an option be to install waterproof outlets like the one below?

Sure.  Unless the problem is inside.  In that case, finding the source is the goal.

To the OP,

 

Whenever I discover outdoor outlets that are prone to 'issues' I'll typically rewire them to have their own nearby RCD. This offers a bit more protection both from shock/electrocution and potentially allows it to auto-isolate from rest of the electrical system, so no full house blackouts. 

[xtrnuno41]

5 hours ago, lujanit said:

We had an electrician over yesterday.  He checked ever light and outlet.  He found two outlets beside each other contaminated with water/moisture.  No idea where the leak is.  He is coming back on Wednesday to see if he can fix it.

 

Would an option be to install waterproof outlets like the one below?

 

 

You have to see what is the IP code, it should be on the electric device.

In table you can see what it means for the device.