Circuit Breaker teardown and defective Siemens latching mechanism

[mbrooke]

Ah, it was just old file photo. It was that way when the house was bought second hand. I since added the following common trip handles:

Very good :thumbsup:

Btw.. for two poles.. either side should trip right?

A handle tie alone is not common trip. Meaning if one side trips, it will not kick off the other. But close enough- technically code does not require common trip for a straight 240 volt circuit.

We have so many fake breakers too or counterfeit. In the following an American who married a filipina came to the country and built a home with knowledge of US electrical system. But he noticed only one of the 2-pole can trip during a short and randomly which side. His comments:

https://myphilippinelife.com/philippine-electrical-wiring/

"The assumption that the two halves of DP breakers can serve as SP breakers proved to be very wrong. The double-pole breakers are NOT just two single pole breakers physically joined. We found this out the hard way when we had a total short in one of our circuits and the 20 amp breaker did not trip, but instead melted a #12 AWG wire. This must have been a huge overload, far beyond 20 amps.We then tested the breakers on a test circuit. We found that only one side of our double pole breaker provide short circuit protection. It’s unknown which side may provide over current protection. Presumably, breakers made to be used as single-pole provide both protections in a single breaker, as do double-pole breakers used as a unit."

The following was the GE breakers he described:

Is it normal behavior or counterfeit?

Also in your experience, what other American breaker brands have compatible spring clips and bus bar stubs as the GE?
​

I know what this is about- because I discovered it by mistake when playing with a few GE breakers I took apart.


If you take an older 2 pole common trip GE breaker, and then remove the handle tie, then turn one of the poles to off, were you to short circuit/over load the other pole thats still on it would jam trying to trip.

Reason I found being that when one pole is switched off, the bulky common trip mechanism starts to lean forward. When the other pole unlatches, its catch hits the leaning forward mechanism and snags on it. This is a design flaw in older GE breakers under 40amps- but I do not entirely blame GE as double pole breakers are not intended to have their handle ties removed and used as 2 single pole breakers. But despite being a code violation to modify stuff like that, I've seen it done on a few occasions in the US when an electrician ran out of singles on his truck. Fortunately the modern GE, Homeline and Square D breakers I also played with did not jam in this mode.


So to answer the question I doubt those breakers are counterfeit, it is normal for GE breakers to jam like that when the handle tie is removed.


Regarding breaker compatibility- stick with the same manufacturer as who made the panel. What will work in your local panels I have no idea. But if GE has been getting the job done I'd stick with GE.

 

[tersh]

Very good :thumbsup:



A handle tie alone is not common trip. Meaning if one side trips, it will not kick off the other. But close enough- technically code does not require common trip for a straight 240 volt circuit.






I know what this is about- because I discovered it by mistake when playing with a few GE breakers I took apart.


If you take an older 2 pole common trip GE breaker, and then remove the handle tie, then turn one of the poles to off, were you to short circuit/over load the other pole thats still on it would jam trying to trip.

Reason I found being that when one pole is switched off, the bulky common trip mechanism starts to lean forward. When the other pole unlatches, its catch hits the leaning forward mechanism and snags on it. This is a design

What do you mean by "bulky common trip mechanism"? Were you referring to the handle tie? Or did you mean there was another common trip mechanism inside the unit itself that binds them together? Any schematic of such inside? In the 2-pole GE breakers of my panel. You can separately remove each piece so they are really separate 1 pole. What's disadvantage of this compared to the binded 2-pole GE breakers where there is another common trip mechanism inside??

flaw in older GE breakers under 40amps- but I do not entirely blame GE as double pole breakers are not intended to have their handle ties removed and used as 2 single pole breakers. But despite being a code violation to modify stuff like that, I've seen it done on a few occasions in the US when an electrician ran out of singles on his truck. Fortunately the modern GE, Homeline and Square D breakers I also played with did not jam in this mode.


So to answer the question I doubt those breakers are counterfeit, it is normal for GE breakers to jam like that when the handle tie is removed.


Regarding breaker compatibility- stick with the same manufacturer as who made the panel. What will work in your local panels I have no idea. But if GE has been getting the job done I'd stick with GE.

 

[LarryFine]

Handle ties are only installed to ensure both handles move with manual operation.

Two-pole breakers have an internal link to ensure both handles move when tripped.

Even with the handle tie removed, both poles should trip with overloads or shorts.

 

[tersh]

Handle ties are only installed to ensure both handles move with manual operation.

Two-pole breakers have an internal link to ensure both handles move when tripped.

Even with the handle tie removed, both poles should trip with overloads or shorts.

In the commercial building. I found breakers installed where some are composed of single piece 1-pole and some are 2-pole binded together:

For purely 2-pole 240v operation. What would be the problem if single 1-pole are used to act as 2-pole compared to the pure two poles with common trip inside itself? Would the former function less optimally? What is the exact disadvantage?

Also why is there a 40C in the right breaker? Isn't it breakers are rated with 60C, 75C, and 90C conductors?

 

[tersh]

Very good :thumbsup:



A handle tie alone is not common trip. Meaning if one side trips, it will not kick off the other. But close enough- technically code does not require common trip for a straight 240 volt circuit.






I know what this is about- because I discovered it by mistake when playing with a few GE breakers I took apart.


If you take an older 2 pole common trip GE breaker, and then remove the handle tie, then turn one of the poles to off, were you to short circuit/over load the other pole thats still on it would jam trying to trip.

Reason I found being that when one pole is switched off, the bulky common trip mechanism starts to lean forward. When the other pole unlatches, its catch hits the leaning forward mechanism and snags on it. This is a design flaw in older GE breakers under 40amps- but I do not entirely blame GE as double pole breakers are not intended to have their handle ties removed and used as 2 single pole breakers. But despite being a code violation to modify stuff like that, I've seen it done on a few occasions in the US when an electrician ran out of singles on his truck. Fortunately the modern GE, Homeline and Square D breakers I also played with did not jam in this mode.

After watching this video of a double pole breaker teardown. I finally understood what you meant by the internal bulky common trip mechanism. It's also there inside the 2-pole I opened but didn't know the function before.

So in 240v panels with individual 1-pole breaker unit that is only linked at the handle (see photos below). How do you think only one breaker tripping can affect the partner?

When a breaker trips. It is in middle or trip position as the catch opens. But the other partner isn't tripping. But because they were connected by the handle lever. Then the other partner just goes to OFF position, so I think it pushes the entire handle to the OFF position instead of the trip position?

Note the panels I shown earlier is supposedly composed of 2-pole breakers but since these are really individual 1-pole breakers therefore there are really 32 single pole breakers. The following photo shows a 1-pole breaker being pulled up.

How each (of the 32) 1-pole breaker looks like:

This is the spec of it.

The house was bought second hand so engineering didn't know about it.

What if the handle lever can't push both of them to the OFF position or the plastic lever breaks or detached. what do you think would happen if only one 1-pole breaker is OFF, while the partner breaker is on? There is no more power to the load but one leg is still hot. Other consequences you can think of?

So to answer the question I doubt those breakers are counterfeit, it is normal for GE breakers to jam like that when the handle tie is removed.


Regarding breaker compatibility- stick with the same manufacturer as who made the panel. What will work in your local panels I have no idea. But if GE has been getting the job done I'd stick with GE.

 

[kwired]

In the commercial building. I found breakers installed where some are composed of single piece 1-pole and some are 2-pole binded together:

For purely 2-pole 240v operation. What would be the problem if single 1-pole are used to act as 2-pole compared to the pure two poles with common trip inside itself? Would the former function less optimally? What is the exact disadvantage?

Also why is there a 40C in the right breaker? Isn't it breakers are rated with 60C, 75C, and 90C conductors?

Using two single pole breakers would be sort of like using two fuses, During a fault only one might trip, leaving voltage to the circuit from the other. Overcurrent protection has been achieved, but there is still voltage out there on the circuit. Common trip always opens both supply conductors from the protected circuit or all three poles on a three phase application.

I bet all your breakers say 40C somewhere on them. That is the ambient temp they are designed for and when you look at trip curve information it is based on 40C ambient. The termination rating is still 60 or 75C

 

[LarryFine]

Years ago, I separated a defective 2-pole breaker just to see what connected the two sections (other than the rivets.) There was a small, rectangular piece of material between the bodies, in a slot that turned when one pole tripped, turning the same part of the other section. I turned the same part in a single-pole breaker of the same type with a flat-blade screw-driver, and sure enough, it caused the breaker to trip.

 

[mbrooke]

What do you mean by "bulky common trip mechanism"? Were you referring to the handle tie? Or did you mean there was another common trip mechanism inside the unit itself that binds them together? Any schematic of such inside? In the 2-pole GE breakers of my panel. You can separately remove each piece so they are really separate 1 pole. What's disadvantage of this compared to the binded 2-pole GE breakers where there is another common trip mechanism inside??

Not the handle tie. The handle tie just makes sure both poles open and close at the same time when operated manually.

There is another mechanism inside the unit itself which trips the neighboring pole when the first pole trips automatically on a short circuit or overload.



Here is a pic from a 1987 GE breaker, arrow points to the common trip piece:

 

[mbrooke]

Handle ties are only installed to ensure both handles move with manual operation.

Two-pole breakers have an internal link to ensure both handles move when tripped.

Even with the handle tie removed, both poles should trip with overloads or shorts.

Correct- if both poles are in the "on" position. On older GE breakers having one pole off and the other pole on can cause the breaker to jam- its not intentional but an inadvertent design defect. The common trip on older 2 pole GE breakers was not well designed and very bulky, latter versions do not have this issue. See pic of a new GE 2 pole 100amp breaker vs the old 20amp one in the last post. (sorry I do not have a pic of a newer 20amp on this computer) but as you can see the common trip is smaller and does not have the issue with binding.

 

[mbrooke]

For purely 2-pole 240v operation. What would be the problem if single 1-pole are used to act as 2-pole compared to the pure two poles with common trip inside itself? Would the former function less optimally? What is the exact disadvantage?

The only down side is that if a line to ground fault occurred on one phase, only one breaker will trip. The other breaker would remain closed. If loads were switched on power would go through the load, through the fault point and down to earth. There is no hazard of wires melting or anything, it is safe in that regard because if the other breaker saw to much current it would trip too.

Also why is there a 40C in the right breaker? Isn't it breakers are rated with 60C, 75C, and 90C conductors?

40*C is the rated ambient temperature. No worries, you are fine.

 

[kwired]

The only down side is that if a line to ground fault occurred on one phase, only one breaker will trip. The other breaker would remain closed. If loads were switched on power would go through the load, through the fault point and down to earth. There is no hazard of wires melting or anything, it is safe in that regard because if the other breaker saw to much current it would trip too.





40*C is the rated ambient temperature. No worries, you are fine.

And supplying with fuses does the same thing. For 240 volt circuits we have to have a switch ahead of the fuse holders- that still gives simultaneous disconnect when manually operating, we just don't automatically open both sides when overcurrent conditions occur.

 

[mbrooke]

After watching this video of a double pole breaker teardown. I finally understood what you meant by the internal bulky common trip mechanism. It's also there inside the 2-pole I opened but didn't know the function before.

Correct, its there so if one pole trips, the other forced open. If you read the specs they say "internal common trip" Internal is the key word. A typical breaker does not have enough strength the kick the other breaker off via handle tie.


In fact the breaker is designed such that the internal spring puts very little pressure on forcing a handle itself to the trip potion because you would not want a person closing a breaker into a short circuit and then holding the lever. Breakers are designed such that if you close the breaker into a short and hold the lever, the insides still trip open. This is mandated by code.

So in 240v panels with individual 1-pole breaker unit that is only linked at the handle (see photos below). How do you think only one breaker tripping can affect the partner?

It will not effect the partner in any way during a trip.

When a breaker trips. It is in middle or trip position as the catch opens. But the other partner isn't tripping. But because they were connected by the handle lever. Then the other partner just goes to OFF position, so I think it pushes the entire handle to the OFF position instead of the trip position?

It does not push the partner to off. The strength of the tripped breaking moving to the middle position is not enough to open the other breaker. In fact if one of the breakers open on a fault, at first glance it will appear like nothing has tripped because the handle tie is being held in the on position by one lever and the trip position by the other lever.

Note the panels I shown earlier is supposedly composed of 2-pole breakers but since these are really individual 1-pole breakers therefore there are really 32 single pole breakers. The following photo shows a 1-pole breaker being pulled up.

How each (of the 32) 1-pole breaker looks like:

This is the spec of it.

The house was bought second hand so engineering didn't know about it.

What if the handle lever can't push both of them to the OFF position or the plastic lever breaks or detached. what do you think would happen if only one 1-pole breaker is OFF, while the partner breaker is on? There is no more power to the load but one leg is still hot. Other consequences you can think of?

One leg is still hot, meaning load will see 120 volts if the other leg has faulted to ground. You will get things like lights lighting up very dim and appliances not working or acting bizarrely.


2 pole breakers is the best option, however, the code does not view 2 single pole breakers with a handle tie as enough of a safety hazard to outlaw them for use in straight 240 volt circuits. Technically its not a code violation.

 

[mbrooke]

And supplying with fuses does the same thing. For 240 volt circuits we have to have a switch ahead of the fuse holders- that still gives simultaneous disconnect when manually operating, we just don't automatically open both sides when overcurrent conditions occur.

Very true.

 

[mbrooke]

FWIW, here is a comparison of a 20amp 2 pole late 80s vintage GE breaker vs a 20amp single pole late 80 vintage GE breaker.


Notice the common trip in one and the absence in the other, in fact you can even see a circular indent in the plastic of the single pole breaker where the internal common trip bar would go through on a 2 pole.


FWIW, the single pole has a few wraps of copper around the magnetic pole piece, this is lower the magnetic rating since single pole breakers are typically going into general use circuits instead of heavy inrush applications like AC units.

 

[RumRunner]

The 30A GFCI breakers use AWG 10 wire to the sockets. The 60A GFCI breakers use AWG 6 to the subpanel. It is the main panel. The electrician and even some engineers didn't suggest 20 space Siemens load center last year as we were not even sure it could work, so settled for the 12 space (6 breakers only). I mean, what if it would nuisance trip on the fridge, air conditioning units, others. Fortunately it has zero nuisance tripping, unlike the GFCI receptacles which can trip on the fridge twice a day for example.

Technically this is a code violation- 15amp sockets can not be on a circuit larger then 20amps.Technically- but if its custom throughout the Philippines it is what it is.

..................

My comment:

Throughout this thread I see numerous references to general use circuit protected by 30 Amp breakers.

This is not a code violation in British standard. . . it is a wiring designed for compatibility with their BS 1363 consumer socket (plug) and their appliance male plugs that have fuses.

It is important to note that the British call “socket” what Americans would call “wall plug” or appliance plug. They use these terms also in Singapore and Malaysia.
Although Australia is close to being British, lol (don't tell this to the separatists ) they don't use the BS 1363 standard. They have their own plug called crowfoot.

The British use the ring main style wiring extensively as opposed to the North American radial style. They also use our radial system in what they call “spur circuits” along with their Main Ring.

For more about British practices look here:

http://main.linuxfocus.org/~guido/javascript/awg.html

It seems like I'm talking foreign because “ring main wiring system” is not mentioned in NEC or any reference to it in electrician's handbook. So I'm quite certain that majority of US master electricians don't even know what I'm talking about.
They do have a good reason not to learn the system. . . why would they ever want to learn them?

While each side of the Atlantic claims that their system is safer than the other. . . each system has its advantage and disadvantage. It is not important to get into the “molecular” level at this time but I will cover a small detail just to provide some perspective on how this main ring system work and how the comments are related to this British Standard.

I'm not saying that the Philippines use the British System throughout the country, but, as OP had always said, their wiring system is a hodge-podge of wiring styles depending on where the electrician acquired his skill.

The Philippines is rich in human resources that you will find workers of different trades working in the construction industry—from the Arabian Peninsula to the oil platforms in Lake Maracaibo in Venezuela. I've been there.

I won't be surprised if the electricians that OP were referring to had work in one of the countries like Malaysia, Singapore or Hongkong.
Electricians in these countries were mentored by British engineers.

I was hired by a Chicago-based consulting firm to oversee the construction of a radar station in Southeast Asia years ago (location classified). I saw a lot of “ locals” along with electricians brought in from the mainland US. The first thing I asked the Field Engineer was...if these local workers were trained to work using US standard. I am familiar with MIL-SPECS. . . and I was there to make sure the work was done to conform with MIL-SPECS. This is what I report to my boss.

The Field Engineer's response was, they were hired in Chicago and they came from Chicago. . . well. . . that takes care of that one.
No wonder they all speak English (no offense implored). . . and good English too.

The reason I brought this up is, OP (Tersh) is mingling the two standards (US and UK) that often lead to confusion. Even a seasoned US electrician could be thrown off as indicated by comments that are often tainted with sarcasm fueled by ignorance. They sometimes dismiss newbies' comments as jumbled and fumbling (I can site those comments).


The main ring system branch circuit -- along with other branch circuits in the panelboard-- is distinguishable by being protected by a 30 Amp or 32 Amp fuse or CB. This branch circuit is usually supplied by a 6.0 mm2 conductor which is the equivalent of 10 AWG.

We never use a 30 Amp circuit for convenience outlets for eg. egg-beater or vacuum cleaner. Those 30 amp circuits are common in electric clothes dryers and stoves/ovens or special purpose appliances etc.
It is also common to see 5 Amp fuses and circuit breakers in foreign panelboards.
They are a rarity (if at all) in US panelboards. These 5 Amp for lighting branch circuits are wired with 1.5mm2 conductors which is the equivalent of 14 AWG but a bit smaller.

In-a-nutshell, those comments made by the questioner or responder are not incongruous or irrational-- rather-- their support base differs widely which makes their response rather odd.

I love diversity.

 

[tersh]

Correct, its there so if one pole trips, the other forced open. If you read the specs they say "internal common trip" Internal is the key word. A typical breaker does not have enough strength the kick the other breaker off via handle tie.


In fact the breaker is designed such that the internal spring puts very little pressure on forcing a handle itself to the trip potion because you would not want a person closing a breaker into a short circuit and then holding the lever. Breakers are designed such that if you close the breaker into a short and hold the lever, the insides still trip open. This is mandated by code.




It will not effect the partner in any way during a trip.




It does not push the partner to off. The strength of the tripped breaking moving to the middle position is not enough to open the other breaker. In fact if one of the breakers open on a fault, at first glance it will appear like nothing has tripped because the handle tie is being held in the on position by one lever and the trip position by the other lever.

I realized you were right. I tried the Westinghouse breaker I toredown earlier and when the catch was manually released, the handle can still be in the on position. You said this was purposedly designed so that that if you close the breaker into a short and hold the lever, the insides still trip open, and how this was mandated by code. This is brilliant. Something my electrician and even electrical engineer hadn't realized. They didn't know the other leg is still hot. In the country, most may not know this. This was why the previous contractor used individual breakers because they didn't know (all contractor companies use civil engineer, structural engineer, sanitary engineer and of course electrical engineer.

This is the most important thing I learnt in this thread. In fact it's so important that my electrical engineer mentor and electrician and I just discussed a while ago. Instead of replacing the 32 individual breakers with 2-pole plug in. We would just remove the entire plug in panel and replace it with din rail. Din rail is now used in new constructions like condominium or houses. This will be subpanel to the main Siemens main panel with 6 Siemens 2-pole GFCI breakers. One of them is 60A which will be feeded to the din rail subpanel. The loads won't be simultaneously used so we can be certain ambient leakage can't reach more than 5mA and trip the 60A GFCI

Also because we would buy new breakers, we would follow NEC and not other countries (as far as amperage is concerned because I know USA doesn't have any din rail). Meaning we would only use 15A for lighting, 20A for outlets. There is a room with only 2 lights connected to the former 30A breaker, the lights were only 0.5A. So it makes sense to connect this to 10A din rail breaker (since 5A Din Rail doesn't exist). Isn't it? In case it exists. In the US if your load is certainly only 0.5A lights, you can use 5A breaker?

Thanks for much for all the helpful tips. This external handle and internal tripping mechanism detail is just so critical, it changed everything all of a sudden.

​

One leg is still hot, meaning load will see 120 volts if the other leg has faulted to ground. You will get things like lights lighting up very dim and appliances not working or acting bizarrely.


2 pole breakers is the best option, however, the code does not view 2 single pole breakers with a handle tie as enough of a safety hazard to outlaw them for use in straight 240 volt circuits. Technically its not a code violation.

 

[mbrooke]

I realized you were right. I tried the Westinghouse breaker I toredown earlier and when the catch was manually released, the handle can still be in the on position. You said this was purposedly designed so that that if you close the breaker into a short and hold the lever, the insides still trip open, and how this was mandated by code. This is brilliant. Something my electrician and even electrical engineer hadn't realized. They didn't know the other leg is still hot. In the country, most may not know this. This was why the previous contractor used individual breakers because they didn't know (all contractor companies use civil engineer, structural engineer, sanitary engineer and of course electrical engineer.

Those who write the code know their stuff- most time anyway.


The only place I would consider single pole breakers is on a 230 volt L-N system.

This is the most important thing I learnt in this thread. In fact it's so important that my electrical engineer mentor and electrician and I just discussed a while ago. Instead of replacing the 32 individual breakers with 2-pole plug in. We would just remove the entire plug in panel and replace it with din rail. Din rail is now used in new constructions like condominium or houses. This will be subpanel to the main Siemens main panel with 6 Siemens 2-pole GFCI breakers. One of them is 60A which will be feeded to the din rail subpanel. The loads won't be simultaneously used so we can be certain ambient leakage can't reach more than 5mA and trip the 60A GFCI

DIN is a good idea, because you know the "busbar" is approved for the breakers being used. Make sure the leads jumping from breaker to breaker are sized correctly- I say that because I've seen guys on the internet use 2.5mm2 jumping from breaker to breaker in a 100amp consumer unit

And of course make sure your breakers are 2 pole right out of the box.

Also because we would buy new breakers, we would follow NEC and not other countries (as far as amperage is concerned because I know USA doesn't have any din rail). Meaning we would only use 15A for lighting, 20A for outlets.

You can do that, 100% ok. Are you using USA wire sizes or IEC wire sizes? Just wondering.




There is a room with only 2 lights connected to the former 30A breaker, the lights were only 0.5A. So it makes sense to connect this to 10A din rail breaker (since 5A Din Rail doesn't exist). Isn't it? In case it exists. In the US if your load is certainly only 0.5A lights, you can use 5A breaker?[/QUOTE]


There are no 5A breakers in the US- minimum circuit is 15 amps. However if you have lights only on the circuit I see no issue in a 10amp DIN rail breaker.

Thanks for much for all the helpful tips. This external handle and internal tripping mechanism detail is just so critical, it changed everything all of a sudden.

​

Welcome- and don't be afraid to ask questions. To me sharing knowledge is effortless and rewarding in fact, so I am not bothered when you or anyone asks.


I see it like this: by sharing knowledge I am improving the lives of people which will ultimately improve the lives of everyone in a nation. The Flynn effect is real, and it takes place when people have the knowledge to engage in practices which protect human life, give mercy and eliminate suffering.

 

[tersh]

Those who write the code know their stuff- most time anyway.


The only place I would consider single pole breakers is on a 230 volt L-N system.

DIN is a good idea, because you know the "busbar" is approved for the breakers being used. Make sure the leads jumping from breaker to breaker are sized correctly- I say that because I've seen guys on the internet use 2.5mm2 jumping from breaker to breaker in a 100amp consumer unit

And of course make sure your breakers are 2 pole right out of the box.



(image snipped)

You can do that, 100% ok. Are you using USA wire sizes or IEC wire sizes? Just wondering. ​

I couldn't find any Siemens 2-pole DIN 125A, but found the Schneider 125A and ABB 100 at local distributor. The former seems to have better specs:

https://www.schneider-electric.com/...120h---circuit-breaker---2p---125a---c-curve/

Please click Product Datasheet inside, you think it's perfect?

The electrical engineer computed it to be 125A based on the service size of 38mm^2 (which is between AWG 2 and 1). Do you know what standards are these sizes? These are locally manufactured and the wires used in the building.

https://phelpsdodge.com.ph/wp-content/uploads/2015/07/COPPER-BUILDING-WIRE-TYPE-THHNTHWN-21.pdf

In the US. AWG 10 is 5.2mm^2. Here it is 5.5mm^2.

38mm^2 is between (AWG 2 (33.63mm^2) and AWG 1(42.4mm^2)
Here is the weird thing. 38mm^2 is right in the middle between AWG 2 and 1
watch:

(33.63+42.4)/2 = 38

Know a hidden reason for it? And who created the 38mm^2 wiring standard used in Phils?

Our electrical engineer used the 75C ampere halfway between AWG 2 and AWG 1 which is 122.5A.

Since the original main panel breaker is 125A. I asked him what happens if wire temperature reaches 122.5A and temperature reaches 75C (assuming 75C is used and not THHN (90C)). I asked him what would happen whether the wire would ignite before the 125A breaker trips. He said it might trip. What do you think? We can't use 90C table because the breaker terminal ampere is only rated at 75C.

There is a room with only 2 lights connected to the former 30A breaker, the lights were only 0.5A. So it makes sense to connect this to 10A din rail breaker (since 5A Din Rail doesn't exist). Isn't it? In case it exists. In the US if your load is certainly only 0.5A lights, you can use 5A breaker?

There are no 5A breakers in the US- minimum circuit is 15 amps. However if you have lights only on the circuit I see no issue in a 10amp DIN rail breaker.





Welcome- and don't be afraid to ask questions. To me sharing knowledge is effortless and rewarding in fact, so I am not bothered when you or anyone asks.


I see it like this: by sharing knowledge I am improving the lives of people which will ultimately improve the lives of everyone in a nation. The Flynn effect is real, and it takes place when people have the knowledge to engage in practices which protect human life, give mercy and eliminate suffering.

Well. When the electrical engineer and electrician learnt more right stuff after I shared them what I learnt, then they can spread the knowledge to others.

And then remember I'm an engineer too or I won't be concerned with all these details that normal people in the Philippines would never bother. They just hire electrician and electrical engineer and let them handle everything without double checking anymore.
The negative result was having all 30A breakers in panel that is 1-pole powering lights load like in the old house owner and contractor relationship, lol.​

 

[mbrooke]

I couldn't find any Siemens 2-pole DIN 125A, but found the Schneider 125A and ABB 100 at local distributor. The former seems to have better specs:

https://www.schneider-electric.com/...120h---circuit-breaker---2p---125a---c-curve/

Please click Product Datasheet inside, you think it's perfect?

Its perfect- I see no problems.


Everyone is sure type C curve is good? I only ask because I come from a land with high magnetic trip breakers.

The electrical engineer computed it to be 125A based on the service size of 38mm^2 (which is between AWG 2 and 1). Do you know what standards are these sizes? These are locally manufactured and the wires used in the building.

https://phelpsdodge.com.ph/wp-content/uploads/2015/07/COPPER-BUILDING-WIRE-TYPE-THHNTHWN-21.pdf

In the US. AWG 10 is 5.2mm^2. Here it is 5.5mm^2.

38mm^2 is between (AWG 2 (33.63mm^2) and AWG 1(42.4mm^2)
Here is the weird thing. 38mm^2 is right in the middle between AWG 2 and 1
watch:

(33.63+42.4)/2 = 38

Know a hidden reason for it? And who created the 38mm^2 wiring standard used in Phils?

I am going to be honest- I have no idea whats going on. I saw the same mm2 wiring sizes in your code- and if they actually are the size said to be- they would be to small for the listed current.


The graph is wrong- 14 gauge is 2.08mm2, 12 gauge is 3.31mm2 and 10 gauge is 5.26mm2.

Our electrical engineer used the 75C ampere halfway between AWG 2 and AWG 1 which is 122.5A

.

Here is the table from our NEC:


https://wabashelectric.com/ASSETS/DOCUMENTS/CMS/EN/Amp Chart.pdf


AWG 1, or 42.41mm2 is listed at 130 amps at 75*C.

Since the original main panel breaker is 125A. I asked him what happens if wire temperature reaches 122.5A and temperature reaches 75C (assuming 75C is used and not THHN (90C)). I asked him what would happen whether the wire would ignite before the 125A breaker trips. He said it might trip. What do you think? We can't use 90C table because the breaker terminal ampere is only rated at 75C.

I doubt the temperature would reach 75*C- the tables are very conservative. AWG 1 would hold 125 amps and a more without issue.

Well. When the electrical engineer and electrician learnt more right stuff after I shared them what I learnt, then they can spread the knowledge to others.

And then remember I'm an engineer too or I won't be concerned with all these details that normal people in the Philippines would never bother. They just hire electrician and electrical engineer and let them handle everything without double checking anymore.
The negative result was having all 30A breakers in panel that is 1-pole powering lights load like in the old house owner and contractor relationship, lol.

Knowledge is power- as people learn they get better and better.

 

[mbrooke]

Here is the table from your Code, the Philippine Electrical Code. The thing is, the amapcities are identical to our old table which is good, but the mm2 listed do not reflect the actual size of our wires. They seem to be rounded up or down- for example 2.08 is rounded down to 2.0, 3.31 is rounded up to 3.5mm2, 5.26 is rounded up to 5.5mm2.


My question is, if you have a 12 gauge wire in the Phillipines, is it actually 3.31mm2 or 3.5mm2? What does the jacket say on the wires?