Circuit Breaker teardown and defective Siemens latching mechanism

[mbrooke]

What's feeding it is a breaker (right most) in the same main service panel where the arc flashed 3 phase breaker occurred (at the left side not shown). The reason the ground wire turned from black color to red is because halfway he spliced it. Now I'm afraid to let electrician even turn off any breaker without wearing any PPE:

What is below the panel?

This is especially after an expert wrote me in the arc flash forum: "What you describe is what Alicia Stoll's experiment was testing for and is known as the Stoll curve. It is equal to 1.2 cal/cm2 at 1 second and extends out to about 2.0 cal/cm2 at 2 seconds. This is the onset of a second degree burn. However your question is also talking about the onset of a second degree burn to a hand. IEEE 1584 uses the onset of a second degree burn to the face/chest area so the arc flash boundary would be defined at 18" away. In open air the incident energy quadruples if you half the distance. So 1.2 cal/cm2 at the face/chest would be 4.8 halfway down the arms. Let's just say that other than avoiding burns in the first place, we are never going to protect the hands."

What if I let the electrician wrap 2 shirts around his arms just to turn off one breaker in case the room or subpanel to it needs servicing. This would protect his arms in the event of spontaneous arc flash from the dusts (some may be conductive). Isn't it?

But there are thousands of service panels that don't encounter arc flashes. But in my case, the contractor omit to install the main breaker upstream of it and the 3 phase open delta just serve my office building and another besides it so the incident energy at the panel would be greater than any other place. ​

Well, I think with proper gear it wont be all the bad. You are only fed via two 75kva? pigs and there is distance between them. Is there a main breaker or 6 throws?

 

[mbrooke]

Typical US color code:

IEC main switch and fuse TN-S:

 

[tersh]

Ok, as I promised, some good electrical installs as examples and to go by.


Here is a panel full of 208 volt circuits- the main wires have not been pulled yet:

Residential:

Wow very neat. So you are allowed to use blue wire for one of the live phases, not just black and red?

Late last year when I learnt about EGC. I told the electrician to install EGC in the aircon condensers and connect it to existing ground wire in the panels. But we can't touch it because the tenant electricians installed it years ago and we can't modify any wiring. Therefore I told the electrician to just tap the chassis anywhere. But we don't know how to tap it. If we drill the iron brace, it can rust. Do you have any idea how the inside of the condenser ground terminal is connected to the chassis (any picture)?? Note in external condensers. There is no pre-existing plug unlike in window type aircon where the plug is built it. The previous installers didn't include the ground wire in the installation. Any idea how to tap any ground wire inside and where to insert that can't be penetrated by rain. I would discuss this to tenant after I have clear idea how the electrician can tap them.

I need EGC installed in them because I always pass by them and my body or hands always touch the chassis whenever I passed by the smaller entrance opening at the center aircon condenser.

Thanks.

 

[tersh]

What is below the panel?

It's the ground terminal lugs connected directly to the transformers centertapped neutral. The electrician many years ago measured 120v between the either of the 2 phases to the terminal and 208 v between the last phase and the terminal lugs (typical of open delta)..

See the right most breakers.
X1 is the right most wiring and lugs.
X1 to neutral is measured as approx. 210 volts (or 208 Volts).. the high leg voltage
X2 to neutral is measured as 120 volts.
X3 to neutral is measured as 120 volts.

But between X1-X2, X1-X3, X2-X3.. they are all 240 volts. The 2 phase breaker at left is connected to the X1 and X2 producing split phase and hence the same as your US split phase 120/240Volts (the power system in office building is indeed more complicated than your US single phase home supply).

This proves the following open delta schematic:

Wait. Is there any relevance or arc flash relation to the right most terminal being the 208 volts hence have higher incident energy when it was connected to the carbonized surface 3-pole we discussed the past days? ​

Well, I think with proper gear it wont be all the bad. You are only fed via two 75kva? pigs and there is distance between them. Is there a main breaker or 6 throws?

The distance is only 3 meters from the pole to the service entrance. And there is no main breaker upstream of the arc flashed 3-phase breaker because the contractor was into cost cutting and omitted to install the 200A 3-phase main breaker. He told me the cost for it was used up in other parts of the building. I was mad at him that time.

 

[mbrooke]

Wow very neat. So you are allowed to use blue wire for one of the live phases, not just black and red?

Yes. Blue can safely be used as a hot. Actually it can be used as both hots for a circuit.

Late last year when I learnt about EGC. I told the electrician to install EGC in the aircon condensers and connect it to existing ground wire in the panels. But we can't touch it because the tenant electricians installed it years ago and we can't modify any wiring. Therefore I told the electrician to just tap the chassis anywhere. But we don't know how to tap it. If we drill the iron brace, it can rust. Do you have any idea how the inside of the condenser ground terminal is connected to the chassis (any picture)??

Can you take the cover off? There should be a PE terminal in there.

Note in external condensers. There is no pre-existing plug unlike in window type aircon where the plug is built it. The previous installers didn't include the ground wire in the installation. Any idea how to tap any ground wire inside and where to insert that can't be penetrated by rain. I would discuss this to tenant after I have clear idea how the electrician can tap them.

Can't the EGC be fished through the conduit?

I need EGC installed in them because I always pass by them and my body or hands always touch the chassis whenever I passed by the smaller entrance opening at the center aircon condenser.

Thanks.

Not just you, but anyone else for that matter.

 

[tersh]

Yes. Blue can safely be used as a hot. Actually it can be used as both hots for a circuit.

Can you take the cover off? There should be a PE terminal in there.



Can't the EGC be fished through the conduit?

The conduit and all of it is constantly exposed to rain, even to Katrina class hurricane. Fishing through the conduit can destroy the waterproof insulation and the tenant would blame me if something got wrong. If there is a PE terminal inside, how could the electrician tap it from outside without boring a new hole? Any idea? That was why the electrician and I were discussing just tapping the metal chassis like the iron brace but worried what if it would rust soon. Would this work? How do we make sure the iron brace tapping part won't rust?

Not just you, but anyone else for that matter.

 

[mbrooke]

It's the ground terminal lugs connected directly to the transformers centertapped neutral. The electrician many years ago measured 120v between the either of the 2 phases to the terminal and 208 v between the last phase and the terminal lugs (typical of open delta)..

See the right most breakers.
X1 is the right most wiring and lugs.
X1 to neutral is measured as approx. 210 volts (or 208 Volts).. the high leg voltage
X2 to neutral is measured as 120 volts.
X3 to neutral is measured as 120 volts.

But between X1-X2, X1-X3, X2-X3.. they are all 240 volts. The 2 phase breaker at left is connected to the X1 and X2 producing split phase and hence the same as your US split phase 120/240Volts (my power system in my building is indeed more complicated than your US single phase home supply).

This proves the following open delta schematic:

​

All correct- 100% correct for an open delta.

Wait. Is there any relevance or arc flash relation to the right most terminal being the 208 volts hence have higher incident energy when it was connected to the carbonized surface 3-pole we discussed the past days?

​

Yes- but an arc flash expert would truly know how voltage effects the arc.

The distance is only 3 meters from the pole to the service entrance. And there is no main breaker upstream of the arc flashed 3-phase breaker because the contractor was into cost cutting and omitted to install the 200A 3-phase main breaker. He told me the cost for it was used up in other parts of the building. I was mad at him that time.

So in other words you have a gutter underneath those breakers, and there are 6 or fewer of them acting as the main? Technically ok per NEC:

 

[tersh]

All correct- 100% correct for an open delta.

​

Yes- but an arc flash expert would truly know how voltage effects the arc.






So in other words you have a gutter underneath those breakers, and there are 6 or fewer of them acting as the main? Technically ok per NEC:

What? No. The gutter is not below the breakers but above it. So it's the last illustration that is indicative of my setup. The arc flashed service panel is the one with all the breakers serving unit 1, unit 2, etc. Why did you state the gutter is below the breakers??

 

[mbrooke]

What? No. The gutter is not below the breakers but above it. So it's the last illustration that is indicative of my setup. The arc flashed service panel is the one with all the breakers serving unit 1, unit 2, etc. Why did you state the gutter is below the breakers??

So the main wires from the street go into the gutter and then drop down into the breakers?


I assumed by everything I saw that the gutter was at the bottom. But I can certainly be wrong as in many ways its a 50/50 guess.

 

[mbrooke]

Perhaps this may help?



https://www.youtube.com/watch?v=0tCtUGCIWW4

 

[tersh]

So the main wires from the street go into the gutter and then drop down into the breakers?


I assumed by everything I saw that the gutter was at the bottom. But I can certainly be wrong as in many ways its a 50/50 guess.

Yes, the wires from street or pole go this gutter first:

Then it drop down to the service meters for each breaker and then the arc flashed panel with each breaker to the units.

Do you think a main breaker must be put before the gutter above? If it is put. Won't this decrease the arc flash incident energy?

Usually how many cycles equivalent is the tripping time of breakers? less than 1? If it's 10 cycles. It wont help decreasing the incident energy or duration of the flash since cycle 1 or 2 is enough to cause 2nd degree burn to the electrician hands.

 

[mbrooke]

Yes, the wires from street or pole go this gutter first:

Thank you! I understand now!

Then it drop down to the service meters for each breaker and then the arc flashed panel with each breaker to the units.

Do you think a main breaker must be put before the gutter above? If it is put. Won't this decrease the incident energy?

Having a main will TREMENDOUSLY decrease the incident energy. Though it is not required since you have less then 7 disconnects.

Usually how many cycles equilibrium is the tripping time of breakers? less than 1? If it's 10 cycles. It wont help decreasing the incident energy or duration of the flash since cycle 1 or 2 is enough to cause 2nd degree burn to the electrician hands.

I'd say a few cycles when tripping magnetically. At 10ka thats typically not a lot to cause severe burns.

 

[mbrooke]

BTW, that service neutral wire might be undersized... but close enough.

 

[tersh]

Thank you! I understand now!



Having a main will TREMENDOUSLY decrease the incident energy. Though it is not required since you have less then 7 disconnects.






I'd say a few cycles when tripping magnetically. At 10ka thats typically not a lot to cause severe burns.

Why. What is the minimum cycles before incident energy of 1.2 cal/cm2 is reached? I thought only 2 cycles is enough for it so wondering how main breaker can help. But if 1.2 cal/cm2 can only happen with tens of cycles and main breaker can cut it to half or less. Then I will need to apply at city hall for main breaker.

 

[mbrooke]

Services and the code:



http://www.iaei-western.org/Files/2...rticle 230 - 2011IAEI Western Section Mtg.pdf

 

[mbrooke]

Why. What is the minimum cycles before incident energy of 1.2 cal/cm2 is reached? I thought only 2 cycles is enough for it so wondering how main breaker can help. But if 1.2 cal/cm2 can only happen with tens of cycles and main breaker can cut it to half or less. Then I will need to apply at city hall for main breaker.

Well I'll put it like this. 5 cycles total clearing time vs no clearing time... Remember, if shorting the service those conductors may never even trip.

 

[tersh]

Well I'll put it like this. 5 cycles total clearing time vs no clearing time... Remember, if shorting the service those conductors may never even trip.

So do you commonly see a main breaker for less than 7 disconnects? Why is main breaker not required for less than 7 disconnects?

My concern about main breaker last year was how easy it is for robbers to shut it off. Without it. They would have more difficulty opening the panel with many breakers and disabling each.

Inside the building is composed of very sophisticated security (like motion detectors, etc), fire alarm system and others that can even call my cell phone late at night if intruders got inside or the fire alarm triggers (there is no one in the building at night). Actually when the power building gets disabled. I can get alert too but not loud ring, just text alert. Therefore sometimes I think putting main breaker can make the security less.

Also sharing all these pictures can make my security less if main robbers see it and learnt my location therefore this thread should slowly get lost soon among the thousand threads here. I have understood so much in these threads. Thanks so much mbrooke

 

[mbrooke]

So do you commonly see a main breaker for less than 7 disconnects? Why is main breaker not required for less than 7 disconnects?

Sometimes yes, sometimes no. Code lets you skip the main if you have only 6 breakers.

This was allowed in US home panels (split bus) but ended. Still common in commercial.

My concern about main breaker last year was how easy it is for robbers to shut it off. Without it. They would have more difficulty opening the panel with many breakers and disabling each.

No lock?

Inside the building is composed of very sophisticated security (like motion detectors, etc), fire alarm system and others that can even call my cell phone late at night if intruders got inside or the fire alarm triggers (there is no one in the building at night). Actually when the power building gets disabled. I can get alert too but not loud ring, just text alert. Therefore sometimes I think putting main breaker can make the security less.

Also sharing all these pictures can make my security less if main robbers see it and learnt my location therefore this thread should slowly get lost soon among the thousand threads here. I have understood so much in these threads. Thanks so much mbrooke

Doubt it- There is no way to tell what service that building goes to.

 

[mbrooke]

And oh- my pleasure. Welcome

 

[romex jockey]

Having a main will TREMENDOUSLY decrease the incident energy. Though it is not required since you have less then 7 disconnects.

Or a series of mains , not that i'm very good at the 70E math......:ashamed1:~RJ~