4 pole main disco

[Marc M]

Hey Jerry,
I have a 4 pole disconnect (main) that is hot on only one pole at both the front a rear of the disco which suggests its likely to be a connection from the bus or feeder. I say this because there was ZERO load imposed. Anyhow, can you show me a diagram that shows how the power is distrubuted thru the disconnect?
Usually, when there is heat from a main at the bus, there is usually heat along that phase of the bus, and seen in other areas of the panel (on that hot phase).
What is atypical here; is that the heat is isolated to only one bus tab, and only one single pole of the 4P breaker. So like I said, if the 4 pole splits the 240 I thought I'd see the heat on another bus/breaker connection, of that same phase.
BTW, the heat was north of 50+ above ambient w/zero load. Hotter at the feed side of the disco.
Thanks
Marc

[Jerry Peck - Codeman]

there was ZERO load imposed.

Marc,

I'm trying to figure out how you are getting heat with ZERO load.

I will find a drawing for you.

[Marc M]

Yea.., weird. I guess there was "some load". If you count the electric clock on the microwave or range. Let me know...thanks

[Jerry Peck - Codeman]

Marc,

Your second photo shows one heck of a load on that front conductor in that bundle, it appears to be the hottest item in the photo.

[Marc M]

I agree. So Jerry, how does a 4 pole disconnect distribute its 120/120 onto the bus? Is it A-B-A-B ? e.g. A=120 and B=120
And what advantages do 4 poles offer that a 2 pole cannot?
I would assume the heat is the result of possible conflict between the disco and the bus such as corrosion.

[Jerry Peck - Codeman]

Marc,

I apologize for the delay in replying, I have not been able to find a good schematic drawing of a 4 pole breaker connected into the circuit, so I will use this photo:

ITE Siemens 4 pole breaker.jpg

As shown on in the above photo, the left two breakers (poles) are connected to one phase, and the right two breakers (poles) are connected to the other phase.

The current for that 150 amp 4 pole breaker shown should, all things being correct, go through each breaker as 75 amps, with the two left breakers making that 150 amp leg, and the two right breakers making that 150 amp leg.

"All things being correct", that is.

If there is a burned out terminal connection to the bus connected to the rusty left terminal on the left breaker in the photo, then the entire 150 amps (or whatever amount of current there is) will go through the shiny terminal on the second from left breaker. Or there could be a bad breaker and nothing goes through one of the 75 amp breakers, which means that all the current must go through the other 75 amp breaker on that leg, which means the breaker will trip at 75 amp (thereabouts) instead of tripping at 150 amps. I discussed this with our friend Roger F. on the other board and he came up with the scenarios of why that could happen, and that could be what is happening in your photos. Roger was able to fill in the mental blanks I kept coming up with.

[Marc M]

Nice work. The seperate 75x4 idea makes total sense. And looking at the disco, that is what it looks like to me, at least. I appreciate you time, thanks Jerry.

[Roger F]

Thought I would drop in here to confirm my discussions with Jerry about your 4 Pole main breaker question. Part of the problem with understanding these breakers is the schematic drawings showing the design to be the pairs of breakers (left and right pairs) connected to each hot leg of the service.
It becomes even more head scratching when you see the different ways these main breakers are labeled. I've seen them labeled for amperage rating on the tie bar, I've seen them having an amperage on just one breaker and Jerry showed me a picture with each breaker body labeled for amperage.
I've spent the better part of this morning searching for information that would erase the question of how these breakers are designed but I have always understood them to have sensing units in each breaker. Your photos and the physical construction sure seem to suggest just that. That being the case then it would operate as described by Jerry in the earlier post. My understanding of the NEC is that this type breaker is allowed in accordance with 240.8. It doesn't make a lot of sense in my mind that they would tie 4 breakers rated at maximum service size together unless there is only one sensor per pair of breakers. If that were the case it would seem extremely expensive to make them as shown in your picture so I seriously doubt they manufacture them that way. Probably the only way to solve the mystery is to contact technical services at one of the makers of these breakers for clarification. So I'll see if I can get a reply from GE or one of the other manufacturers on just exactly what the design is for 4 tied breakers used as service equipment on 3 wire 120/240 residential services.

Roger F.

[Marc M]

Fantastic Roger,I appreciate your concern. I look forward to seeing what you find.

[Jerry Peck - Codeman]

Roger,

Thank you for providing the additional information, and any other additional information you find.

[Roger F]

I'm waiting to hear back from GE. I did find a good picture of 4 breakers handle tied for use as a service equipment disconnect. I can't explain the different labeling methods. Could have something to do with the pairs of breakers connected to the same pole or hot leg/bus and that being rated 200 amps.

http://www.geindustrial.com/publibrary/ ... 82|generic

[Jerry Peck - Codeman]

Roger,

The link document in that link shows a 4 pole 200 amp main breaker with each breaker marked 200, and the wiring diagram shows the left 2 breakers as being connected to one phase and the right 2 breakers being connected to the other phase.

Being as each separate breaker is on a separate breaker tab, I think that breaker is basically just 4 single pole breakers mounted together, but (obviously) each breaker could not be a 200 amp breaker as that would allow 400 amps through each phase before the breaker trips. Do you agree with that assessment of what is shown?

[Roger F]

Yep and that is why I posted that picture from GE. I do agree with your assessment. I'm wondering what the labeling requirement must be? For example if the manufacturer labels the handle tie 200 amps would they necessarily have to label the individual breakers and vice versa.

[Roger F]

Still no reply back from GE...I'm just about ready to disassemble one to see how it is designed.

[Jerry Peck - Codeman]

Still no reply back from GE...I'm just about ready to disassemble one to see how it is designed.

Same response, lack of, I got from GE.

[Roger F]

Well ...no reply from GE so I'm going to go elsewhere ... I'll post back.

[Roger F]

OK .. I spoke with an electrical supply that I have done business with for many years. The owner confirms that the breaker is designed as we have discussed. I also went to another electrical forum and discussed the design with an engineer that I have the utmost respect . He also confirms the design as we have discussed and added that the largest breaker in that form factor is 125 amps so the necessity for parallel pairs of calibrated breakers when the main gets above 125 amps.