breaker replacement diy - torque strength

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  #1  
Old 11-07-13, 04:09 PM
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breaker replacement diy - torque strength

Hi-

I had to replace a breaker for my grandfather in a pinch. It was siemens brand.

I turned off the main and checked voltage etc. After I was done everything seems OK.

But my question is in regards to the connection.

I torqued down pretty hard until the screw would not move (unless I would strip it and I didnt do that).

I didnt resplice the wire either, just inserted as it was in the old breaker.

I wasnt sure how hard to press it into the power bus... I slid the under the lip first and then pushed the other side with the clip over the bus. It didnt make a loud snapping noise or anything..... Also It jiggles a bit up and down with the cover off and seems to hold firm with the cover on.

I also went ahead and snugged down on the rest of the screws on the other breaker.... but that is where I second guess myself.

The rest of screws were all able to be torqued down more. I then read that I needed a torque screwdriver which led me to believe that these breakers may have been done at sometime with a torque driver and then I just overtightened them....

my question, does it sound like I "overtightened" these connections or otherwise did something wrong? Should I open it back up and do something different? Should I be concerned about my first circuit breaker replacement?
 
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Old 11-07-13, 04:22 PM
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You did fine. You cant really "overtighten" them IMO unless you break them. In fact you likely did a good thing going through and snugging the others down. Connections can loosen over time (many years) if they get hot and cool down because of a heavy load.

Your breaker installation also sounds fine.
 
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Old 11-07-13, 04:56 PM
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I done nothing but hand tighten breakers for over 40 years and never had any issues.
 
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Old 11-07-13, 09:06 PM
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I've used a torque wrench a number of times on the termination screws on breakers. Every time I've done that, I've found several that were tightened more than the panel label specified and fery few that weren't tightened as much as they should have been. This has all been done on new installations, not panels that have been in service for years.

The point of the torque limitation is not to avoid damaging the breaker. It's to avoid damaging the conductor by squeezing or flattening it to the point where its conductivity is reduced and/or overheating can be induced.

Originally Posted by Nadhkat1
I done nothing but hand tighten breakers for over 40 years and never had any issues.
Me too. The ones I did that way checked out with the torque wrench. Some of my associates were more energetic than I am.

I gave them the torque wrench and told them to go back over a couple of their panels. The accuracy really improved after that.
 
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Old 11-08-13, 06:00 AM
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I was more concerned about the way it attachs to the power bus.

If the manufacture suggests torque values for the screws I wonder why there isnt a second bolt to hold it to the bus.

How do I know I have that portion secure?
 
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Old 11-08-13, 07:33 AM
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If the manufacture suggests torque values for the screws I wonder why there isnt a second bolt to hold it to the bus.
There is! Siemens, Square D, (and others) manufacture "bolt in" panel-boards that is used in commercial applications. They are much larger then a "residential load center" panel

If the plug in breaker is seated all the way in, it is secure. The breaker may move a little, but it is likely the external case moving around the internal components.
 
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Old 11-08-13, 01:29 PM
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Thanks again.

Out of curiosity I called around to 3 places that rent tools in my area and all 3 were very confused when I asked if they had a torque screwdriver.... none of them did after I explained what I was looking for. Seeing online they cost in the 150-300 range, I cant see how common it would be that breakers get torqued to the proper value at all....

I once saw an electrician use a cordless driver to tighten down a circuit breaker screw... is that a bad practice?
 
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Old 11-08-13, 01:35 PM
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I once saw an electrician use a cordless driver to tighten down a circuit breaker screw... is that a bad practice?
My personal opinion is that would be a very bad practice.
 
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Old 11-08-13, 02:12 PM
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I don't feel at all like I can control the torque with a power driver, I usually stop before the screw is all the way in and finish tightening by hand if I'm at all concerned about just how tightly the screw is installed (in any application).
 
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Old 11-08-13, 08:32 PM
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I called around to 3 places that rent tools in my area and all 3 were very confused when I asked if they had a torque screwdriver.... none of them did after I explained what I was looking for. Seeing online they cost in the 150-300 range, I cant see how common it would be that breakers get torqued to the proper value at all....
It isn't common but it is done. Every company I've worked for had the tools. At $150 to $300 per set, they were by no means the most expensive tools in the gang box. Cheaper than many and on a par with many others.

Note, however, that those were torque wrench sets with screw-fitting bits. Note also that we were making up 42-space 3-phase commercial panels with bolt-in breakers.

I once saw an electrician use a cordless driver to tighten down a circuit breaker screw... is that a bad practice?
I use mine for that all the time. I've learned that setting the clutch on "3" on my particular drill/driver will pretty much hit the spec. When you have say 3 or four panels to take from hanging wires to closed and energized in a day, it's a make-it-happen tool.
 
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