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Space Options, Molokai HI
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Discussion Starter #1
Does anyone have any comments on the durability of plug on vs. bolt on breakers? We are using Square D QO & QOB breakers for our installations. On some of our jobs we are also responsible for maintenance over long periods and are interested to know if anyone has data or opinions on maintenance ramifications of using QOB vs. QO type breakers. Thanks.

Chris Crawford
Molokai Hawaii
 

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I deal with more siemens equipment. I have seen both fail. I tend to like the plug because it is easier changed in a live panel, screws don't break off or strip. just my opinion.
 

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RIP 1959-2015
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I deal with more siemens equipment. I have seen both fail. I tend to like the plug because it is easier changed in a live panel, screws don't break off or strip. just my opinion.
I agree with that plus the bolt on type are more expensive.

Whether or not they are better?

I don't think they make any difference in my opinion.


Chris Crawford;..:)

Welcome to the forum enjoy the fun and games..:thumbup::thumbup:
 

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Square D products will last a long time, so will eton, siemens, GE...

I think the debate should be load center vs panel board. same function but the panel board has a wider range of bussing options and aic ratings for different applications.

One thing I do like about Square D is the visible trip feature. Comes in great when doing a large job and you have numerous panels grouped together or integrated like a cpi system for finding a tripped breaker quickly.
 

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I like the bolt in simply because the load centers accept either QOB or QO breakers in the same cabinet. That said, I have seen both fail, but mostly the QOB because the original installer failed to fully tighten the tab, or cross threaded it, which is the same thing really.
 

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You use bolt on in commercial / industrial panelboards because they are much more likely to experience vibration from machinery nearby (or even not so nearby). More plug in breakers will fail in those cases, but the average residence doesn't have that kind of constant vibration going on, so it's not much of a problem.

Using bolt on breakers also means they are much less likely to be changed by someone other than a qualified electrician and the proper safety procedures will be followed (or at least known about :whistling2:). That's why in the majority of industrial plants that have specifications, you will never see load centers / plug in breakers allowed.

But mostly, panelboards allow the use of multiple types / frames of branch breakers in the same panel, because to connect them to the bus all you need are the correct straps with holes in the right places. With a load center you are limited to only the plug in type branch breakers, which are going to be 240V and below, 125A and under. If that fits what you need to do, then it works.
 

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crispy critter
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but mostly the QOB because the original installer failed to fully tighten the tab, or cross threaded it, which is the same thing really.
Not the same thing:no:. Cross threading is much worse :eek:
 

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You use bolt on in commercial / industrial panelboards because they are much more likely to experience vibration from machinery nearby (or even not so nearby). More plug in breakers will fail in those cases, but the average residence doesn't have that kind of constant vibration going on, so it's not much of a problem.

Using bolt on breakers also means they are much less likely to be changed by someone other than a qualified electrician and the proper safety procedures will be followed (or at least known about :whistling2:). That's why in the majority of industrial plants that have specifications, you will never see load centers / plug in breakers allowed.

But mostly, panelboards allow the use of multiple types / frames of branch breakers in the same panel, because to connect them to the bus all you need are the correct straps with holes in the right places. With a load center you are limited to only the plug in type branch breakers, which are going to be 240V and below, 125A and under. If that fits what you need to do, then it works.
You can get up to 200 amp breakers for siemens load centers.
 

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The thing I know about bolt on breakers is that overtime they can become loose (the bolt) and need re tightening.

Personally plug on QOs are about the same in reliability yet cheaper and easier to work with than bolt ons.
 

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I pretwist and then use wire nuts. Solder pots rule.
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We have a lot of Square D panels here. The bolt ons last for years if installed correctly. No tweaking the screws every year on a maintenance schedule.

If a circuit is maxed out all the time then the QOB will loosen.

Go for the inspection and repair as needed on your yearly maintenance. Please don't do what we did here. A yearly tweaking to tighten by the lowest paid guy. That always resulted in failures.
 

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You can get up to 200 amp breakers for siemens load centers.

Thanks for pointing that out. Just looked it up and my cost on a QPJ 3200 is $260 and is 10K rated. I wonder how legit the bending radius would be on the conductors. I much prefer to use a panel board if I had a load of this size comming off it.
 

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We have a lot of Square D panels here. The bolt ons last for years if installed correctly. No tweaking the screws every year on a maintenance schedule.

If a circuit is maxed out all the time then the QOB will loosen.

Go for the inspection and repair as needed on your yearly maintenance. Please don't do what we did here. A yearly tweaking to tighten by the lowest paid guy. That always resulted in failures.
good post. so true. :thumbsup:
 

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Space Options, Molokai HI
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Discussion Starter #14
:thumbsup: Thanks to all for the thoughtful comments. Good point JRaef about the vibration being a factor. I also agree with Wirenuting that it is not good to be tweaking the bolts and the inspection and and repair is the best plan. About 20 years ago an electrical engineer told me the bolt ons have a longer service life so have been leaning towards those for jobs we maintain if we are in a position to specify breakers and panel boards. Intuitively it does seem that using the bolt ons and properly torquing (with a torque screw driver) is better than depending on the tension of the of the tabs on the plug ons staying tight. I am still not sure though whether the extra hassle of using the bolt on QOB type pays off enough in less problems down the road. For jobs we are maintaining for maybe 10-20 years are the bolt ons worth it? I have seen plenty of burn outs with the plug ins and avoiding even one failure like that is worth a lot.
 

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evil bastard
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:thumbsup: Thanks to all for the thoughtful comments. Good point JRaef about the vibration being a factor. I also agree with Wirenuting that it is not good to be tweaking the bolts and the inspection and and repair is the best plan. About 20 years ago an electrical engineer told me the bolt ons have a longer service life so have been leaning towards those for jobs we maintain if we are in a position to specify breakers and panel boards. Intuitively it does seem that using the bolt ons and properly torquing (with a torque screw driver) is better than depending on the tension of the of the tabs on the plug ons staying tight. I am still not sure though whether the extra hassle of using the bolt on QOB type pays off enough in less problems down the road. For jobs we are maintaining for maybe 10-20 years are the bolt ons worth it? I have seen plenty of burn outs with the plug ins and avoiding even one failure like that is worth a lot.

If you install a loadcenter, and 15 years later, a breaker fails, do you really think they'll hold that against you? I've never thought twice about installing loadcenters. Honestly, I only put in panelboards if specc'd that way.
 

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Just went on an emergency call to a waste water plant that had power fluctuations at one of the buildings. Come to find out the screw was loose on one of the fingers feeding that breaker in the mdp. After shutting off the main and further inspection found that every single screw was loose on all the breakers. Apparently they had Cutler-Hammer out a couple years ago to clean up all the bussing and check torque. They also put what appeared to be noalox on all the copper bussing. We are in the process of pricing to do a whole plant preventative maintenance. Just not sure if I wanna clean off the crap they put on that buss or what to use to clean it.
 

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cog
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Just went on an emergency call to a waste water plant that had power fluctuations at one of the buildings. Come to find out the screw was loose on one of the fingers feeding that breaker in the mdp. After shutting off the main and further inspection found that every single screw was loose on all the breakers. Apparently they had Cutler-Hammer out a couple years ago to clean up all the bussing and check torque. They also put what appeared to be noalox on all the copper bussing. We are in the process of pricing to do a whole plant preventative maintenance. Just not sure if I wanna clean off the crap they put on that buss or what to use to clean it.
maybe the stuff the MV splicers use to clean with?
 

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Nothing wrong with antioxidant on copper bus. The loose screws are the culprit not the de-ox.
 

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Space Options, Molokai HI
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Discussion Starter #19
I basically agree with InPhase277 but if it is really noalox or penetrox (grey colored), not sure if they are best for copper bus as these products are meant for aluminum to aluminum or aluminum to copper connections (but I am not an expert). For copper connections in a corrosive environment we use KOPR-SHIELD by Thomas & Betts. It is a paste with copper particles in it and looks copper colored.
 

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While I prefer bolt on I think it is way overkill that they are always spec'ed in shopping malls, condos, exct. They have their place in industrial
 
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