Switch Gear buss bar torque values. - Electrician Talk - Professional Electrical Contractors Forum

ElectricBill · 11-12-2009, 08:44 PM

I have to replace a 200A 120/208V breaker in a main switch gear. The breaker is a GE Spectra RMS SFHA36AT0250 with a 200 A rating plug.
I hope this picture link works. Haven't tried it before.
http://s1013.photobucket.com/albums/...aBrkDamage.jpg

The GE breaker specs do not call out a torque value for the connection to the buss bars which does seem reasonable since it is very dependent on what it is being bolted to.

The switch gear does not list any torque values. Are there any rules of thumb to follow. I imagine it is tinned copper buss but I have not yet opened it up yet. Still awaiting budget approval before I proceed.
Thanks

jredwood301 · 11-12-2009, 09:01 PM

usually 25 lbs for 3/8" bolts and 50 for 1/2" bolts

hogsmoss · 11-13-2009, 08:21 PM

thats what i use

Zog · 11-13-2009, 08:55 PM

Quote:

Originally Posted by ElectricBill

I have to replace a 200A 120/208V breaker in a main switch gear. The breaker is a GE Spectra RMS SFHA36AT0250 with a 200 A rating plug.

that is a 600V breaker. 3 phase, most likely a 480V system. Not 120/208. I hope you tested this breaker before you install it. Why is this being replaced?

Quote:

Originally Posted by ElectricBill

The switch gear does not list any torque values. Are there any rules of thumb to follow. I imagine it is tinned copper buss but I have not yet opened it up yet. Still awaiting budget approval before I proceed.
Thanks

Rules of thumb only get you in trouble, follow ANSI/NETA specs, see attachments, be sure to use the right one.

ElectricBill · 11-13-2009, 11:28 PM

Thanks for the bolt torque tables.
I got the okay to inspect the system. It is 120/208V breaker sitting in a 1600A switch gear. If you look at the photo link in the OP you can see the oxidation/residue build up that triggered the investigation. It was taken with a cell phone so I hope it is clear enough. If needed I can post clearer pictures.
Since my OP I found another breaker with similar oxidation build up. This prompted me to make a call to GE breaker support line which inturn got me in touch with the Spectra breaker project manager. I was impressed with the quick response from GE.
GE's claim is that the residue build up is the result of a flame retardant additive used in the breaker case which is reacting for some unknown reason and causing the oxidation/residue. What they don't explain is why is it happening only near the rating plug. These breakers are 10 years old at this point. GE claims that this problem has been seen a lot but that there is no evidence from their testing that the residue build up affecs breaker operations in anyway. I opened the switch gear and found the connected load and wire terminations okay. I did not pull the rating plug out yet since that would require a shut down. Anybody else seen this problem.
Thanks

Zog · 11-13-2009, 11:52 PM

Quote:

Originally Posted by ElectricBill

Thanks for the bolt torque tables.
I got the okay to inspect the system. It is 120/208V breaker sitting in a 1600A switch gear.

SFHA36AT0250

SFHA is the type, 3 is 3 phase, 6 is 600V, AT250 is the frame size. With a 200A rating plus in 1600A gear this is a misapplied breaker.

Quote:

Originally Posted by ElectricBill

If you look at the photo link in the OP you can see the oxidation/residue build up that triggered the investigation. It was taken with a cell phone so I hope it is clear enough. If needed I can post clearer pictures.
Since my OP I found another breaker with similar oxidation build up. This prompted me to make a call to GE breaker support line which inturn got me in touch with the Spectra breaker project manager. I was impressed with the quick response from GE.
GE's claim is that the residue build up is the result of a flame retardant additive used in the breaker case which is reacting for some unknown reason and causing the oxidation/residue.What they don't explain is why is it happening only near the rating plug. These breakers are 10 years old at this point.

GE has some production issues 10 years ago with a lack of anti oxidants on thier circuit boards, that could be part of the issue. Another possible issue would be a sulphur rich atmosphere, maybe a paper mill?

Quote:

Originally Posted by ElectricBill

GE claims that this problem has been seen a lot but that there is no evidence from their testing that the residue build up affecs breaker operations in anyway. I opened the switch gear and found the connected load and wire terminations okay. I did not pull the rating plug out yet since that would require a shut down.

This breaker needs to be tested to ensure it is operating properly.

ElectricBill · 11-14-2009, 11:24 PM

Zog
The application is an elementary school's main switch gear. No heat, moisture or other extreme conditions to be concerned with. Any estimate of what it costs to get a breaker tested? I've never had to do that before.
I take it that you feel the breaker was way over spec'd. I now see this can be a bad thing when you look a the price of replacing a component that has failed. Thanks for your assistance.

Zog · 11-15-2009, 09:30 AM

Quote:

Originally Posted by ElectricBill

Zog
The application is an elementary school's main switch gear. No heat, moisture or other extreme conditions to be concerned with. Any estimate of what it costs to get a breaker tested? I've never had to do that before.

Testing a sinlge breaker is so small a job it may not be worthwhile for a testing company to come out to you, they would most likely charge you a 4 hour minumum service call, which costs more than replacing this breaker. Send it to me, I will test it for free, you just pay for shipping.

Quote:

Originally Posted by ElectricBill

I take it that you feel the breaker was way over spec'd. I now see this can be a bad thing when you look a the price of replacing a component that has failed. Thanks for your assistance.

This could just be a rating plug issue, but even so, you can replace this breaker for around $400-$500