Replace draw out CB
- Thread starter anbm
- Start date
- Status
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
If by "crank handler" you mean a remotely operated motorized crank operator, with everyone outside the arc fault hazard distance during the process, yes.
Coppersmith
Senior Member
- Location
- Tampa, FL, USA
- Occupation
- Electrical Contractor
If the circuit breaker is off, manually cranking it out to replace it doesn't seem like an arc fault hazard. Please elaborate.
- Location
- Illinois
- Occupation
- retired electrician
The breaker is mechanically interacting with the bus and a mechanical fault while racking the breaker in or out can result in a electrical fault and an arc flash.
Most places around here now use remote racking equipment for this reason.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
One of the simplest possibilities is a mechanical failure that breaks either the bus or the CB jaws loose. Think of pulling out a meter from its socket and finding yourself holding a meter with one wire still attached.
More complicated scenarios include a tool left inside falling across the buses.
Unlikely does not mean impossible, and the consequences are so bad that you need to anticipate even unlikely events.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Racking a breaker onto or off of live bus is usually considered to be a very high risk for creating an arc fault event. Most manufacturers offer remote racking provisions because of this risk.
Coppersmith
Senior Member
- Location
- Tampa, FL, USA
- Occupation
- Electrical Contractor
Thanks for the replies. When I was an apprentice I was working with a j-man who was manually racking out a breaker. He promised he would teach me how to do it, but it never happened. I've always felt like that was a hole in my training.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Fortunately, you never had to do it.
The alternative is a full-on bunny suit. But with high enough arc energy the mechanical forces and shrapnel could still kill you.
Coppersmith
Senior Member
- Location
- Tampa, FL, USA
- Occupation
- Electrical Contractor
Well I've had the opportunity to consider bidding on some local gov't work where we would be doing maintenance of switchgear or doing on-call work. As I said, I don't feel competent to rack out a breaker, but I can hire industrial electricians who are. I figured if I happened to win one of these, I could have my employee teach me how to do it.
Based on what you guys have said, and assuming they don't have remote racking, now I'm thinking that this would be a big workman's comp liability issue and at minimum I would have to provide a high cal arc flash suit which I assume is expensive. I probably won't be bidding these kind of jobs, but now I feel like I'll never have a chance to learn this skill.
- Location
- Illinois
- Occupation
- retired electrician
And there is a lot of industrial swithgear where the incident energy from a fault at the bus exceeds 40 cal. Often these are marked with a label prohibiting local operation while the equipment is energized. That includes both on and off operations as well as racking operations. Typically facilities with this marking have remote operation and racking equipment available on site.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
if there is a "high risk" of an arc fault, I think I would not be engaging in that activity even if I had a blast suit on and the IE was fairly low.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
I agree.
I have been trying to not call them 'blast suits' as they only protect you from heat. I find people that are not NFPA 70E qualified think you are protected from all hazards when wearing an '40 call rated outfit.
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