racking out breakers

[diamondrobot]

In our industrial setting, we rack out our 480v breakers to perform lockout / tagout. The question has came up about being safer to not rack out the breaker, due to flash protection zone (NFPA 70). Our stand was that the locking tab did not provide a true lock out point, but acted as a mechanical interlock. A quote from our electrical specialist.... has guideline 1910.333 b 2 ii B which states "... circuits and equipment to be worked on shall be disconnected from all electric energy sources. Control circuit devices, such as push buttons, selector switches, and interlocks, may not be used as the sole means for de-energizing circuits or equipment. Interlocks for electric equipment may not be used as a substitute for lockout and tagging procedures." Many new questions with the NFPA 70 standard.

 

[69boss302]

Re: racking out breakers

Control circuit devices, such as push buttons, selector switches, and interlocks

I have had this battle many times. The lockout on the breaker is not a control interlock. It does not electrically isolate the control ckt where a simple push button or short ckt will still allow the breaker to close. It is a physical, mechanical lock that will not allow the breaker to close. I always ended up asking the question, Do you remove breakers from distribution panels or buckets from MCC's to lock them out?

I will also admit I lost most of the time (but not all the time) and they said it's a simple enough procedure to rack out the breaker. Well that is no longer applicable. You still need to take all applicable safety precautions to check the power off before working on the locked out equipment.

Edit to add: Another thing to explain, with a breaker racked out, it's easy enough to put in another breaker, whereas the way most larger rack out breakers are designed, is if you lock them out using the lock out on them, they can not be removed either. You need to check your breaker design.

[ August 19, 2005, 09:35 AM: Message edited by: 69boss302 ]

 

[charlie tuna]

Re: racking out breakers

i heard of an incidence where following this proceedure the maintainance workers racked out the wrong breaker and the interlock did not open the breaker being racked out! the breaker was under full load! before it was over two guys were seriously burnt and the back of the switchgear had a hole big enough to drive a car through!!

 

[don_resqcapt19]

Re: racking out breakers

We rack out to the disconnect position using the required PPE and then place a lock so that the breaker cannot be racked back in to the connected position until the lock is removed. On some breakers there are holes in the track for this purpose, on others, the is locking cover on the racking screw.
Don