opening and closing disconnects

[william.broach@cwservices]

We've all learned the left hand rule for opening and closing disconnects. Is this truly the best practice with with the newer PPE requirements (Face Protection. Face shields shall have an arc rating suitable for the arc flash exposure. Face shields with a wrap-around guarding to protect the face, chin, forehead, ears, and neck area shall be used)? I believe facing the handle on the hinge side, throwing the handle with left hand while eyes closed looking towards the floor and exhaling while throwing to be a better practice. This will help direct the blast away from the EE and help prevent inhalation injury.... Comments please.

 

[zbang]

"Left-hand rule"?

There's a lot missing here, starting with "what's the risk to be mitigated?" and "what's the arc flash category?"

 

[retirede]

"Left-hand rule"?

When I first started out, the older electricians in our plant swore by this. The idea is that since standard disconnects have the handle on the right edge, operating it with the left hand forces you to stand to the side of the cabinet, instead of directly in front. I guess they thought the door was going to get blown off?

 

[william.broach@cwservices]

"Left-hand rule"?

There's a lot missing here, starting with "what's the risk to be mitigated?" and "what's the arc flash category?"

The Risk would be from an Arc flash. HRC 1-4. In my mind the your left arm would help assist in blocking the door and thus re-direct most of the blast away from you, better a broken arm than being to the right of the disconnect being directly in the travel of the blast.. Facing the disconnect handle would help in "prevention" of the plasma from "sweeping the face shield. Looking down would aid in UV protection from the arc., and exhaling preventing inhalation hazard.

 

[kwired]

The Risk would be from an Arc flash. HRC 1-4. In my mind the your left arm would help assist in blocking the door and thus re-direct most of the blast away from you, better a broken arm than being to the right of the disconnect being directly in the travel of the blast.. Facing the disconnect handle would help in "prevention" of the plasma from "sweeping the face shield. Looking down would aid in UV protection from the arc., and exhaling preventing inhalation hazard.

The typical safety switch has door hinges on the left and the operating handle on the right. If I understand what you are saying you would end up standing in front of or at least partially in front of the safety switch and reaching across your body to operate the handle. Something like a 1200 amp switch would be large enough you likely are fully in front of it or you may need to be incredibly strong as well as have a long reach just to operate the handle, where if you were standing to the right of the switch you would have more leverage to operate the thing.

 

[william.broach@cwservices]

The attached shows position of me as I am disconnecting/connecting the disconnect. My ultimate question, as I am instructing others, is is this the best practice or is there a better way and why?

 

[kwired]

The attached shows position of me as I am disconnecting/connecting the disconnect. My ultimate question, as I am instructing others, is is this the best practice or is there a better way and why?

I think it would be difficult for some or even most people to operate many larger switches while reaching across the body with left hand to do so.

Some the 200 amp switches I encounter would even be difficult to operate from that sort of positioning.

 

[william.broach@cwservices]

Most switches our people operate are NEMA 0-6 on MCC gear.

 

[jim dungar]

We've all learned the left hand rule for opening and closing disconnects. Is this truly the best practice with with the newer PPE requirements (Face Protection. Face shields shall have an arc rating suitable for the arc flash exposure. Face shields with a wrap-around guarding to protect the face, chin, forehead, ears, and neck area shall be used)? I believe facing the handle on the hinge side, throwing the handle with left hand while eyes closed looking towards the floor and exhaling while throwing to be a better practice. This will help direct the blast away from the EE and help prevent inhalation injury.... Comments please.

This sounds like nit-picking.

If it was really a concern, I am sure it would have been incorporated in NFPA70E or OSHA work requirements some where over the past 20 years that arc flash has been a concern.

 

[jim dungar]

I guess they thought the door was going to get blown off?

Arc Blast is a related but separate issue than arc flash.
At present, there is no industry accepted standard method for evaluating arc blast. It is not directly related to arc flash incident energy. For example, many extremely high, over 40cal, locations are due to a relatively low level fault lasting for many seconds if not minutes, while blasts occur in milliseconds if not microseconds.

 

[garbo]

We've all learned the left hand rule for opening and closing disconnects. Is this truly the best practice with with the newer PPE requirements (Face Protection. Face shields shall have an arc rating suitable for the arc flash exposure. Face shields with a wrap-around guarding to protect the face, chin, forehead, ears, and neck area shall be used)? I believe facing the handle on the hinge side, throwing the handle with left hand while eyes closed looking towards the floor and exhaling while throwing to be a better practice. This will help direct the blast away from the EE and help prevent inhalation injury.... Comments please.

A few years before retiring my great foreman told us besides using your left hand to operate a safety switch or circuit breaker ( right hand if a south paw) then take in a deep breath & hold it. If an Arc Fault or Arc Blast did occur you would not breath in super heated sir possibly causing major burns to your lungs. While an apprentice when I closed an old rusted 200 amp safety switch that found out later one of the door hinges were broke When I turned it on closed on a dead short and luckily door only blow open on at an angle just missing my face. I was following the electricians order. After that I used our Simpson model 260 meter to perform test followed by the old reliable hand cranked Biddle megger. That was before we had PPE.