Your minimum PPE for residential breaker box work

[ericsarratt]

Do they have much 600v in NC?

I don't know. It is an old community college. The teacher said it was 600v 3 phase. It was a Trane unit. We did the maintenance on it.

 

[jim dungar]

Is there some simple online calculator where you can put in the electrical parameters of what you are working on and get the arc flash and arc blast distances?

There is no way to calculate arc blast. Mention it in your safety program but don't dwell on it or try to go into detail.

Look at other NFPA 70E resources like arcflashforum.com by Jim Phillips at Brainfiller.com

 

[kwired]

I don't know. It is an old community college. The teacher said it was 600v 3 phase. It was a Trane unit. We did the maintenance on it.

I think 600 volts is more common in Canada. Good guess is that it was 480 volts, though it very well may have 600 volt rated equipment associated with it. Things like contactors, fuses, terminal blocks will often be 600 volt rating on 480 volt equipment as some these items typically are not made with a 480 volt rating

 

[kwired]

Yes. And, I am developing it.

I am a utility contractor and I hold multiple other trade licenses/certifications. I am not a licensed electrician...yet.

I have taken OSHA 10 for general industry and OSHA 30 for construction.

I also have also been consulting with OSHA in North Carolina, but I went beyond their knowledge area for electric and so I started reading and hunting down electric courses.

I asked about residential electric safety because I have been doing some work on my own home's breaker box.

I also do work for customers on pump control panels for septic systems (120v-240v) and sewage lift pumps for plumbing.

And I am in school for HVAC--my wife calls me a career student. We have trained on single phase 240v and 3 phase 600v.

There are almost no electrical safety trainings available in my State and they don't teach us anything about electric safety in school.

I will say that many choose to use 70E simply because they don't want to take on the potential liability of creating their own standard. It is a well recognized standard and should an incident occur where you are being challenged about whether you have a sufficient safety program, 70E would be recognized as suitable enough where your own set of rules could be picked apart and challenged and if they find any fault with it then that is on you since you created it.

Just a little FYI, not saying you can't have your own standard.

AFAIK OSHA doesn't mandate using 70E, but because of what went into creating it and the fact it is constantly being worked on and updated periodically makes it a preferred standard to use.

 

[PaulMmn]

I wear a baseball cap always though too especially in the attic.

In the attic you might consider a hard-hat. Those roofing nails are pointy!

 

[gadfly56]

At minimum I say 3 Hail Marys, As the voltage and/or available fault current go up I add in some Our Fathers, and a few Apostle's Creed. Then I turn my face away and take a deep breath and hold it.

Don't do that if you're wearing a face shield. Turning away creates a funnel between the face shield and your face that will direct any arc fault products into the side of your head and right across your face. If there is a boom, counterintuitively, you want to directly facing it.

 

[letgomywago]

In the attic you might consider a hard-hat. Those roofing nails are pointy!

Hard hats fall off when you're belly crawling to the corner of the eaves. Baseball cap keeps the nail out of your skull even if it does get ya.

 

[David Castor]

My recommendation is to wear 4 or 8 cal/cm2 shirt and pants all the time, and use a face shield on a hard hat and gloves for energized work. The risk at 120/240 V is low, but not zero. 480 V is another world when talking about arc-flash hazards. Look at PPE requirements in NFPA 70E for Category 1.

 

[Joethemechanic]

face shield

What face shield?
I close my eyes really hard

 

[mtnelect]

How about just turning the power off ?

 

[4-20mA]

What face shield?
I close my eyes really hard

with one hand in a pocket, too

 

[jim dungar]

How about just turning the power off ?

Yep.
Unless there is a constant source like a UPS/battery involved every circuit can be denergized regardless what the customer says. It may be inconvenient and expensive but it happens everythime the utility 'blips'. Even hospitals with generators leave you in the dark for several seconds.

 

[hillbilly1]

How about just turning the power off ?

You still have to wear the appropriate PPE rating to verify it’s dead.

 

[mayanees]

My recommendation is to wear 4 or 8 cal/cm2 shirt and pants all the time, and use a face shield on a hard hat and gloves for energized work. The risk at 120/240 V is low, but not zero. 480 V is another world when talking about arc-flash hazards. Look at PPE requirements in NFPA 70E for Category 1.

I think this is probably your best advice. In the old days when 5 homes were powered from a poletop 10 kVA transformer there wasn't any expectation for arc flash; however, nowadays 10 homes are powered from a 75 kVA padmount transformer and there is much more potential for an arc flash event.
Arc flash events are typically three-phase, but a single-phase event could occur. Using SKM's unbalanced/single-phase module a 75 kVA transformer could have 7 calories on the 240/120V secondary. It's all related to the strength of the source so as the transformer gets bigger, so does the arc flash incident energy.

 

[letgomywago]

I think this is probably your best advice. In the old days when 5 homes were powered from a poletop 10 kVA transformer there wasn't any expectation for arc flash; however, nowadays 10 homes are powered from a 75 kVA padmount transformer and there is much more potential for an arc flash event.
Arc flash events are typically three-phase, but a single-phase event could occur. Using SKM's unbalanced/single-phase module a 75 kVA transformer could have 7 calories on the 240/120V secondary. It's all related to the strength of the source so as the transformer gets bigger, so does the arc flash incident energy.

I've only seen one situation personally with transformers that large for single family homes.

 

[hillbilly1]

I think this is probably your best advice. In the old days when 5 homes were powered from a poletop 10 kVA transformer there wasn't any expectation for arc flash; however, nowadays 10 homes are powered from a 75 kVA padmount transformer and there is much more potential for an arc flash event.
Arc flash events are typically three-phase, but a single-phase event could occur. Using SKM's unbalanced/single-phase module a 75 kVA transformer could have 7 calories on the 240/120V secondary. It's all related to the strength of the source so as the transformer gets bigger, so does the arc flash incident energy.

A lot of utilities have doubled their line voltage too, increasing system capacity, which increases the available fault current. I think that’s why they started putting 22k mains in loadcenters. They doubled the line voltage on the line at my house about 20 or so years ago. They changed the pole transformers to multiple tap, and just flip a lever before they re-energize the lines with the higher voltages. They changed out the pole insulators too.

 

[jim dungar]

I think this is probably your best advice. In the old days when 5 homes were powered from a poletop 10 kVA transformer there wasn't any expectation for arc flash; however, nowadays 10 homes are powered from a 75 kVA padmount transformer and there is much more potential for an arc flash event.
Arc flash events are typically three-phase, but a single-phase event could occur. Using SKM's unbalanced/single-phase module a 75 kVA transformer could have 7 calories on the 240/120V secondary. It's all related to the strength of the source so as the transformer gets bigger, so does the arc flash incident energy.

Of course that assumes that a single phase arc flash actually behaves like a three phase one. But, based on the fact that in over 20 years IEEE 1584 has not published a single test result or a peer reviewed AFIE formula for low voltage single phase arcs there is nothing else we can do, except maybe follow the number of injuries and fatalities attributed to these arcs. Maybe we should also look at collateral injuries, such as falling off a ladder, due the unexpected flash and bang.

Probably the most consistent dangerous activity, on 120/240V circuits, is contacting energized conductors. Turn off the circuit and work denergized. Wear appropriate PPE.

 

[ericsarratt]

I will say that many choose to use 70E simply because they don't want to take on the potential liability of creating their own standard. It is a well recognized standard and should an incident occur where you are being challenged about whether you have a sufficient safety program, 70E would be recognized as suitable enough where your own set of rules could be picked apart and challenged and if they find any fault with it then that is on you since you created it.

Just a little FYI, not saying you can't have your own standard.

AFAIK OSHA doesn't mandate using 70E, but because of what went into creating it and the fact it is constantly being worked on and updated periodically makes it a preferred standard to use.

So, for an electrical safety policy and procedure I can just say that my company has adopted NFPA 70e?

And, of course train employees in 70e.

Thank you. This is new to me.

 

[ericsarratt]

My recommendation is to wear 4 or 8 cal/cm2 shirt and pants all the time, and use a face shield on a hard hat and gloves for energized work. The risk at 120/240 V is low, but not zero. 480 V is another world when talking about arc-flash hazards. Look at PPE requirements in NFPA 70E for Category 1.

Thanks! I don't work live except when troubleshooting.

But, what about arc flash from the lugs at the top of the breaker panel? Even with the main breaker off the lugs are still active.

Would those little plastic lug covers stop arc flash OR are they just useful for incidental contact?

I don't mind buying safety equipment.

 

[ericsarratt]

You still have to wear the appropriate PPE rating to verify it’s dead.

Always do.