Main breaker in seperate enclosure

[iwire]

Why does it rarely happen....? Because you don't ask for one?

I would say the biggest draw back is the coordination issues. Knowing who to call at the power company, working out a date and time that works for the POCO, the EC and the customer.


Then there is the significant added cost to what could be a low cost job to start with.

Just adding an outlet beside the panel really requires a shutdown to comply with the hot work rules.


How does a EC cover his time waiting for the power company to show up?

 

[don_resqcapt19]

Why does it rarely happen....? Because you don't ask for one? Most, if not all, POCO's will do a service disconnect either at the pole or the meter at no charge, as long as it's done during normal working hours. We, as a utility, would much rather take the time to do a disconnect than have someone get across the line side of a service disconnect. Most transformers have no secondary protection, and it takes a HUGE fault on the secondary to blow a primary fuse. Why risk it? As far as arc fault in a service panel, I guess it could be possible to have an arc fault, but most seem to originate at the meter, and a cover over the main would not make any difference. Seems to me like a solution to a non-problem.

Because you get a 2 to 4 hour window as to when they will be there...who pays for the waiting time ?... especially where the wait time is longer than the time it takes to do the work

 

[user 100]

Is there a real problem to be solved here? Aside from the technical aspect of working in an enclosure with live conductors, has there been a genuine safety and fire hazard identified through field reports that this solution would "solve"? It strikes me as being only a little more sensible than the whole AFCI breaker fiasco.

I have changed or added a breaker or two in my residential panel and each time I tripped the main before proceeding. Notwithstanding, I confess to a certain uneasiness knowing that the hots at the top of the panel would cheerfully deliver the available fault current if I wasn't careful. I don't believe, however, that my personal trepidation is a good basis for driving the code.

I agree with this, though the enclosed mains certainly wouldn't hurt anything and while it would add cost to equipment, it would still be cheaper than adding a sep disco (and yet another point of potential failure with more connections however remote) betwixt the meter and mcb/bcp to quash the concern here.

 

[electrofelon]

Is there a real problem to be solved here? Aside from the technical aspect of working in an enclosure with live conductors, has there been a genuine safety and fire hazard identified through field reports that this solution would "solve"?

:thumbsup:

Or how about OSHA amending there rules to reflect some degree of reality, such as,say, allowing hot work if voltage to ground is 150V or under?

Another issue with the proposition in the OP is what if it is MLO service equipment? Square D's I-line stuff is pretty nice as they have a hinged shield that covers the lugs and the busing is substantially covered. I think that in general panel boards could be designed with much less exposed live parts, even with covers removed, but there is clearly no requirement to design them this way and the manufacturers dont take it upon themselves to do it.

 

[iwire]

:thumbsup:

Or how about OSHA amending there rules to reflect some degree of reality, such as,say, allowing hot work if voltage to ground is 150V or under?

Because more people are killed by systems under 150 volts to ground then above.

Because 150 volts to ground has nothing to do with arc flash.

Because OSHAs directive is safety it is not make things easier.

You are free to blow yourself up, but employees need to be protected from management that would put them in a dangerous situation just to save a buck.

 

[mbrooke]

I don't think it is physically possible to completely shield the line side lugs without the use of a complete cover or enclosure. You could make the shield "finger safe" but I don't think you could build a lug shield that prevents any access to the live terminal.

Just make them finger safe with a boot. Why shield everything?

 

[mbrooke]

Because more people are killed by systems under 150 volts to ground then above.

Because 150 volts to ground has nothing to do with arc flash.

Because OSHAs directive is safety it is not make things easier.

You are free to blow yourself up, but employees need to be protected from management that would put them in a dangerous situation just to save a buck.

Ok, Ill stir the pot so to speak. :thumbsup: In residential, how bad is arc flash? Unless the transformer is within feet of the meter it is often a lot lower then 10,000amps.

http://www.alabamapower.com/busines...df/A E Fault Currents Tables FINAL 8 2003.pdf


I know you will being up city secondary networks, but I will leave those aside for now.

 

[jumper]

Ok, Ill stir the pot so to speak. :thumbsup: In residential, how bad is arc flash? Unless the transformer is within feet of the meter it is often a lot lower then 10,000amps.

http://www.alabamapower.com/busines...df/A E Fault Currents Tables FINAL 8 2003.pdf


I know you will being up city secondary networks, but I will leave those aside for now.

The shield cover has nothing to do with arc flash mitigation. It for protection against accidental shock hazards.

 

[mbrooke]

The shield cover has nothing to do with arc flash mitigation. It for protection against accidental shock hazards.

Which goes back to me idea of slip on boots over the lugs.

 

[jumper]

Which goes back to me idea of slip on boots over the lugs.

Don answered that in post 14.

 

[kwired]

Last I knew the need to turn power off before gaining access is easily solved by having additional disconnecting means - which is a design issue.

So you put a shield over the main breaker/supply side lugs - that is one way to design it.

There will still be many that open the panel while the main is closed, most likely all that do it now will continue to do so.

Where does one stop with this requirement? Put a fused disconnect ahead of the panel, there really needs to be similar shield on line side of the disconnect for safe servicing the fuses.

I feel the NEC tries to address a lot of things with requirements that really are design issues.

Strict enough enforcement of safe work practices will eventually change design practices. This is one reason why you see a lot of class 2 control circuits instead of class 1 control circuits.

 

[don_resqcapt19]

I agree with this, though the enclosed mains certainly wouldn't hurt anything and while it would add cost to equipment, it would still be cheaper than adding a sep disco (and yet another point of potential failure with more connections however remote) betwixt the meter and mcb/bcp to quash the concern here.

When I was not having any success in getting a requirement for a line side barrier in the code, one of my proposals said that the enclosure that contained the OCPD could not have non-service OCPDs within the same enclosure.

 

[don_resqcapt19]

Just make them finger safe with a boot. Why shield everything?

Because the creation of an arc flash is a much bigger issue than is the shock protection. Finger safe only addresses shock protection.

 

[kwired]

When I was not having any success in getting a requirement for a line side barrier in the code, one of my proposals said that the enclosure that contained the OCPD could not have non-service OCPDs within the same enclosure.

I would go for that kind of option - still gives you some design choices instead of one size fits all requirement.

 

[growler]

Last I knew the need to turn power off before gaining access is easily solved by having additional disconnecting means - which is a design issue.

So you put a shield over the main breaker/supply side lugs - that is one way to design it.

I feel the NEC tries to address a lot of things with requirements that really are design issues.

I fully agree ( didn't see that one comming did you ? ).

I like to use a meter main combo and have the service disconnect on the outside of the house. I think this solves lots of problems and is not that expensive.

A new product could solve the same problems but these products already exist and don't take anymore space for the supplier. We keep adding new requirements for new products but we can't get rid of the old ones because they will be there for the next 50 years and need repairs. So why not design the system with existing products (materials ).

 

[kwired]

The shield pictured in the link in the OP is nothing new, it just isn't typically provided in panels sold in the US, but is required in Canada.

The US products have the mounting holes there for the shield and have had them for years in the Square D product lines they just don't install it.

I often wondered what some of the holes in those loadcenters were for until I saw a picture of one of the Canada versions with shield several years ago.

 

[growler]

the only legal way to do that work is to have the utility kill service and we know that rarely happens.

I must admit that all of these rules are turning me into an anarchist. The only thing worse than having no rules is having to many rules.

 

[don_resqcapt19]

I would go for that kind of option - still gives you some design choices instead of one size fits all requirement.

That option is not gone. The UL standard that requires the line side barrier only applies to service equipment. If you have a service disconnect upstream of the panel, the panel is not required to have a line side barrier.

That may be the case starting on 1/1/2020 for dwelling units. There is a requirement in the 2017 code that will become effective 1/1/2020 requiring an outside service disconnect.

 

[jumper]

Don, who submitted that proposal?

Can you post it?

I am on phone and cannot look it up.

 

[gadfly56]

That option is not gone. The UL standard that requires the line side barrier only applies to service equipment. If you have a service disconnect upstream of the panel, the panel is not required to have a line side barrier.

That may be the case starting on 1/1/2020 for dwelling units. There is a requirement in the 2017 code that will become effective 1/1/2020 requiring an outside service disconnect.

Oh fer cryin' out loud! So, exactly how many firefighters have been electrocuted in responding to residential fires? I foresee a new sport, teenage boys going out at 0200 and simultaneously blacking out an entire neighborhood for "fun".