I can not imagine why any electrician would want to jam more & more wires into a panel board due to the use of Mini Breakers? 40 circuit panels with 40 pole spaces mean just that, unless marked otherwise. We do not allow the installation of mini's period. They cause excessive "fill" in any panel board and places like "Home Depot" sell minis that are cut to fit any panel regardless of manufacturers specs. I needed a hockey mask when I took the cover off of a 40 circuit panel that had 14 mini's installed. You would think when you are out of neutral spaces that might be a hint you went to far? What about cubic inch capacity? I can't recall if I have ever seen it listed on a panel. Maybe we need to get into Volume allowance Required per conductor for panel boards? Sell them a new sub panel and skip the mini's!
Mini Breaker & Safety
- Thread starter CBE
- Start date
- Status
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Re: Mini Breaker & Safety
Right on.
CBE, welcome to the forum!
Right on.
CBE, welcome to the forum!
bphgravity
Senior Member
- Location
- Florida
Re: Mini Breaker & Safety
There are some instances where tandem breakers are both economical and convienent without creating an unsafe condition.
I also agree that this can be abused, however, the better trained and higher qualified electrician should be able to make the call when a tandem is no longer appropriate.
There are some instances where tandem breakers are both economical and convienent without creating an unsafe condition.
I also agree that this can be abused, however, the better trained and higher qualified electrician should be able to make the call when a tandem is no longer appropriate.
mdshunk
Senior Member
- Location
- Right here.
Re: Mini Breaker & Safety
Well, a 40 circuit panel with 14 tandems is already in violation of the 42 ckt max anyhow. The hazard is not the tandems, it is installing tandems in slots and in panels where they are not permitted. There are already rules on this, and no more are necessary. This is why we've had CTL type tandems since the late 60's, even though the big box stores still persist in selling loads of non-CTL type tandems to overload a panel.
Well, a 40 circuit panel with 14 tandems is already in violation of the 42 ckt max anyhow. The hazard is not the tandems, it is installing tandems in slots and in panels where they are not permitted. There are already rules on this, and no more are necessary. This is why we've had CTL type tandems since the late 60's, even though the big box stores still persist in selling loads of non-CTL type tandems to overload a panel.
charlie tuna
Senior Member
- Location
- Florida
Re: Mini Breaker & Safety
there is not much difference than going into a commercial office building electrical room and finding a 42 circuit panel sub fed from another 42 circuit panel by a three pole sixty amp breaker. we as electricians know this is not a good practice, but actually it is engineered and installed and inspected!
there is not much difference than going into a commercial office building electrical room and finding a 42 circuit panel sub fed from another 42 circuit panel by a three pole sixty amp breaker. we as electricians know this is not a good practice, but actually it is engineered and installed and inspected!
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: Mini Breaker & Safety
for outlets it allows you to have every office on a seperate circuit, so two people in difererent offices can have their electric heaters on simultanesously without tripping the breaker. but clearly not every office will have an electric heater running simulataneously so there is not much overall current draw, but there is the potential for a few outlets to draw a lot without tripping CBs.
what's wrong with such an installation. usually the reason such things are done is for convenience, and if the loads are actually low enough that this works, who cares? especially if you are using the CBs as light switches. Gives you more control over what lights are on a single circuit.
for outlets it allows you to have every office on a seperate circuit, so two people in difererent offices can have their electric heaters on simultanesously without tripping the breaker. but clearly not every office will have an electric heater running simulataneously so there is not much overall current draw, but there is the potential for a few outlets to draw a lot without tripping CBs.
jwelectric
Senior Member
- Location
- North Carolina
Re: Mini Breaker & Safety
408.35 Number of Overcurrent Devices on One Panelboard.
Not more than 42 overcurrent devices (other than those provided for in the mains) of a lighting and appliance branch-circuit panelboard shall be installed in any one cabinet or cutout box.
A lighting and appliance branch-circuit panelboard shall be provided with physical means to prevent the installation of more overcurrent devices than that number for which the panelboard was designed, rated, and approved. For the purposes of this article, a 2-pole circuit breaker shall be considered two overcurrent devices; a 3-pole circuit breaker shall be considered three overcurrent devices.
408.35 Number of Overcurrent Devices on One Panelboard.
Not more than 42 overcurrent devices (other than those provided for in the mains) of a lighting and appliance branch-circuit panelboard shall be installed in any one cabinet or cutout box.
A lighting and appliance branch-circuit panelboard shall be provided with physical means to prevent the installation of more overcurrent devices than that number for which the panelboard was designed, rated, and approved. For the purposes of this article, a 2-pole circuit breaker shall be considered two overcurrent devices; a 3-pole circuit breaker shall be considered three overcurrent devices.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Mini Breaker & Safety
I see nothing wrong with this. If the computed load is 60 amps or less, what is the problem?
charlie tuna
Senior Member
- Location
- Florida
Re: Mini Breaker & Safety
ryan,
if the original panel was a three phase feed thru 30 circuit 200 amp mlo panelboard --- as time goes by and additional circuits are added to the new 42 circuit panelboard ---that 3 pole sixty amp breaker is gonna get overloaded --- the original installation is great but later when other tenants begin to expand the problems start!
ryan,
if the original panel was a three phase feed thru 30 circuit 200 amp mlo panelboard --- as time goes by and additional circuits are added to the new 42 circuit panelboard ---that 3 pole sixty amp breaker is gonna get overloaded --- the original installation is great but later when other tenants begin to expand the problems start!
- Location
- Massachusetts
Re: Mini Breaker & Safety
That is not within the NECs jurisdiction, look at the code exception that allows the total overcurrent protection of service conductors to exceed the service conductors rating.
I have to say 'so what'
That is not within the NECs jurisdiction, look at the code exception that allows the total overcurrent protection of service conductors to exceed the service conductors rating.
Re: Mini Breaker & Safety
I believe some thought should be given in the way the panel is tested. If a specific panel that has a specific interior volume, such as a 42ckt panel, is tested with 42 spaces (poles) filed and loaded to a given total load to get a UL listing(I'm not familiar with what the UL testing requirements are).The testing is conducted in a specific ambient temperature and there will be a given amount of heated watts generated by the panel. Should the heating watts be great enough within the panel it will derate the breakers such that they are not capable of carrying the current that they were designed to carry.
By adding duplex breakers beyond the listed pole capacity of the panel you can potentially generate additional heating watts above that which the panel was tested for.
What are the chances of the panel overheating if one were to cram more poles into a panel that wasn't listed for them? Probably slim to none because I would doubt that ant given panel is not loaded near to its tested capacity anyway.
But, that isn't our call. Our responsibility is to comply with NEC art 100-3(A) and (B).
I believe some thought should be given in the way the panel is tested. If a specific panel that has a specific interior volume, such as a 42ckt panel, is tested with 42 spaces (poles) filed and loaded to a given total load to get a UL listing(I'm not familiar with what the UL testing requirements are).The testing is conducted in a specific ambient temperature and there will be a given amount of heated watts generated by the panel. Should the heating watts be great enough within the panel it will derate the breakers such that they are not capable of carrying the current that they were designed to carry.
By adding duplex breakers beyond the listed pole capacity of the panel you can potentially generate additional heating watts above that which the panel was tested for.
What are the chances of the panel overheating if one were to cram more poles into a panel that wasn't listed for them? Probably slim to none because I would doubt that ant given panel is not loaded near to its tested capacity anyway.
But, that isn't our call. Our responsibility is to comply with NEC art 100-3(A) and (B).
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Mini Breaker & Safety
My issue is that me as an inspector cannot turn this down, even if I wanted to. Again, I see no problem with it, and to be frustrated that it was inspected and passed is unwarranted.
charlie tuna
Senior Member
- Location
- Florida
Re: Mini Breaker & Safety
i understand it meets code --- i just think it's poor engineering practice. and from the problems i have found during infrared testing it creates a problem that the original customer had little to do with. i have seen 200 amp - 3 phase - 42 circuit panel fed with a three pole 30 amp breaker. consider that you, the tenant pays for this expansion panel, and then two years later the main starts to trip due to the addition of circuits over time to other tenants. common sense may prevent this problem from occuring, the same as adding piggyback breakers into an existing panel!!!
i understand it meets code --- i just think it's poor engineering practice. and from the problems i have found during infrared testing it creates a problem that the original customer had little to do with. i have seen 200 amp - 3 phase - 42 circuit panel fed with a three pole 30 amp breaker. consider that you, the tenant pays for this expansion panel, and then two years later the main starts to trip due to the addition of circuits over time to other tenants. common sense may prevent this problem from occuring, the same as adding piggyback breakers into an existing panel!!!
- Location
- Massachusetts
Re: Mini Breaker & Safety
However it is buyer beware and thats when the salesman in me kicks in and I explain that the people got what they payed for when they turned down our quote for the low baller.
Many times it is poor practice, I also get frustrated when I go back to one of our professionally built electric rooms only to find some one has installed a Home depot contractor special single phase plug in panel.
However it is buyer beware and thats when the salesman in me kicks in and I explain that the people got what they payed for when they turned down our quote for the low baller.
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: Mini Breaker & Safety
I for one hate to mini breakers.They can cause over heating.Was very disapointed with one EC that i helped out for a few weeks.Very upscale home and he hande me a GE 20/40.No other place did he cut corners.What did he save ? $50 ?
I for one hate to mini breakers.They can cause over heating.Was very disapointed with one EC that i helped out for a few weeks.Very upscale home and he hande me a GE 20/40.No other place did he cut corners.What did he save ? $50 ?
mdshunk
Senior Member
- Location
- Right here.
Re: Mini Breaker & Safety
I'm not so sure how upscale the home could have been. I sometimes have a challenge getting a regular home nowadays in to be just 40 circuits. I would call 'upscale' at least 2 or 3 panels on a 320 or 400 (or bigger) service.
[ June 07, 2005, 10:09 PM: Message edited by: mdshunk ]
Saved space?
I'm not so sure how upscale the home could have been. I sometimes have a challenge getting a regular home nowadays in to be just 40 circuits. I would call 'upscale' at least 2 or 3 panels on a 320 or 400 (or bigger) service.
[ June 07, 2005, 10:09 PM: Message edited by: mdshunk ]
charlie tuna
Senior Member
- Location
- Florida
Re: Mini Breaker & Safety
iwire,
on the original installation----sizing the feeder--consider the difference in costs to providing say a feeder that was half the rating of the panel. a 3 pole 100 amp breaker! if at the time, this was an optional cost to the installing tenant, i bet 80 per cent would say, "go with the common sense feeder size". what i see more and more of is the addition of un-necessary sub panels. this is basically caused by existing circuits being buried during the demolition of tenant spaces. if a new buildout is engineered correctly, either by the electrical contractor or a professional engineer, the existing circuits should be re-used. i have seen an office electrical room with eight 42 circuit panels that could be properly served by one panel. at one time we(electrical contractor) would do the demo and the tenant buildout and then provide the engineer with the "as builts" to transfer the circuit information to the record set of plans.
iwire,
on the original installation----sizing the feeder--consider the difference in costs to providing say a feeder that was half the rating of the panel. a 3 pole 100 amp breaker! if at the time, this was an optional cost to the installing tenant, i bet 80 per cent would say, "go with the common sense feeder size". what i see more and more of is the addition of un-necessary sub panels. this is basically caused by existing circuits being buried during the demolition of tenant spaces. if a new buildout is engineered correctly, either by the electrical contractor or a professional engineer, the existing circuits should be re-used. i have seen an office electrical room with eight 42 circuit panels that could be properly served by one panel. at one time we(electrical contractor) would do the demo and the tenant buildout and then provide the engineer with the "as builts" to transfer the circuit information to the record set of plans.
kevinsarnold
Member
Re: Mini Breaker & Safety
The forum started out stating a "mini-breaker". If this is the case, there is a difference between mini-breaker and breaker. For example, a mini-breaker is listed to UL1077 and a regular breaker should be listed to UL489. What this means, is the mini-breaker is not approved for branch circuit protection. An example would be having the mini-breaker in the equipement such as an oven or stove, and then having the branch breaker in the panel.
The forum started out stating a "mini-breaker". If this is the case, there is a difference between mini-breaker and breaker. For example, a mini-breaker is listed to UL1077 and a regular breaker should be listed to UL489. What this means, is the mini-breaker is not approved for branch circuit protection. An example would be having the mini-breaker in the equipement such as an oven or stove, and then having the branch breaker in the panel.
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