230.71(A), 90.4, and a MLO panel

[dnem]

David,

According to Rule 20 of the UL Marking Guide for Panelboards.

Ron,

I hope you have enough time to jump back into this thread because I'm reading thru items 20 to 24 and it's just not clicking. I'm sure there's a turning point where it will all start to "click" but I haven't hit that point yet.

Does subitem A of item 20 refer to the same thing that jim dungar was referring to ?

Question 3: Yes
There are many situations where more "breaker space" than normal is required for to accomodate 6 disconnects in a panel (i.e. shunt trip breakers often take more space, plug-on TVSS units, and finally actual breakers feeding TVSS and power monitoring).

If this is the kind of thing that's referred to in subitem A of item 20 then would it be correct to say that 42 slot MLO panels could not be used as a main regardless of the number of disconnects originally installed ?

408.34(A) says that lighting and appliance panels are ones with more than 10% of their breakers on circuits of [408.34] 30 amps or less. The note between subitem A and subitem B of item 20 says *See Item 23 for lighting and appliance panelboards. which seems to be saying that the other items [20, 21, 22, & 24] are not applicable to lighting and appliance panels. Is that correct ?

David

 

[jwelectric]

So we have 200, 200, 100, 60, 40, & 30 which equals 630 amps of breakers.
The service conductors are parallel 4/0 AL.

408.34(A) says that lighting and appliance panels are ones with more than 10% of their breakers on circuits of [408.34] 30 amps or less. The note between subitem A and subitem B of item 20 says *See Item 23 for lighting and appliance panelboards. which seems to be saying that the other items [20, 21, 22, & 24] are not applicable to lighting and appliance panels. Is that correct ?

408.36(A) states that a lighting and appliance panelboard must be protected by not more than two mains.
In your panel as outlined above you have one thirty amp breaker which would constitute 1.2% of the Overcurrent devices in that panel.
If this 30 amp breaker supplies a circuit that also utilizes the neutral then this is a lighting and appliance panel and would require a main.
If this 30 amp breaker supplies a circuit that does not utilize the neutral then it is a power panelboard and does not require a main.

Now to address your questions;

Does subitem A of item 20 refer to the same thing that jim dungar was referring to ?

Question 3: Yes There are many situations where more "breaker space" than normal is required for to accomodate 6 disconnects in a panel (i.e. shunt trip breakers often take more space, plug-on TVSS units, and finally actual breakers feeding TVSS and power monitoring)

The key words found in rule 20 of UL?s marking guide is ?A panelboard with the neutral insulated from the enclosure?
When using this type panel then all spaces must comply to the six disconnect rule. This panel has the neutral insulated from the enclosure and is not the main.

If this is the kind of thing that's referred to in subitem A of item 20 then would it be correct to say that 42 slot MLO panels could not be used as a main regardless of the number of disconnects originally installed ?

No, back up and read lines 18 and 19 to see what makes a panel Suitable for Use as Service Equipment.
Line 20 is only addressing a panel that has the neutral that is isolated from the enclosure.

408.34(A) says that lighting and appliance panels are ones with more than 10% of their breakers on circuits of [408.34] 30 amps or less. The note between subitem A and subitem B of item 20 says *See Item 23 for lighting and appliance panelboards. which seems to be saying that the other items [20, 21, 22, & 24] are not applicable to lighting and appliance panels. Is that correct ?

No, What is being addressed is the use of a panel when it is being used a main. It is possible to have a panel that contains a main and the lighting and appliance circuits all in the same enclosure. These type panels are used every day in homes.
Every thing mentioned between lines 18 and 24 is addressing a panel that is Suitable for Use as Service Equipment.

Notice that this marking guide published by UL keeps referring back to the NEC and the rules that pertain to the service. These marking (listing and labeling) will always conform to the rules found in the NEC.
Nowhere in the Marking Guide will you find a rule that a panel being used as a service disconnect as outlined in 230.71 is bound to the same number of spaces as breakers.





.

 

[petersonra]

Ron, your answer seems well reasoned, and as an inspector perhaps you can help me understand the code, David hasn't. Doesn't 90.4 just give the ultimate AHJ the power (or authority) to adopt he NEC and modify if they desire. It has nothing at all to do with my installation as long as I follow the published codes not the ones made up, as the inspectors personal interpretation of the codes? If you want to cite 90.4 it shoud also refrence the local AHJ rule that is in conflict with the NEC ,if the citation is to make any sense, and then it is really only a local violation not necessarily a NEC violation.
"Be careful though, if you cite 90.4 more than twice a year you don't know what your doing."

The NEC gives no one any power at all.

The power to enforce the NEC comes from state and/or local legislation.

 

[don_resqcapt19]

Mike,

No, back up and read lines 18 and 19 to see what makes a panel Suitable for Use as Service Equipment.
Line 20 is only addressing a panel that has the neutral that is isolated from the enclosure.

Line 20 is speaking to a panel where the factory has not made a bond between the panel and the grounded conductor terminal strip. They will have provided a main bonding jumper that can be installed by the electrician as needed. This type of panel is marked as "suitable for use as service equipment" and can be used as service equipment or as a "sub-panel". The other type of panel is one where the manufacturer has made a permanent bond between the panel and the grounded conductor terminal strip. This type of panel can only be used as service equipment and is marked "suitable only for use as service equipment". Most panels are of the first type.
Don

 

[don_resqcapt19]

David,
Based on the informatin in the UL Marking Guide, it appears that extra space to install more than 6 means of disconnect may be a code violation. At this point it boils down to one question. Is the UL marking guide part of the listing, or is it just information. If it is part of the listing then there is a code issue, if its just information there is no code issue.
Don

 

[RB1]

As ususal Don hits it right on the head.

Some panelboards, I-Line for example, have the length of the busbars determined by the quantity and size of breakers that will be installed. If your order was based on particular breaker frame size and smaller frame breakers were installed, you would have an installation that could result in more than six circuit breakers. It is not until you install the seventh breaker (or should I say, get caught installing the seventh breaker) that have you have a problem.

I have seen companies ship 42 circuit panelboards, conditionally marked as service equipment, with tamper-proof screws on the lower bus positions.

It is interesting that the breaker quantity limitations include any factory installed disconnects. In this case the two 200-amp mains. I would call UL and see if the company is appropriately marking their equipment. If the NRTL doesn't have a problem with this equipment, I don't either.

It would be nice to have the model number of this equipment.

 

[RB1]

From the White Book:

Some panelboards are suitable for use as service equipment and may be so marked. Such marking is part is part of the listing mark as note below or is an integral part of other required markings.

In my opinion if there is not a combination of breakers that will result in only six disconnects, the paneboard is not properly labeled. For example, 18 spaces for three-phase plug-in, or 12 spaces for single-phase plug-in, minus any factory installed mains of course.

I may not be right but I would say it with conviction.

 

[LarryFine]

I may not be right but I would say it with conviction.

Like me: not always right, but never in doubt.

 

[dnem]

408.34(A) says that lighting and appliance panels are ones with more than 10% of their breakers on circuits of [408.34] 30 amps or less. The note between subitem A and subitem B of item 20 says *See Item 23 for lighting and appliance panelboards. which seems to be saying that the other items [20, 21, 22, & 24] are not applicable to lighting and appliance panels. Is that correct ?

408.36(A) states that a lighting and appliance panelboard must be protected by not more than two mains.
In your panel as outlined above you have one thirty amp breaker which would constitute 1.2% of the Overcurrent devices in that panel.

Hang on a minute, you?ve already lost me.
200, 200, 100, 60, 40, & 30 that?s 6 twopole breakers. The 30 would be 1/6th of the total number of breakers or 16% of the breakers.

?one thirty amp breaker which would constitute 1.2% of the Overcurrent devices in that panel?

I don?t understand what you?re saying.

408.36(A) states that a lighting and appliance panelboard must be protected by not more than two mains.
In your panel as outlined above you have one thirty amp breaker which would constitute 1.2% of the Overcurrent devices in that panel.
If this 30 amp breaker supplies a circuit that also utilizes the neutral then this is a lighting and appliance panel and would require a main.

Are you saying this because the 30amp is 16% which is over the 10% requirement ?
Are you saying that it can have only one main or a max of two mains [408.36(A)] ?
And where does 408.36(A)x2 come into play ?

The key words found in rule 20 of UL?s marking guide is ?A panelboard with the neutral insulated from the enclosure?
When using this type panel then all spaces must comply to the six disconnect rule. This panel has the neutral insulated from the enclosure and is not the main.

?When using this type panel then all spaces must comply to the six disconnect rule.?

What do you mean by that ? ?must comply? ?
If the neutral is not factory insulated from the enclosure, there is a 6 disc max.
If the neutral is factory insulated from the enclosure, if a main bonding jumper is installed to use the panel as a main, there is a 6 disc max.
There?s no difference according to 230.71.
We apparently are talking about to different concepts but I can?t figure out what you?re saying.

?This panel has the neutral insulated from the enclosure and is not the main?

And then I add a main bonding jumper and then it is a main.

Does subitem A of item 20 refer to the same thing that jim dungar was referring to ?

Question 3: Yes There are many situations where more "breaker space" than normal is required for to accomodate 6 disconnects in a panel (i.e. shunt trip breakers often take more space, plug-on TVSS units, and finally actual breakers feeding TVSS and power monitoring)

If this is the kind of thing that's referred to in subitem A of item 20 then would it be correct to say that 42 slot MLO panels could not be used as a main regardless of the number of disconnects originally installed ?

No, back up and read lines 18 and 19 to see what makes a panel Suitable for Use as Service Equipment.
Line 20 is only addressing a panel that has the neutral that is isolated from the enclosure.

So what does this sentence mean:
There must be at least one combination of switching units that can be mounted to occupy all available space for switching units.

David

 

[dnem]

David,
Based on the informatin in the UL Marking Guide, it appears that extra space to install more than 6 means of disconnect may be a code violation.

If what you're trying to tell me is that a result of Not Approved was the right call, I don't even care about that right now. I want to understand the reasoning.

Walk thru the White Book items that are bringing you to whatever call you're making and explain what you're thinking as you go along.

David

 

[jwelectric]

Hang on a minute, you?ve already lost me.

200, 200, 100, 60, 40, & 30 that?s 6 twopole breakers. The 30 would be 1/6th of the total number of breakers or 16% of the breakers.

?one thirty amp breaker which would constitute 1.2% of the Overcurrent devices in that panel?

I don?t understand what you?re saying.



Are you saying this because the 30amp is 16% which is over the 10% requirement ?
Are you saying that it can have only one main or a max of two mains [408.36(A)] ?

My bad on the math. I don?t know where that 1.2 came from either. Just didn?t have my mind on the math.

Yes if the 30 amp breaker utilizes the neutral then this panel would be required to conform to 408.36 (A) but still would not be in violation of 90.4

The rest of this I am not sure about so I will sit back and learn myself. One thing that I am sure of is that 90.4 has not been referranced by UL yet.

.

 

[jwelectric]

If what you're trying to tell me is that a result of Not Approved was the right call, I don't even care about that right now. I want to understand the reasoning.

Walk thru the White Book items that are bringing you to whatever call you're making and explain what you're thinking as you go along.

David

Yes someone please do as I am confused about this myself.

 

[don_resqcapt19]

David,
If you look at the info in section 20 of the UL panelboard marking guide you will find the following statement.

20. A panelboard with the neutral insulated from the enclosure may be marked ?Suitable for use as service equipment when not more than six main disconnecting means are provided? when the following conditions are met:
A. There must be at least one combination of switching units that can be mounted to occupy all available space for switching units; and, whether by using handle ties or similar devices, not more than six main disconnects will result (including factory-installed disconnects).
B. With this combination of switching units, no more than six overcurrent-protective devices will be connected to each ungrounded service conductor.
Note that a panelboard marked ?Suitable for use as service equipment when not more than six main disconnecting means are provided? may permit some combinations of switching units varying in ampere ratings and physical size that would exceed the six disconnect rule on a completely filled panelboard.

First this section is only for panels that have the main bonding jumper shipped loose. Second, there must be a way to completly fill all of the space in the panel with no more than six overcurrent protective devices per ungrounded conductor installed in the panel. This is new information to me. The code itself does not have this information. They note that with some panel and breaker designs that it may be physically possible to install more than six overcurrent devices per ungrounded conductor, but that the code limits you to six or less.
Don

 

[George Stolz]

If the use of handle ties would appease this (requirement? information?), then you could install a panel full of 20A breakers with handle ties, so long as you didn't exceed 6 handles.

I don't think this...whatever exactly it is effectively does anything for us, one way or the other.

The NEC looks more restrictive to me than this does.

 

[dnem]

David,
If you look at the info in section 20 of the UL panelboard marking guide you will find the following statement.

First this section is only for panels that have the main bonding jumper shipped loose. Second, there must be a way to completly fill all of the space in the panel with no more than six overcurrent protective devices per ungrounded conductor installed in the panel. This is new information to me. The code itself does not have this information. They note that with some panel and breaker designs that it may be physically possible to install more than six overcurrent devices per ungrounded conductor, but that the code limits you to six or less.
Don

"there must be a way to completly fill all of the space in the panel with no more than six overcurrent protective devices per ungrounded conductor installed in the panel."

Are we now talking about the same thing Jim and Bob mentioned ?

Question 3: Yes There are many situations where more "breaker space" than normal is required for to accomodate 6 disconnects in a panel (i.e. shunt trip breakers often take more space, plug-on TVSS units, and finally actual breakers feeding TVSS and power monitoring)

post #27

In commercial work it would be entirely possible that I would need a 24 'space' MLO panel to supply 6 - 3 pole breakers with shunt trip units.

post #69

But the question is, what if the way to fill all slots is not the way used in the particular installation being inspected ? What if there are 6 breakers used but unused slots still remain ?

At this point it boils down to one question. Is the UL marking guide part of the listing, or is it just information. If it is part of the listing then there is a code issue, if its just information there is no code issue.
Don

The opening page, before the table of contents page, uses the wording ?marking requirements? which would indicate that the manufacturer isn?t going to get an approval for a UL listing if he doesn?t follow these marking parameters. 110.3(A)(1) & 110.3(B) would reference the listing requirements.

I approached the code making panel members at the Akron IAEI meeting last night, Oran Post panel#6, Tom Moore panel #11, and Tim McClintock newly appointed to panel #12. Tom got sidetracked before he could answer and I never caught up with him again. Tim wasn't sure and deferred to Oran. Oran was sure that the max 6 limit applied to capability, not just presently installed, but he wasn't familiar with the panelboard marking guide. Both Tim and Oran urged me to contact Robert Osborne who wrote the guide. So that's what I'm going to do.

David

 

[dnem]

If the use of handle ties would appease this (requirement? information?), then you could install a panel full of 20A breakers with handle ties, so long as you didn't exceed 6 handles.

I don't think this...whatever exactly it is effectively does anything for us, one way or the other.

I disagree

A bunch of singlepole 20amp breakers handle tied into 6 groups would provide 6 throws of the hand for quickly killing all power, which is the only reason that the 6 disc limit exists.

Would handle tying groups be practical and efficient for the customer ? That's a different question with a different answer and goes beyond what the code cares about.

David

 

[dnem]

bold type added

Yes if the 30 amp breaker utilizes the neutral then this panel would be required to conform to 408.36 (A) but still would not be in violation of 90.4

The rest of this I am not sure about so I will sit back and learn myself. One thing that I am sure of is that 90.4 has not been referranced by UL yet.

I'm going to nickname you either pitbull or boa constrictor. You sure stay focused to your main point no matter what happens.

 

[jwelectric]

David,
Thank You for giving me a nick name
Check out the very bottom line

 

[George Stolz]

Mike is a pit bull, indeed.

I've felt the bite many times myself.

 

[jwelectric]

Mike is a pit bull, indeed.

I've felt the bite many times myself.

But I still love ya George and by the way. I don't know if I told you how much it pleases me that you are using JW beside you name.