Is the nameplate tag amperes in panels represents maximum current?

[Cartoon1]

Sorry this might be an elementary question. Electrical panel nameplates that shows panel amperes as shown in the attached pic. Is that maximum current allowed by panel? is it correct to say that this panel is rated for 225A or this panel is rated for a maximum continuous 225A?

Thank you

 

[infinity]

That means that the bus rating of the panel is 225 amps. I believe that the continuous rating would be 80% of that.

 

[kwired]

That means that the bus rating of the panel is 225 amps. Continuous rating would be 80% of that.

Or is it dependent on rating (whether it is 100% rated or not 100% rated) of the OCPD protecting it?

That said most 100% breakers are seldom or even never used in a typical panelboard supplying general use type branch circuits so those are usually going to be an 80% continuous rating.

 

[jim dungar]

That means that the bus rating of the panel is 225 amps. I believe that the continuous rating would be 80% of that.

Panels would be rated similar to other conductors.
Do you consider THHN to be rated at 80% of its 'table value'.

A 225A bus bar gets fed by 225A conductors which are protected by 225A overcurrent protective devices.

 

[kwired]

Panels would be rated similar to other conductors.
Do you consider THHN to be rated at 80% of its 'table value'.

This where it gets more complicated, when determining minimum conductor ampacity you need to increase the load by 125% if it is continuous load, or effectively derating the conductor to 80%. And is a little more complex if you have mix of continuous and non continuous loads.

But yes you can sort of look at that bus same way as a 310.16 conductor, and in op case it's table ampacity is 225 amps, but if the load is 100% continuous it's ampacity is 80% of that as long as non 100% OCPD's are involved.

 

[wwhitney]

Panels would be rated similar to other conductors.
Do you consider THHN to be rated at 80% of its 'table value'.

A 225A bus bar gets fed by 225A conductors which are protected by 225A overcurrent protective devices.

This is something I've wondered about--say you have an MLO panel with 200A busbars, and you supply it with a 200A feeder from a 200A 100% rated OCPD (which will be in its own separate enclosure). That's all copacetic, the 200A busbar rating is a continuous rating? You could supply 200A of continuous loads through that MLO panel?

[And then a followup question--say the MLO panel has feed-thru lugs, and you use a 200A feeder to another 200A MLO panel. The feed thru lugs and the main lugs, are they in practice ever 90C rated terminations?]

Cheers, Wayne

 

[jim dungar]

This is something I've wondered about--say you have an MLO panel with 200A busbars, and you supply it with a 200A feeder from a 200A 100% rated OCPD (which will be in its own separate enclosure). That's all copacetic, the 200A busbar rating is a continuous rating? You could supply 200A of continuous loads through that MLO panel?

[And then a followup question--say the MLO panel has feed-thru lugs, and you use a 200A feeder to another 200A MLO panel. The feed thru lugs and the main lugs, are they in practice ever 90C rated terminations?]

Cheers, Wayne

It is extremely unlikely that a panel board, or disconnect switch, is rated for 90°C terminations. Even 100% rated devices have 75°C terminations even though they require 90°C insulated conductors.

 

[kwired]

[And then a followup question--say the MLO panel has feed-thru lugs, and you use a 200A feeder to another 200A MLO panel. The feed thru lugs and the main lugs, are they in practice ever 90C rated terminations?]

Cheers, Wayne

Good question, as a lot of lugs are rated stand alone as 90C, but the equipment they attach to often still has 75C rating. This is true on a lot of circuit breakers or fused switches in particular.

 

[wwhitney]

It is extremely unlikely that a panel board, or disconnect switch, is rated for 90°C terminations. Even 100% rated devices have 75°C terminations enough though try require 90°C insulated conductors.

I get why that would be true for terminations on a thermal magnetic breaker, but in my example the lugs are just connected to busbars. So I'm not understanding why the terminations couldn't be rated for 90C. Is the extra temperature going to adversely affect the busbar? Or sufficiently conduct to the breakers themselves to affect their operation? Or is it just too hard or not worth it to get it listed as a 90C connection?

Thanks,
Wayne

P.S. Since you didn't answer my first question, I'm guessing that means the rating on busbar is a continuous rating, which is what you meant by your first post.

 

[jim dungar]

I get why that would be true for terminations on a thermal magnetic breaker, but in my example the lugs are just connected to busbars. So I'm not understanding why the terminations couldn't be rated for 90C. Is the extra temperature going to adversely affect the busbar? Or sufficiently conduct to the breakers themselves to affect their operation? Or is it just too hard or not worth it to get it listed as a 90C connection?

Thanks,
Wayne

P.S. Since you didn't answer my first question, I'm guessing that means the rating on busbar is a continuous rating, which is what you meant by your first post.

I have seen this restriction on bus bar lug landing pads used with large ampacity devices.

I said, panel bus bars are rated the same as are other conductors. Do you consider wire with THHN insulation to be continuous rated?

 

[GoldDigger]

One thing that is not completely clear is when the nominal rating of the panelboard is given as 200A it may actually be built using a 225A bus, and a 100A board may use as much as a 150A bus.
This distinction is of no practical importance except where a line side PV connection is being made in or through that board.
When the nominal rating is a round number it may be difficult to find out from the manufacturer what the actual bus rating is.

 

[ggunn]

One thing that is not completely clear is when the nominal rating of the panelboard is given as 200A it may actually be built using a 225A bus, and a 100A board may use as much as a 150A bus.
This distinction is of no practical importance except where a line side PV connection is being made in or through that board.
When the nominal rating is a round number it may be difficult to find out from the manufacturer what the actual bus rating is.

We have it in writing that all Eaton CH panels rated from 150A to 225A use the same rated (225A) busbars.

 

[GoldDigger]

We have it in writing that all Eaton CH panels rated from 150A to 225A use the same rated (225A) busbars.

Good to know. Was it hard to get the written information?

 

[kwired]

One thing that is not completely clear is when the nominal rating of the panelboard is given as 200A it may actually be built using a 225A bus, and a 100A board may use as much as a 150A bus.
This distinction is of no practical importance except where a line side PV connection is being made in or through that board.
When the nominal rating is a round number it may be difficult to find out from the manufacturer what the actual bus rating is.

When it comes to "load centers" I think you will generally find that the bus itself is either 125 or 225, at least for units with over ~8 breaker spaces.

They likely not going to change manufacturing processes for no more material than they might save to get one rated 100 or 200 instead of 125 and 225.

A main lugs load center in over 8 spaces is almost always 125 or 225 on the labeling.

A main breaker load center however will usually be labeled same as rating of the main breaker even though it likely has the same 125 or 225 bus in it.

Same likely goes for most true "panelboards" assembled from in stock items.

 

[rlitland]

You should not deviate from the rating marked on the panel.

 

[FionaZuppa]

What does the UL # on panel say?

I believe under UL word-smithing, "rated" means that # at 100% duty cycle.
"rated 225A" means 225A continuous.

How you can use that thingy, well, is for someone else to say.
UL --> NEC --> AHJ