Spaces and circuits

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OK Sparky 93

Senior Member
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Electrician
Can anyone explain how, or why one 200 amp panel could have 42 spaces and since I don't know let's say it list to be a 42/54, and another list for 42/84?

I know in the past at least on a Eaton BR Part of the buss would have a notch. This was or is an indication that it could be twinned to add more circuits.

But, what could the ramifications be if it wasn't intended or listed to have more than 42 circuits and you twin it up to add another 42 more? The buss is protected. How could it ever have more load than what the main would allow?
 
42/54 or 42/84 mean exactly what you said and think: 42 spaces, but will accept enough tandems to allow for 54 or 84 circuits, respectively.
 
I get it. But just a little thought.

Obviously, now, I don’t have to have a notch in the buss, to install a tandem breaker.

Before I did. What’s the difference?

I will tell that in the early days of this career
It was “get that cheater twin”. Doesn’t have that metal strip to prevent you from installing on a buss without a notch.

Now that seems to be what everyone carries (Eaton).

Also now, since it is my skin, I want to know that I am right. So if it isn’t listed to have more circuits than spaces, it doesn’t get them.

But still the question.
 
OK Sparky 93 said:
Obviously, now, I don’t have to have a notch in the buss, to install a tandem breaker.

Before I did. What’s the difference?
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You don't need the notch because Eaton wants you to use a Non-CTL twin breaker. For Eaton panels the CTL and Non-CTL thing is gone. You're still limited by the listing of the panel as to how many twin breakers you can install. So a listed 30/40 panel would only allow 10 twins even if you could fit 30 of them.
 
Another limitation is the number of neutral termination points. It seems like there are never enough of them unless you have a few 240V circuits with no neutrals like electric heat. A 20 circuit panel will be lucky to have 20 neutral terminations. Putting 40 circuits in a 20 circuits panel would make neutrals a challenge.
 
suemarkp said:
. A 20 circuit panel will be lucky to have 20 neutral terminations. Putting 40 circuits in a 20 circuits panel would make neutrals a challenge.
Click to expand...
Would a modern panel have a neutral terminal for its listed number of circuits?
 
infinity said:
You don't need the notch because Eaton wants you to use a Non-CTL twin breaker. For Eaton panels the CTL and Non-CTL thing is gone. You're still limited by the listing of the panel as to how many twin breakers you can install. So a listed 30/40 panel would only allow 10 twins even if you could fit 30 of them.
Click to expand...
So what is the difference between CTL and only allowing a certain number of tandems? I didn't realize there was some that didn't have a rejection feature and are just honor system?
 
infinity said:
Would a modern panel have a neutral terminal for its listed number of circuits?
Click to expand...
Not sure. They seem to be close. Im not sure if the listing requirements demand that or not. You can also lose some if you have a GEC taking a terminal or have a large feeder that needs a bigger lug using an adapter that takes two spots.
 
OK Sparky 93 said:
But, what could the ramifications be if it wasn't intended or listed to have more than 42 circuits and you twin it up to add another 42 more? The buss is protected.
Click to expand...
Sure busbar is protected
For total load exceeding rated
But before total load exceeding, damage done as internal heat excessive, localised overheating before total load exceed to main breaker trip
Thermal/mechanical failure and not overload failure.
 
electrofelon said:
So what is the difference between CTL and only allowing a certain number of tandems? I didn't realize there was some that didn't have a rejection feature and are just honor system?
Click to expand...
I looked at a few random Eaton panels and they all accepted twin breakers in every slot. As far as a honor system one always existed when you used Non-CTL breakers in panels that had for example 30/40 listings.
 
hbiss said:
Yeah, if there are any spaces left after the neutrals. I have seen every combination imaginable of EGCs and neutrals together in one hole.

-Hal
Click to expand...
I was responding to your comment about ground bars. Neutrals aren’t (supposed to be) landed on ground bars.
 
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