Residential Load Center Puzzle

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  #1  
Old 07-25-11, 04:30 PM
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Residential Load Center Puzzle

I've seen variations of this question asked here but here are my specifics:

I have a Cutler Hammer panel I inherited when I bought my house 11 years ago. The house was built in 1955 but the box appears to be newer. The box has a 42 slot door but only 40 slots are available on the bus. All slots are full and there are 2 15 amp tandem breakers. So I'm at the (old) limit of 42 circuits/breakers.

When I dug into this a bit I really started questioning the tandems the more I read. So I tried to find out all I could about the box. Big problem number one is there's no info. on the panel door. If I remove the front cover there's a sticker inside the box partially covered by wiring. I read what I could off that. I also took down all numbers I found on the box and door and also those on two UL stickers in the box. This is where it gets a bit strange. The UL sticker says "Class CTL Panel Board, Issue Number C-373" so it would appear to be a CTL box. All the breakers are also labeled as CTL breakers. This includes the two tandems. On the back of the front panel there's a bunch of information but it basically says for my main breaker (CS2200) everything defaults to CTL. Sounds good so far. But when I call CH (Eaton) with the numbers on the box, they tell my the boxes with those numbers were not CTL boxes. The main number on the inside sticker is CH40KKM200N -- that's the number the guy was working off of.

The tandems also appear to fit in any slot I put them in. I've only tried a few slots but I see no limiting/reject factors built into them or the connecting bar/bus. I was under the impression that tandems should only fit in certain CTL slots. All that looks different about them is a bigger connecting "hook" on the back end of the breaker. Theoretically they could have been modified to fit anywhere -- I haven't found any CTL tandems locally, just the old replacement non-CTL tandems. If they were modified one of those was put in during some AC work we had done after we moved in. Seems unlikely the AC contractor would purposely violate code but he was down to no available slots (and I've learned not to trust all contractors to do the right thing).

The CH support guy theorized that maybe someone replaced the guts of the box. Seems possible but unlikely. Seems more likely to me that they've just lost some of the details of their older boxes.

Everything is working fine and I am scheduling an electrician to look at things. But I'm curious about these tandems. Why do they fit anywhere? And is my box really overloaded at 42 if it only has 40 slots?

Any guidance appreciated.
 

Last edited by srs06; 07-25-11 at 07:12 PM.
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  #2  
Old 07-25-11, 06:34 PM
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Sounds like someone installed non-CTL breakers in your panel.
 
  #3  
Old 07-25-11, 06:46 PM
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In the past, tandems and panels did not have the limiting devices they do now. Even though the panel was not listed for it, you could pretty much put as many tandems where ever you wanted. Then I think UL, or the manufactures, started realizing that the panels could be overloaded and started putting devices that allow tandems to be installed in certain locations in the panel, therefore limiting how many you can install.
 
  #4  
Old 07-25-11, 07:10 PM
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The panel says it's a CTL panel -- there's a UL sticker that claims that and the docs on the back of the door panel (when I remove it) say it's CTL based on my main breaker. All the breakers also say they're CTL breakers. Everything I read says the whole point of CTL is to be able to limit the breakers/circuits. So if both the panel and the breakers say they're CTL, why does there seem to be no limit to the number of CTL tandem breakers I can install in it? That's what's puzzling. What I can't tell is if the old tandem breakers have been modified somehow. They say CTL on them. I have not seen any tandems at the local big box stores that say they're CTL -- just the old replacement non-CTL breakers.

Bottom line: If everything says CTL on it, why does the panel seem to behave like a non-CTL panel?
 
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Old 07-25-11, 07:12 PM
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And is my box really overloaded at 42 if it only has 40 slots?
The 2008 NEC lifted the 42 space limit of past years, but you still should go by the maximum number of spaces or circuits the manufacturer says the loadcenter is rated for. I agree with pcboss, it sounds like you have non-CTL tandem breakers in your panel. Is the panel electrically overloaded? Probably not. Is it a code violation to have 42 circuits in your panel? That depends on the maximum number of circuits Cutler Hammer says that panel is designed for. I believe that is a 40 circuit panel and in my opinion, yes, it's a code violation. I think you need a subpanel.
 
  #6  
Old 07-25-11, 07:20 PM
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I agree on the subpanel. If not now, I'll need one later. On the breakers: I pulled both the tandem 15 amp breakers and the label on each one says "Class CTL Type CH." All the non-CTL breakers at the store also have that big "for replacement only" warning label on them. But I can't tell what on these breakers is supposed to be the limiting/reject factor ... it seems possible someone could have modified the breakers. Since I haven't found any at the local store yet I have nothing to compare to. I've been searching for good diagrams/pictures on the web.
 
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Old 07-25-11, 07:23 PM
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Cutler-hammer submitted the proposal to end the 42 ckt requirement. You still need a subpanel, because this panel is listed to no more than 40 circuts.
 
  #8  
Old 07-25-11, 07:34 PM
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Theoretically, someone who did AC work here violated the code because they added one of those tandems when they had no space left. That was years ago but I only recently realized this. Also, some of breakers on unused circuits (wired but not used) were off before -- 1 or 2 at least. So it was probably right around 40 used at the time of the AC work. I recently rewired one of those unused circuits to a new set of outlets and that's where the questions started. I'm going to have someone look at it but I'm finding a lot of confusion here, even among licensed electricians. If everything says CTL I think my box should be functioning differently. There seems to be the possibility of someone creating some sort of hybrid box. However, the fact that the box says it's CTL and the breakers all say they're CTL has me stumped. Maybe some early CTL panels had no true limiting factors at all? It seems like that's specifically what CTL was devised for though. Makes no sense. If I removed all breakers maybe I'd see something I'm missing.
 
  #9  
Old 07-25-11, 08:04 PM
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Try comparing your tandem breakers to this one.

Amazon.com: Cutler Hammer Tandem Single Pole Circuit Breaker: Home Improvement
 
  #10  
Old 07-25-11, 09:24 PM
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This got me on the right track I think. I looked the model number up at the Eaton (Cutler Hammer) site and found this:

http://www.eaton.com/ecm/groups/publ...b00500002e.pdf

At the bottom of page 62, section 26.2-20 there's a picture of what I think I should see -- the tandem slots on the right have extra tabs that fit into the CTL tandem breakers.

I think I need to pop them out again and (a) see if any such tabs exist; (b) get the part number off the breaker. In general photos, the CTL and non-CTL breakers look the same to me. With a part number I should be able to find the details. Then I should be able to see if the breaker or box have been modified or if the breakers are somehow being used in a way they shouldn't be but that works.
 
  #11  
Old 07-26-11, 09:40 AM
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You'll occasionally see that someone has filed off the CTL rejection tab in order to use a tandem breaker where it doesn't belong. I suspect that is what happened in your house. Mechanically speaking the breakers are identical, so it is very unlikely to be a hazard. However the panel is not listed for tandems so it is in violation and should be fixed if you are so inclined.
 
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