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Old 02-08-2012, 07:45 AM   #1
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Default Use of twin circuit breakers

Could someone please set me straight on nyc code restrictions regarding the use of twin breakers. I know the code states a panelboard can have no more than 42 breakers not including the main... but does that mean that a 20 ckt. panel can have 20 twins? In renovations with a full panel and a cheap customer i need to make room for a couple of arc faults and would rather know ahead if the twins won't fly with the inspector.
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Old 02-08-2012, 08:12 AM   #2
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If the panel is designed to accept twins then you may use them. There are some straight 20 cir panels but they are usually a 20-32 or 20-40. You need to read the labeling on the cover or just look at the cir. diagram of the directory on the panel door.

BTW- the 42 cir. concept is gone-- you can have 60 cir. in a panel if the panel is listed for it.
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Old 02-08-2012, 08:58 AM   #3
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The kicker is the new 40/60 panels from SqD are no different than the existing 40 ckt panel.
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Old 02-08-2012, 09:12 AM   #4
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Quote:
Originally Posted by greenlee View Post
Could someone please set me straight on nyc code restrictions regarding the use of twin breakers. I know the code states a panelboard can have no more than 42 breakers not including the main... but does that mean that a 20 ckt. panel can have 20 twins? In renovations with a full panel and a cheap customer i need to make room for a couple of arc faults and would rather know ahead if the twins won't fly with the inspector.
I would not tell the inspector that you installed the twins in the first place you are using AFCI breakers for the new circuits that should keep him happy...


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Old 02-08-2012, 01:39 PM   #5
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If a panel is listed for twins, it will say so on the label or box. The indicators are like 12/24 (12 full or 24 twin).

If the label or box is missing, in many cases, in modern panels, you can look at the bus and determine if twins are accepted and how many.

Seimans, Murray, Homeline and Cutler Hammer BR have a notch cut into the buses that will accept twins.
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Old 02-08-2012, 02:43 PM   #6
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Seimans, Murray, Homeline and Cutler Hammer BR have a notch cut into the buses that will accept twins.

What about the "Replacement use only" ones for non CTL panels
I know ITE and Square D QO have them .
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Old 02-08-2012, 02:47 PM   #7
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What about the "Replacement use only" ones for non CTL panels
I know ITE and Square D QO have them .
CH offers a BR style breaker without the rejection clip in it.
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Old 02-08-2012, 03:13 PM   #8
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Sqd has two twin breakers, QO and QOT. QOT comes with the rejection clip. QO tandems have a 'hump' in the molding to prevent you from putting it into a panel that does not accept tandem breakers.

If the panel can accept the QOT breakers, the part number on the loadcenter will tell you that. If you are still uncertain or cannot find the part number, look at the circuit spaces opposite the mains. There will be a slot/notch to accept the hook (aka rejection clip) found on the QOT breakers.

i.e. If the panel was a 20 space 30 circuit, then the ten spaces opposite the mains end of the panel is the only place tandems will fit.
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Old 02-08-2012, 10:03 PM   #9
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Whats the purpose of a murray breaker with the rejection clip when for five bucks more they sell one without it? Are the ones without it o.k. to use even if the buss isn't notched as far as the code is concerned?
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Old 02-08-2012, 10:13 PM   #10
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Whats the purpose of a murray breaker with the rejection clip when for five bucks more they sell one without it? Are the ones without it o.k. to use even if the buss isn't notched as far as the code is concerned?

You can use the more expensive breaker without the rejection clip in any place on the bus. You can only use one with the rejection clip in spots where the bus is notched.
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Old 02-09-2012, 03:42 AM   #11
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Those "go anywhere" QO twins are about $50 a pop. Sometimes it's cheaper to do a panel change or add a sub-panel than twin the beegeebers out of an existing undersize panel.
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Old 02-09-2012, 01:31 PM   #12
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Originally Posted by greenlee View Post
Whats the purpose of a murray breaker with the rejection clip when for five bucks more they sell one without it? Are the ones without it o.k. to use even if the buss isn't notched as far as the code is concerned?

I suppose that would depend on the number of breakers installed. If the notched spaces were filled with twins and you added one more, then yeah.
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