QO Circuit Breaker/Combining Circuits Questions

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Old 04-25-08, 07:36 PM
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QO Circuit Breaker/Combining Circuits Questions

Hello. Sorry in advance for the long post.

I am needing to make room in service box (Square D Type QO). I can either combine two smaller circuits onto one breaker, or use the double-pole breakers that fit into a single breaker slot.

Based on earlier answers to a similar question, I was going to go the route of using double-pole breakers. However, the type QO double-breakers that I bought have a "hook" for one of the attachment points, which doesn't work in my box. I did see double-pole breakers with attachment points that match the current breakers in the box, but they were twice as expensive ($30 vs. $15).

With that said, why the different types of QO attaching points? My box appears to be fairly recent, probably less than 15 years old.

Is it safe to combine smaller circuits onto one breaker? By smaller I mean a couple lights and a couple of living room outlets. The breakers can have two wires attached. Will having to separate commons be any problem?

If it is not advisable to combine two circuits, then I'll get the $30 breakers. Just wanted to explore my options.

Thanks for the help! (And excuse my ignorance...I'm trying to learn!)
 
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Old 04-25-08, 07:49 PM
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Post the part # of your panel, and we'll go from there.

What you are referring to are not "Double pole breakers", but rather "TANDEMS" or "PIGGY BACKS".

I suspect the reason that the "HOOK" doesnt fit , is because you have a "CTL" class panel. The more expensive breakers will have a label on them stating "Replacement use only in "NON CTL" class panels.

You may be in a jam, as the Non ctl breakers are not approved for use in your panel application.
 
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Old 04-25-08, 07:52 PM
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Just ran into this last week.
Look at the rail that the back end of the breaker clips to and see if you see some slots in it.
If so, these are the only positions where your breaker will fit.
If you don't have the slots, you will have to purchase the expensive breakers.
As long as the wire is rated to accept two conductors and you are not overloading it, you are good to go.
 
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Old 04-25-08, 08:00 PM
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If you don't have the slots, you will have to purchase the expensive breakers.
I must respectfully disagree.....

The expensive breakers are for pre 1967 NON CTL panels, and not approved for use in a CTL panel. It is highly likely that The OP's panel is not able to accept tandems, and Defeating the "Rejection Feature" would be a violation of the panels "LISTING"...
 
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Old 04-25-08, 08:01 PM
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These are also known as dual, tandem, piggyback and two-pole thin.

They must be listed for panelboard and used and installed per the manufacturer's instructions and minimum code requirements.

The panelboard should be marked to indicate the acceptable use and installation of these circuit breakers, ex: of “8-16 circuit” means any combination of eight twin circuit breakers or sixteen full size circuit breakers.

The panelboard and/or circuit breaker may have a mechanical feature to limit the use and installation of twin circuit breakers to specific panelboards.

From a Code standpoint, 408.15 limits the number of overcurrent devices on a lighting and appliance panelboards at the time these were manufactured to 42.

FYI single-pole overcurrent devices that are half the width of a standard full size single-pole circuit breaker are known as half size and single-pole thin.

In my area some AHJs prohibit the use of these even if listed for the panel.
 
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Old 04-25-08, 08:35 PM
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From what I can see inside the box, the issue no. is V-2813. The panel cover is listed as a QOC30UF Series S01 Type 1 Enclosure. Does this shed any light?

I also took a closer look at the rails in the box and it appears that the bottom 1/3 on each side have slots that may work with the "hooks". I will have to try this out tomorrow. Box has 30 spots, 15 on a side.
 
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Old 04-25-08, 08:44 PM
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I did not read thru all the posts, but do not double circuits on one breaker to make additional room without checking with a certified electrician
 
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Old 04-25-08, 08:59 PM
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QOC30UF

Not really, as this is only the spec for the cover.

On the interior label.....Look for a list of approved breakers.....Anything that uses the prefix QOT will accept tandems.....if not then it wont.
 
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Old 04-26-08, 03:14 AM
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Originally Posted by kck71 View Post
From what I can see inside the box, the issue no. is V-2813. The panel cover is listed as a QOC30UF Series S01 Type 1 Enclosure. Does this shed any light?

I also took a closer look at the rails in the box and it appears that the bottom 1/3 on each side have slots that may work with the "hooks". I will have to try this out tomorrow. Box has 30 spots, 15 on a side.
Look inside the load center on the left hand side, and you should see a sticker with a model number in bold print, which may read something like this:QO13040M200. It will also state near the model number the maximum number of single pole circuits that the box will accomodate. From what you describe, it sounds as if you may have a 200 amp 30 space/40 circuit load center, which means there are 30 slots, but 10 of those will accept tandems of the QOT, or hook style type.
 
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Old 05-14-08, 11:43 AM
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Sorry to bring this back up again, but I want to make sure I'm doing the right thing...

I want to replace an unused twin 20a breaker with a twin 15a breaker. I have a Siemens breaker panel model W0816ML1200FTCU. It is about 18 years old. It is located in my shop behind my service entrance (meter loop). It is a "feed thru" panel in that there are lugs at the bottom of the busses. Wires go from those lugs underground to feed the breaker panel in my house. The 20a breaker I'm replacing (new lighting circuits) is a type QT part number Q2020, and the sticker on the breaker says "Class CTL". The "UL listing" area on the panel also says "Class CTL Enclosed Panelboard".

So, it sounds like I have a circuit limiting panel, and I must replace the breaker with a "Class CTL" 15a breaker, and not the "NOT FOR CTL ASSEMBLIES" MP1515N type MH-T Murray twin 15a breaker I bought thinking it must be somehow better because it cost more than the similar CTL breaker. Correct?

The only physical differences I can see between the two breakers are a couple of slots in the bottom (bus side) surface near the "hook" on the non-CTL breaker. It looks like it would plug in. I'm not going to use it, but what would be the danger if I did?

Thanks,
Ira
 
 

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