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Old 05-10-2012, 04:22 PM   #1
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Tandem breaker positions in main service panel


I have a Siemens W3040B1200CU main service panel. The diagram on the inside of the door indicates 5 bottom positions on each pole- total of 10- for tandem breakers. There are currently 6 tandem breakers but they are located in the upper positions. Do tandem breakers have to be in the exact positions indicated on the diagram and why? I believe the previous owner replaced an old panel with this one. The wires are definitely not long enough to put the circuits on tandem breakers in the bottom slots.

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Old 05-10-2012, 04:24 PM   #2
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Tandem breaker positions in main service panel


Yes, they have to be positioned where the diagram shows. If the wires are too short, splice some wire on to extend them to the bottom of the panel.

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Old 05-10-2012, 04:31 PM   #3
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Tandem breaker positions in main service panel


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Yes, they have to be positioned where the diagram shows. If the wires are too short, splice some wire on to extend them to the bottom of the panel.
Why do they need to be in those exact positions? Splicing with wire nuts? and is this code compliant?
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Old 05-10-2012, 04:40 PM   #4
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Tandem breaker positions in main service panel


The need to be installed in those locations because that is how the panel was listed an approved to be sold.

Wirenuts in a panel are perfectly acceptable.
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Old 05-10-2012, 04:47 PM   #5
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Tandem breaker positions in main service panel


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The need to be installed in those locations because that is how the panel was listed an approved to be sold.

Wirenuts in a panel are perfectly acceptable.
My inquisitive mind still would like to know why a panel is approved and listed for tandem breakers in specific positions. I am not an electrician. I was a low voltage contractor for 25 years. Can someone give me a technical explanation?
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Old 05-10-2012, 04:49 PM   #6
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Tandem breaker positions in main service panel


It could be for a variety of reasons.

could be that the buss is designed to only allow tandems in those locations, and the reason they are in the upper spots is that the breakers were modified

could be that that is what Siemans speced to the listing agencies and that is how it was approved
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Old 05-10-2012, 04:53 PM   #7
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Tandem breaker positions in main service panel


You may also want to check and see if the panel was reversible and if it was reversed. Siemens Murray make many panes that can be reversed so it can be either bottom or top feed. So it is possible that it's done correctly.
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Old 05-10-2012, 05:39 PM   #8
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Tandem breaker positions in main service panel


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You may also want to check and see if the panel was reversible and if it was reversed. Siemens Murray make many panes that can be reversed so it can be either bottom or top feed. So it is possible that it's done correctly.
My main service connects at the top. Looking at it I do not think it was reversed but I am not 100% certain what I am looking for. What I can tell you is the bottom 10 positions- 5 on each pole- have short fork like copper connections for the breakers and the remaining upper positions are flat copper contacts. I am guessing this follows what the diagram is indicating for the positions for tandem breakers?
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Old 05-11-2012, 12:27 AM   #9
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Tandem breaker positions in main service panel


AFAIK the modern Siemens breaker box with tandem breakers the quickest way to tell is look at the phase bussbars and with tandem breaker postion the bussbar will be notched so that is the area you can use the tandem breakers.

They useally are on the bottom 5 rows if the main breaker or main lug is top so if the main breaker or lug is reversed aka bottom feeders then it will be reversed.

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Old 05-11-2012, 04:42 AM   #10
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Tandem breaker positions in main service panel


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AFAIK the modern Siemens breaker box with tandem breakers the quickest way to tell is look at the phase bussbars and with tandem breaker postion the bussbar will be notched so that is the area you can use the tandem breakers.

They useally are on the bottom 5 rows if the main breaker or main lug is top so if the main breaker or lug is reversed aka bottom feeders then it will be reversed.

Merci,
Marc
I referred to the bussbar connection as "forked", you say notched. I am sure we are talking about the same thing. So the bottom 5 rows are occupied by 2 pole breakers for hot water heater, electric dryer, electric stove, hvac, etc. and the tandem breakers are in the upper rows. I thought I read somewhere that tandem breakers can only connect into their designated spots because of the way the connection is configured but apparently on this panel they can plug anywhere. Anyway is there a danger in having the tandem breakers and 2 pole breakers not where they are supposed to be? It's been that way for at least the 1 1/2 years I've lived here.

Last edited by elmaur; 05-11-2012 at 04:44 AM.
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Old 05-11-2012, 06:24 AM   #11
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Tandem breaker positions in main service panel


They make cheater tandems. These will go anywhere in a panel. They also make tandems that have a hook on them that will only go into their designated space on the buss bar.
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Old 05-11-2012, 06:32 AM   #12
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Tandem breaker positions in main service panel


CTL panels have a rejection feature to prevent tandem breakers from being used in the wrong location. My Seimens panel must be a CTL panel since it has the notched bussbar connection in the positions indicated for tandem breakers but I have tandem breakers in locations not specified for tandem breakers. Does this mean the tandem breakers are non CTL and if so is this bad?
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Old 05-11-2012, 06:35 AM   #13
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Tandem breaker positions in main service panel


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They make cheater tandems. These will go anywhere in a panel. They also make tandems that have a hook on them that will only go into their designated space on the buss bar.
You responded while I was typing. So I have cheater tandems. All I need to know now is it a hazard? Is it code compliant?
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Old 05-11-2012, 08:23 AM   #14
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Tandem breaker positions in main service panel


It would not meet the code having the non-CTL tandems in the panel or in the wrong locations.
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Old 05-11-2012, 02:28 PM   #15
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Tandem breaker positions in main service panel


if it is like sqd there are 2 types of tandem breaker one is listed for ctl panel (us panels, have a hook so ti can be used only at specific places) and the other non ctl (canadian panel, doesn't have hook, they are exactly like single pole breaker), but the canadian ones can fit any spaces on the us panel

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