Tandem Breaker Problem

[barnee]

Ive been planning a subpanel due to crowding in the main panel, and while studing my current situation I think I discovered a problem.

My panel is a SquareD QO30M200 series G1, and according to the manufacturer this panel does not accept tandem breakers (panel installed around 1991).

In 1994 I put an addition on the house and the electrician installed 9 tandem breakers in the panel due to space issues. There are now 31 circuits in this 30 space panel (9 tandems, 5 single pole, 8 double pole)

Knowing what I know now, I will size my subpanel to get rid of this situation, but Im wondering how the tandems were installed if the panel cant accept them? Is it likley that the main panel is damaged at this point?

 

[hh76]

Can't remember exactly how it works with QO's, but with most breakers you would just have to remove a small bit of plastic on the breaker to make the tandem fit. It wouldn't ruin the panel.

 

[Norcal]

There 2 types of twin breakers /panels, "CTL", & "non-CTL", your loadcenter is a CTL type which has rejection means to not allow more breakers to be installed then was listed for, the non-CTL breakers are manufactured for loadcenters made before 1968 which fit anywhere, your electrician used improper breakers, IMO.

 

[barnee]

Thanks for the information. The tandem breakers have no identification on them (without removing the cover) so I cant get any info on them other than they are 15 amp each.

Sounds like I can install a subpanel with enough spaces to correct this as opposed to replacing the main panel (with more spaces) which is likely much more expensive.

Electrician long out of business, but was a legitimate company while he lasted. I wish I knew more about this back then.

This brings up another question, if I install a subpanel to this main, can I use a subpanel that allows tandem breakers? I would buy new tandems and ditch the old ones.

 

[Charles (in GA)]

Ive been planning a subpanel due to crowding in the main panel, and while studing my current situation I think I discovered a problem.

My panel is a SquareD QO30M200 series G1, and according to the manufacturer this panel does not accept tandem breakers (panel installed around 1991).

In 1994 I put an addition on the house and the electrician installed 9 tandem breakers in the panel due to space issues. There are now 31 circuits in this 30 space panel (9 tandems, 5 single pole, 8 double pole)

Knowing what I know now, I will size my subpanel to get rid of this situation, but Im wondering how the tandems were installed if the panel cant accept them? Is it likley that the main panel is damaged at this point?

If the panel is full and has nine tandems, then you have 39 circuits in the panel. 240v circuits which are powered by full size double pole circuit breakers, count as TWO circuits for the purposes of circuit count in the panel.

Pics: first is two variations of tandem breakers, LH one only fits panels and spaces designed to accept them, RH will fit in any slot of any panel that takes that brand of breaker.

Second pic is a normal stab, that will not accept a tandem (see LH breaker above)

Third pic is a stab that has the notch that allows a tandem to be installed.

Charles

 

[barnee]

Thank you Charles for the very helpful photos and correction on the circuit count. I think the message here is that this project is quickly moving up my list of priorities since Im using 9 tandems where none are allowed, and Im 9 circuits over my 30 circuit limit.

How concerned should I be at this point? This situation has existed for 16 years the way it is but Im not really a thrill seeker if you know what I mean.

 

[rlitman]

This is not relavent. The OP is talking about a SquareD QO panel. Totally different beast. I do not believe that tandem breakers were made by SquareD back when that panel was originally installed. They're a pretty new item, they -may- be fine to be used on an older panel. Do not exceed the maximum number of circuits allowed in that panel though.

 

[hammlm]

This is not relavent. The OP is talking about a SquareD QO panel. ..... They're a pretty new item, they -may- be fine to be used on an older panel. Do not exceed the maximum number of circuits allowed in that panel though.

Really? QO Tandems are "pretty new"? Can you define what pretty new is? I would swear that I've been seeing them, installing them and having them in-stock since I got my first pair of Klien Linesman's pliers in 1989. I'm not saying you are wrong, I just thought that they had been around for a while at that point, given how often I saw them in place. Maybe I'm not remembering right and only saw them in GE / Siemens / etc--- but I don't think so.

 

[ishiboo]

Thank you Charles for the very helpful photos and correction on the circuit count. I think the message here is that this project is quickly moving up my list of priorities since Im using 9 tandems where none are allowed, and Im 9 circuits over my 30 circuit limit.

How concerned should I be at this point? This situation has existed for 16 years the way it is but Im not really a thrill seeker if you know what I mean.

I wouldn't be concerned at all. You're still limited to the main breaker in terms of bus capacity, the issue is there are probably not sufficient neutral/ground holes in the bus bars and the gutters are cramped. There is no safety issue really, the electrical connection on slots which accept and are not supposed to accept tandems is the same.

If it were my house, I'd leave it until it's time to add a new circuit, and then add a sub-panel and move a couple over.

 

[Charles (in GA)]

This is not relavent. The OP is talking about a SquareD QO panel. Totally different beast. I do not believe that tandem breakers were made by SquareD back when that panel was originally installed. They're a pretty new item, they -may- be fine to be used on an older panel. Do not exceed the maximum number of circuits allowed in that panel though.

OK, here is a Square D single pole (front), vs a Square D tandem (rear). Both are genuine Square D products.

Notice the humps behind the contact clip. This is designed to keep the tandem from seating if it is being installed in a place that is not designed for it. You could, of course, take a sander, rasp, etc, and remove the humps and fit it anywhere you wanted (though not legal or good practice). The humps keep the breaker from seating, thus the cover won't go on. The Siemens I show above works the same way, won't seat if not in the right place, and the cover won't go on.

Charles

 

[ishiboo]

OK, here is a Square D single pole (front), vs a Square D tandem (rear). Both are genuine Square D products.

Notice the humps behind the contact clip. This is designed to keep the tandem from seating if it is being installed in a place that is not designed for it. You could, of course, take a sander, rasp, etc, and remove the humps and fit it anywhere you wanted (though not legal or good practice). The humps keep the breaker from seating, thus the cover won't go on. The Siemens I show above works the same way, won't seat if not in the right place, and the cover won't go on.

Charles

There are two types of QO tandems though - circuit-limiting (CTL) and non-. The circuit-limiting ones have those humps, so you do not "overload" a panel or place them in spaces not designed to accommodate tandems. The non-CTL tandems do not have those humps, and can be installed in any QO panel/space.

It's not appropriate - they are designed for pre-CTL load centers, but they're safe to use and no sanding/etc. required.

 

[IONH]

Great info in this thread.