QO Breakers

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I'm looking at doing some upgrading / replacement of breakers to coincide with a room addition I'm doing in my house. I have a QO-16M T3 series combination service panel made by SquareD. It is currently filled to capacity with single breakers (and one tandem).

My questions are as follows:
1)Why can I not find any tandem breakers where the toggles are one on each end of the breaker? (The one that's in the panel is like this. All others that I can find are side by side mini-toggles). While I don't mind even changing out the tandem that's there if it was due to a design flaw/etc, I would like to know why they don't seem to be used.

My second question pertains to the type of tandem break I should be using. A look at Home Depot, Grainger's, or even the SquareD catalog turns up the following. Two types of breaker, absolutely identical in specification, only different in price. The QOT1515 is $38.60. The QO1515 (with a side note of: "For Use in Old Style Non-Class CTL QO Load Centers") is $48.50. A message off to Grainger's doesn't give me any useful information. Which tandem breakers should I be using?

Cheers
 

tom baker

First Chief Moderator
Staff member
Use the type listed on the panel instructions. If it does not list tandem breakers than they can't be used. The CTL type limit the number of breakers that can be installed.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
AltonToth said:
1)Why can I not find any tandem breakers where the toggles are one on each end of the breaker? (The one that's in the panel is like this. All others that I can find are side by side mini-toggles). While I don't mind even changing out the tandem that's there if it was due to a design flaw/etc, I would like to know why they don't seem to be used.
It's just a design change. I've seen older tandem QO's that have stab-in terminals. You're not missing anything by using newer-style ones.

A look at Home Depot . . . turns up the following. Two types of breaker, absolutely identical in specification, only different in price. The QOT1515 is $38.60. The QO1515 (with a side note of: "For Use in Old Style Non-Class CTL QO Load Centers") is $48.50.
That's interesting. My freshly-updated HD-Pro tell me that they're $16.24 and $32.49, respectively.

How old is that panel, before or after 1967?
 
Apologies. The prices were quoted from the Grainger's catalog. I'm probably going to go through EB Horsman or EECOL or a similar wholesaler for them (can get discounts through my work). This house is about 38 or 39 years old. I'm not sure if the panel would have been replaced/updated in that time, but based on the fact that it's in a little built out cubby in the corner of the living room (with an access hatch that, when you open, you're looking at studs and water pipes) in the basement suite...I'm going to assume it's original, and (I guess), JUST after 1967.

Edit: Being an older house, and likewise, an older panel....very little in the way of labels, and NO paperwork available. I can't even find this panel on the web (as I have a number for it). Unfortunately, the label on the tandem breaker is also not intact, so I can't get any info from it.
 
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dezwitinc

Senior Member
Location
Delray Beach, FL
Beware of generic breakers.
I ran into some FPE stablocks the other day that were made in China.
When I questioned the supplier, he could not come up with a UL listing for them.
Would you want to install these?
 

jim dungar

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Location
Wisconsin
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PE (Retired) - Power Systems
AltonToth said:
I'm looking at doing some upgrading / replacement of breakers to coincide with a room addition I'm doing in my house. I have a QO-16M T3 series combination service panel made by SquareD. It is currently filled to capacity with single breakers (and one tandem).

A Square D QO16M panel is not rated for use with any style tandem breaker. The wiring diagram on the panel cover and inside of the panel box will confirm this. A "sub" panel is the only proper way to add circuits to this service.

QOTxxxx breakers are the only breakers that should be used in panels listed by UL as CTL. QOxxxx breakers shiould only be used in panels UL listed for use with tandem breakers prior to the adoption of the CTL rating (early 70s?).
 

Rampage_Rick

Senior Member
AltonToth said:
Why can I not find any tandem breakers where the toggles are one on each end of the breaker?
If I were to conjure a guess, it would have to relate to handle ties. It would be an interesting conflagration to behold in the event of a MWBC, that's for sure.

As an aside, SqD sure charges through the nose for the little QOT 'ties'
 

480sparky

Senior Member
Location
Iowegia
dezwitinc said:
Beware of generic breakers.
I ran into some FPE stablocks the other day that were made in China.
When I questioned the supplier, he could not come up with a UL listing for them.
Would you want to install these?

Did you get a lead-test kit for those? :grin:
 

davedottcom

Senior Member
Rampage_Rick said:
If I were to conjure a guess, it would have to relate to handle ties. It would be an interesting conflagration to behold in the event of a MWBC, that's for sure.

That wouldn't matter since you can't use both tandem terminals for a MWBC anyway.
(They are both from the same phase)

The opposite would be possible though. You could place 2 "Old style" tandems side by side and with "old-style" tie-bars making them into (2) 2-pole breakers.

But, if the panel isn't listed for tandems to begin with, it's a no-no.
 
As I've mentioned, the labels on the inside of the panel are no longer there. The only thing I had been able to make out was the model number of the panel. If there's something maybe behind all the breakers, I don't know, and I'm not ready to pull all the breakers on an off-hand chance. As a side note, Jim, I don't doubt your say on the matter, but do you have a reference point for that claim that I can check out?

And now I'm going to go and show off the apprentice-aspect of myself....what is it that makes a panel rated or not rated for tandem breakers? Not just some ULC numbers, etc, but physically, mechanically? I'm just slightly ticked that the previous electrician put in a tandem, and now I've got to compensate for that and fix it.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
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PE (Retired) - Power Systems
AltonToth said:
As I've mentioned, the labels on the inside of the panel are no longer there. The only thing I had been able to make out was the model number of the panel. If there's something maybe behind all the breakers, I don't know, and I'm not ready to pull all the breakers on an off-hand chance. As a side note, Jim, I don't doubt your say on the matter, but do you have a reference point for that claim that I can check out?

Look in any Square D Digest, go to www.squared.com and try their FAQ.

A Square D loadcenter that accepts tandem breakers has always had a two part part number while a loadcenter with only a single number accepts only standard breakers. Your panel would need a number like QO16-24 to accept tandems (the current generation of single phase loadcenters begins with QO1 and no longer contain a dash).
 
Thanks jim. scoped that out, and based off everything that they've said, this is completely the case. Now, I'm not about to go and do something dangerous like put more in, but for informational purposes....the existing tandem is in the 4th row of the panel. Has this breaker been modified, or are they generic in seating, and they just rely on people's 'good faith' to not install them/ install them into different positions than recommended? Perhaps I'm getting too deep into a simple situation? (And the situation simply being can't do it. haha)
 

Rampage_Rick

Senior Member
davedottcom said:
That wouldn't matter since you can't use both tandem terminals for a MWBC anyway.
(They are both from the same phase)

The opposite would be possible though. You could place 2 "Old style" tandems side by side and with "old-style" tie-bars making them into (2) 2-pole breakers.

But, if the panel isn't listed for tandems to begin with, it's a no-no.
That's kind of my point, although somewhat backwards.

With a pair of QOTs you'd have terminals A B C D. A&B one one phase, C&D on the other. You can use a QOTHT to tie B&C together, and you can be quite creative in the combinations. (like QOT1520 + QOT2015 + QOT1530 with ties on the 20s or 15s; that's why they make them with left and right configurations)

Funny, the ones I get are metal...
TNAIL-1D339.JPG


I think I've seen the old-school QO tandem once, many years ago. I'm not certain of the load-side terminal configuration, but from what I remember they were a pain in the but to connect the deeper terminal. The terminals on a pair of breakers would be arranged like so:
A C
B D


Now, assuming one tied the handles closest to the bus, which terminals would you connect to? I'm not saying that it's not difficult to figure out, just that it creates opportunity for mistakes. I know that it would be A&C, but what if someone assumes B&D? The same could be said for a tandem with different ratings. Someone could accidentally transpose the 15A and 30A circuits. As I recall the wiring markings are only on the side, not on the face, which could lead to possible confusion during installation. The QOT can be easily understood as it's terminal layout is 2-dimensional and easily correlates to the handle locations. Flipping them with gloves on, that's another story. ;)

QO1515.jpg
QOT1515.jpg


No argument about using tandems in panels not listed for such use, though SqD seems to be doing something about it themselves:
173060102.jpg
 

Bob NH

Senior Member
I have some QO-T2020 from about 1965 that have identical connection to the bus as a current single-pole breaker. Therefore, they can be physically installed anywhere a standard QO breaker can be installed.

There are holes in the handles that can accommodate handle ties; either the Square D model, or a clipped-off nail, or a piece of solid copper wire. Therefore, they could be used for 240 Volt or MWBCs.

They have stab connections; probably because of the lack of space to put two screw terminals.

The internal connection is that the handle closest to the bus connection goes to the connection that is nearest the front of the panel. The circuit diagram is molded into one side of the case.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
The QOTxxxx breaker has the rejection feature per UL CTL requirements. This design came out in the early to mid 60's.

The QOxxxx breaker does not have the rejection feature and should really only be used for replacement purposes in loadcenters designed for tandems and built prior to the CTL requirements. Use of the QOxxxx breakers in newer non-CTL panels is "cheating".
 
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