Square D panel question

[480sparky]

18 of 24, that leaves 6 with main breakers that are listed for tandems.

I guess I mistyped. That's my point, however. It doesn't matter whether the panel has a main or not. It's whether it's listed by Square D to accept tandems.

What happens to a main-breaker panel if you remove the main and install lugs? Does it somehow accept or not accept tandems then?

 

[benaround]

Whatever !!!!

 

[Smart $]

At the moment I have no photo , I will try to get one tomorrow,but just to be clear -this is a square D panel not QO , it is a homeline. Again I will read the label tomorrow .
I really appreciate everyones help, but now I am a bit confused about which one will , or will not be ok to use a tandem breaker ?
I'm not sure how we got to talking about QO I never said it was a QO.Ahhh yes I did say QO (Sorry that was a mistake ) It is a homeline.

FWIW, QO is also a Square D product line.

The label on the cover may not give you/us the info needed. What we actually need is the Panelboard Catalog Number, usually on a sticker on the interior of the enclosure. The cover label may give you the maximum number of circuits but doesn't necessarily tell you how many spaces, or what spaces accept tandem breakers.

The Catalog Number starts with HOM folowed by 2, 3, or 4 number segment before another letter (M-main breaker, L-main lug, or U- universal mains). The number segment indicates the number of space/circuits. For example 8 would indicate an 8 space, 8 circuit panel... whereas 816 would indicate an 8 space, 16 circuit panel where all 8 spaces will accept tandem breakers. A 2030 panel has 20 spaces, 10 of which will accept tandems for a total of 30 circuits, and so forth...

For panelboards which not all spaces accept tandems, one has to refer to the wiring diagram to determine which will accept tandems. Usually the spaces which accept tandem's are the bottom-most spaces.

 

[dcspector]

FWIW, QO is also a Square D product line.

The label on the cover may not give you/us the info needed. What we actually need is the Panelboard Catalog Number, usually on a sticker on the interior of the enclosure. The cover label may give you the maximum number of circuits but doesn't necessarily tell you how many spaces, or what spaces accept tandem breakers.

The Catalog Number starts with HOM folowed by 2, 3, or 4 number segment before another letter (M-main breaker, L-main lug, or U- universal mains). The number segment indicates the number of space/circuits. For example 8 would indicate an 8 space, 8 circuit panel... whereas 816 would indicate an 8 space, 16 circuit panel where all 8 spaces will accept tandem breakers. A 2030 panel has 20 spaces, 10 of which will accept tandems for a total of 30 circuits, and so forth...

For panelboards which not all spaces accept tandems, one has to refer to the wiring diagram to determine which will accept tandems. Usually the spaces which accept tandem's are the bottom-most spaces.

Good post.

 

[jim dungar]

What happens to a main-breaker panel if you remove the main and install lugs? Does it somehow accept or not accept tandems then?

No, it does not.

Tandems may only be udes in panels that have been listed with them.

I was trying to provide a quick method for determining the possibility of using tandem breakers. My point was that with Square D QO panels, you only have a 33% chance that a main breaker panel is listed to accept tandem breakers. For Homeline panels it is a little better than 50% odds.

To add to Smart's answer. Square D uses the same cover for several different 'size' panels. But, the cover will always have a directory that shows which breaker locations will accept tandems. You simply ignore the breaker spaces that do not exist in your specific panel.

 

[brantmacga]

What happens to a main-breaker panel if you remove the main and install lugs? Does it somehow accept or not accept tandems then?

The buss-bar in the slots that accept tandems for homelines is physically different; it looks like a two-pronged fork instead of the normal flat bar going across.


in a QO, there is a slot in the rail to accept the hook coming off tandem QO breakers. You can place a non-CTL QO tandem at any point in a QO panel, but they are twice the cost of the CTL version.

 

[jim dungar]

You can place a non-CTL QO tandem at any point in a QO panel, but they are twice the cost of the CTL version.

While the non-CTL breaker physically fits any where, it it only supposed to be used in those specific panels/locations identified as accepting tandem breakers. It is listed as being for use in OLD-STYLE non-CTL panels. Old-style means prior to at least 1967.

And, yes these breakers are often (usually?) mis-applied.

 

[brantmacga]

While the non-CTL breaker physically fits any where, it it only supposed to be used in those specific panels/locations identified as accepting tandem breakers. It is listed as being for use in OLD-STYLE non-CTL panels. Old-style means prior to at least 1967.

And, yes these breakers are often (usually?) mis-applied.

I didn't mean to say you can "legally" place them at any position. :smile:

 

[Roach]

Ok fella's as it turns out it is in fact a QO panel , and they are all on the B phase there was actually a piece of paper folded up lying inside the panel that said (CAUTION B Phase wired for 240v ) Seems pretty stupid to leave a note instead of writing it on the panel cover , but it is written clearly on the panel now I made sure to do that.
However, as it turns out there were 4 breakers installed in the panel but never used for anything anyway , I should have looked closer I would have seen that huh!.
No tandems will be needed but I will bring you the panels part number because I am very curious now ,how to resolve this tandem question in the future.
I apologize for taking everyone the long way around,I came here to get answers and I should have been more prepared with exact information.
Thanks again and I should have the part number and the pics tomorrow.
Anyone know where I can get a reference manual for various panels that will provide info such as this in the future?
Like I said I'm still learning but I really do appreciate everyones help.



Thanks Rich

 

[Smart $]

Ok fella's as it turns out it is in fact a QO panel , and they are all on the B phase there was actually a piece of paper folded up lying inside the panel that said (CAUTION B Phase wired for 240v )...

Hmmm...

Sounds like it may be fed by a 240/120 3? 4W system, otherwise known as a high-leg delta service, where A and C phases to ground are 120V nominal, and B Line to Neutral/Ground is 208V. Generallly the B phase is not used for line to neutral loads. That's why all the empty spaces are on B phase.

 

[Sierrasparky]

HUMMM is it really a QO. Is is 3 phase ..........

I'd be carefull in the future Roach. Plugging in a 120v circuit into the High leg can cause a big sizzle and cost you lots of cash. When working on commercial panels always make sure you check the voltage. Some Electricians don't mark thier work.

I have seen copiers and coffee machines sizzle to death in a instant.
Your hard earned money up in smoke.Plus the embarrasement of the mistake.

Good luck
Sparky

 

[jim dungar]

Square D makes both 3-phase QO loadcenters and NQO, NQOD, and NQ panelbaords that accept QO breakers. Square D does not list any 3-phase panel for use with tandem breakers.

 

[Roach]

Yes ,I read that here as well ,it is a QO and it says
"Caution Red Leg B phase 240V " however since I found this written on a paper lying inside the panel ,I am concerned that there may be slots that are not marked with that red tape or possibly don't have that blocker type tab installed.
I guess I really need to know the best way to determine which of the slots I can use for 120V
Is it true that the breakers numbered 1 , 3 , 5 ,7 ,9 etc are 120V
And the even numbered breakers are 240V ?

Obviously I will not use any that have that little tab thing with the red tape on it,because you can't put a breaker in those slots without removing those ,so I will not even attempt that.
Now there are 4 breakers in the panel that have nothing connected to them at all, (all 20amp single pole breakers) I am concerned that if I use them , could they possibly be installed on that 240V since I did not install this panel.
What I mean to say is how can I test these to be sure they are providing the proper 120V , at this point the breakers are in the off position and so far I an reluctant to connect them to anything.

 

[jim dungar]

Measure the nominal voltage Line-Neutral.
120V is good to go.
208V means you are on the wild/high leg.

Straight 2-wire 240V loads can be connected to the wild leg

 

[Sierrasparky]

Is it true that some of the old meters do not measure the High leg?
I had heard that if you connected a 208 load to nuetral and the High leg the POCO would not measure.

I know this would be unsafe as the nuetral is not sized for this nor is it this acceptable.

just one of those tales I heard.

 

[Smart $]

...Is it true that the breakers numbered 1 , 3 , 5 ,7 ,9 etc are 120V
And the even numbered breakers are 240V ?

...

Depends on how the breaker/space numbers are arranged. Some have left side numbered 1,3,5,7,9,... and others 1,2,3,4,5,..., and it also depends on whether it is a top fed or bottom main panel. It's pretty easy to figure out. A and C phase will measure 120V to ground while B phase will measure approximately 208V to ground.

 

[Sierrasparky]

Depends on how the breaker/space numbers are arranged. Some have left side numbered 1,3,5,7,9,... and others 1,2,3,4,5,..., and it also depends on whether it is a top fed or bottom main panel. It's pretty easy to figure out. A and C phase will measure 120V to ground while B phase will measure approximately 208V to ground.

Always check with a volt meter.

 

[jim dungar]

Is it true that some of the old meters do not measure the High leg?
I had heard that if you connected a 208 load to nuetral and the High leg the POCO would not measure.

Definitely not true.

 

[Smart $]

Always check with a volt meter.

I suppose the phrase "measure ___V to ground" could be taken to mean using something other than a volt meter, but for the life of me, I haven't a clue as to what else one might use

 

[Roach]

Thanks again guys , I will use my voltmeter to test each breaker tomorrow, my concern now is to mark this panel properly so that this won't happen to the next guy or possibly get someone hurt .
And by the way , When I got involved with this job the owner told me (after the fact of course ) that one of his guys was installing several flourescent shop lights and when he energized the circuit all 6 lights fried. I figured there had to be a good reason for that ! It is in fact fed from the top but piped in from the bottom , (the Main is on top).
I can't imagine why anyone would leave this in such a state of confusion but I will be sure to get it marked clearly to define which is 120V and which are 240
It just seems like the right thing to do.


Thanks so much for all of your knowledge and eagerness to help!

PS: I have'nt forgotten the pictures to post , I just can't seem to get to it yet, but I will post them because they may be helpful for some other poor guy who gets surprised the way I did.