New 30 space 40 Circuit load center question

[SuperRA]

Hello, i just bought a new Square D QO panel with 30 spaces / 40 circuits. So I understand that I can use 10 tandem breakers and 20 full size breakers to get 40 circuits in 30 spots. My question is what keeps someone from putting in 60 circuits? (Besides the inspector and code..) I don't see any physical means from keeping tandems out of certain spaces. Does this mean that I can install the tandem in any space and as long as I don't have more than 10 tandems (or 40 circuits) I'm ok?

Thanks.

 

[5mall5nail5]

The tandems are only allowed on spots that have provision for the stabs. You will see that there are only some tabs that have a different style tab position. There will be a chart on the box also that shows which positions can take a tandem. Technically you can use any old "replacement only" tandem and put 60 in the box, but no one will recommend that and it truly is a hazard as you could overheat the bus.

 

[SuperRA]

The tandems are only allowed on spots that have provision for the stabs. You will see that there are only some tabs that have a different style tab position. There will be a chart on the box also that shows which positions can take a tandem. Technically you can use any old "replacement only" tandem and put 60 in the box, but no one will recommend that and it truly is a hazard as you could overheat the bus.

Box model : QO13040L200GC

I see the provision on the breaker that would theoretically keep me from installing it in some places, but the bus bar still appears to allow them in any space. I've clicked it into 3 spots throughout the bus and it appeared to fit just fine in any space. (I didn't try all the spaces). There's a nub on the breaker that needs a indent in the bus to fit, but all the slots have the indent. The label also doesn't have a diagram saying which spots are for tandems. It only says 40 circuits max

Don't get me wrong, I don't want to put more than 40 circuits in. I just want to know if I can install them in any position if it doesn't physically prevent me from doing so. The circuits I want to put on the tandems are in random spots, and I only want to keep them in those spots to make the wiring as neat as possible (crossing as few wires as necessary).

 

[Charles (in GA)]

Square D QO is different. The stabs, due to their design are not any different, but the tandems have a hump on the BOTTOM of them, the spots where the tandems are allowed, have a corresponding recess for the hump.

Charles

Below, the bottom of a standard QO breaker on the left, a tandem on the right. Try to insert the tandem in a space where it is not permitted, it won't go.

If your tandems DO NOT have the humps on the bottom, you have the wrong tandems. There are some made without the humps, but are only approved for panels made before a certain date, about 1985 or so.

 

[SuperRA]

Square D QO is different. The stabs, due to their design are not any different, but the tandems have a hump on the BOTTOM of them, the spots where the tandems are allowed, have a corresponding recess for the hump.

Charles

Below, the bottom of a standard QO breaker on the left, a tandem on the right. Try to insert the tandem in a space where it is not permitted, it won't go.

If your tandems DO NOT have the humps on the bottom, you have the wrong tandems. There are some made without the humps, but are only approved for panels made before a certain date, about 1985 or so.

Yes, my tandem breakers have the humps, but what I'm saying is that every slot on the panel has the corresponding indentation. So I could install them in any position, or someone could theoretically install them in every position (not what I want to do)

 

[Charles (in GA)]

Have you tried? the panel should not accept them except in the places shown by the labeling on the panel.

Charles

 

[pattenp]

This has me curious because when a panel says 10 tandems then only 10 spaces should accept tandems.

Have you tried? the panel should not accept them except in the places shown by the labeling on the panel.

Charles

 

[SuperRA]

Ok, so I went and tried installation in all spaces. Here is the proof. The only slot a breaker didn't fit in was the top left but only because the plastic neutral shield was a bit sloppy. I don't think any breaker is going to fit in that slot as is..

Sorry, i forgot to rotate the images before uploading...

 

[pattenp]

Page 30 of this data sheet shows the bottom 10 spaces, 5 each side are for the tandems. Bottom row, fifth diagram

http://www.farnell.com/datasheets/1626663.pdf

 

[Charles (in GA)]

The panel has a place on the inside of the door for you to identify the breakers as to function. It has places to write in and is numbered something like this....

1.....2
3.....4
5.....6
7.....8
9.....10
11....12
13....14
15....16
17....18
19....20
21A...22A
21B...22B
23A...24A
23B...24B
25A...26A
25B...26B
27A...28A
27B...28B
29A...30A
29B...30B

The A and B should indicate the half width breakers and only be on the bottom five rows (ten breakers).

Charles

 

[Norcal]

The NON-CTL twin breakers are for 1968 and older loadcenters.

 

[SuperRA]

Ok, thank you for the responses. I take it they are trusting the customer to follow the instructions.

 

[SuperRA]

Ok, I'm finally getting ready to install this panel and I have a couple more questions.

The feed from the main circuit breaker comes in from a conduit on the back of the panel. The location of the conduit is not where one of the stock knockouts are located. Can I cut my own hole and mount the conduit in it?

Similar question. I'm having a hard time finding romex cable clamp connectors that say they are rated for at least 2 12-2 cables. With the number of wires I'm going to have exiting this box, I will run out of small knockouts. Can I drill more holes and use connector clamp if I can only run one wire per clamp?

 

[MrMark]

Lowes nm clamps are rated for 2 12-2. Home Depot Halex brand only 1. Most electrical supply places sell the clamps rated for 2 12-2.

 

[SuperRA]

Lowes nm clamps are rated for 2 12-2. Home Depot Halex brand only 1. Most electrical supply places sell the clamps rated for 2 12-2.

Hmm, the ones I have I bought at Lowes.. It says on the box "for two 14/2 or one 12/2 NM" They are the Pro Conex brand. I guess I'll have to look a little harder.

I did find a plastic clamp that was rated for two 12/2 cables, but I wanted to see if I could find the metal ones with screws first before giving in to those plastic ones.

 

[JoeFin]

I am thinking they have to limit the number of breakers to 42 - the maximum allowed by the NEC for a panel board

 

[jvitez]

In Canada there is no limit to the number of tandem breakers under the Canadian Electrical Code. So we can install a 40/80 panel and fill it with 40 tandem breakers.

Is your panel rated for Canadian installation? Perhaps Square D just labels the panel to meet NEC code but actually manufactures them for sale in the US and Canada, thereby allowing the installation of tandems in all slots?

 

[SuperRA]

Oh sorry, perhaps I should have started a different thread, but the tandem breaker question has been answered. While you can physically install tandems in all the slots, the manual and or label on the door shows where and how many you can have.

I am now asking if I can bore my own holes in the panel for the main entrance and for branch circuits in addition to the factory knockouts. This is because I am having a difficult time finding NM connectors that support two 12/2 cables.

 

[Norcal]

Oh sorry, perhaps I should have started a different thread, but the tandem breaker question has been answered. While you can physically install tandems in all the slots, the manual and or label on the door shows where and how many you can have.

I am now asking if I can bore my own holes in the panel for the main entrance and for branch circuits in addition to the factory knockouts. This is because I am having a difficult time finding NM connectors that support two 12/2 cables.

Done all the time, just be aware of wire bending space on larger cables.

IMO, the best way to punch out knockouts (KO's) is w/ a KO punch followed by a Unibit® (Stepped bit), then my least favorite way is a hole saw, they are a bit rough but quick. depending on where they are punched out you may have to use a reducing washer to cover the opening where the factory KO's fall out. Being able to punch out KO's where ever I chose is one reason I like panelboards over loadcenters, the box end panels are avail with or without KO's but their higher costs mean that it's pretty rare that they will be found in a residential application.

 

[SuperRA]

Done all the time, just be aware of wire bending space on larger cables.

IMO, the best way to punch out knockouts (KO's) is w/ a KO punch followed by a Unibit® (Stepped bit), then my least favorite way is a hole saw, they are a bit rough but quick. depending on where they are punched out you may have to use a reducing washer to cover the opening where the factory KO's fall out. Being able to punch out KO's where ever I chose is one reason I like panelboards over loadcenters, the box end panels are avail with or without KO's but their higher costs mean that it's pretty rare that they will be found in a residential application.

Thanks for the reply. I figured it should be ok, but i just wanted to ask and be sure. I'll definitely have to use a hole saw for the main entrance which is 1-1/2"-2". The others I can use a step drill. I think quality KO punches are going to cost alot or cheap ones like at harbor freight will probably break in the middle of the job. I'll definitely look a bit harder for the connectors that can handle two cables first.