I have a Square D sub panel that appears to have room for additional breakers but the lugs in the panel do not extend down far enough. Can I buy longer lugs and replace the ones that are in there? There is a label that says the “Interior Cat. No.” is QON12L125, if that helps. The plastic back plane looks like it could accept longer lugs (I think that’s the name for the metal strips the breakers click into.) Any help would be greatly appreciated!
The panel is sized for a certain number of spots; the extra room is so you can wire things without the box getting cramped. The NEC dictates how many wires you can fit in a given volume of junction box (panels count as junction boxes.)
If you need more breakers, the proper thing to do is install a subpanel.
No. Panels are designed for a specific number of breaker spaces, and can’t be enlarged.
If you need to add more breakers, you can do 3 options:
- replace the whole panel with a larger one.
- add a subpanel (like freido said).
- replace some of the breakers in your panel with tandem/duplex breakers.
More information on tandem breakers:
Thank you everyone for your replies. I found a site that has “Replacement” busses but the cost is almost as much as a new box which I was trying to avoid. “Tandem” breakers are a Great idea! I had some of those in another house I owned but it wasn’t a Square D box and I couldn’t find any online because I was using the wrong term… I was looking for double breakers and got confused with micro breakers I found but as soon as I typed in “Tandem breakers” there they are! Thanks for all the help. This is a great forum.
I personally don’t like using tandem breakers. You have to be very careful when adding circuits in the panel, especially if you’re sharing neutrals and such. It’s complicated.
Also, most residential panels don’t have interchangeable guts. I’ve never seen one.
I wouldn’t recommend going that route even if it was available.
The NEC also has something to say about what you do in that panel. Some circuits need to be GFCI or Arcfault protected which would prevent you from using a tandem on that circuit. There are work-arounds, but I wouldn’t recommend performing any circuit manipulating in your panel without the guidance of an electrician. You could end up with an unbalanced neutral and a possible overload condition.
You might have more room in the panel than you realize, as far as consolidating existing circuits, but you wouldn’t know unless you took some readings and did some circuit tracing.
A sub-panel or panel replacement is the best way to go, unless you’re talking about a very basic circuit addition or modification.
I once installed a basement sub and fitted it with 4 tandems instead of 8 regular breakers. Dunno why, the aesthetics just pleased me, I guess. Inspector balked but ultimately signed off on the work. He never did explain why my set up gave him the grumbles. The only thing I can think of was that the 6 or so empty slots invited a future genius to wire in 12 more circuits on tandems which would potentially introduce too much of a load on the panel. Any non-hacks (for I am a hack) care to tell me if I’m thinking about that the right way?
The limit will be determined by the UL listing of the panel. Some smaller panels will say “12 space, 24 circuits” allowing for 12 tandem breakers. I think the upper max is 42 circuits. So a 30 space panel could only use 12 tandems and so forth. UL listing and Authority Having Jurisdiction come into play, as well as local and state laws.
That’s definitely a possible reason. I also don’t like tandem breakers because there is a good chance that they’ll lead to a panel being overcrowded. It’s a slippery-slope thing. There’s nothing wrong with adding one if your panel is full and you need just one more circuit. But then you may need another circuit, and another, oh and here comes your new central air system which requires a two-pole, and soon you’ve got a rat’s nest and a fire hazard on your hands where you could have just had a subpanel (or embiggened your main panel.)
And common sense. You can only load a feeder or Overcurrent Device to 80 percent of it’s listed rating, continuously. You’d be tripping breakers and burning up wires otherwise.
In such a situation it’s on future genius not to overload the panel. If it’s code compliant today then it passes inspection today. That said, some panel configurations come with buss designed to reject more than a certain number of tandem breakers. -
It’s my understanding that the panel board IS the mainbuss assembly. Typically sold preinstalled in an enclosure, with deadfront/trim sold separately quite often. Which means that panels with longer buss are sold in an equivalent enclosure size and; that deadfronts are sold to match more than one configuration.
OP the question you haven’t addressed is how much load there is going to be on sub panel. Do your existing devices use a lot of current? Are you adding devices that draw a lot of current?
A professional electrician probably wouldn’t have done it that way just because of cost: a tandem breaker costs more than twice as much as a standard one. So you can install 2 standard breakers cheaper than one tandem one.
I don’t know why this would bother an inspector, unless it’s just his electrician experience coming out.
Right, It’s not something that I have ever done. It has never occurred to me to “save spaces” for future work in this manner. We have other ways of providing for future expansion.
Interesting. I’m just a homeowner that can competently and safely manage household electrical stuff. Meaning, I get the stuff right the code covers, but where there is room for creativity I tend to use it. So, not wrong but sometimes a little “wtf?” I’m the guy that threads 12g on 15amp circuits just because I got annoyed with brittle 14g on one project house. Yeah, I know 12g is kind of a pain to work with but you pick your demons. I tend to care a lot less about cost than about durability and organization.
In this case, I believe I was annoyed about having to replace the old sub (which was old, discontinued, inadequate, and sloppy even to my amateur eyes). So I ran some new wire, tidied up the rest, and in my way was being considerate of the next guy by leaving room to thread wire and slots for additional breakers.
Understand perfectly. It just isn’t economical (to me or the customer) to always plan for the next guy. But if you have the time and means to do so there is nothing wrong with that.