Let me start off with the facts:

  1. I have 125 amp service that is fed via overhead lines to a center fed panel.
  2. I am maxed out on breakers, as every 110v breaker is now a tandem breaker.
  3. When other homes in my area have upgraded to 200 amp service, they did not replace the feed lines. They are rated for, at least, 200 amps already.
  4. My panel is exterior to the home.
  5. I need a 220v (20 amp) circuit and a 110v (15 amp) circuits run to my garage.
  6. Line slack is not a consideration here.

Now to my questions: Can I add a subpanel to my current panel? Or should I bite the bullet and upgrade the service to 200 amps? I can't really afford the full panel upgrade though.

I was thinking (as a layman) that I could remove one 220v (30 amp) breaker from the main panel and put in a 220v (60 amp) breaker to feed a subpanel. Then I could feed the stove (old 220v @ 30 amp) from the new subpanel, as well as the adding a new 220v @ 20 amp breaker for the new table saw. As well as add the 110v @ 15 amp circuit.

In my uneducated brain, this makes sense. But I feel like I am missing something here. Please help.

Panel

Panel Label

New contributor
Joshua is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct.
  • 1
    Hello, and welcome to Home Improvement. I'm not the person to answer, but I bet the make of your breaker panel, ideally with a picture of it with the cover off, would help one of our electrical pros help you. – Daniel Griscom Dec 6 at 3:27
  • 1
    Formatting in this system is sometimes a little wacky. But once you get used to it, it works pretty well. Don't worry about it - most (hopefully) format editing is well-intentioned. – manassehkatz Dec 6 at 3:38
  • 1
    What make and model is your main panel? Furthermore, can you post a clear photo of it? – ThreePhaseEel Dec 6 at 4:13
  • 1
    Furthermore, since your panel is a center-fed unit, may I ask if it is a meter main that has the main panel and the meter socket in the same box? – ThreePhaseEel Dec 6 at 4:15
  • 1
    How many square feet is your house? – ThreePhaseEel Dec 6 at 4:45

One of the pros will give a long detailed answer, I'm sure.

But the short answer (from reading all their long detailed answers over many months) is that provided the existing panel is in decent shape, you can replace an existing double-pole breaker with a bigger breaker for a subpanel and use that subpanel to power several circuits, as you described.

However, you should put in a really big panel - i.e., big enough that it can eventually be your new main panel. A big (like 42 space) panel might cost you an extra $100 or $150 now compared to a small panel, but will allow you to gradually move circuits over time. Moving all those circuits is the big cost, particularly if you use the opportunity to add GFCI and/or AFCI as appropriate. But this way you don't have to spend it all at once. Then once you have everything moved you make the subpanel into your main panel, add a neutral-ground bond, and get rid of the old main panel.

Since you said "I am maxed out on breakers, as every 110v breaker is now a tandem breaker.", there is no way you can add GFCI or AFCI breakers right now. While you can add GFCI at the first receptacle in each chain and get full protection, and you can add AFCI in a separate box, it is a lot easier to put in breakers. Code generally allows you to keep the old stuff as-is, but for safety's sake, as well as if you do other upgrades (e.g., bathroom or kitchen remodel), you may want and/or need to make those upgrades at some time. With a new larger (sub)panel, you can do that easily. If the existing cables won't quite reach, you can splice them inside the existing panel, with that panel eventually becoming a large junction box when the the subpanel becomes your main panel.

  • 1
    I had not really considered future needs. Thank you. – Joshua Dec 6 at 3:48
  • Your key sentence is I am maxed out on breakers, as every 110v breaker is now a tandem breaker. I'll add more about that. – manassehkatz Dec 6 at 3:50

"Rule of Six" panel with some defects

There's a rule that you have to be able to cut power to a building with six breaker throws. Houses had been single main breaker, but breakers larger than 60A were prohibitively priced. So builders proposed this type of panel, with up to six of the cheaper <=60A breakers, which together are the "main breaker", rule of six. Your panel is a cheapie and only has four. (In some configurations it has five, as indicated by the label, that's why the "service disconnect" sticker is so tall). Fortunately your panel is also Murray, which is quality. I hope the builder really enjoyed the frappucino he financed by sticking you with a small panel.

The lower left of the "main disconnect" area has a 60A breaker. That powers the rest of the panel. That's right, the lower area, spaces 7-20, is already a subpanel. Too much load in that "subpanel area" will trip the 60A breaker.

Your main-breaker area is correctly configured. Your subpanel area has some defects.

  • alien breakers that misfit the busses. Only the colored Murray breakers are correct; those black Cutler Hammer/Eaton BRs do not belong in this panel, are hazardous and should be replaced with Siemens/Murray, just like the panel instructions say. Total waste, the correct ones cost the same. Not even a frappucino here.
  • double-stuff breakers in spaces 15 and 16 (upper right quadrant of subpanel area), that is not allowed per the panel diagram. Only full size breakers can go there, e.g. Move the big 2-pole up while changing it to Siemens.

Expect about a $35 bill on the correct breakers.

A subpanel is a grand idea

However you will want to power it out of the "main" area of the Rule of Six" (Four), as you have planned. I am not thrilled with the oven coming out of one panel and the range from the other, though. And this is a time to think about upgrades.

First, as you discussed, a service upgrade. You could plan for the subpanel to become the new main panel, perhaps indoors where it won't be insulted by painting contractors. It should be a 200A main breaker panel, and be positioned so running fat conduit to it from the meter will be easy.

Another thing to think about is generator. If you have aspirations for a generator, solar/battery system etc. it's time to look forward and see how to lay out subpanels for this, so you're not reduced to using one of those lousy "8-circuit changeover switch deals" that cost $350. It's really not far out of your way if you put your thinking cap on now.

I also trust you've heard the "Get a really big panel. No, Really big..." conversation, 42 space is literally not too much for a properly provisioned house. It's a few frappucino's today, but gives you liberty to do what you want. More kitchen circuits, done. Plug-in hybrid, easy. Hot tub, sure. Etc. There's no reason to be limited by your panel.

Lastly, tell you a secret. Your service drop is not 200A. Neither are your neighbors'. The power company didn't upgrade those. Huh!? The power company knows what drop you have, and what your electric bill is. (Also: smart meter). When they see you actually pulling more than the drop can handle, they'll come replace it.

  • Thank you for this information. Moving the panel inside the garage has been a reoccurring thought of mine. It sure would make my future shop upgrades that much easier. I am perhaps misunderstanding your last statement though. I live in AZ. My neighborhood has APS as their power company. When a panel upgrade is done, in this neighborhood, a permit is granted and a date is set for APS to come out and disconnect the feeder lines. Then the work is done on the panel and the City inspector comes out (usually same day) and does his job. If he passes the upgrade... – Joshua Dec 6 at 21:18
  • APS then comes and does their own inspection before hooking back up the feeder lines. If the feeder lines were not rated for 200 amp service, they would not reconnect the feeder lines. I know most everywhere else seems to not involve the power company (so it seems) and do the upgrade with live wires. We don't do that here. – Joshua Dec 6 at 21:20
  • @Joshua I am referring to the service drop, the overhead line from their pole to your weatherhead. That is their responsibility and they typically do not replace it unless they have to. They disconnect it up at the pole, if you need to replace your meter / vertical line from the weatherhead to the meter. – Harper Dec 6 at 22:06
  • Thank you for the clarification. I was unaware that they would use two different gauges of wire. Since my house was built in the 60's the standoff does not meet current minimum requirements (18 inches in my case). So doing a panel upgrade would seemingly always necessitate those lines being replaced. If for no other reason than the length of the run being extended. Thanks again. – Joshua Dec 7 at 1:58
  • Thats good news, though. It means you can fit the subpanel at your choice of location, you are no longer married to the location of the current service drop. Then later when you're ready to do 200A service, you can fit new meter pan, new pole and weatherhead, and "flip it" - make the sub the main, old main now the sub, whilst they move the service drop to the new weatherhead. Very low downtime. – Harper Dec 7 at 4:02

If your panel is full of double breakers and you Now want to change a 30 amp breaker to a 60 amp and feed another breaker how are we to know ? You have a 125 amp service so what is your actual load? With gas appliances I have seen 3000sq ft homes in my area have plenty of power with a 100 amp service , but a few miles away no gas all electric the owner wanted on demand electric water heater upgrades his service to 400 amp very well insulated home, still not enough for what he wanted. More info is needed but I would say you need a larger service.

  • I just added a picture. I do not know the proper way to calculate the total load. I assume it is more complicated than adding all the breaker amp values together. – Joshua Dec 6 at 4:47
  • 1
    We need the size of the home and the size and type of electric appliances is the furnace gas I don't see a large breaker for heat. The 30 amp in the bottom right is that a dryer or water heater? With these values we can provide a minimum size required to meet your needs. Figuring the load size is not adding all the breakers but if you did you would end up with a larger size than you have, for example the entire bottom section is less than 60 amps it is being fed by the 60 kind of like a sub in itself. So you would have to move the stove, oven or AC breaker to make a sub. – Ed Beal Dec 6 at 14:16
  • Thank you. I have answered many of these questions, as well as providing more detailed information in the comments above. Due to character restrictions, please allow me to point you to those comments rather than retyping them. The A/C is a rooftop package unit that has electric heating built in. The furnace was removed years ago. Thanks. – Joshua Dec 6 at 14:33

Your Answer

Joshua is a new contributor. Be nice, and check out our Code of Conduct.

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.