Older 1960's house.

The outside panel is a FPE Stab-Lok that needs upgraded.

Will be using this panel to upgrade it, which has a 125-amp main breaker:

The current box is directly to the left of the outside meter. The box currently has a 70-amp circuit that leads to a sub-panel (about 20 feet away), a 50-amp breaker for the oven, and two 20-amp 120v breakers. Grounding bar is outside but it is not bonded to copper plumbing.


  1. Any issues there or will that panel and hook-up be OK?
  2. The 70-amp breaker will be changed out for a 100-amp breaker (since the subpanel will be upgraded to 100 amp). Is #4 copper good to run between these?

Next, the inside panel also needs upgraded. It is only 70-amp and the house will get electric heat/HVAC system (has only had window units but has had forced gas air so the vents and closet are in place). So it will be upgraded to 100-amp.


  1. I'm sure that box is OK for the purpose?
  2. There is copper plumbing very close to this box. Is it safe to also provide bonding of the separate ground bar to the copper plumbing with the outside main panel ground bar connected to the ground rod in the ground?
  3. I'm seeing all kinds of conflicting info on this. I understand that the neutral and ground on the sub-panel should not be bonded / connected together correct? Some people say yes and others say no. Seen others actually connect a wire between the two, but that makes no sense to me.
  • You might want to break this up in to multiple posts. The site works best when each question only asks a single specific question.
    – Tester101
    Commented Apr 6, 2016 at 20:47
  • Question #2 (the first one) is a dupe. diy.stackexchange.com/questions/29057/… Commented Apr 6, 2016 at 21:10
  • After further investigating, it appears #2 copper is going to be what I use. It appears to be a bit more than needed, but I'd rather future-proof it. And finding #3 copper is more difficult it seems. I'm sure the panels are fine as well. That just leaves the second set of questions 2 and 3. Commented Apr 6, 2016 at 21:26
  • Yeah you only need #4 for a 100 amp service to a dwelling unit. That is why #3 is hard to find. And do NOT bond the ground and neutral at a sub-panel that is a code violation.
    – ArchonOSX
    Commented Apr 6, 2016 at 22:27
  • ArchonOSX - table 310-16 shows 4-4-4-6 is only good for up to 85 amps at 75. Would rather ensure to over-build than be under. Commented Apr 7, 2016 at 14:06

1 Answer 1


I'm fine with the idea of a main panel with only 2 things in it feeding a sub-panel with everything in it.

Question #1 - I'd rethink putting a service panel outdoors at all. Weather is rough on panels, even if they claim to be outdoor rated. I'm a little nervous about a 100A breaker supplied from the normal bus bars, but if the manufacturer stands behind it, okay. The 100A wires are going to be a mother to wrestle onto that 100A breaker. Are you quite sure the power company has provisioned you 125A service? 100A is more common.

Question #1 (the second): You're gonna want more slots than 24, since this box powers pretty much your whole house. Nobody ever installed an addition and went "Gosh, that job was sure made harder and more expensive by having too many slots in the panel". It's a false economy, especially since bigger boxes are often bundled with more breakers. Your house may be ok now, but do a kitchen remodel and lookout!

Question #2 (the second): Don't bond your grounds to random plumbing that happens to be going by. It's not code, and someday you might have a plumbing problem and the plumber replaces a downstream chunk of it with PVC. Whoops. Also, they've been upgrading customers to PLASTIC water meters. Double whoops. Bond properly and to code.

Question #3 (the third): Bond ground and neutral only in the (singular) main panel. As such, you need 4 wires between main and subpanel.

Just for your edification, it's only a sub-panel if it's fed from a main panel. If it's fed directly from a transformer, it's a main panel.

  • Good reply. The house already has an outside box with conduit and connections outside. So that is why it will be replaced. With regard to the 24-slot box, it will leave me with 8 extra slots upon based on what is in the current panel plus the new breakers for AC. Lastly, the cold water grounding is required in Florida. So the plan is to run a copper ground from the subpanel to the copper plumbing where it enters the house, which is in the utility room. Any objections to this? Commented Apr 6, 2016 at 21:36
  • Actually, if you have a metal water piping system entering the house it is required to be bonded to the grounding system within 5' of its entrance to the dwelling. Use a proper ground clamp and the proper sized bonding conductor.myounshould still have a grounding electrode and a grounding electrode conductor besides the water pipe.
    – ArchonOSX
    Commented Apr 6, 2016 at 22:25
  • In some areas, an outdoor disconnect is required (seismic, flood, etc. areas). In those places it's common to have panels outside.
    – Tester101
    Commented Apr 6, 2016 at 22:43

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