Just bought a new house, first time homeowner. Familiar with electric (studied electrical/computer engineering) which helps but doesn't directly translate to AC stuff. Currently making plans for redoing things and wanted to get another set of eyes on it. I want to be clear that I am not an electrician, but I DO want to do the work myself (learning is half the fun) and I want to go above and beyond code to make inspection and future work easy.
The home was built in '51, and the electric that was in place when we were negotiating the purchase was fused. Part of the purchase agreement had the sellers getting electric re-done with breakers. The breaker box itself looks fine – 100A service, and 14 circuits. That said, the work that was done seems lazy to me: a lot of the original wiring was left in place – and it was only 2-prong stuff, no ground, so I'm not sure if that's even kosher/grandfathered given the panel upgrade – and the labeling is really vauge: 3 separate 15A breakers in a row labeled "lights" while outlets, water heater, and furnace aren't listed anywhere.
Fortunately the basement and attic are open, which should make running new lines pretty straightforward. My tentative plan is something like this:
- Flip the main 100A service breaker off to cut power to the house.
- Pull all 2-prong-only wires
- Reposition good lines (line out to A/C seems good, but I'll try to group it in the MSP in a more logical place next to utilities – line to the range seems good but we're remodeling the kitchen and moving the range to the other side, so I need to relocate the outlet)
- Rip out all non-3-prong outlets, including one placed confusingly between the shower and toilet near the ground
- Install old work boxes for new switches
- Place 3-prong outlets into original work boxes if they're in good shape, otherwise place old work boxes
- Add ceiling light fixtures/fans to each room (there are 2 total ceiling light fixtures anywhere in the building)
- Add dedicated circuits for each garbage disposal, refrigerator, and to-be-installed dishwasher
- Run all necessary new wiring (mostly outlets and lights)
- Flip off all breakers
- Flip on main 100A breaker
- Flip on breakers 1 at a time checking for problems
I've also been planning out what circuits will go to what regions of the house, and derated rather generously, but I'm not sure what qualifies as a "circuit" – for example, I currently have 2 breaker slots occupied for a 30A breaker going to the range: is this 1 circuit or 2? In the text below, I'm calling it 2 – but for permitting if that's only 1 that's great. Unless specifically noted, these are 15A 120V breakers.
Living Room: 1 circuit: 5 ceiling light fixtures, half a dozen outlets, entry way and porch lights.
Garage: 3 circuits: (2) for 240V socket for future EV charger, (1) 20A for lights, garage door opener, and outlets (particularly for
tools which might need higher current)Dining Room/Kitchen: 6 circuits: (1) for lights + outlets (GFCI in kitchen), (1) for Fridge, (2) at 240V for range, (1) for dishwasher,
(1) for garbage disposal.Bathroom/Hall: 1 circuit: GFCI outlets in bathroom, lights in bathroom/hall, hall outlets, bathroom fan
Primary Bedroom: 1 circuit, 20A as a future-proof because I have a lot of electronics: lights/ceiling fan, closet lights, outlets
Secondary Bedroom: 1 circuit: lights, ceiling fan, outlets
Downstairs landing area: 5 circuits: (1) for washer, lights, outlets, and downstairs backdoor light – think I might need to do a
dedicated circuit for washer, unsure (2) at 240V for dryer, (2) at
240V for A/C which is physically close to this area in the basementUtility Room: 1 circuit: light, outlets, furnace (natural gas), water heater (natural gas), possibly future on-demand water heater
(also natural gas).Guest Room/Bathroom: 1 circuit: lights/outlets/ceiling fan/closet lights, GFCI outlets in bathroom, bathroom lights, bathroom fan
Theatre Room: 1 circuit: lights, outlets (TV/sound system will be on outlets here)
Primary Downstairs Bedroom: 1 circuit, 20A for future-proofing: lights/ceiling fan, outlets, closet lights, bathroom outlets (GFCI),
bathroom lights, bathroom fan
I count a total of 22 – or 23 if the washer needs a dedicated circuit – circuits, assuming that the double-wide breakers count as 2 circuits.
Is anything obviously amiss with my plans?
Any tips that will help make this a smoother process – particularly inspection?
Any problem with nearly filling the 24 breaker slots on my MSP?
Will I need to upgrade service to >100A?
Best Answer
Please - get a book, better several books on home electrical and read them through and through. Do not attempt to plink the knowledge with Google... Google only answers questions, it does not tell you which questions to ask.
Past electronics skills do not prepare you for mains electrical, which is all about mechanical execution of work and has no EE at all. It is also wired as an isolated system with each circuit having a neutral that serves only it. Very important, that.
Asking the seller to do it means you got the cheapest possible execution. One generally prefers a 40-space panel for a whole house - spaces are cheap (up to 40, at least).
Doing a panel upgrade does not break the grandfathering on the other old work. (old Zinsco and Federal Pacific panels are actively dangerous, as are classic Rule of Six panels, and both should be replaced with all due haste, so they make panel replacements as low-friction as possible).
Here is a great video talking about America's split-phase power system. Note the weird breakers and the way the panel is interleaved. The important thing is your 240V loads take 2 breaker spaces.
Do not install two 240V circuits for EV charging. Multiple-EV charging should be done using Power Sharing, where the two EVSEs (wall charge units) automatically coordinate to use a single current allocation best. This is live, in-production tech right now, sold on a variety of units e.g. Clipper Creek... and Tesla gen 2 and gen 3 units, including the one with a J1772 port, so it's available in mixed homes.
EVs only need 2 wire + ground, no need for neutral. However, the free EV "travel unit" has a NEMA 14-50 RV socket specifically so you can charge at RV parks while traveling, as a last ditch option... misunderstanding this, many lemmings will tell you that you need a 14-50 socket to charge at home. This advice is several kinds of wrong. But if you do fit a 14-30 or 14-50, it needs a neutral because it's a socket.
Garages also require one 20A dedicated receptacle circuit, for ironically EV charging. I will argue this is dumb if installing a dedicated 240V EV circuit.
When you do this kind of rewire, you must bring it up to current codes. Kitchens require at least two 20A circuits dedicated to general-purpose (e.g. countertop) receptacles. As a practical thing, most kitchen plug-in heat appliances are 1500W (12.5A) so only 1 per circuit at a time. The dedicated fridge circuit is not required (it's a small load) but it is wise, so a trip from other appliances doesn't knock out the fridge.
Don't get tidally locked to the concept of "1 circuit per room". This is somewhat dumb, and wastes wire. Outside of kitchen and bathroom, you are welcome to mix-and-match other rooms as you see fit. One way I think is economical is "1 circuit per wall" (within reason). That keeps run lengths short (no circumnavigating rooms, lines passing each other in shared walls). It also gives each room access to 2-4 circuits, so that when you have a home office or craft room that needs a lot of power, you can find it.
Laundry and garage each require 1 dedicated 20A circuit. However (unlike kitchen and bathroom) they are welcome to have any other circuits also serve receptacles there.