Kitchen Sub Panel Pt.1

The modern kitchen usually needs an electrical sub-panel because nearly everything in the kitchen needs its own circuit. Basically the best rule of thumb is if there's power going to something, it needs a circuit.

How many circuits could this small, galley kitchen really need? I'm keeping the cabinets and layout for now because a kitchen remodel for the house will involve pushing out a wall that will probably need to be cantilevered etc. etc.... expensive.

I started marking out the circuits of this basic kitchen: 

The C outs 1&2 is for counter outlets. You need two circuits. I have two outlets on one side and one on the other. That's 2 20A circuits for 3 outlets. It's much more than adequate but that's code. 

This is a silly amount of circuits. A regular 20 amp outlet circuit is good for like 20 outlets that could have high draw things like electric space heaters. Why would you need a circuit for an outlet for the gas range? Most gas ranges only use the outlet for the clock or light (old school) or igniter which are WAY below the 20 amps afforded by the wiring and breaker.

One reason is cosmetic - the click of the igniter could make overhead lights flicker. Besides that, I'm not sure since you don't need to turn off the circuit to unplug a gas range, which would be another reason to have a breaker for something, so you could shut off power to change out the appliance. Just in case you need to move the outlet every time you change ranges? I don't know...

Anyway, I started making note of all the circuits and getting ready to put in the sub panel. 

Above you can see an 8 slot, 125A sub panel that will be sufficient for the current kitchen and future kitchen. The conduit formerly called BX now MC, is to protect the cable when it is exposed like under the house where it will be running. I used 3/4" for 4/3 copper because that's all they had but I recommend 1" conduit (also called FLEX). 

27' of 4/3 copper and 25' metal conduit is about $130! 

The max current draw (amperage) is determined by the application. Common amperage ratings are 15A for lighting, 20A for outlets, and 30-50A for an electric oven.  The largest draw of electricity is turning electricity directly into heat - like a space heater, hair dryer and electric oven.

Amperage also determines the wire size. 15A is 14 gauge, 20A is 12ga., 30A is 10ga. etc. When the wire has a lot of current going through it, it can get hot and spark and cause a fire. That's what the breaker is there to prevent - to much amps. You can have an undersized breaker or fuse for the wire, but not an undersized wire for the fuse because that would be dangerous. 

Here's a chart at Home Depot: 

WOW COOL! NOT CONFUSING AT ALL! 

If the sub panel is 120A, then we need #4 copper NM wire. But that's only rated for 70A you say. Ahh very observant, grasshopper! 4/3 is #4 wire, 3 conductor, with ground. You actually have 2 hot wires, each rated at 70A - so 140A for a 120A panel - we are good. The two hots are so that  each side of the panel has its own wire.

But the four slots on one side can hold more than 70A! you say. That's OK because we have a breaker upstream. This is a sub panel and has a main breaker going to it in the main panel. Since the main panel is going to be a huge expensive pain with PG&E, I will tie into the former range oven "safety switch," which is a dual 60A switch. 

Here is the electric range shutoff, which may be original but may be added in the 50s - not sure. Regardless the kitchen originally had an electric range, which was VERY unusual for '27, and also a common Maybeck feature. 

Here is our dual 60A safety switch formerly used for the electric range. I am using it temporarily as the kitchen sub panel shutoff, until I can afford a new main panel and service. 

Above: each hot (black and red) has a 60A fuse, allowing 120A of 110v, perfect for 4/3, each #4 rated at 70A max, plus a #4 neutral, white, and a smaller ground.

I don't recommend pulling 4/3 through a 3/4" flex conduit. Use 1" or bigger, or 4/3 MC cable (already wrapped), and save yourself a struggle. This is the line from the sub panel. 

On the left top and bottom are some 3/4" BX conduit. The bottom is the feed to the former electric range. The top is the power coming in, that comes from the main junction box, behind the main shutoff switch.

Cleared out the old stuff, pulling that 4/3 into the box  

The sub panel is hooked to a main switch now so when this switch is down, I can work on the sub. I had to turn off the main power to the house to work in this box. Fortunately, now I can simply switch off the sub panel and only the sub panel here now. The neutral and ground are "bonded."

Now I have the kitchen sub panel on a shutoff and I can safely work on wiring up these kitchen circuits. To be continued...