Use an abandoned 10 gauge 3-wire 220v home run to power a subpanel?

Thread Starter

jb18114

Joined Feb 2, 2018
8
Hello guys,

I ran across a situation where I'm not sure I can do this but I don't see why not. Maybe you all can help me see why I can't...

Home owner removed an electric range and Jennair system that was fed by two separate 10 gauge - 3 conductor branch circuits where each is protected by a 30amp double pole breaker. The electrical system in the house is fairly maxed out, no more room in the panel and he could really use a few more branch circuits, maybe a couple 20amp and a couple 15 amp.

The old runs are long enough that I could reroute them into the laundry room where I think they could each feed their own small sub panel. If I understand it correctly, each hot leg is capable of supplying a max (not nominal) of 30 amps? So each sub panel would safely supply two 20amp branches no problem, correct? As long as they were on separate phases I think this would work.

So if this is possible, the subs would be in the same structure, and I don't know if I would need to ground each to a new ground rod or could I bond to a water pipe? Not sure how that works either.

Any help would be much appreciated! Thank you.
 

dl324

Joined Mar 30, 2015
16,840
#10 will carry up to 30A total on each hot wire, but the sub panel needs to be installed by an electrician.
 

dl324

Joined Mar 30, 2015
16,840
An electrician will know better and install the sub panel according to your local codes.

But it's going to cost around a thousand dollars.
 
You can think of panels as two types. 1) Main Lug and 2) main breaker.

It''s sometimes convenient to install a sub panel as a main breaker panel

Modern panels need a conversion kit to turn it into a sub-panel. It usually gives you a set of ground bars. You then have to remove the neutral/brond bond in the new panel.

In the same structure (Attached), you will need an independent ground, L1, L2 and Neutral back to the main panel. They stay isolated and local to this panel.

Main lug just means no breaker to turn the sub-panel off in the sub-panel. The main breaker for the sub is in the main panel.

Main breaker = says you have a disconnect means in the sub-panel. Now you CAN over rate the main breaker to say 200A as long a the wire/breaker in the main panel are protected correctly,

Quickly, loading contains "continuous" and intermittant loads. A stove is considered intermittant in the home setting, but continuous in a restauraunt,

You can't load a circuit more than 80%. The rule of thumb is around 3% drop in voltage for a new circuit.

That's quick and dirty. You can read the NEC code online for free. No printing etc.
 

Thread Starter

jb18114

Joined Feb 2, 2018
8
You can think of panels as two types. 1) Main Lug and 2) main breaker.

It''s sometimes convenient to install a sub panel as a main breaker panel

Modern panels need a conversion kit to turn it into a sub-panel. It usually gives you a set of ground bars. You then have to remove the neutral/brond bond in the new panel.

In the same structure (Attached), you will need an independent ground, L1, L2 and Neutral back to the main panel. They stay isolated and local to this panel.

Main lug just means no breaker to turn the sub-panel off in the sub-panel. The main breaker for the sub is in the main panel.

Main breaker = says you have a disconnect means in the sub-panel. Now you CAN over rate the main breaker to say 200A as long a the wire/breaker in the main panel are protected correctly,

Quickly, loading contains "continuous" and intermittant loads. A stove is considered intermittant in the home setting, but continuous in a restauraunt,

You can't load a circuit more than 80%. The rule of thumb is around 3% drop in voltage for a new circuit.

That's quick and dirty. You can read the NEC code online for free. No printing etc.
Thank you, that's very helpful!
 
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