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Installing A 2-Pole Circuit Breaker In A Panel With Only 1 Space Available

July 13, 2008

breaker box Josh asks:
I need to install a 60 amp 240 two pole breaker in my box for a hot tub, but only have one spot for a single pole breaker in the box. What can I do to be able to install the breaker?

The first thing that you need to do is determine if you have enough power to do this. If your existing electric service is 125 amps or less and your breaker box is full, then you probably do not have enough power and you need to upgrade your electric service. However, if your electric service is 150 amps or more, then you are probably ok.

After you determine if you have enough power or not, then there are a few options. The first one I would check is the meter / main breaker box outside. Most areas require one of these boxes and there are usually at least 4 breaker spots available here. If this is not an option for you, then your breaker box may be able to accept 1/2 sized breakers.

To determine if your breaker box will accept 1/2 sized breakers legally, check the label on the door to see if you have a Class CTL panelboard. This will also tell you the maximum amount of circuits allowed in your breaker box without overloading it. For example, let’s say your breaker box is 30/40 spaces. However, when you count the physical amount of space you only have 30. This means that you may use 10 half sized breakers and they typically go in the last 5 positions on each side.

If none of the above options work, then you need to add a sub-panel. The best way to do this is to add the sub-panel right next to your existing breaker box. Then you would move one circuit from your existing breaker box into the new sub-panel. This will allow 2 spaces to add a 2-pole breaker to feed your sub-panel. I recommend feeding your sub-panel with 100 amps. With the new sub-panel installed and power up, then you may add your 2-pole 60 amp circuit breaker.

When installing a sub-panel, be sure that your neutrals and grounds are separated. Most breaker boxes come with some type of bonding strap that either connects the neutral and ground bars together or connects the neutral bar to the frame of the breaker box. This needs to be removed. The neutral and ground are only permitted to be connected together at the first point of disconnect and no where else.

Be sure to turn off the power when working on your breaker boxes before beginning any work and verify that the power is off using a voltage meter. You also need to check with your local building coded department to determine if you are able to do this work and if you need a permit. If no permit is needed, then I highly recommend an electrical inspection when you are finished. If your sub-panel is wired wrong this will cause problems with the rest of the circuits.

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3 Responses to “Installing A 2-Pole Circuit Breaker In A Panel With Only 1 Space Available”

  1. lawson williams on July 14th, 2008 8:28 pm

    Question: I have a 60amps and need to upgrade to 150amps it’s a single family house. What do i need to do?.
    Where the existing fuse box is located, i do not have space for a 30/40 breaker
    box. In fact the available space is 16×22. and on the outside there is a meter socket and switch box (fuse box).

  2. c miller on August 3rd, 2008 7:15 am

    How do I change a three wire service to a four wire? How do I add the extra ground lug to a square d box?

  3. carl trout on June 20th, 2011 8:13 am

    I bought an old house. It needs new electric wire though out the house. I don;t have the budget to hire out help. i want to add a new breaker box. is this posible without calling the company to shut off electric from the pole?