Can I use twin breakers in my breaker panel?

Twin, or ‘two-for-one’, breakers allow the connection of two, separately-protected circuits in the space of one standard breaker. Two circuit overcurrent protective devices (COPDs) connect to a single leg of the phase bus bar in the breaker panel, effectively doubling the capacity of the breaker panel in terms of number of branch circuits connected. The total power capacity of the panel does not change with the addition of twin type breakers (and is largely unaffected by what breakers may be installed — a common misconception that can lead to the wrong conclusion that a panel is overloaded simply because the Ampere rating of all breakers adds to more than the main breaker Ampere rating).

How do I tell whether my breaker panel accepts twin breakers?

Most breaker panels are rated to accept at least a few twin breakers. Some accept twins throughout the panel, and some accept no twins at all. The diagram inside the panel cover should indicate which breaker positions accommodate twin breakers (see photos).

See also:

• 200A service upgrade vs. panel upgrade for existing 100A service?

200A Service Upgrade and new receptacles

This project on S Melville St. features:

200A Service Upgrade and new receptacles

• 200A service upgrade and new receptacles from existing 100A, with 30+ breaker positions and GFCI receptacle at panel location in garage.
• Add 4 receptacle outlets, including a GFCI for the 2nd floor bathroom.
• Convert (3) 220V receptacles to (3) 120V receptacles on dedicated AFCI breakers.

200A underground service upgrade

This was a straightforward 200A service upgrade job on the service side, but a nest of badly labeled branch circuit conductors in a shared raceway (3/4″ conduit) made re-connection at the new service disconnect/breaker panel more difficult than it could have been.

I include a GFCI receptacle with service equipment replacements/upgrades, and in this case I also installed a switched utility service light to facilitate finding breakers or further work at the service disconnect/distribution breaker panel location.

Frayed service cable / power quality

Frayed service cable / power quality

What type of electric service cable damage are you looking out for?

If you can see exposed aluminum strands on your service entrance cable, it has frayed to the point where you should replace it. Cost may vary from $750 – $2200, depending on your service capacity (usually between 100A – 200A for residential electric accounts) and the capacity of your replacement service (for those wanting central air conditioning, an upgrade from 100A to 150A or 200A will often be needed; subsequent solar PV or micro wind power installations over 5kW capacity may be cheaper to install if the existing service is larger than 100A).

More on causes and effects of worn electric service entrance cable >>