This is a question we get asked often.
The question arises when circuits are being added to an existing electrical system. Often we can replace existing circuit breakers with space saver breakers or reconfigure existing wiring so that a sub-panel is not required. This always the first option before installing a sub-panel.
Sub Panel to the left of the Main Panel
Top Reasons for Installing a Sub-Panel
1. Adding a Suite, Outbuilding or an Addition we will usually recommend installing a sub-panel to serve the new location. This way the new electrical system can be kept separate. By code, the electrical circuits for power in a suite must be accessible from within the suite or in a common area accessible to all who live in the building. Basically, you don’t want your tenant, or yourself, to have to go into someone elses space to reset a circuit breaker. Or to turn off a circuit to safely work on it
2. Additional electrical circuits. Car Chargers, Hot Tubs, AC Units, Welders, Kilns are all large electrical loads and may require a sub-panel. Electrical panels in older houses sometimes only have space for 12-16 circuits. If a new kitchen, bathroom or heating system is being installed and the original panel is full a sub-panel is needed. Sometimes, instead of installing a sub-panel, it makes more sense to replace the main panel with a larger one. For example, we would replace the original 12 circuit panel with a new 30-80 circuit panel
3. Illegal/unsafe wiring. Sometimes new wiring will be installed back to the electrical panel by a homeowner or handyman and they do not know what to do when there are no spaces left in the electrical panel. To replace the panel, install space saver circuit breakers or install a sub-panel is too daunting of a task. Hey!… two wires fit on this circuit breaker! The circuit works and the home handyman feels proud of his accomplishment. Circuit breakers are not designed to have two wires installed under the single lug that connects the wire to the circuit breaker. When two wires are connected to the same breaker there’s a much higher chance of arcing, fire and breaker damage because of the poor connection. A sub-panel, spacesaver breakers, or a new panel can be installed to connect the new circuit safely.