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What is an Electrical Subpanel

By JDFerris | Electrical

Oct 04

What is an Electrical Subpanel?

An electrical subpanel is essentially a separate hub at a midpoint between the main service panel, and whatever branch circuits the wiring is going to. An electrical subpanel can also be known as a service subpanel or circuit breaker subpanel. In essence, an electrical subpanel can be considered a tiny service panel.

Though not as common, even some manufactured homes make use of subpanels for the differentiation of their electrical service and circuitry.

Electrical Subpanels Differentiate the Home’s Circuitry

Electrical panel picture from an sps inspections home inspection

For the sake of differentiation of electrical circuitry within a home, an electric subpanel will service one different area that has a discrete function, such as a cooking area, shop, workplace, or addition.

The setup of a subpanel should rarely ever be your first option when you need more space inside of your main panel. First, you should search for any slots that might be filled with available circuit breakers. Second, even if a slot is loaded, you can purchase a tandem breaker that shares one slot, however, deliver the same quantity of electrical output.

By setting up a breaker subpanel, you make it clear that circuit breakers and branch circuits apply to which parts of your home. It is simple to segregate the responsibilities of all of the branch circuits by keeping them sequestered within the electrical subpanel.

When the Service Panel is Inaccessible

It can become serious when a tenant in one of your rentals overloads a circuit and the circuit breaks in the central area that is inaccessible to the tenant.

Such incidents are a common scenario with any property leases where the property owner’s location is locked and inaccessible to the tenant. If the tenant’s breaker trips and the property owners are not home, the occupant has no choice but to wait until the proprietor returns.

Electrical subpanel in a garage during a home inspection by SPS Inspections
Electrical subpanel in a garage during a home inspection by SPS Inspections

With an electrical subpanel, though, the tenant can control the circuit breakers in the subpanel to reset their circuitry.

Main Service Breakers Can Shut Off

Although an electrical subpanel has its collection of circuit breakers, all running power to a specific subpanel, the subpanel is still fed from just one circuit located in the primary circuit box. A double-pole circuit breaker protects that feeder circuit itself, and this breaker can shut itself off. Most likely, the subpanel’s breakers would close down first, but the possibility still does exist.

200 amp main service breaker
200 amp main service breaker

Electrical Subpanels Can Differentiate Service

A typical factor for setting up any subpanel system is the need to separate different areas’ circuitry from each other. If perhaps, you are the owner and landlord of a duplex, or maybe if there is a mother-in-law residence on the property, it is advantageous to keep those circuits separate from the circuit that feeds into it, or the primary circuit.

The fundamental structure of an electrical subpanel is the same as a service panel, with the primary feeder wire leading into bus bars and circuit breakers. Branch wire circuits lead off of the subpanel breaker into various parts of the home.

A standard amperage and voltage for a subpanel are maybe 30 amps, 240 volts. Keep in mind that a breaker subpanel does not provide extra electricity to your home; it is merely taking energy off of the main service panel.

This is a picture of an ungrounded outlet found during a home inspection by sps inspections olympia
This is a picture of an ungrounded outlet found during a home inspection by SPS Inspections of Olympia

Electrical Subpanels Allow for More Space

If the main circuit box does not have adequate space to hold circuit breakers for the new circuits that you intend to set up, the electrical subpanel can produce a new area for breakers to be installed, however, in a physically separate place.

Setting up an electrical subpanel near the remodel location allows for the section of the home to be fed with a single cable from the main service panel. Many times, that cable and its routing path may already exist, given that the area having renovations might still have viable wires running to it.

Setting up an electrical subpanel solely for the sake of clarity is seldom an efficient means of accomplishing the differentiation you might want in your home’s circuitry. Clearness is but a favorable off-shoot of subpanel installation.

Electrical Metering Not Separate

Electrical use from the accessory residence can not be separated from the main residential area just by installing an electrical subpanel. Even when this happens, all metering still runs by the house’s main electrical meter before actually being metered.

Instead, to discern separate energy use, set up a residential renter submeter. These small systems help individually keep an eye on electrical sub-usage in 120/240V systems for rental occupants, workplace suites, and workshops.

Roof view picture of a not-so-good service drop which supplies power to the main service panel in the home
Roof view picture of a not-so-good service drop which supplies power to the main service panel in the home

Submeters do not instantly deduct energy usage info from the primary energy meter; in the majority of cases, this needs to be calculated by hand.

Electrical Subpanels Relieve Wire Routes

For home remodel work, particularly for energy-hungry locations such as bathrooms and kitchens, several brand-new cables will many times need to be run from the primary service panel to the project location to provide power. With older homes, it can be tough to route numerous brand-new cables through closed walls, flooring, and ceilings.

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