Switchboard
The main distribution assembly that receives the service and feeds the building.
Quick Answer
A switchboard is a large, usually floor-standing electrical assembly that receives incoming service power and distributes it through breakers or fused switches to feeders and panelboards. Estimators count each switchboard EA from the one-line diagram, carry its sections and breakers, and flag it as a long-lead item.
The Full Picture
A switchboard sits at the top of the distribution system. Power arrives from the utility transformer or a service entrance, passes through main protective devices and metering, and leaves on feeder breakers that serve panelboards, motor control equipment and large loads. It is built from one or more sections, each with its own bus and breaker compartments, and it generally stands on the floor in its own electrical room. Under OSHA's electrical rules, switchboards with exposed live parts must be in permanently dry locations and accessible only to qualified persons.
The one-line diagram is where a switchboard is defined. It shows the name, voltage, bus amperage, the main device, each feeder breaker and its size, and the interrupting or short-circuit rating the equipment must carry. The plans show the electrical room layout, with the switchboard's footprint, its working clearances, and the conduit entries from above or below. The specifications under Division 26 list the manufacturer's options: metering, ground-fault protection, surge protection, and the enclosure type.
The takeoff unit is EA for the switchboard, with a description that carries the sections, bus rating, voltage and main device. Feeder breakers are counted by frame and trip rating, since they are priced individually. Related items are carried on separate lines: the housekeeping pad or equipment base, the conduit and conductors in and out, utility metering equipment where the utility specifies it, and any required testing or commissioning. Because switchboards are made to order, they are routinely flagged for long lead time, and the delivery date affects when the building can be energized.
A recurring estimating mistake is to carry the switchboard as a lump sum without checking the one-line for the number of feeder sections, since adding one section changes both price and floor space. Another is leaving out the requirement for clear working space: the width of the working space in front of the equipment must be the equipment width or 30 in, whichever is greater, which can mean a larger electrical room than the architect first drew.
Real Examples
Common Misconceptions
People assume: Switchboard and switchgear are interchangeable words.
Actually: They are different assemblies with different construction standards, and the specification names which one is required. The estimator should price what the one-line and spec call for, not substitute one for the other.
People assume: The switchboard price is one lump number.
Actually: Sections, bus rating, the main device, each feeder breaker and options like metering or surge protection each change the price. Carry them as separate lines from the one-line and spec.
Does MeltPlan Solve This?
Partially — adjacentCounting switchboards, sections and feeder breakers from the one-line diagram and plans is takeoff work, and MeltPlan's takeoff service uses AI to pull quantities from PDF plans, with US-based experienced estimators reviewing and adjusting them. Equipment pricing, lead-time assumptions and the choice between switchboard and switchgear stay with your estimating team.
Get switchboard and feeder breaker counts from your one-lines →Frequently Asked Questions
What does a switchboard do?
It receives power from the service and splits it through breakers or switches to feeders and panelboards. It is the main distribution point inside a building.
What unit is a switchboard taken off in?
A switchboard is counted EA, with its sections and bus rating described. Feeder breakers are counted EA, and feeders are measured in LF.
Is a switchboard long-lead?
Often, yes. Switchboards are built to order, so delivery times are an estimating and scheduling concern. Confirm the lead time with the supplier at bid time.
Where is a switchboard shown on the drawings?
The one-line diagram defines it, the electrical room plan shows its footprint and clearances, and the specifications list its ratings and options.