In Plain English
Quick Answer
The measure of how much electricity is flowing through a wire at any given moment.
Definition
Definition
The standard unit of electric current, representing the flow of one coulomb of charge per second through a conductor. Amperage ratings determine the capacity of circuits, breakers, and electrical equipment. Exceeding the ampere rating of a circuit causes overheating and potential fire hazard.
Context
Why It Matters in Bidding
Amperage drives the sizing of conductors, breakers, panels, and service equipment, so it directly determines material costs in an electrical bid. An estimator who misreads load calculations or service amperage can undersize the feeder and gear, producing a non-compliant low bid, or oversize it, losing the job on price, making accurate ampacity takeoff central to a competitive and buildable electrical proposal.
Example
Example
Sizing the service for a small commercial building, the estimator confirms a 400-amp service from the load calc and prices the matching switchgear, feeders, and conduit accordingly.
See Also
Related Terms
FAQ
Questions Contractors Ask
How does amperage affect electrical bid costs?
Higher amperage requires larger conductors, bigger breakers, and heavier service equipment, all of which raise material and labor costs. Wire size and conduit fill scale with ampacity, and larger gear takes more labor to install. Estimators size everything from the engineer's load calculations so the bid carries the correct ampere ratings throughout.
Why is conductor ampacity important in takeoff?
Ampacity is the current a conductor can safely carry, and it governs wire sizing under the NEC. Derating for temperature, conduit fill, and bundling can require a larger conductor than the nominal load suggests. Estimators apply these factors during takeoff to avoid undersizing wire, which would cause inspection failures and costly field rework.
What happens if a circuit's ampere rating is exceeded?
Drawing more current than a circuit is rated for causes overheating, breaker trips, and potential fire risk. Proper design sizes breakers and conductors to the connected load with required safety margins. During bidding, estimators rely on the engineered panel schedules and load calcs to ensure every circuit and feeder is correctly rated.
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