Quick Answer: Most 110 V concrete grinders draw 12 to 15 amps and need a dedicated 15 or 20 amp circuit; walk-behind machines and dust vacuums are often 15 amps each. On 220 V power, current drops by half, which is why larger floor machines run single-phase 220 V. Check the motor nameplate, then size the breaker and cord so the tool runs without tripping.

Reading the Motor Nameplate

The nameplate lists volts, amps, and either watts or horsepower. Amps matter most for circuit planning because a motor's starting surge can reach 1.5 to 2 times the running current for a moment. A grinder rated 15 amps at 110 V needs a 20 amp circuit to absorb the inrush without tripping, especially if you also run a vacuum on the same circuit. Never just plug a 15 amp tool into a circuit already loaded by other equipment.

Hand Grinder vs Floor Machine

Hand-held angle grinders run 6 to 13 amps. turbo cup wheel depending on the motor, while single-disc floor machines commonly draw 12 to 15 amps and three-phase machines need 208 or 380 V supply. If you run a dust extractor at the same time, put the grinder and the vacuum on separate circuits or use a high-amp circuit. Plan the longest extension cord first: for 15 amps at 110 V, keep runs under about 15 metres with a 12 AWG cord; longer runs need a heavier cord to avoid voltage drop that starves the motor.

Breaker and Outlet Sizing

Use a breaker sized to the circuit wiring, not just the tool. A 15 amp circuit with 14 AWG wire feeds most hand grinders; a 20 amp circuit with 12 AWG wire covers floor machines and dust collectors. NEMA 5-20 outlets and plugs. double-row cup wheel allow 20 amp draw, while the common 5-15 outlet is limited to 15. On 220 V single-phase machines, match the plug type to the regional standard and use a matching breaker, usually 20 to 30 amps for typical 5 to 7 kW machines.

GFCI and Jobsite Safety

On construction and wet cutting sites, run grinders through a GFCI-protected outlet or a portable GFCI adapter. Concrete floors conduct electricity, and a fault through a damp machine can be fatal. Inspect cords and plugs before each use, and never join damaged cords with tape. Keep the grinder body and the motor housing free of dust build-up, which restricts cooling and raises the current draw.

Why does my grinder trip the breaker on start-up?

Start-up inrush is the usual cause, plus an undersized cord or a circuit shared with other tools. Move the grinder to a dedicated circuit, shorten the extension cord, and confirm the cord gauge matches 15 amps over the run length.

Can I run a 15 amp grinder on a 15 amp breaker?

Technically yes if nothing else is on the circuit and the cord is short and heavy enough, but the motor's inrush can still trip it. A 20 amp circuit is the safer choice for regular grinding.

Conclusion

Match the breaker and cord to the motor nameplate, allow for inrush, and keep grinders and vacuums on separate circuits. With the right amperage planning your grinding discs and floor machine run at full power without nuisance trips, and the job finishes faster and safer.