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Critical questions about workshop wiring

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Find your amp needs guidelines

Find your amp needs guidelines

To determine how much capacity your shop needs, first find your highest amp-draw tool (often a tablesaw or dust collector), and multiply the amperage by 125 percent

Highest amps x 1.25 = (A) _______

Now, total the amperage of the highest draw tools that run simultaneously, such as a tablesaw and dust collector, router and shop vac, etc.

Simultaneous tool amps = (B) _______

Total the amp draw of all other loads that run continuously, such as lighting, heat/air conditioning, air filter, radio, etc. (If amps unknown, such as with lights, divide watts by voltage to get amps.)

Continuous-draw amps = (C) _______


For example:

Highest draw (A):
(18-amp tablesaw) 1.25 = 22.5

Highest simultaneous (B):
(18-amp saw+11-amp dust coll.) = 29

Continuous (C):
(lights, heat, television, air filter) = 24

Minimum Amps Required (A+B+C) = 75.5

Powering this shop adequately requires 80-amps of extra capacity in the existing service panel, or an 80-amp subpanel.

Continued on page 5:  The right size of wiring


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