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I have a regular 2 socket, 15 amp outlet in my garage. I need to run my miter saw and shopvac at the same time, the saw draws 15A and the shopvac 8.5A.

I've currently been running them off one outlet through a 50 foot 14AWG extension cord with a 3 way splitter at the end. The other socket is running to a power strip by an extension cord that is powering by workbench light.

It hasn't tripped the breaker so far.

I know very little about electricity and it's boundaries, how bad is my current set up? What risks are there with this?

UPDATE: I found an old kill-a-watt meter and tried it out on the setup, here are the results.

Miter saw only Startup (Peak): 18A Saw running: 7.5A Saw cutting: 10A

Shop vac only Startup (Peak): 12A Running: 8.4A

Saw and Shop vac: Shopvac running and then starting saw (peak): 21.6A Both running: 16A Both running and saw cutting: 18A

I notice the saw bogs down a bit while cutting and both are running, seems perhaps the motor isn't getting the juice it needs?

I think the answer is clear, I need to get one on another circuit. I thought these were interesting and wanted to share.

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  • And this doesn't trip a circuit breaker?!?
    – Grant
    Jun 14, 2014 at 0:59
  • no, it hasn't yet.
    – v15
    Jun 14, 2014 at 1:22
  • What is the capacity of the circuit? 20 amps? It is common to put multiple 15 amp outlets on a 20 amp circuit, though not in a shop or garage.
    – wallyk
    Jun 14, 2014 at 15:32
  • It's 15 amps i believe. In the breaker box, the garage is on a single '15' switch.
    – v15
    Jun 14, 2014 at 20:20
  • It sounds like you're just at the limit of this circuits capacity. If you ran the combination long enough, you might see the breaker trip. Since miter cuts are usually done in short bursts, the saw probably isn't drawing current long enough to trip the breaker. If you were using a table saw, you might find that the breaker does trip. Without knowing the make and model breaker, I can't say for sure how long it would take to trip the breaker (you'd have to check the breakers trip curve to figure that out).
    – Tester101
    Jun 16, 2014 at 10:07

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Neither device is probably pulling the rated amount, though it might hit those ratings at peak. If you started the vacuum and saw at the exact same time, you might trip the breaker.

Assuming the breaker isn't defective, if it hasn't tripped you're OK from a capacity point of view. Keep in mind there might be other devices on the circuit too.

Ideally you wouldn't use an extension cord at all for this. While you probably won't run into any problems, you might consider a heavier wire gauge for the extension cord. If you don't need all 50', you're also better off with a shorter extension cord.

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