Using a 40 amp dryer outlet for tools - In-line breaker?

[jamil mehdi]

I have a 40 amp circuit for my dryer and want to use that circuit to run a 220v planer or a 220v drum sander when the dryer isn't in use, both of which only need a 20 amp circuit. I can buy a short extension cord adapter for the plug receptacle and use the tools with no problem, but they'll be on a circuit that isn't sized correctly.

My question is, can I wire a 20 amp breaker in-line on the extension cord that will trip if the tools start drawing too much? I'd like to not burn up my tools or my house if at all possible

[Alex Zeller]

Have you checked to see if either/ both tools already have protection? It could be a button on the motor or if they have a magnetic breaker they could have something to protect against drawing too much current. They sell extension cords with breakers. I think they come with the matching plug for the voltage and current rating. I think I've even seen them at Home Depot.

[roger wiegand]

I don't think there is any reason to have a smaller breaker to run your other tools-- after all we pretty routinely do things like plug a 5 watt LED light bulb that uses an 18 gauge wire into a 15-20 amp circuit, or any of an array of power tools that draw 2-8 amps into a 20 amp circuit. The breakers exist, and are sized, to protect the wiring in the building, not the attached device. If the device requires overcurrent protection the manufacturer will have built it in (many motors have an overload button); they cannot assume what size circuit it will have been plugged into.

This is only the answer that logic provides, there may be regulations to take into account.

[Jim Becker]

No need for anything other than a compatible plug. The breaker protects the wire, not the tool

[Ron Selzer]

I have a 40 amp circuit for my dryer and want to use that circuit to run a 220v planer or a 220v drum sander when the dryer isn't in use, both of which only need a 20 amp circuit. I can buy a short extension cord adapter for the plug receptacle and use the tools with no problem, but they'll be on a circuit that isn't sized correctly.

My question is, can I wire a 20 amp breaker in-line on the extension cord that will trip if the tools start drawing too much? I'd like to not burn up my tools or my house if at all possible

Yes you can, get a 2pole disconnect that is typically used for an A/C outdoor unit, install two pole breaker of you choice wire incoming with dryer plug and outgoing with receptacle or cord connector for you machinery needs.

QO24L60NRNM
https://www.menards.com/main/electrical/circuit-protection-power-distribution/safety-switches-disconnects/square-d-trade-60-amp-240v-non-fusible-safety-switch/qo200trcp/p-1444444032285-c-6435.htm?tid=-6054792810930833549&ipos=45
a breaker of your choice QO220 or QO215

dryer cord
https://www.menards.com/main/electrical/electrical-cords-cord-management/appliance-cords/smart-electrician-reg-4-3-wire-dryer-appliance-cord/3702525/p-1444425968838-c-1525700042008.htm?tid=-5758176388181670164&ipos=3

then a receptacle fastened to the box or a cord end with a cord connector

A motor starter with overloads sized properly would even be better. post back with pics of name plates on motors if you want to go this way

Ron

[Adam Herman]

No need for anything other than a compatible plug. The breaker protects the wire, not the tool

if what you are supposing was true, every light and appliance in your house would need an extra breaker. just quoting this to make sure people see it.

as long as the maximum draw of the thing you are plugging in is less than the max of the circuit, you are good to go. the circuit will only provide the current the thing plugged into it uses. nothing more. just like turning on a faucet to a slow drip. amps is the flow rate of electricity and volts is the pressure. like a pipe, the flow rate is determined by pipe size/length, ( wire size/length/resistance) faucet ( thing using electricity) and pressure (voltage).

[Richard Mellor]

Jamil, I was in the same position and ended up using this.
https://www.amazon.com/gp/product/B083ZMGS41/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

[jamil mehdi]

OK. Good to know. I was more worried about the tools not being able to trip the breaker in some sort of scenario where they get too much current and killing the motors, but it sounds like that isn't really a concern. Thanks.

[roger wiegand]

if what you are supposing was true, every light and appliance in your house would need an extra breaker.

Interestingly, that's exactly how the UK system works. Every plug has a built in fuse or breaker sized to the rating of the appliance; I believe the house wiring is generally pretty heavy with breakers at high amperage and, of course, 240V. There's a lot that makes sense about that way of doing things. Most of the rest of the empire didn't adopt it though.

[Bruce King]

Woodworking tools would normally not be turned on unless someone is nearby to notice a locked up motor so circuit breakers and wiring higher than needed would not be an immediate hazard. HVAC outdoor units do have a min and max breaker size with the max designed to detect a locked rotor. Any expensive equipment or something that can produce heat from a common failure should have a reasonable sized breaker. I saw a bath fan/infrared heater unit that specified a 15 amp circuit only.

[Adam Herman]

Interestingly, that's exactly how the UK system works. Every plug has a built in fuse or breaker sized to the rating of the appliance; I believe the house wiring is generally pretty heavy with breakers at high amperage and, of course, 240V. There's a lot that makes sense about that way of doing things. Most of the rest of the empire didn't adopt it though.

in the UK you can get 7kw out of the outlet you also plug your lamp into ,without the breaker/switch at each outlet and its fed from 2 sides on a ring. Here, on a normal circuit the max is about 1800 watts until something trips.

[Mike Henderson]

in the UK you can get 7kw out of the outlet you also plug your lamp into ,without the breaker/switch at each outlet and its fed from 2 sides on a ring. Here, on a normal circuit the max is about 1800 watts until something trips.

So that's why they have those oversized prongs on their plugs.

I suppose they wanted to make the plugs able to handle the maximum load. But today, most things are a tiny load. That little bitty adapter cube for the Apple iPhone that we're accustom to must have to be gigantic to accommodate the UK plug.

Mike

[Rod Sheridan]

OK. Good to know. I was more worried about the tools not being able to trip the breaker in some sort of scenario where they get too much current and killing the motors, but it sounds like that isn't really a concern. Thanks.


That depends wholly upon what the manufacturer says.

My jointer planer is limited to a 20 ampere circuit capable of delivering not more than 5KA short circuit current.

In the electrical world, the manufacturers specifications must be followed regardless of local code issues.....Rod.

[Dan Friedrichs]

if what you are supposing was true, every light and appliance in your house would need an extra breaker. just quoting this to make sure people see it.

as long as the maximum draw of the thing you are plugging in is less than the max of the circuit, you are good to go. the circuit will only provide the current the thing plugged into it uses. nothing more. just like turning on a faucet to a slow drip. amps is the flow rate of electricity and volts is the pressure. like a pipe, the flow rate is determined by pipe size/length, ( wire size/length/resistance) faucet ( thing using electricity) and pressure (voltage).

Adam, I think you and Jim are saying the same thing. When Jim said "protect the wire", he meant the wiring between the breaker and the receptacle, not the appliance cord.

[Jim Becker]

Adam, I think you and Jim are saying the same thing. When Jim said "protect the wire", he meant the wiring between the breaker and the receptacle, not the appliance cord.
Exactly. "The wire in the wall"--the circuit, as it were, is what's protected by the breaker, not the appliance/machine, nor the appliance/machine cord, although presumably, the latter is appropriately sized and would be protected in the same way as the "wire in the wall"...theoretically speaking. Breakers are to prevent fires and other hazards that come when the wire is potentially going to be damaged by over-current.

[Jay Rasmussen]

No need for anything other than a compatible plug. The breaker protects the wire, not the tool

What Jim said. I run all of my 220 machines off the dryer circuit. Never had any issues (30 years).

[Rollie Meyers]

Interestingly, that's exactly how the UK system works. Every plug has a built in fuse or breaker sized to the rating of the appliance; I believe the house wiring is generally pretty heavy with breakers at high amperage and, of course, 240V. There's a lot that makes sense about that way of doing things. Most of the rest of the empire didn't adopt it though.

It's a 32 ampere ring circuit in the UK, they are the only ones who do it that way, the 32A rating is why all the plugs are fused, if my memory serves me correct the fuse is a maximum of 13A, but with a 240V line voltage it is not limiting like it is with 120V.