Quick tutorial on Dryer and Welder Outlet Grounding

When is a neutral used as a ground?

Everyone,

My recent article on EV and welder receptacles generated a lot of comments about existing 240-volt power in garages. But I noticed that there was a bit of confusion about grounding vs neutral conductors in each of these connectors.

So, is it a ground or a neutral?

While both the ground and neutral conductors in a receptacle should eventually end up bonded to the neutral bus in the service panel, they have separate functions. The job of the neutral conductor is to carry load currents, while the job of the ground conductor is to carry fault currents. Keep that in mind as we look at the various wiring diagrams.

50-amp RV outlet wiring (Ground plus a Neutral)

Here’s how all RV 50-amp outlets should be wired. Note that there are two separate Hot conductors ( X and Y) plus a Neutral and a Ground. The Neutral carries the return load current, and also divides the 240-volt split-phase service into two 120-volt circuits. The Ground wire is technically called the Equipment Grounding Conductor (EGC) and is there to create a fault current path that will rapidly trip the circuit breaker in the event of a line-to-chassis short circuit.

50-amp welder or EV charger outlet wiring (Ground without a Neutral)

Note that this welder outlet has a two hot conductors and a ground conductor but no neutral. That’s because welders and EV chargers only have 240-volt line-to-line loads. Since there’s no need to provide 120-volts then there’s no need for a neutral conductor. But the ground conductor is there to create a line-to-chassis fault current path. That’s what prevents a hot-skin voltage from ocuring.

30-amp 3-wire dryer outlet (Neutral without a Ground)

And here’s how the infamous 30-amp dryer outlet is wired. Note that it has two hot conductors (X and Y) and a neutral conductor (W), but no ground conductor. This was a code exception to save copper (or aluminum) wire. But if a dryer uses 240-volts, why is there a Neutral conductor instead of a Ground conductor?

That’s because an electric clothes dryer is not just a 240-volt load. It also has a 120-volt motor to spin the drum and 120-volt control circuit. So the NEC and NEMA decided that they would just use a neutral conductor and allow a bootleg ground in the dryer create a fault current path in the event of a short-to-chassis inside of the dryer.

What about 4-wire dryer outlets?

Note that all modern dryer hookups require separate neutral and ground conductors in addition to two hots, just like your RV. But older homes are not required to upgrade a 3-wire dryer outlet to a 4-wire hookup. So when you buy a dryer you need to purchase a hookup cord separately to match the existing 3 or 4-wire outlet in your house. And the above hookup diagram shows how it’s wired inside of your dryer. Yes, that ground strap is indeed a bootleg ground!

You can read an excellent in-depth article on dryer outlet hookups from Jade Learning HERE.

Lets play safe out there… Mike