As a new member, I was reading back through posts. Great information source!!!! Thanks to all.

I hope it is OK here to diverge slightly from a relatively recent post titled “220 line for an electric dryer posted by JMattero on 02-17-11 10:03 AM.” This discussion was in regard to 3 wire vs. four wire dryer plug connections, with four wire being the correct answer.

My question is should other 230V appliances also follow the same four-wire rule?

Specifically, I have a Miller MIG welder in the garage that plugs into an industry standard, single phase 230V three wire 50 Amp rated receptacle fed by 8 gauge stranded copper wire. The receptacle is polarized with one spade much wider than the other. The third pin is the D shaped ground. It has never caused any problems but this post got my attention.

The welder’s flexible cable and plug end are one-piece molded as installed by the manufacturer with no alterations. So it looks like Miller has neutral return and ground bonded internally. Many 230V window unit air conditioners are also three wire.

Is this simply a case of the equipment manufactures not yet catching up with NEC four wire requirements?

 

Dryers and stoves have both 120 and 240 volt components. The motors and control circuits and lighting are all 120 and require a neutral. The heating elements are 240 volt loads. Hence the need for a neutral and the 4 wires.

Straight 240 like a air conditioner and welders do not require a neutral.

 

I sometimes wish that they would use nema 14, anyway, and just not connect a neutral wire in the plug, although it would waste copper feeding the receptacle.

 

pcboss gave you a good answer. Look at the data plate on an electric range and dryer and then look at the data plate on a window air conditioner and your welder. The range and dryers voltage will be shown as 120/240 which requires a neutral where the welder and window a-c will be shown as 230 or 240 and doesn't need a neutral.