50 or 30 amp RV plug vs welder plug

[Dick in Wisconsin]

I'm not an electrician or electrical engineer.

I understand that a 240volt welder plug has only three prongs (I believe two hots and a common). Am I correct so far? If so, what about the ground? Does a welder not have a ground wire?

An 50 amp RV plug will have four prongs: a pair hots, a common, and a ground.

Lets say an enclosed utility trailer has a freezer, a couple of refrigerators, and a few outlets for food prep machinery. The trailer is used for cooking and preparing food. The trailer has a 30amp RV plug plugged into an onboard generator. The trailer owner has used an adapter to plug the trailer into a 50amp RV outlet.

I've been told ... NEVER, NEVER, EVER plug an RV into a welder outlet (using a homemade adapter) because the welder outlet has no grounding protection and this could/will cause serious problems for the equipment and devices plugged into.

I would like to be schooled on what the deal is with this. I believe the warnings are probably correct, but I don't completely understand the issued because the warnings. Is the risk there, but very unlikely to occur? Or is the risk very likely to occur?

 

[Slowgsr]

Welder has no neutral - straight 240 1ph & ground.

The adapters you need to be careful, usually if your panel has a main rated at the cord supplied it will protect it if it's plugged into an adaptor with a higher amperage rating.,

Rv outlets can be many things, a twist lock 30a with L/L/N/G is common since they fit most generators, my parents was a dryer plug or stove plug, common for most camp site hookups

 

[Speedy Petey]

Typical travel trailer/RV plugs are TT130 (120V-30A, grounding) or NEMA 14-50 (120/240V-50A grounding).

You heard right about plugging an RV into a welder, but for the wrong reason. As stated, a welder receptacle lacks a neutral, but does have a ground.
Anyone who makes an adapter with a 6-50P plug and a 14-50R receptacle is an absolute FOOL!!!

 

[Charles (in GA)]

I'm not an electrician or electrical engineer.

I understand that a 240volt welder plug has only three prongs (I believe two hots and a common). Am I correct so far? If so, what about the ground? Does a welder not have a ground wire?

The welder receptacle/plug (NEMA 6-50) has no NEUTRAL, just a ground. Plugs with grounds will have a round or D shaped pin, plugs with three flat blades such as old dryer and range plugs, have two hots and a neutral and NO GROUND. The lack of a neutral on a "welder plug" is what leads to your next issue

An 50 amp RV plug will have four prongs: a pair hots, a common, and a ground.

Lets say an enclosed utility trailer has a freezer, a couple of refrigerators, and a few outlets for food prep machinery. The trailer is used for cooking and preparing food. The trailer has a 30amp RV plug plugged into an onboard generator. The trailer owner has used an adapter to plug the trailer into a 50amp RV outlet.

This is fine well and good largely. The 30 amp/120v RV/TT plug is safely supplied by a generator producing 120v current. If the generator is not capable of 30 amps, it will merely trip the generator output breaker when overloaded. If the generator is producing more than 30 amps, there is a safety issue of overloading the RV input cord, but hopefully the RV has an internal 30 amp fuse or breaker that will trip in that situation.A 50 amp RV outlet is a NEMA 14-50 and it has two hots, a neutral and a ground, and 120v can safely be drawn from it using an adapter. Note that only one hot is being used by the adapter, the other hot is dead-ended in the adapter.

I've been told ... NEVER, NEVER, EVER plug an RV into a welder outlet (using a homemade adapter) because the welder outlet has no grounding protection and this could/will cause serious problems for the equipment and devices plugged into.

The problem is this, the welder outlet has NO NEUTRAL, and thus cannot be used to provide 120V current. It is ONLY capable of providing 240v current (the two hots). Adapters that provide a 30 amp/120v RV outlet from another type of plug, such as a 14-30 or 14-50 (or locking versions of the same) are using the ground, the neutral, and ONE OF THE HOTS. The other hot is not connected thru the adapter, it is deadended. I bought a store bought L14-30 to 30 amp (120v RV) adapter at Home Depot and figured this out rather quickly. I have a generator, thus a couple of home made extension cords, 8/4 SOOW and male and female L14-30 ends. I wanted to be able to use these for extension cords for the welder, so I installed a L14-30 receptacle at my panel in the shop. Then I wanted to use them as extensions to supply a friends RV, so I bought the male L14/30 to female 30 amp RV adapter. Since I was using it as a extension for the welder, but didn't want to get away from the 6-50 plug on the welder (and associated wall receptacle when using it right at the shop doorway) I made a male L14-30 to female 6-50 receptacle in a box, as an 18 inch pigtail.

You cannot supply a 30 amp 120v RV off a 6-50 receptacle because there is no neutral to give you 120v.

I would like to be schooled on what the deal is with this. I believe the warnings are probably correct, but I don't completely understand the issued because the warnings. Is the risk there, but very unlikely to occur? Or is the risk very likely to occur?

No, I'm not going to go there about using the ground as a neutral, it isn't right and its not worth discussing. We (me or you) are not in the outback of Oz with limited supplies, Home Depot is just down the road.

Charles......

 

[Charles (in GA)]

The risk you want to know about is that using a NEMA 6-50 to supply 120v requires using the GROUND as a NEUTRAL. Indeed the two eventually meet at the service entrance, however, by using the ground improperly, you are traveling current down wires intended as safety ground, and this also can cause problems with electronics.

 

[wyliesdiesels]

I'm not an electrician or electrical engineer.

I understand that a 240volt welder plug has only three prongs (I believe two hots and a common). Am I correct so far? If so, what about the ground? Does a welder not have a ground wire?

An 50 amp RV plug will have four prongs: a pair hots, a common, and a ground.

Lets say an enclosed utility trailer has a freezer, a couple of refrigerators, and a few outlets for food prep machinery. The trailer is used for cooking and preparing food. The trailer has a 30amp RV plug plugged into an onboard generator. The trailer owner has used an adapter to plug the trailer into a 50amp RV outlet.

I've been told ... NEVER, NEVER, EVER plug an RV into a welder outlet (using a homemade adapter) because the welder outlet has no grounding protection and this could/will cause serious problems for the equipment and devices plugged into.

I would like to be schooled on what the deal is with this. I believe the warnings are probably correct, but I don't completely understand the issued because the warnings. Is the risk there, but very unlikely to occur? Or is the risk very likely to occur?

that would be incorrect. A 240v welder outlet (usually a NEMA 6-50) has 2 hots and an EGC. There is no neutral(what youre calling common) because its not needed.

Whoever told u that was wrong.

The issue with using a welder outlet is the abscence of the neutral NOT the EGC.

People will make adapters that use the EGC pin as the neutral. This is not right but is functional IF the welder outlet is connected to the main service panel, then the EGC goes to the same bar as the neutral. But neutral current should NEVER be ran on an uninsulated conductor.