Running 50 amp on 30amp 240v dryer plug

[Jerryr]

It’s currently 92 degrees in my driveway. Just got back from a trip and we’re unloading and cleaning out the Refection 337RLS.

It was 96 degrees inside the trailer so decided to run the AC units to keep from melting while working in the trailer.

I don’t have a 50 amp RV connection at home but my clothes dryer is a 4 wire NEMA 14-30R outlet.

I am running both AC units in the trailer while plugged into the dryer outlet using this very nicely built adapter. https://www.amazon.com/gp/product/B06WGRK4DN/

My EMS is showing 14 amps on L1 and 15 amps on L2. Still have plenty of head room to run almost anything in the trailer with this.

Thought I’d share this in case anyone else could use this solution.

Jerry.

[LCBoyer]

That’s neat. Where did you find it?

[Jerryr]

That’s neat. Where did you find it?

Amazon link https://www.amazon.com/gp/product/B06WGRK4DN/

[Canyonlight]

Jerry - had not heard of this adapter before....thanks, for sharing.

I am not a very knowledgeable electrical guy. Is this adapter essentially allowing the dryer plug to be used like a standard 30 amp RV plug by doing what to have 120 volts rather than 240 ? I think my 30 amp RV on our exterior RV pad garage wall is 10 gauge.........what is the dryer wire gauge ?

Dan

[huntr70]

That adapter is built to power a Tesla electric car charger.

It is not rated to be an RV accessory. It may work, but hasn't been tested or approved for RV use.

[klenger]

Good find.

Back several decades ago, some dryer outlets were only 3 wire outlets with 240 VAC L1-L2 but no common wire. You would NOT want to try to run an RV from such an outlet because it would apply 240 VAC to the 120 VAC circuits. I believe building code dis-allowed those a long time ago. The same might apply to a 220/240 VAC garage outlet for an air compressor or welder if it had no neutral wire.

[Jerryr]

Good find.

Back several decades ago, some dryer outlets were only 3 wire outlets with 240 VAC L1-L2 but no common wire. You would NOT want to try to run an RV from such an outlet because it would apply 240 VAC to the 120 VAC circuits. I believe building code dis-allowed those a long time ago. The same might apply to a 220/240 VAC garage outlet for k8an air compressor or welder if it had no neutral wire.

Code changed in 1996, prior to that 3 wire dryer outlets were the norm. These 3 wire outlets may not have a ground and should not be used to run an RV.

After 1996, NEC Code required a 4 wire dryer 14-30R outlet. It has the same connections as a 14-50R 50 amp RV outlet. 2 hots a neutral and a ground. It is protected by a 30 amp breaker rather than a 50 amp breaker that the RV outlet uses.

Using the adapter I linked in my posting above, with a properly wired and protected 14-30R receptacle works. The only limitation is that if there are more than 30 amps of current on either leg the building breaker will trip.

It’s different than a (TT-30R) 30 amp RV connection because the 30 amp RV connection only provides 1 hot to neutral leg (120v) for 3600 Watts.

A 4 wire 14-30R connection provides 2 hot to neutral 120 volt legs (7200 Watts). On a 50 amp corded 2 air conditioner RV each air conditioner is wired to opposite 120 volt legs allowing both air conditioners to run.

When using a typical 30amp RV dogbone to 50 amp RV adapter, the single 30 amp 120 volt hot leg is wired to both sides of the RV power panel. Running 2 air conditioners with that RV dogbone adapter will exceed the 3600 watt (30 amp 120v) capacity of the 30 amp RV pedestal connection and will trip the pedestal breaker.

[klenger]

Thank you for adding the details.

[offtohavasu]

Many homes built prior to 96 were already using the neutral wire, so if your home was built before that date, just check to see if the neutral is there. Sometimes the neutral was there, but they still installed the 3 prong outlet. Shut the circuit off, open the outlet and see what's there.

[Jerryr]

Many homes built prior to 96 were already using the neutral wire, so if your home was built before that date, just check to see if the neutral is there. Sometimes the neutral was there, but they still installed the 3 prong outlet. Shut the circuit off, open the outlet and see what's there.

Curtis,

You are correct. My recollection was wrong. I corrected my previous posting.

With a 3 wire 10-30R dryer outlet the Neutral from the line input is connected to the receptacle but ground is not. The frame ground and neutral are tied together in the dryer usually with a jumper at the connection lugs of the dryer side.

But in sub panels and at 50 amp RV breaker boxes ground and neutrals are separated. Therefore you need a 4 wire connection to a 50 amp RV.

My 1996 home dryer was originally wired with a 10-30R, 3 wire receptacle, not a 14-30R 4 wire. I opened the box and there was a 10/3 W/Gnd Wire in the box. The red, black and white wires were connected to the receptacle. The solid ground was connected to the metal j box.

I installed a 14-50R receptacle in the same box and wired red, black, white and bare ground to the 14-50R.

I then went to the main breaker box and verified the 2 hots were wired to the 30 amp double pole breaker, the white was connected to the neutral buss bar and the bare ground was connected to the ground buss bar.

I then replaced the dryer cord with a Whirlpool PT400L 4-Feet 4 Wire 30-Amp Dryer Power Cord.

One other thing that needs to be done when converting from a 3 wire to a 4 wire dryer outlet is to modify the connection of the pigtail at the dryer. You have to remove the (chassis bond) jumper at the dryer from neutral to ground and attach the green ground wire of the pigtail to dryer frame ground.

It sounds complicated but its pretty simple.

Jerry