Adapting a 14-30 Dryer Outlet for a 30 Amp RV

[bigbAZ]

Not unsafe but there is already 30 amps of 120V there which is the max that the RV can use. The dogbone is $50. He could probably even get the electrician to come back and install the correct outlet if it was in error, but that's where one has to make sure the TT-30 gets wired correctly, especially by a rookie electrician which appears to be the case.

Also, you'd need the 5,000 watt one to get the full 3,600 watts for the RV, but even that wouldn't work since the 120 volt sockets are only 20 amps.

 

[DonTom]

30 amps of 120V there which is the max that the RV can use.

But with the DonTom method he would be ready for two 30-amp RVs at the same time!

And you cannot tell me some people do not own two RVs .

-Don- Reno, NV

 

[bigbAZ]

I don't see a way to get 30 amps at 120V out of it.

 

[DonTom]

I don't see a way to get 30 amps at 120V out of it.

You must have meant 60-amps total in above, 30-amps to two RVs.

Didn't you say it was a 120-N-120 VAC outlet? That means 120 VAC at 30 amps each for a total of 7,200 watts.

Across the two hots will be 240 VAC @ 30 amps, still 7,200 watts (no power gained, no power lost).

Now the transformer, step down the voltage to half (120 VAC) as it increases the current capacity to double 60-amps).

120 VAC times 60 amps=7,200 watts.

Perhaps a 5% loss at the transformer, still very close to 60 amps at 120 VAC (the 7,200 watts).

And then no reason to be concerned with the neutral.


-Don- Reno, NV

 

[NY_Dutch]

You must have meant 60-amps total in above, 30-amps to two RVs.

Didn't you say it was a 120-N-120 VAC outlet? That means 120 VAC at 30 amps each for a total of 7,200 watts.

Across the two hots will be 240 VAC @ 30 amps, still 7,200 watts (no power gained, no power lost).

Now the transformer, step down the voltage to half (120 VAC) as it increases the current capacity to double 60-amps).

120 VAC times 60 amps=7,200 watts.

Perhaps a 5% loss at the transformer, still very close to 60 amps at 120 VAC (the 7,200 watts).

And then no reason to be concerned with the neutral.


-Don- Reno, NV

The bottom line is that no transformer is needed to power the OP's 30 amp RV. Only the listed adapter or a knowledgeable electrician to swap out the outlet.

 

[bigbAZ]

You must have meant 60-amps total in above, 30-amps to two RVs.

Didn't you say it was a 120-N-120 VAC outlet? That means 120 VAC at 30 amps each for a total of 7,200 watts.

Across the two hots will be 240 VAC @ 30 amps, still 7,200 watts (no power gained, no power lost).

Now the transformer, step down the voltage to half (120 VAC) as it increases the current capacity to double 60-amps).

120 VAC times 60 amps=7,200 watts.

Perhaps a 5% loss at the transformer, still very close to 60 amps at 120 VAC (the 7,200 watts).

And then no reason to be concerned with the neutral.


-Don- Reno, NV

No, what I meant is there is no 30 amp 120 volt outlet on the transformer, just 3-120 volt 20 amp outlets.

 

[bigbAZ]

On the subject of 2 30 amp RVs, just for fun, that existing 10/3 would still work. One line to each TT-30, pigtail the neutral into two and pigtail the ground into two then you have a multiwire branch circuit (MWBC) with 2 outlets capable of 3,600 watts each at 120 volts.

As long as you use a 2 pole 30 amp breaker installed so that there is 240V between the two lines everything is safe and legal.

 

[DonTom]

No, what I meant is there is no 30 amp 120 volt outlet on the transformer, just 3-120 volt 20 amp outlets.

OIC, but all three are just in parallel.

On the subject of 2 30 amp RVs, just for fun, that existing 10/3 would still work.

Yep, as I said, the only problem is getting the correct adapters. Can easily be made as a plug-in using all three (only safe with all three 120 VACs plugged in!). IOW, three 20-amp outlets to two RV-30's.

Better yet is to see if there is a 240/120 vac transformer available that has two RV-30's as its output. If not, can make the adapters.

I have made various weird AC adapters for my electric motorcycles, such as shown here, where it says "I modified a Marinco 6375M AC plug and made an adapter." BTW, do you know what that outlet is called ( 240 VAC outlet for some type of boat?):

First I have seen:

 

[DonTom]

The bottom line is that no transformer is needed to power the OP's 30 amp RV. Only the listed adapter or a knowledgeable electrician to swap out the outlet.

Or we can say:

"The bottom line is that no electrician is needed to power the OP's 30 amp RV"

Will cost less and will have more choices of what the outlet can do.

-Don- Reno, NV

 

[Gary RV_Wizard]

View attachment 2463087

Assuming that adapter is properly wired, that will indeed provide 30A/120v from the 30A/240v outlet. No "step down transformer" is needed when the source is a split phase 240v outlet. The adapter uses just one of the two hot legs (each @ 120v) and the neutral and ground.

 

[bigbAZ]

BTW, do you know what that outlet is called ( 240 VAC outlet for some type of boat?):

First I have seen:

View attachment 2463422

I had to look it up. That configuration has an interesting history. It is a "California Standard" 125/250 volt twist lock used for emergency power, construction power and marine power.

https://forums.mikeholt.com/threads/50-amp-125-250-volt-california-standard-connector.2555720/

 

[DonTom]

I had to look it up. That configuration has an interesting history. It is a "California Standard" 125/250 volt twist lock used for emergency power, construction power and marine power.

From that, I was able to look it up the number. It's a CS6364.

Perhaps the "CS" stands for "California Standard."

It costs $116.28 on Amazon:

 

[NY_Dutch]

Or we can say:

"The bottom line is that no electrician is needed to power the OP's 30 amp RV"

Will cost less and will have more choices of what the outlet can do.

-Don- Reno, NV

The posted adapter costs the least and gets the job done. A transformer would be a costly and unnecessary additional failure point. The adapter has one 30 amp socket, and that's all that's needed.