50amp vs 30am hookup question

When the campsite offers both 50amp & 30amp hookups, do any of you use the 50amp post with a 50/30 drop down attachment or do you use the 30amp post?  Any advantages or disadvantages either way?

Bruce

When the campsite offers both 50amp & 30amp hookups, do any of you use the 50amp post with a 50/30 drop down attachment or do you use the 30amp post?  Any advantages or disadvantages either way?

Bruce

  Assuming you have a 30A service to the coach (Thought you bigguns were 50A for the second AC?)   then using the adapter would add another point of possible failure, and add resistance.  I have seen the adapters make the cord so far away from the post outlet it droops, and reduces blade contact.

BUT... if you regularly trip the post 30A breaker with your rig, the 30A adapter to 50A outlet would allow you to pull a little more and not trip the 50A breaker. So there is a possible advantage there. But be sure the adapter and cord stay fully seated in their sockets!

Bruce,

Volkemon has detailed the only advantage/disadvantage I can think of in this decision, unless one of the post outlets is excessively worn or suspect.

Volk, all Phoenix models (even the "bigguns") are standard with 30A and one A/C, unless the buyer spec'd the 50A option.

Mike

Bruce,

Volkemon has detailed the only advantage/disadvantage I can think of in this decision, unless one of the post outlets is excessively worn or suspect.

Volk, all Phoenix models (even the "bigguns") are standard with 30A and one A/C, unless the buyer spec'd the 50A option.

Mike

Gotcha!  I had (wrongfully) assumed  anything that large had (2) AC units. Florida mindset.    THANKS for the correction.

No advantage.   The 50 amp breaker pedestal is 240v L1 to L2  but an adapter only connects to one side.   The main breaker in your RV distribution panel has only a 30a mains breaker.

See below

Thanks, Don.  Good to know.

Bruce

I find the 50amp plug to generally be in better shape, less use than the 30. 

I find the 50amp plug to generally be in better shape, less use than the 30. 

But... You have to add another connection.... The adapter which may or may not have better connectors and can slightly lower the load capacity.

If the 50amp connection has two-25amp halves which I understood to be typical, then wouldn't going with the straight 30amp connection provide 5 additional amps?

I always get confused with this topic.

If the 50amp connection has two-25amp halves which I understood to be typical, then wouldn't going with the straight 30amp connection provide 5 additional amps?

I always get confused with this topic.

No sir.  The 30A has a 120V 'Hot', a Neutral to 'return' the current, and a ground for safety.   3 wires total.

The 50A has (2)  120V 50A 'Hot' wires, a neutral and ground.  4 wires total.

The 30A has ~3600 watts available, and the 50A has ~12,000 watts available, 6000 for each 120V leg (or 'Hot' wire)



When you use the 50 to 30 adapter, only one 'hot' of the 50A service is used, along with the neutral and ground. 
 Lets say the 30A breaker on the post is old. It has cycled many times, both from being used as a switch and by tripping on overload. Allow also for it living outside in the elements, it has a hard life. This may cause it to trip a little 'earlier' than when new. Say your coach is pulling maximum current when on shore power. Where the 30A breaker in the coach may tolerate being 'on the edge', the worn one on the pole may not. Switching to the 50A adapter, the 50A breaker on the pole (even if worn like the 30) will allow more current to reach the coach.   That is the only advantage I could think of in doing so over using a 30A service.

The shore power cabling for both is 10G, so the 'extra' current that the 50A breaker allows to the coach is still in the permissible range for the wire, and will trip before the wiring between the post and coach breaker becomes a safety issue.

Here are a few pics of my 50A  'power distribution box' I carry.





The cord on the bottom is a 6' 50A male cord, and stores inside when traveling. It is currently plugged into the 50A 240V outlet in our garage.  The 30A cord exiting right is going to our coach in the driveway.

This allows me to plug in the 30A service for the trailer, and the 30A service for the camper at the same time.      I also have (2) 20A GFCI outlets for cords. VERY popular with the tenters around me at festivals.  When closed, the box is raintight. I have been VERY pleased with this setup, and used it many times.

I agree totally with Donc13.

I have made a 50 to 30 adapter using the OTHER leg of the 120.  Although I have not had experience with this, I understand that if the campground is nearly full and 'on the edge' of low voltage - and the 50 amp is available you may have better luck with the locked rotor voltage drop on initial A.C. startup. 

DonC13 comments?

And I LOVE Volkemon's Craftsman box setup.  I need to make one of those!!  Volkemon, do you have a picture of the underside?  I assume you use different hot legs for each 30 amp plug connection.  I can wire it if you don't.

Steve

Thanks Steve! 

Here ya go -



All the solid wire jumpers are 10Ga,   they look tiny next to the 6GA incoming wire.

Yes, eagle eyed electricians will notice that I should have run the neutral from the duplex outlets directly to the incoming neutral lug on the upper 30A outlet. Mea culpa, but there was not enough room to take (3) 10Ga and the (1) 6Ga into that lug. I SHOULD have made a neutral buss bar.... Being that the whole box wouldnt pass inspection anyway, please allow that one deviation.    The grounds are OK like that, they should NOT be current carrying wires. 

RE:50A to 30A

FOR THE GUESTS VIEWING THE FORUM:  This forum is set up so if you are a guest, you cannot see attachments in posts.    You cant see the diagram I am referring to from a previous post. The reason you can see the pictures in my (and Ron D's) posts is because we host them 'off site' so non members can see them.

I seem to have a different setup than what DonC13 has.    If I am reading his diagram right, the right hand of the diagram is a receptacle, a NEMA 14-50R , like below:



  So there is 3 outlets in the post?  I thought it might be a typo, but a 14-50P would make less sense. The way that diagram shows, there is a 50A 240V receptacle, a 30A 120V receptacle, and  50A receptacle that only gives you the same leg on both L1 and L2.   

I defer to others experience, I am new to RV'ing. I have yet to see this setup on a post in my brief time camping in full hookup. I am pretty sure that an outlet wired like that would not pass inspection nor be allowed.
 But if the adapters 'male' side was wired like that, when plugged into a correctly wired 50A outlet you would have a brief 'event' before the breaker tripped from the short. 

I have one of these in my 'Shore Power' box -



In the original post, a ""50/30 drop down attachment"" was referenced. Am I correct in thinking this is referring to this item or the dogbone style? 

The 'dogbone' style is MUCH better IMO, it avoids the height of the stacked adapter/cord pulling out due to gravity. But I carry this one as an emergency use item for when I might not have packed the 'Power Distribution Toolbox'.

This adapter, (and the dogbone style), are internally wired differently than shown in the diagram. (My artwork is not as good as DonC13's, I am a hack using MS Paint  )



This gives you 120V, 50A service to the camper. The wiring of the adapter can be easily checked with a continuity meter to prove this, both the adapter and meter are on my desk now.    I wanted to be SURE before giving electrical advice!! .

 The female side is a Nema TT-30R, which is only rated for 30A, but the supply from the 50A outlet in the post is rated and supplies 50A, so it will deliver 50A to the shore power cable. Which as I originally stated, is the only advantage to using a 50 to 30 adapter.

ALL OF THE ABOVE INFORMATION SHOULD BE VERIFIED BY A LICENCED, QUALIFIED ELECTRICIAN BEFORE YOU USE IT TO MAKE ANYTHING. FOR ALL YOU KNOW I AM A DRUNK RHESUS MONKEY WITH A LAPTOP. ALL THIS INFORMATION IS INTENDED FOR SPECULATIVE DISCUSSION ONLY!!

Steve - could you post a diagram of how you have your custom adapter wired? You seemed to agree with DonC13's diagram, and I am obviously missing something. Would NOT be the first time, either. I have learned a lot from other people showing me where I am mistaken. 



   

Volkemon,

Thanks for your Detailed post above.  You did exactly what I was thinking of using both legs and simply routing them to different 30 amp outlets.   And I'm sure the neutral bus bar may have been the 'electricians' choice.  Many extra Kudos for your sharing!

I am not an electrician.  I have done some wiring on my 30amp from a re-utilized 230 amp water pump using only one leg for Coach and the other let for shop stuff built in my backyard.  Worked great.

I always do some search first to confirm my thoughts.

All 50 to 30 amp dogbones that you buy from the store use Leg 1 of the 50 amp and the Leg 2 is unused.  So all I did was to use Leg 2 on the 50 amp side and NOT use Leg 1 [Remember- that is only 30 amps, (not 50)].  That (from what I read) is likely to be less used in a busy campground and therefore have perhaps a few more amps (or higher voltage) available.

Please correct me if I'm off base.

Volkemon:
Might want to consider some overcurrent protection for the two GFI's.
I know the 30 amp receptacles on a 50 amp circuit is done all the time (though I don't know why it is allowed) but up to 50 amps on a 120volt extension cord could present a danger.
Probably the easiest way to make it safer would be to stick an inline fuse ahead of the GFIs.
Just my 2 cents.