Converting from 30a to 50a

[Vicr]

Craig, how did you find two different 50a adapters that pick up different phases off the receptacles? Different brands? Damn good idea. Depending on how poorly engineered/ maintained the RV park distribution system is you could have a huge disparity in voltage between A and B phase.

[craigav]

Originally Posted by Vicr

Craig, how did you find two different 50a adapters that pick up different phases off the receptacles? Different brands? Damn good idea. Depending on how poorly engineered/ maintained the RV park distribution system is you could have a huge disparity in voltage between A and B phase.

In my case it was a bit of luck involved.

I had purchased a used 5th wheel years back and was in Oklahoma on a very hot day and everyone was running their A/C's. I plugged into the 30a receptacle and the digital voltage meter that I keep plugged in to an inside outlet indicated ~106 volts which of course was very concerning to me. The previous owner had left me a 50a to 30a adapter which was in good shape so I decided to try it on the 50a receptacle and sure enough the voltage went up to ~115, however I had also purchased a brand new adapter and thought perhaps I would just use my shiny new one and keep the older one for a spare and then when I swapped out the adapters my voltage went back down to the ~106v. That is when I got my meter and determined that each adapter was pulling from the opposite 50a leg than the other adapter. Two different brands, but I don't remember which brands. Next time I am at the RV I will check and see if the brand names are listed. One has a pull handle and the other one doesn't. Both now look like new as I cleaned the older one up with some fine sandpaper and keep a bit if dielectric grease on it (both of them). I have never seen any 50a to 30a adapter advertised in regards to which leg it is pulling from, so in my case it was simply a bit of luck. ~CA

[TCNashville]

Originally Posted by craigav

Not to add any additional confusion, and you are correct. I have been to more than one poorly wired RV campground that for whatever reason they wired the pedestals 30a receptacle to the same leg as all the others and if you have low voltage on the 30a receptacle and when\if you check the voltage on each leg of the 50a circuit, one of them comes in at the same and lower voltage that the 30a receptacle is on. With this in mind, I have two 50a to 30a adapters, the difference between the two is that they each one adapts from the opposite leg of the 50a to the single 30a. So that allows me to use whichever adapter when\if needed provides for the higher voltage. The only easy way to know any of this is to have a vom (voltage ohm) meter. At one time many years back I built an 50to30a adapter with a switch on it so I could simply switch the switch to the higher voltage leg, and more recently and perhaps by luck I determined that I already had two adapters that pulled from the opposite leg negating the need for my special built adapter any more. In any case, not to go any deeper, RV 50a connections have TWO 50a legs and the 30a RV's have ONE 30a leg, so as designed a 50a connection (not speaking of adapters) would be able to provide ~100a total capacity and the 30a connection would be able to provide 30a. (I say that as a high level statement reality is most breakers will trip after 80% of what they are rated for with enough time exceeding the 80%). ~CA

Thank you Craig and others, very helpful info. My main concern here is the protection of my 30 amp power cord. My power hookup is as follows: First I inspect the 30 amp receptacle and if I looks bad or worn I'll get out the 50 to 30 adaptor. Before I plug in the adaptor, I flip the 50 amp breaker off, then plug in the adaptor. Then I plug in my Progressive Industries 30 amp EMS into the adaptor, flip the breaker on and wait for the EMS to approve the use of the receptacle. Flip the breaker back off and plug my power cord into the EMS. Flip the breaker back on and after the EMS wait time I usually see voltage in the 118-123 range coming from the 1 50 amp leg I'm hooked into. Sound good?

[craigav]

Originally Posted by TCNashville

Thank you Craig and others, very helpful info. My main concern here is the protection of my 30 amp power cord. My power hookup is as follows: First I inspect the 30 amp receptacle and if I looks bad or worn I'll get out the 50 to 30 adaptor. Before I plug in the adaptor, I flip the 50 amp breaker off, then plug in the adaptor. Then I plug in my Progressive Industries 30 amp EMS into the adaptor, flip the breaker on and wait for the EMS to approve the use of the receptacle. Flip the breaker back off and plug my power cord into the EMS. Flip the breaker back on and after the EMS wait time I usually see voltage in the 118-123 range coming from the 1 50 amp leg I'm hooked into. Sound good?

What you are already doing is the way to do things. I will add just a bit of thought, it is very hard to determine the condition of the internal female receptacle contacts, and if they are in bad shape and even if your plug is in good shape a lot of heat could build up, which in part is why I suggested in an earlier comment to check your plug for heat build-up preferably (imo) with a laser pointer temp gun. I would suggest that on your side that you often check (before and after each usage) your male plug(s) and consider using fine sandpaper (if needed) to keep it shiny and clean, and protect it with a very light coat of dielectric grease. A bad receptacle can certainly cause your otherwise good plug to become damaged. Your idea of using the ems to approve the receptacle prior to usage is good, my ems is built in so I can't use it to determine anything prior to plugging in, however it is likely the same Progressive EMS you are using (except hardwired in) and shouldn't pass the current if a fault is detected. ~CA

[craigav]

Originally Posted by Vicr

Craig, how did you find two different 50a adapters that pick up different phases off the receptacles? Different brands? Damn good idea. Depending on how poorly engineered/ maintained the RV park distribution system is you could have a huge disparity in voltage between A and B phase.

As a thought based on your question, if I didn't have what I already have, (and had one 50a to 30a adapter already). I would likely purchase another adapter and a 50a plug and cut the male plug off the adapter (unless it was already on the opposite leg) and then wire the new 50a plug to the other leg. That is likely what I will do when\if I ever need to replace one of my two adapters (I don't use them often so they likely will last a long time). ~CA

[Cavie]

Originally Posted by TCNashville

LOL, Ok let me get this all straight before the thread is closed. A 50 amp plug is [2] 120 volt legs, correct? A 30 amp plug is [1] 120 volt leg, correct? Sooo when I plug my Progressive Industries 50 amp adaptor, which [1] side is a dummy plug not connected to anything, into the 50 amp plug, I'm only receiving [1] leg of the 50 amp connection or 120 volts to my 30 amp plug that's plugged into the 50 amp adaptor, correct? Wow, I think I may have just confused myself, lol.

You confused me and I am a master electrician. ROTFLMAO.

[TCNashville]

Originally Posted by craigav

What you are already doing is the way to do things. I will add just a bit of thought, it is very hard to determine the condition of the internal female receptacle contacts, and if they are in bad shape and even if your plug is in good shape a lot of heat could build up, which in part is why I suggested in an earlier comment to check your plug for heat build-up preferably (imo) with a laser pointer temp gun. I would suggest that on your side that you often check (before and after each usage) your male plug(s) and consider using fine sandpaper (if needed) to keep it shiny and clean, and protect it with a very light coat of dielectric grease. A bad receptacle can certainly cause your otherwise good plug to become damaged. Your idea of using the ems to approve the receptacle prior to usage is good, my ems is built in so I can't use it to determine anything prior to plugging in, however it is likely the same Progressive EMS you are using (except hardwired in) and shouldn't pass the current if a fault is detected. ~CA

I have a thermal temp gun I usually check my hubs with while towing the camper when stopped. I will use it now to check plug in temp as well. Should I assume a normal plug temp to be around ambient air temp at the time? It would probably be hotter the more load that is put on it, huh. I also use dielectric grease liberally on things such as my boat tail lights, simple butt wire connections, etc. Not sure why I didn't think to use it on my 3 prong 30 amp plug. Great advice, thanks.

Originally Posted by Cavie

You confused me and I am a master electrician. ROTFLMAO.

Deep down you guys gotta love electrically challenged people. Especially those who aren't afraid to ask. Knowledge is power, thank you.

[craigav]

Originally Posted by TCNashville

I have a thermal temp gun I usually check my hubs with while towing the camper when stopped. I will use it now to check plug in temp as well. Should I assume a normal plug temp to be around ambient air temp at the time? It would probably be hotter the more load that is put on it, huh. I also use dielectric grease liberally on things such as my boat tail lights, simple butt wire connections, etc. Not sure why I didn't think to use it on my 3 prong 30 amp plug. Great advice, thanks.

Yes, the temperature of the plug and cable should be close to the ambient temp or slightly higher. The melt-down and fire potential problem really comes in when the plug starts to get close to the melting point of the plastic, however by that time you already have a problem that you could have proactively avoided. I try to check my connection shortly after the A/C has been turned on for ~5 minutes or so (or any heavy load such as an electric heater) and then again maybe an hour or so later, followed by a visual check every so often when I come and go from the RV. I generally don't use the temp gun though and just touch the plug and cable, which is a bit hypocritical of me to suggest one thing and then do another . I will say that using the non-touch temp gun provides for a much higher level of safety and as I think about it I will use mine more often as one can never be "too" safe imo.

Some people may have different thoughts to share regarding the dielectric grease, I only use enough for a very thin coating, keep in mind that dielectric grease is not a conductor and the over use of it is not necessarily a good thing in every case. On your boat light bulbs the bulb contacts actually pushes through the grease and makes the low voltage and low current connection and the remaining grease helps keep the water and contaminants out which is a good thing, on an electrical plug that is already loose and\or diminished in one way or another, a lot of grease can actually make the connection worse and not better. My advice, just use enough grease to allow for a very thin coating on the male plug to help keep it shiny and clean and not use any more than that. ~CA

[SmokerBill]

Originally Posted by slabat

Yes, I would like to put an second air conditioner on my camper.

Hey slabat,

You've gotten a ton of information here. Have you decided what you're going to do, or are you ready to give up RV'ing and buy a tent?

[Route 66 Traveler]

Originally Posted by TCNashville

My power hookup is as follows: First I inspect the 30 amp receptacle and if I looks bad or worn I'll get out the 50 to 30 adaptor. Before I plug in the adaptor, I flip the 50 amp breaker off, then plug in the adaptor. Then I plug in my Progressive Industries 30 amp EMS into the adaptor, flip the breaker on and wait for the EMS to approve the use of the receptacle. Flip the breaker back off and plug my power cord into the EMS. Flip the breaker back on and after the EMS wait time I usually see voltage in the 118-123 range coming from the 1 50 amp leg I'm hooked into. Sound good?

I basically do the same thing, but before plugging in my Progressive PTX-50 I turn off the main breaker and spray the female socket with some CRC Contact cleaner. Wait until it dries, then plug in my EMS.

Did I mention I wired my RV with the new SmartPlug socket and plug? 1000 times better than the 1930's socket and plug that tends to overheat and catch fire.

https://www.technorv.com/smart-plug-50-amp-kit/

That should stir up more controversy........

[dynarider]

Originally Posted by Vicr

The over current protection (breaker) for the 50 amp pedestal receptacle is 50 amps. The conductors in the RV supply cable is rated for 30 amps therefore the supply cable conductors are undersized to be on a 50 amp circuit.
NEC Article 240.

The circuit breaker is to protect the circuit from the receptacle back not the plugged in device in this case the trailer cord.

[Vicr]

Originally Posted by dynarider

The circuit breaker is to protect the circuit from the receptacle back not the plugged in device in this case the trailer cord.

WOW! Well obviously you don't know that EVERYTHING down stream from the breaker is considered part of the circuit in the case of the service pedestal receptacle and that includes the service cord to the RV. You need to read NEC articles 240 and 551. The receptacle isn't the load to be protected, its what you plug into the receptacle which needs the over current protection.

[RPR]

Question for the master electricians. If the campground has three phase coming off the service pole transformer and they used what I call the stinger lead for 50 amp service at the sites is that good, normal or does not matter?

[Vicr]

Well first of all 3 phase with a stinger (high) leg is very rare these days. The last time I encounter a 3 phase service with a stinger leg was in Goleta, CA back in the 80's. I myself wouldn't use the high leg for anything but 3 phase power without a neutral, usually motor loads. The danger with the high leg is that it's 208v to ground/neutral so if you used the high leg for one phase and lost the other leg for some reason you'll single phase (melt your stuff) because all you 120v loads will have 208v running thru them. We used to use orange phase tape or use orange wire to identify the high leg in as a warning, can't remember if it was a code or not, too long ago.


VSR
IBEW Local 46
Seattle, WA

[Cavie]

Originally Posted by dynarider

The circuit breaker is to protect the circuit from the receptacle back not the plugged in device in this case the trailer cord.

Breakers never in place to protect a plugged-in device. They sized the protect the wire used in the circuit. The 30 amp cord is not a device.

[SmokerBill]

Someone should design a 50 amp to 30 amp adapter that has a built-in 30 amp breaker or fuse. That would give the main 30 amp power cable proper protection, wouldn't it?

[Cavie]

Originally Posted by RPR

Question for the master electricians. If the campground has three phase coming off the service pole transformer and they used what I call the stinger lead for 50 amp service at the sites is that good, normal or does not matter?

It is not good and probably not done. My guess is they used Plastic snap-in blanks in every 3rd slot in the service panel and feed 240 volts to the peds with two 120 volt legs. If they did not do that they have a few peds with a 120 leg and a 208 leg. NOT GOOD.

[JFlightRisk]

Thread closed per request by multiple members.