Two A/C operation on Winnebago Brave

[Robert Perkins]

I have a 1998 Class A Winnebago Brave with two roof A/C units. Both will operate at the same time when using the generator for power. When connected to shore power at the camp site only one will work. I have been told this is normal. I want both to work at the same time when connected to shore power. What do I need to do to make this happen? Do others have the same problem? Thanks for any help.  Bob

[Robert Perkins]

I found the answer , just convert to 50 amp service quite simple and less tha $300. If anyone else needs the info just email.  Bob

[John "T" Nordhoff]

   If you want to run BOTH rooftop AC's when plugged into shore power, YOU NEED 120/240 VOLT 50 AMP 4 POLE (Hot 1, Hot 2, Neutral, Ground) PLUG SERVICE. If youre only on 120 volt 30 amp 3 pole (Hot, Neutral, Ground) service you can only run one.

  On bigger later model RV's with 120/240 volt 50 amp 4 prong plugs, you get not one but two legs of 120 volts (its 240 volts line to line but the RV doesnt usually use 240 volt appliances) and one runs one AC the other leg runs the other AC.

  On smaller RV's with 120 volt 30 amp 3 pole service theres but one leg of 120 volts which runs the one AC

 

  John T 

[Robert Perkins]

Thanks for the reply, I found this out and will be doing the conversion today. After researching this seems fairly easy and straight forward. Thanks Bob

[Robert Perkins]

If you can run both A/C units from the generator the wiring is handling the same curent when you switch to the 50 amp. The second 120 volts to run the rear A/C unit is the only thing being supplied from the 50 amp service.

[John "T" Nordhoff]

 If the Genny is a 5000 watt it can supply something over 40 amps and its wiring and the RV's distribution wiring from genny to panel and panel throughout RV, is Im sure sufficiently rated (theyre too much a fire hazard to NOT run big enough wire Im sure).

 

 HOWEVER if were (Pats post above) talking about a CORD from the RV to the parks outlet IT HAS TO HAVE BIG ENOUGH WIRE and thats NOT the same as the RV internal distribution wiring from genny to panel etc. If its only 30 amp wire then I advise you DO NOT let more current pass through it, those cords get hot enoiugh the way it is

 

 BUTTTTTTTTT if the RV is wired so theres only 30 amps (80% or 24 not 30 is all the max continuous load I designed for) that can pass thru that 30 amp cord AND AT THE PARKS OUTLET ITS PROTECTED BY A 30 AMP BREAKER  HEY NO PROBLEM

 

  I cant say sittin here how the RV or any modificatiosn or upgrades are wired???????? but I can say as an electrical distribution design engineer the above rules must be followed to prevent overheating and fire hazards.

 

 John T  Retired Electrical Engineer now semi retired Attorney at Law

[John "T" Nordhoff]

Good point Pat NOPE 10 gauge 30 amp wiring will NOT handle 50 amps of current without overheating. Those 50 amp plugs and cords are rated at 50 amps and the RV Park 50 amp 4 pole receptacle uses a two pole 50 amp overcurrent protection device (circuit breaker).

 

 The 50 amp plugs are 4 pole: 2 Hots, Neutral, Equipment Ground AND 50 AMP RATED WIRE. Im sure you ALREADY know this, but for the others one more time Hot leg 1 runs one AC at 120 the other Hot 2 leg runs the other AC at 120. The 50 amp 4 pole system has TWO LEGS OF 120 VAC and is fed off a 50 amp breaker to protect 50 amp rated wire.

 

 The RV Parks 120 volt 30 amp 3 pole (Hot, neutral, Ground) outlet uses a 30 amp breaker as the wire is only rated for 30 amps

 

 John T  BSEE, JD Retired Electrical Distribution Design Engineer

[Robert Perkins]

As I stated above the one 50 amp leg is only running the rear A/C unit rated at 12.5 amps that is the only thing on that leg. The other leg is 50 amp available but still running the same items the 30 amp service ran The coach main breaker is still 30 amps so there is no increase in current draw even if more amperage is available. To put it simple so you can undarstand the power line coming into your house can supply 300 to 500 amps but your main breaker panel in the house is 200 amps and that is all the current that can go to the house. Also I have added a 20 amp breaker to the circuit for the rear A/C unit.

[John "T" Nordhoff]

  Good job Robert, sounds like youre getting there, so glad we were able to lend you a hand and thanks for the feedback. Feel free to ask more if needed WERE HERE TO HELP. And you dont have to put it simple terms for me to unerstand, it even thought its always good to do so for the benefit of others, thats what I was trained in professionally BSEE Purdue University 1969/1970 and what I did for a living on and off 43 years (Electrical Power Distribution Design Engineer)  BTDT Got the T Shirt as they say lol

 

 You stated:  "As I stated above the one 50 amp leg is only running the rear A/C unit rated at 12.5 amps that is the only thing on that leg".

  CORRECT, A 50 amp 120 volt Branch Circuit supply can certainly run a 12.5 amp AC NO PROBLEM

 

 You stated: " The other leg is 50 amp available but still running the same items the 30 amp service ran"

  CORRECT, Again, if you indeed do have another leg of 50 amps available?????? (Lets see thats TWO LEGS YOUR USING NOW RIGHT???) that can sure supply what only was a 30 amp max current draw before .

 

 You stated" The coach main breaker is still 30 amps so there is no increase in current draw even if more amperage is available."

 THAT PART IS CORRECT

  If the RV main breaker is still only 30 amps, then 30 amps is sure the max you can supply out of that distribution panel otherwise the main will trip out.

 

 NOTE: In the normal configuration a 30 amp 120 volt RV panelboard IS ONLY A SINGLE POLE 120 VOLT while the normal 50 amp configuration is a two pole 240 volt (120 either Line to Neutral) panel. The 30 amp 120 volt SINGLE POLE can only supply one leg of 120 VAC at 30 amps HOWEVER a 50 amp 120/240 can supply not one but TWO LEGS OF 120 VAC at 50 amps (one AC on one leg other AC on other leg)

 

 QUESTION FOR YA ROBERT  (just to be sure for your sake and help) You talk of having two legs available, so for two legs of 120 VAC you need not 3 but 4 wires ya know??? An RV 50 amp plug is a 4 pole remember (unlike only a 3 pole 30 amp 120 volt) !!!!Thats two Hots L1 & L2,,,,,,One Neutral a GrounDED Conductor,,,,,,,,,,One Equipment GroundING Conductor. For only one leg of 120 VAC you only need 3 wires, 1 Hot, 1 Neutral a GrounDED Conductor, One Equipment GroundING Conductor. I JUST WANT TO MAKE SURE YOURE AWARE OF THAT AND HAVE IT CORRECT Robert, dont wanna see a hazard out there, it can ruin a camping trip plus cost your life ya know !!!!!!!!!!!!!!!!!!!!!!!!!! 

 

 ANOTHER QUESTION FOR YA ROBERT So how many wires and what gauge cord and how many cords  are you going to end up running from the RV parks outlet to your RV?????????? Dont forget you still cant exceed the cords wire ampacity and if youre converting completely to the regular modern 50 amp 4 wire RV service thats a 4 pole 50 amp plug and 6 gauge wire youre gonna need. ALSO they dont normally try to run TWO AC's off a only 30 amp service !!!!!!!!!! Even if they only pull 12.5 amps (25 total) they take 4 to 6 times more current at start up so it would be awful tough to run two AC's off a 30 amp service YIKESSSSSSSSS

 

 FINALLY YOU STATED:  "To put it simple so you can undarstand the power line coming into your house can supply 300 to 500 amps but your main breaker panel in the house is 200 amps and that is all the current that can go to the house".

 VERY VERY CLOSE heres how its done. If your home has a 200 amp service, the three wires from the service transformer leading to your house ARE ONLY RATED FOR 200 AMPS NOTTTTTTTTTT 500 buttttttttttttt hey youre partly right, thats not to say 500 couldnt flow for a short time until the wires melted or a fuze opened!!! ALSO the 200 amp main breaker in your home panel ONLY LIMITS THE CURRENT INNNNNNNNNNN (downstream and after the main breaker) NOTTTTTTTTTT TOOOOOOOOOO THE HOUSE. The current TOOOOOOOOO the house depends on the Voltage available at the Transformer and the load. Yes normally if theres no problems or shorts or extra current paths the current wont be greater then the 200 amps the house panel can supply, but wires go bad, insulations get frayed or damaged, shorts develop etc etc so even if the panels main breaker limits current INNNNNNNNN the house thats not to say there might not be more current (over 200) flowing out of the transformer. HOWEVER theres backup limits and protection also, the wire can open or the fuze at the transformer can pop out ya know !!!!!!!!!!

 

 Sooooooooo maybe a little nit picky but just to try and help and educate the readers of this great site BUT ITS IMPOSSIBLE TO COVER IN A FEW SENTENCES HERE WHAT TAKES YEARS OF EDUCATION AND PRACTICE AND EXPERIENCE TO ACCOMPLISH SO dont feel bad if its still A bit fuzzy lol

 

 God Bless ya Robert, so glad to help so do it right AND BE SAFE, we dont want anyone hurt

 

 Ol John T in Indiana  BSEE, JD 

[Robert Perkins]

I have the female 50 amp plug installed and wired only wired the one hot for the coach power. I wired from the generator junction box wire for the rear A/c and over to the shore power junction box. I started the generator and the rear A/C works and I have power to the 50 amp receptical for the coach power. I still need to buy a short 50 amp male plug/cable to wire into the shore power junction box this will plug into the coach plug (generator power) and then buy a 50 amp service extention cable. This was a little harder than I first thought and total cost $250. It is worth it to be able to run both A/C units, it gets hot here out west and one A/C just does not cool the coach. I also need a adapter from the 50 amp plug to a 30 amp in case the RV park does not have 50 amp service. Thanks for all the help if you see anything wrong let me know.

[John "T" Nordhoff]

  I believe you about it getting hot out in the arid Southwest at least and needing two AC's. I tried to get a reservation at Picacho Peaks State Park seems like its near Casa Grande Arizona?? for June and the lady tells me OH WERE CLOSED THEN BECAUSE IT GETS TOO HOT HERE BY THEN............Were en route then on way to San Diego but after that its Utah and Colorado to higher elevations and cooler nights at least.

 

  Wal mart sells a 50 Male to 30 Female adapter around $16 for RV's with a 30 amp plug if the RV park has only 50 amp outlets (Ive been places that do), but of course that only gives you one leg of 120 volts but thats all you need in your 30 amp one AC RV like my Class C.

  ALSO they make that 50 down to 30 you mentioned (FOR PARKS THAT DONT HAVE 50 AMP OUTLETS), it has a 50 amp female for your RV's 50 amp 4 pole male plug and a 30 amp 3 pole male plug to fit into the parks regular 30 amp 3 pole outlet.  Of course, you cant run but one AC with that setup, its only one leg of 120

   ALSO I think they make a cheater adapter for guys who want 2 legs of service if the park ONLY has the one leg 30 amp 120 volt outlet PLUS a regular smaller 20 amp duplex receptacle right there beside it in the same box like many older parks use. I DOUBT IF ITS UL APPROVED LOL It has a 30 amp male and a 20 amp male that you plug to the parks regular  typical boxes THEN ALL THAT GOES INTO THEIR BOX AND IT HAS A 50 AMP FEMALE RECEPTACLE so your regular 50 amp 4 pole plug fits in. What it does is electronically verify the 30 amp and 20 amp in the RV park box are on seperate legs (L1 & L2 as typical) and if so it feeds a leg to each of the 50 amp receptacle poles NOTE you still only have 30 amps on one leg and 20 on the other (It cant make energy) buttttttttttt either of those should still run an AC so BOTH your roof AC's can work.

 I forget where I saw them for sale??????????? but I know the RV parks prob dont like them and as an enginner its NOT the way I do things lol

 

 THERE WE PRETTY WELL BEAT THIS TO DEATH AND COVERED ALLLLLLL THE BASES

 

 See you on the road maybe, read my National Parks Tour blog up above or below here somewhere

 

 John T