Stuck 2 carrier aircon units on the roof of our bus...pics

[bigtim44]

Yeah, yeah get the third A/C.

What class do you race at bonneville?

Phil
I run in AA/CGALT car # 622...I PM'd you a message,check your user info box at the top left for messages.
Tim

[prevosman]

 "This gives you two legs of 50 amps at 120 volts. I think it would be really hard to utilize that much power at any one time. Possibly some all electric coaches might use this much but I seriously doubt it. "

You will have to trust me on this because there are a ton of factors which will contribute to 50 amps being inadequate. I can give you a few simple scenarios. Two ACs on one leg both running. I will ignore the start up load for this illustration. That is about 26 amps if the voltage is 120. A lot of campground have lower voltage, but lets look at a good situation. Then consider that the coach has two inverter chargers and the chargers are not set for a low charging rate, but a full bulk charge capability. That could add as much as 20 amps if only one charger is on a leg. Add a refrigerator, a coffee maker, a hot water tank recovering after the morning showers, and then momma plugs in her hair dryer.

The scenario I described is with common devices. As the coach gets more sophisticated as some of the newer store bought conversions are getting, you can plan on an auxilliary air compressor for all the air operated systems such as pocket doors, floor slide and the leveling system and we haven't even considered the entertainment systems, the bay refrigerator, the Jenn Air grill, the two element electric range, etc.

Richard, I agree it is hard to comprehend 50 amps being inadequate, but if we drive buses to have the quality, safety and conveniences you can't carry in a sticks and staples, then power system design and management is the key. As recently as 15 years ago converters were using 12.5 KW generators and with the on-board systems you would be hard pressed to use all that output. Now the typical coach has a 20 KW generator because it is possible to use almost all of that capacity if you used all your systems at once.

I've followed the efforts of some of the folks on these sites and it is clear they are building coaches to equal any store bought conversion and those builders will have devices that will quickly exceed the capacity of the typical 50 amp power outlet. Then if you are in a campground whose power is usually 105 to 110 the power absolutely has to be managed.

[DrivingMissLazy]

I do agree with you that power must be managed and part of that management is in the initial wiring of the coach. If someone were to put both A/Cs on one leg of the 50 amp service, there could be a problem. When you get to three units, then two units must be on one leg and other large draw items must be on the second leg.

Do not forget that you have two 50 amp legs at 120 volts available for a total of 100 amps. The examples you utilize show only one leg of 50 amps if I understand you correctly.

I never saw any case of my total load being over 50-60 amps with everything on at maximum. I still has at least 40 amps in reserve.

As you state, generally you do not have to calculate initial inrush current that lasts for a couple of seconds only. All breakers and wiring is designed to handle this momentary overload. This is assuming that all wiring has been completed to meet code requirements.
Richard

"This gives you two legs of 50 amps at 120 volts. I think it would be really hard to utilize that much power at any one time. Possibly some all electric coaches might use this much but I seriously doubt it. "

You will have to trust me on this because there are a ton of factors which will contribute to 50 amps being inadequate. I can give you a few simple scenarios. Two ACs on one leg both running. I will ignore the start up load for this illustration. That is about 26 amps if the voltage is 120. A lot of campground have lower voltage, but lets look at a good situation. Then consider that the coach has two inverter chargers and the chargers are not set for a low charging rate, but a full bulk charge capability. That could add as much as 20 amps if only one charger is on a leg. Add a refrigerator, a coffee maker, a hot water tank recovering after the morning showers, and then momma plugs in her hair dryer.

The scenario I described is with common devices. As the coach gets more sophisticated as some of the newer store bought conversions are getting, you can plan on an auxilliary air compressor for all the air operated systems such as pocket doors, floor slide and the leveling system and we haven't even considered the entertainment systems, the bay refrigerator, the Jenn Air grill, the two element electric range, etc.

Richard, I agree it is hard to comprehend 50 amps being inadequate, but if we drive buses to have the quality, safety and conveniences you can't carry in a sticks and staples, then power system design and management is the key. As recently as 15 years ago converters were using 12.5 KW generators and with the on-board systems you would be hard pressed to use all that output. Now the typical coach has a 20 KW generator because it is possible to use almost all of that capacity if you used all your systems at once.

I've followed the efforts of some of the folks on these sites and it is clear they are building coaches to equal any store bought conversion and those builders will have devices that will quickly exceed the capacity of the typical 50 amp power outlet. Then if you are in a campground whose power is usually 105 to 110 the power absolutely has to be managed.

[Beatenbo]

I bet if you check your campground 50 amp is two 25 amp legs providing 50 amps total. I have seen people in camprounds use a 50 amp adapter on a 30 amp hookup thinging they were geetiiing more but really less. Adapts one 25 amp 120volt. Correct me if I'm wrong. I just read my gen specs today. My 10KW is rated at 40amps per leg that gives me 80 amps ( 10,000watts divided by 120 volts = 83.3 amps) my gen will run more than any campground I've ever been in. Blwssings, Charlie

[DrivingMissLazy]

If the campground is wired correctly, and I have never run into one that was not, The 30 amp service is one leg of 30 amps at 120 volts for a total of 3600 watts
.
A 50 amp service is rated at 50 amps 240 volts. Therefore you have two legs of 120 volt power at 50 amps for a total of 12,000 watts.

Some people do not understood this and think they are only increasing from one leg of 30 amps, 120 volts to one leg of 50 amps at 120 volts for a total of 6200 watts when they go from 30 amp service to 50 amp service. This is incorrect. 
Richard

I bet if you check your campground 50 amp is two 25 amp legs providing 50 amps total. I have seen people in camprounds use a 50 amp adapter on a 30 amp hookup thinging they were geetiiing more but really less. Adapts one 25 amp 120volt. Correct me if I'm wrong. I just read my gen specs today. My 10KW is rated at 40amps per leg that gives me 80 amps ( 10,000watts divided by 120 volts = 83.3 amps) my gen will run more than any campground I've ever been in. Blwssings, Charlie

[Beatenbo]

My math was wrong, don't kwow what I was thinking My gen 10,000 watt divided by 240=41.6 amps total Your 50amp is 2 legs of 120 to get 240, but I always thought 2X25= 50 total. 2 50 amp leggs would produce 100 amps. I try to make my wife think I know everything but really I don,t.

[Nick Badame Refrig/ACC]

Hi Charlie,

Richard speaks the truth, 50a camp service is 2 legs of 50a each.

Either 50a at 240v. or  2 115v 50a each.   Don't worry, it really IS complicated!  Ha Ha !

Nick-

[bigtim44]

Good info on the shore power capability

[Christyhicks]

BUT, when you dogbone two 30 amp recepts together, you only end up w/60 amps, which means you can draw only about 48 amps continously. Plus, if you have 240v wired appliances and those two 30 amp recepts on are the same side of the main (i.e. same leg of power), you will only get 120v and the 240v appliance will not work .  Just food for thought .  Christy

[JackConrad]

   If you combine a 30 amp and 20 amp at the campground post into your 50 amp wired coach you will be limited to a total of 50 amp. However, you only have 20 amp on one leg and 30 amp on the other before the campground breaker(s) trips (If the campground is wired correctly with the 20 and 30 on separate legs of a 240 service). If you are trying to use 240 volt, you would be limited to 20 amp before the campground 20 amp breaker would trip. At least this is my understanding, correct me if I am wrong (wouldn't be the first time Or The Last)  Jack

[DrivingMissLazy]

Jack and Christy, I think you are correct.

Said another way, I found that there were two different type adapters.

One box has two 120 volt connectors that you could plug one of them into a 20 amp outlet and one of them into a 30 amp outlet on the campground power pole. You then plug your 50 amp shore cord into the box. That gives you two legs of 120 volt power,  for a total of 50 amps. Generally the two outlets on the campground pole are different phases so you actually have 240 volts between them. But not always!.

The other adapter that I had was a 30 to 50 amp adapter. This was for use when you have a 50 amp shore cord and the only pole outlet is a 30 amp source.

You plug your 50 amp shore cord into the 50 amp side of the adapter. The 30 amp connector on the other end of the adapter you plugged into a 30 amp outlet on the power pole. This adapter connected the 30 amp source to both of the hot legs of the 50 amp shore cord and then supplied a total of 30 amps, 120 volts to the coach. At least, that is how I remember it. Sure gets confusing, doesn't it?
Richard

   If you combine a 30 amp and 20 amp at the campground post into your 50 amp wired coach you will be limited to a total of 50 amp. However, you only have 20 amp on one leg and 30 amp on the other before the campground breaker(s) trips (If the campground is wired correctly with the 20 and 30 on separate legs of a 240 service). If you are trying to use 240 volt, you would be limited to 20 amp before the campground 20 amp breaker would trip. At least this is my understanding, correct me if I am wrong (wouldn't be the first time Or The Last)  Jack

[prevosman]

Richard, I think we are both correct when talking about power and its management.

My point about having two AC units on the same leg is because when you have three, that is what occurs. That leaves the system designer with a dilemma. What of the remaining circuits is to be on that leg or the other. Despite excellent engineering, my Liberty conversion is capable of tripping any 50 amp campground circuit it I do not pay attention to what is on on each leg.

Or put another way, even if I am careful, I have to be aware that if the AC cycles, even though my running loads are safe I may trip the circuit if the start up load is added.

BTW, as long as we have good 120 volt power managing power is a snap. It is when the available voltage drops that we really have to be careful because the current draw climbs.

[Beatenbo]

Don't wanna ride this horse to death, butttt-I have my bus wired 110 30 amp . there is a100 amp box with a 50 amp pigtail, 2 50 amp plugs. No auto switch. The gen is wired standard 2 legg 240v to one leg. Shore is 30amp with a jumper in plug to make both sides hot. The reason for 30 amps is I don't get in a lot of campgrounds and sometimes I have to plug into 20amp and run 1 a/c and basics. I have 3 a/c . I have the front on a plug in bay so I can unplug and run seperate if needed.What I want to know now that I've learnd RV parks are 50amp per leg isssss can you take a 50-30 adapter which drops one leg for 110 and plug a 30amp into the 50 namp and run 2 a/c using the 50 amp 1 leg 110volt.  I KNOW how quick you can weld a plug together or melt down to a fire hazard. a 30 amp is border line for 2 a/c and that little extra would help...whew!

[prevosman]

I know this has been repeated many times before, but think of a typical campground power outlet with what the industry calls a 50-30-20 configuration as a single 20 amp 120V receptacle, usually a GFCI. It also has a single 30 amp 120V receptacle. Both of these receptacles are pure 120 V, and in the typical power outlet are on separate legs.

The 50 amp outlet is what tends to confuse a lot of people. As Richard pointed out earlier, that is a four wire receptacle with two hot legs, a common and a ground. Between the two hot legs is 240 V. Between either hot leg and the common is 120 V, and each of the two legs has 50 amp capacity.

There are a lot of misconceptions about the power coming from these boxes and how to get it into our coaches. My only advice is that unless you know exactly what you are dealing with in the power outlet and your coach, do not start getting creative. I am especially concerned about amatuer built conversions especially when the owner is unsure of how they were wired, especially as relates to grounding.

By code, all new power outlets require a 20 amp GFCI outlet. Generally they will not allow a 20/30 amp combined cheater cord to give you 50 amps of 120V because the GFCI will trip.

[DrivingMissLazy]

Well said my friend, well said. I think you and I are on the exact same page, I just did not say it as well as you.
Richard

I know this has been repeated many times before, but think of a typical campground power outlet with what the industry calls a 50-30-20 configuration as a single 20 amp 120V receptacle, usually a GFCI. It also has a single 30 amp 120V receptacle. Both of these receptacles are pure 120 V, and in the typical power outlet are on separate legs.

The 50 amp outlet is what tends to confuse a lot of people. As Richard pointed out earlier, that is a four wire receptacle with two hot legs, a common and a ground. Between the two hot legs is 240 V. Between either hot leg and the common is 120 V, and each of the two legs has 50 amp capacity.

There are a lot of misconceptions about the power coming from these boxes and how to get it into our coaches. My only advice is that unless you know exactly what you are dealing with in the power outlet and your coach, do not start getting creative. I am especially concerned about amatuer built conversions especially when the owner is unsure of how they were wired, especially as relates to grounding.

By code, all new power outlets require a 20 amp GFCI outlet. Generally they will not allow a 20/30 amp combined cheater cord to give you 50 amps of 120V because the GFCI will trip.