[Jon]

If you just keep your amp use on each leg well under 15 amps you should be fine. High amp usage such as bulk charging, water heater, cooktop and microwave as an example have to be monitored and must be on separate legs.

[Dick]

Keep in mind two important things. First, no matter what the power rating is, the safest and most reliable is 80% of that value or less. The breaker manufacturers make them to trip at the rating or below and to avoid premature tripping of the service stay under 80%.

The second is the potential confusion by how the service is described. In a power panel such as found for hook ups in an RV park we refer to the service as 20, 30 or 50 amp power. In fact the 20 and 30 amp service is accurate and despite it being ideal to balance the loads between the legs you can load either leg with the total load, but 50 amp is actually 50 amp per leg for a total of 100 amps. If either leg exceeds 50 amps however the breaker will trip so theoretically you can have a 100 amp load as long as the loads are balanced between the legs.

[Dick]

Amps, volts, and watts (both AC and DC) are often confusing and mystery to many people, especially motorhome owners. Where they often had no limits or constraints on their electrical use at home, on the farm, or at their business the motorhome presents a whole new set of challenges and a learning curve.

If you’re confused or just plain don’t understand amps, volts, watts, or the terminology (legs, neutral, ground, etc) or how they impact your coach and the use of your coach ask questions. That’s how most of us learned about this stuff.

[Jerry]

Watts = Amps x Volts (in laymens terms).

Math is distributive, so you can make your own formulas using each term as long as you don’t violate the distributive law.

ie. Amps = Watts / Volts. A good example of this is a microwave. Lets say a microwave is rated at 1200 watts and runs on 120 volts. How many Amps does it draw under load? That would be 1200 watts / 120 volts. Roughly 10 amps! If you’re on 20 amp service, that’s half your potential full capacity right there….just in running 1 microwave. As Jon mentions above, you should only count on 80% of the 20 amp service, so thats only 16 amps you have to play with and you just used 10 amps of the 16 amp total on running the microwave. Don’t forget a refrigerator that is probably running, lights, automation systems, dash radio, TPMS that may be wired to stay on all the time, backup camera, house battery charging, chassis battery charging, etc……they all add up.

Jon…..you might know (I have never tried it). Can a modern Prevost coach run on 20 amp incoming shore service for storage? I know its a function of what’s running, but assume no A/C’s, but keeping a refrigerator running, keep the house charging at a maintenance rate, no chassis battery charging, no water heater and yes to all the other system of the coach (Crestron, etc. Just the mission critical stuff. I carry a 50 amp RV to 20 amp converter, but in thinking about it, probably not worth the effort or weight. Then again, there is always the generator

[al]

Often we have discussions about storage with only 20 amp service.

The answer is yes, but the better question is if it is wise.

I have an opinion but I do not know if it is correct. To begin my coach has about 4 amps of phantom loads at 120V, or .4 amps at 12V or ,2 amps at 24V. That enters my thinking because those are typically not controlled by me, but undoubtedly are small loads like clocks, alarms like the security system, maybe antenna boosters, etc.

Then we have loads we almost always leave on because to turn them off and restart or reboot them is inconvenient. A Crestron system as an example is not happy when power is gone so that means in storage leave its 120V circuit on. I have no clue how much a system of that type draws because it is on one of the 120V outlet circuits. But I do know keeping it on also keeps its batteries and other parts of the system alive so when we stop to visit the coach in storage it is alive and we can turn on lights and use its other functions which can range from things like turning on lights to any of hundreds of other possible functions.

So before anything else is turned on for storage we have some loads we likely need. The primary reason for power in storage is to maintain the batteries for the house. Typically that means the use of our inverters and that means we have to understand our coach. Some converters on some vintages of coaches did not have inverter by pass so you may have to run two converters to keep some outlets active. You need to know if there are any loads that will not have power if you put one inverter to sleep to reduce loads on that single 20 amp service.

What I do know is if you need to go beyond maintaining batteries in storage, and need heat or air to deal with the weather it is almost a given 20 amps is not going to be enough.

My opinion and my gut tells me 20 amps is plenty for early vintage coaches, but as newer coaches got more sophisticated and had more gadgets at best 20 amps is not something I would depend on. So the answer to the question is maybe.

[al]

Jon. your math is wrong

4 amps @ 120v

=

40 amps @ 12v

=

20 amps @ 24v

is what I think you meant?

[Lundy]

Good catch Don. I knew what I meant and my brain reversed it.

Makes anything I post highly doubtful.

[Jon]

GMJDW: Check your manuals, but I wouldn’t be surprised if there are dip switches on the rear of your inverter control panels which will allow you to adjust the inverter charging power use. Stupid pita place to put them.

Your vintage coach should have no problem being stored on 20 amps as long as you don’t need heat or a/c and provided you’ve set the inverters to limit battery charging draw. My coach is stored on 20 amp service.

Maybe you could find the upgrade control panel(s) used on ebay.