110 or 30 shore install

[JeyM]

Good afternoon everyone,

I am getting ideas together for my first shore power install. But I am definitely running into some confusion. I’ve really been trying to do my own research so I don’t have to bother others with questions I could find on my own. But this one has my confused..

I watched a video where someone simply installed an 3 prong inlet to the outside of their vehicle, They used it to run a regular extension cord from the inlet to their power source (110 outlet)

On the inside their inlet ran to a two place breaker box (2x 20amp breakers) and each breaker ran to one outlet in their vehicle for two outlets total.


My question is, What’s the main difference between running a setup like that (110) vs installing a 30amp inlet setup? More power availability?

Would I need one breaker per outlet in vehicle?

What amp breakers would I need?




I plan to run an AC, TV and lights at the same time when hooked into shore power.

Would the 30amp inlet be wired the exact same way into a breaker box - outlets or is there more to it?

Thank you

 

[david.dgeorge07]

That’s a kind of big question and there are a lot of elements of your post that are cans of worms to open up. The first thing I would say is don’t move forward until you have a good understanding of what to do because there are significant safety concerns involved with running a shore power 120 V or 110 V electrical system inside your bus.

To your main question, both of the scenarios that you described are 110 V, but the standard plug that you’re talking about is a 15-20 amp 110 V where as the common RV plug style is a 30 amp 110 V. Simply put: you can get more power from a 30 amp connection.

Even if you use a 30 or 50 amp inlet it is easy with the use of an adapter to plug it into a standard 20 amp outlet. The caveat of course is that you only get 20 A out of the standard plug but often that is enough to be much better than nothing.

You don’t mention and your original post how much air conditioning you plan to run. Of all the things that you mentioned air conditioning is the only one that would make it likely that you would need 30 amp service. Even so, installing 30 or 50 amp service is not a bad idea in case you plan to upgrade later.

I wired my bus before 50 amp service just in case.

There’s a lot to consider in this aspect of the build especially if you plan to do anything more than very basic. Continue to ask questions here but there is a depth of understanding of the topic that is hard to really reproduce in a forum, and you may be best served to see if there is someone local who knows electrical who can help with a few key parts of this aspect of your build.

To your question about breakers, breakers are designed as a failsafe against overheating and fire. If you overload the wires they can heat, melt the insulation and catch fire. So really the breaker size is about what size of wiring is downstream of the breaker.

It is common to have multiple receptacles on a single 20 amp breaker, the idea being that if too many things are plugged in the breaker will trip but it is understood that any individual thing plugged in on that circuit would exceed 20 A.

Most RV air conditioners require a 30 amp connection, but some smaller units as well as most 110 minisplits can run happily on 20 A.

Things like microwaves and hairdryers require a lot as well.

 

[david.dgeorge07]

*understood that it would NOT exceed 20 A.

 

[roach711]

Good info in the above post.


With an AC unit in the design I'd definitely go with the 30 amp hookup. 50 amps would be needed if you were planning on using an electric cooktop or two AC units in the future. A small electric water heater will work fine on a 30 amp system.



Blending AC and DC in the same vehicle can be a bit of an adventure so read up on it all you can before beginning your install.

 

[JeyM]

Thanks for the info, It was really helpful!

It looks like 30amp minimum is the way I need to go.

Our current AC is “rated input 900w current 8amp” 6500btu stand alone unit.

I forgot to mention we will also need to run a fridge, Although we do not currently have a model in mind.

I may call around and get some quotes on having it done for me but I’m more of a do it myself type of person. however electricity is something I have never worked with.

 

[Doktari]

I can wire whole systems but figuring out all the different plugs is PITA. Sorry, rant over. I would do a 30 amp service as a minimum. Good luck.

 

[farok]

Even if you use a 30 or 50 amp inlet it is easy with the use of an adapter to plug it into a standard 20 amp outlet. The caveat of course is that you only get 20 A out of the standard plug but often that is enough to be much better than nothing.

Here's a follow-up on this topic - adapting the plug to a lower-amperage plug.
If you have a 30-amp setup inside the bus, which includes a battery charger that can on its own pull 20 amps, how do you ensure that when adapting to a 15 or 20 amp plug at someone's house (i.e. or anywhere when there isn't a 30-amp hookup available) that you don't overload the line you plug into? I'm still thinking of how to wire my short bus, and am wondering if a battery charger can adjust its power draw, or if you need to plan a charger appropriately for a case such as this so that it's only rated to charge at a lower amperage? Thanks!

 

[Doktari]

The short answer is “ unless the breaker panel is right there and you can see what size breaker it has you won’t know if it will trip until you try it”.
Adjustability is one good reason to spend the money and buy a inverter/charger with adjustable parameters.
For example the Victron Energy Multi inverter/charger has a optional control panel so charge amps can be changed by a twist of the wrist on a knob. They are commonly used in marinas worldwide with unpredictable power supplies. I’ve not been to a RV park in the USA for 35 years but would hope they are better standards. That’s why I don’t know much about the different 20, 30, or 50 amp plugs available. I’ve always boondocked or plugged into ordinary 15 amp outlet on my 120 volt generator or on private property.
It occurs to me that routinely checking the polarity of unfamiliar outlets with a test plug is a wise idea.
I plugged into a marginal suspect outlet recently . I reversed the hot and neutral on the plug. Glad I checked it. Now if it only had a ground. I turned my Outback charger down to 4 amps to back up the poor Winter solar near Seattle.
Back to the subject of DC charging. The only relatively cheap option I’ve found is to build a small engine driven alternator. And build in adjustability. The inexpensive way is to use a big 100 watt rheostat. The expensive but trick way is to use a high voltage mppt charge controller or maybe a smart 3 stage charge regulator. I’m working on a mini engine driven DC charger for my sealed batteries that dont like high charge rates or high voltage. It will be compact, efficient, connected in parallel with solar, heat water with Surplus energy, and also run on wind when driving. No need to hack into the vehicles charging system. It can be removed fairly easily and used on another vehicle if needed. It is more for van dwellers and smaller systems than some big coaches need. I have a micro bird shorty cut-away van Skoolie I’m working on. Bigger DC chargers are similar just bigger ratings. I’ve got two, a diesel and a gasoline/propane, unused and should probably sell one as I dont need that much power. And can’t charge at a high rate with these darned sealed batteries. I’m keeping one big charger for when I upgrade to bigger FLA batteries and a bigger bus.
Money saved by not purchasing a big inverter/charger could go into more solar panels and a engine driven DC charger. This strategy might work for some. Especially if boondocking in cloudy areas part of the year.

 

[Doktari]

I will add that a engine driven DC charger/ alternator is best combined with solar. The engine can power the bulk high amperage charge then shut down and the solar takes over to finish the charge. Same with a ordinary 120 VAC AC generator. It’s inefficient to run it for hours trickling in the absorb and float charge.
These ideas are mainly for boondocking. For those who can plug into the grid then a power factor corrected charger is best. Many of the big invereter/chargers are PFC. I’m not aware of a stand alone charger that is. Does anyone know of any PFC chargers? My understanding is using a PFC charger with a ordinary 120 VAC generator is almost as efficient and fast as a engine driven DC charger. Is this correct?
Running a 240 volt generator probably opens up charging options. A 240 volt to 120 volt auto transformer can used as a balancing transformer for more even loading of the 240 volt generator by 120 volt loads. Otherwise only half the GenSet is being loaded.
You’d think charging a battery would be simple.

 

[david.dgeorge07]

Here's a follow-up on this topic - adapting the plug to a lower-amperage plug.

If you have a 30-amp setup inside the bus, which includes a battery charger that can on its own pull 20 amps, how do you ensure that when adapting to a 15 or 20 amp plug at someone's house (i.e. or anywhere when there isn't a 30-amp hookup available) that you don't overload the line you plug into? I'm still thinking of how to wire my short bus, and am wondering if a battery charger can adjust its power draw, or if you need to plan a charger appropriately for a case such as this so that it's only rated to charge at a lower amperage? Thanks!

Two things here:

20 amps @ 12 volts is only 2 amps @ 120 volts because of A = W/V.

So if you are charging a battery at a rate of 20 amps at 12 volts, you are only using 2 amps from your 120 volt shore power.

The other thing is that even if you were to exceed 20 amps on your shore power, all that would happen is that the breaker for your shore power would trip. This assumes that your shore power is set up properly, but in my experience most homes with outdoor receptacles are wired correctly.