Inverter to shore power

[TheSpareTire]

Hi all, I was wondering why no one plugs their shore power cable into the inverter.

As noted in this thread people have done this, its not common it is not unheard of.

The issue is for most folks with a smaller inverter it is not practical for much more then TV and few small appliances. Also for most folks they don't have robust batteries that hand handle the high amp drain that a inverter places on the batteries. Once you get into a moderate sized inverter they almost always want to take advantage of the other features such as built-in chargers and auto-cut over. You also have a fair amount of loss doing it. Most inverters are only efficient at very low wattages, if you pull a moderate amount it could easily be less then 70% efficient. Finally you are limited how long you can do this without solar or generator.

If you can make the wattage work for you and you have the batteries no reason you can't do it as long as you don't try to run any high AMP devices such as the water heater, AC, fridge, fireplace though it. Make sure you follow manufactures instructions, oversize your DC wiring from the battery and make sure you have the appropriate size fuse to the inverter. You will also want to check the C rate of the battery to make sure you can pull the number of AMP from that battery without damage.

[wbjohn]

This is what I am doing now. I have a written procedure for switching over. Most people will tell you to shut off the breaker for the converter. I shut off the breakers for the converter, A/C, and microwave so nobody is tempted to use them on battery power. I had a second battery installed and use a 2000 watt pure sine wave inverter.

[Rich G]

I hope this doesn't reveal my ignorance but couldn't you plug from the inverter into a 110V outlet and not have to go to the main 50A service line? I would think that you are really just back feeding the power back into your trailer....does it matte where it is coming from?

I was stationed in Guam. We had frequent brown outs and loss of power was a daily occurrence. When we wanted power we started the generator (construction grade mind you), but we ran the power cord into the house and plugged it into the dryer outlet and cut the main power breaker (so we are not backing feeding the power to our neighbors (lol). That worked..so couldn't you just plug it in to the closet outlet with an extension cord?

[Barbara & Dave]

50 amp service is 220 volts. It's two 120volt circuits sharing a common neutral. Plugging into a 110V outlet would feed just one "side" of your circuits, whichever ones are on the same "side" as the outlet you plug into.

Not to mention the hazards of that one time you forget to switch the main breaker off. [emoji33] That's why power companies require those using alternate power sources (solar, wind, etc.) to have an automatic disconnect.

Dave


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[Aridon]

Not a pro, how i understand what is being asked:

Two legs of 120v with a single neutral and ground. The loads on the neutral are 180 degrees out of phase and actually cancel each other out as you apply load on each side. So while you can draw 50 amps on each leg for a total of 100 amps the neutral would have 0 amps on it if the loads were perfectly balanced and in full use which would never happen in real life.

So if you back feed an outlet you'll only do it for the leg that is on that outlet.

If you plug into the inverter with an adapter with your main power cord you'll power everything unless you selectively turn off breakers for the things you don't need which is highly advisable. The issues with this if you aren't careful are:

1. If you don't turn off the breaker for the power controller you'll drain down the batters really fast as the system tries to bulk charge off what it sees as 120v unlimited to draining batteries.

2. Overloading your setup. Same as 1, if you don't turn off breakers to big things like air conditioners your coach is going to try and fire stuff up that shouldn't be running. In addition to that, all the little extra thing are going to draw down your battery. If you don't have all those extra things like DVR's, Rokus, computers etc then no big deal. I think many of us do now though and they will draw power.

3. Overloading your adapter. You have to get your 50 amp plug down to a 15 amp adapter. You need to watch your loads and not exceed what the adapter can handle or it will get hot and melt.

[johnedvg]

so... the switching off the converter problem was solved by this guy with a 120v coil relay that is wired to the inverter ac out to switch off when the inverter is on: http://www.doityourselfrv.com/rv-inverter-install-diy/

you could put that same type of relay on your ac and whatever else you might not want on when the inverter is on.