Best way to wire inverter/converter/shore power for seamless AC power

[justgoclimb]

I've been reading about a bunch of different ways to wire up all my power sources and I still can't seem to wrap my head around the best way to set it all up. I came across this article - RV Inverter Install: Four Different Methods to Get Off the Grid - which is helpful, but still leaving me with questions.

I am doing a rebuild and working with a fresh setup - no furniture to work around or anything - so I really want to go about this in the best way possible now. I will be off-grid the majority of the time and want to be able to use all the outlets in my Airstream, powered from my 2000 watt inverter. But I also want to be able to plug into shore power and use that to power the outlets.

A transfer switch sounds like the best solution, but I'm confused about how the split distribution panel would work to keep the inverter from powering the converter. I bought a 60amp progressive dynamics converter + AC/DC distribution panel. Since that AC distribution panel is already wired to the converter, would I just add another AC distribution box dedicated to the inverter, and pigtail all my AC circuits so that they tie into both panels?

Or does anybody have a better solution?

A bit about my setup - I'll have four 100 watt panels charging two 6v 225ah batteries (connected in series) through an MPPT charge controller. I have a 60amp progressive dynamics converter + AC/DC distribution panel (the mighty mini I think it's called). I'll be installing an inlet for shore power and have three AC circuits.

[J. Morgan]

My solution was to use two 30 amp DPDT switches, one to control shore and switch 2 input, and the second to toggle between the inverter and generator input.

Simple and cheap, especially if you shop around for the switches.

In the photo, the switch on the right is up for shore line power.

If the switch on the right is moved to the bottom it puts the switch on the left in play and if up switches on inverter power, and if down it switches on the generator input.

[J. Morgan]

It is not overly complicated, even with the addition of the LED displays.

If you didn't have to worry about switching between generator and inverter one of these switches would suffice.

This allows me to control the input for the entire panel with the flip of a switch, and it is impossible to have more than one input at a time active, so back feed is impossible.

[KYAirstream]

The article attached in the OP stated the converter should not be on when using the inverter because extra battery drain will occur.

This may be a dumb question and perhaps I'm missing something obvious, but how are the 12v interior lights, water pump, etc powered if the converter is shut down when the inverter is on?

[Rich W]

Originally Posted by KYAirstream

The article attached in the OP stated the converter should not be on when using the inverter because extra battery drain will occur.

This may be a dumb question and perhaps I'm missing something obvious, but how are the 12v interior lights, water pump, etc powered if the converter is shut down when the inverter is on?

We rarely use our inverter but if you aren't on shore power and you turn off the converter (which is done by setting Use/Store to Store) you'll be sitting in the dark. You need it to be in Use for the lights to be on. If you're on shore power and it's in Use, the batteries get charged, if you're in store the batteries are NOT being charged. But the lights and everything else is on / working.

Lights, pump and other 12vdc items run off the battery. If on shore power the battery is recharged and the converter provides the necessary 12vdc for their power. If not on shore power you're running off the batteries/battery. The inverter uses the 12vdc battery power to create 110vac on a couple of outlets, also using battery power to run itself.

So bottom line, if not on shore power, you need the switch to be in Use so all the 12vdc things get power, like the fridge . The converter has nothing to convert because there is no 110vac. The inverter, even if nothing is connected to it, will use battery power to create the 110vac. If you leave the AS, leave the switch in Use and turn off the lights. Don't leave the inverter on unless you're actively using the 110vac, like for a TV or small appliance; conserves battery reserves.

[KYAirstream]

I see what you are saying about there's nothing for the converter to convert when there's no shore power, so the batteries do the work.

I think the article linked in the OP is saying that to conserve battery use the converter should be left off (or "store" as you mentioned, although my 79 doesn't have such a switch), otherwise the converter itself is drawing juice off the batteries via the inverter and attempting to cycle the charge back through.

[daveswenson]

Instead of transfer switches why not just use an inverter with pass through? Lew needs to jump in here.

[switz]

The Magnum MS2812 inverter/converter/charger takes the incoming power from a selector switch that chooses either shore power or generator to keep the battery(s) charged. When the inverter function is energized in our case, all the 120VAC outlets are hot. The solar system will keep the battery(s) charged in daylight.

[justgoclimb]

What's an inverter with a pass through?

As far as I can see, there is no on/off switch or any sort of control on my converter. It's built into the all-in-one case with the ac and dc fuse panel.

The more I think about it and read, the more unsure I am about it all. Like KYAirstream mentioned, I also don't understand how you turn off the converter when using the inverter and still get 12v power, unless the battery is hooked up directly to the 12v circuits. To my understanding, the 12v circuits are basically wired in with the converter.

[lewster]

First, let's get the terminology right so there is no confusion:

A converter/charger uses shore power to power all of the trailer's DC loads AND produce 12VDC (nominal) charging voltage to keep the batteries charged. When no shore power is present, all DC loads are powered directly from the batteries.

An inverter/charger operates in an entirely different way. First and by definition, an inverter/charger (there is no converter in this device) has an internal automatic transfer switch, which I will get into in a minute. When on shore power, the charger section of the unit is producing 12VDC (nominal) to charger the batteries. All DC loads are drawn directly from the batteries, unlike a converter, which will also power the DC loads when on grid. Also an inverter/charger's internal transfer switch will 'pass-thru' the incoming 120VAC from the shore power to whatever 120VAC outlets are wired to it. It will also not allow the unit to be 'inverting', as this function is strictly reserved for off-grid battery power (see below) and will essentially be in standby mode during this time.

Next, when off-grid and the inverter section of the device is activated, the unit produces 120VAC power from the battery bank and sends it to whatever 120VAC outlets are wired to it. These are the SAME outlets as described in the paragraph above. This is where the transfer switch comes into play.

The transfer switch will either be passing thru shore power if present and energizing the charging section, or will switch over to power the outlets from the batteries when off-grid and disable the charger.

It is entirely possible to power your entire trailer with a 2000 watt inverter. I do not install stand alone inverters that require an external automatic transfer switch and also a converter as a charging source. The wiring is complicated and messy if it is to meet code. All of this can easily be achieved with an integrated inverter/charger, like any of those in the Magnum Energy offerings.

In order to energize your entire trailer, you will also need a main breaker box for input power to the inverter/charger from the shore power input, and a second sub panel for all of the 'inverter powered' and pass thru outlets to meet code. Unfortunately, a Mighty Mini is not suitable for this application.

Installing an inverter/charger for an application to power an entire trailer requires an intimate knowledge of AC and DC circuits and their interactions. If you are not completely comfortable with these requirements, it is best left to one that is, as the consequences of improper wiring could be disastrous!

[vinstream]

Lewster has many valid points and for the most part is correct. I would add that in most cases 2000 watt to run the entire trailer does not cut it, I would highly recommend 3000 watt and only ever use a "pure sin wave" Inverter. I also echo the Inverter/charging in one units! I would disagree with the transfer switch with respect to set ups with Gen power. Another area that should be mentioned is Multi stage Charger over single stage. Single stage chargers like the ones found in most trailers should be remained to battery destroyers rather than chargers, a multi stage charger is a must! You should also look at battery types and solar options to topic of research. I have installed many 12volt 110v systems and truly think there is are very few correct factory systems out there and Its my opinion the best way is to build your own system from scratch...

[switz]

Read the AM Solar primer on their website to better understand the terminology and the workings of a solar/shore power/generator system. The hardware is only part of the equation as proper wire sizes must be selected from the solar panels the roof, between the battery bank and the inverter and to the A/C power sub panel.

Welcome to AM Solar_Your RV Solar Specialists since 1987

We installed the two 30 amp pole Magnum MS-2812 as the heart of the solar system on the Classic with 50 amp service which is wired as 240Vac incoming from the shore power pedestal, but all the interior appliances are only 120Vac. We could balance the A/C power load on each leg.

On a 30 amp 120Vac service trailer, we installed the Magnum MSH-3012 hybrid which has a 60 amp single pole relay. It can add battery power to a 2,000 watt generator power input to help start and run the air condioner as long as the gasoline (or propane if converted) lasts.

In both of our trailers, all the A/C outlets are powered through the Magnum all the time. The Airstream 1,000 watt inverter option may power three of the outlets and not the microwave if one is installed.

[lewster]

Originally Posted by vinstream

Lewster has many valid points and for the most part is correct. I would add that in most cases 2000 watt to run the entire trailer does not cut it, I would highly recommend 3000 watt and only ever use a "pure sin wave" Inverter. I also echo the Inverter/charging in one units! I would disagree with the transfer switch with respect to set ups with Gen power. Another area that should be mentioned is Multi stage Charger over single stage. Single stage chargers like the ones found in most trailers should be remained to battery destroyers rather than chargers, a multi stage charger is a must! You should also look at battery types and solar options to topic of research. I have installed many 12volt 110v systems and truly think there is are very few correct factory systems out there and Its my opinion the best way is to build your own system from scratch...

My comments were general in nature and stated as a guideline. If you really want specifics, let's go point by point.

"I would add that in most cases 2000 watt to run the entire trailer does not cut it, I would highly recommend 3000 watt and only ever use a "pure sin wave" Inverter". I always isolate the air conditioner systems from the inverter connections unless installing a MSH-3012M hybrid 3000 watt inverter/charger and lithium batteries, but every other AC load will easily be handled by a 2000 watt Magnum. Magnum Energy inverter/chargers are the only units that I will install. I only use their pure sine wave models as well.

"I would disagree with the transfer switch with respect to set ups with Gen power." An inverter charger doesn't care where the 120VAC input comes from, as long as it is entering the trailer from the shore power input. If you are talking about on-board generators, then there needs to be an external automatic transfer switch to prevent 2 120VAC power inputs from entering the RV simultaneously. In addition, newer Airstreams have 2 shore power inlets, one in front and one on the street side rear. These both feed into an auto transfer switch that will allow only one source to enter the trailer at a time.

"Another area that should be mentioned is Multi stage Charger over single stage. Single stage chargers like the ones found in most trailers should be remained to battery destroyers rather than chargers, a multi stage charger is a must!". ALL Magnum inverter/chargers have fully programmable multi-stage chargers integrated into the hardware, and are completely adjustable using the ME-RC remote. Airstream is way behind the curve in their battery charging technology in everything they make with the exception of the Interstate.

In addition, I looked at the link provided above. I would take NOTHING from that video, as almost none of it would pass a marine inspection, nor would I ever post a video with information that could be taken out of context. That is a law suit waiting to happen!!! I do all of my installations to the ABYC E-11 marine specifications wherever possible thru years of training, experience and professional certifications, not home grown Mickey Mouse solutions.

Be VERY careful out there!!!

[J. Morgan]

Sometimes simplicity is just more reliable.

[SkipS]

For J. Morgan (or anyone that knows): if using a simple dpdt switch, should it be a 2 position (on) (on) or three position (on) (off) (on)? Also, where did you find your switches, I can only find NKK looking on the internet. Thank you. Skip Simpson

[lewster]

Originally Posted by J. Morgan

Sometimes simplicity is just more reliable.

Agreed! My final comments were directed toward the vides in the link, NOT your solution.

I've seen many older or lower end motor homes that use a single 30 amp outlet and 2 plugs that must be connected manually; one for shore power and the other for generator.

Simple and effective for power input isolation purposes.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[justgoclimb]

Simple is definitely what I am looking for. A lot of info here, while very informative and thorough, sounds a lot more sophisticated and expensive than what I need. My 2000 watt inverter is already kind of overkill for what I'll be powering on it. We basically got it to be able to use a blow dryer. Other than that, we're just powering LED lights, a small LED tv, and charging stuff. We won't have an AC unit either.

So what would be the simplest, cheapest setup I could do that would allow me to...A. use my outlets when I'm off-grid, and...B. Charge my battery, use my outlets, and run all the 12v when plugged into shore power?

At this point, I haven't even installed my shore power inlet yet. I was just going to put a regular 15 amp inlet on the trailer because I don't know why I'd ever need a 30 amp. Should I return the mighty mini and use something else?

[justgoclimb]

So looking into inverter/chargers a little bit more, and it sounds like getting one like this might actually make things a lot simpler. Would it?

[J. Morgan]

Originally Posted by SkipS

For J. Morgan (or anyone that knows): if using a simple dpdt switch, should it be a 2 position (on) (on) or three position (on) (off) (on)? Also, where did you find your switches, I can only find NKK looking on the internet. Thank you. Skip Simpson

I ordered mine from Amazon.com, I think about $35.

[J. Morgan]

Maybe I paid more than $35,,, but I dont think I paid $80...


I remember I did a lot of shopping with lots of different search criteria to find a cheap price.

Leviton 1288 30-Amp 120-Volt Toggle Double-Pole AC Quiet Switch, Brown https://www.amazon.com/dp/B003AUPTP8..._FbG8vbE3XQE3B

I remember now, I bought through Amazon, but from Global industrial.