RV Inverter Wiring Question - First Ever Solar Project

[ibthalucky12]

Greetings,

First time poster here. I am adding a 600W solar array & 560 ah LifePO4 battery bank to a Lance truck camper. I feel pretty confident about the design, with the exception of the inverter. I want to power the existing AC system in the camper, I don't want to do a sub panel.

My plan is to use a normally closed fan relay to turn the DC converter off when the inverter is turned on so as to prevent a power loop by having the converter charging the batteries the inverter is running off of. I have debated installing a manual switch as well or in lieu of the relay for fear I wouldn't know if the relay failed, and the power loop was occuring unbeknownst to me. I would appreciate any thoughts on this.

The big question I have, is if it causes any problem for there to be two power sources to the main breaker panel and potential issues arising from:

A, The prongs on the unplugged shore power plug would presumably be energized if off grid and the inverter has energized the AC system. Is there simply a cap I could keep on the plug when not in use?

B. The inverter hard wire terminals would be energized when shore power is connected. Is this an issue? Is this a known concern and base is covered in how inverters are made to allow this?

I am a beginner, and I realize most everywhere I look, it is advised to create a sub panel rather than energize main breaker panel. However truck campers are small and space is at a premium. I need to simplify and have as few components as possible.

I am also aware that if my intentions of using an inverter are simply not possible or correct I can instead buy a inverter charger with an internal transfer switch and pass through of sufficient amps as to wire the shore power directly to the inverter prior to the main AC panel. This is my second choice due to price, size, and lots of unfavorable reviews of most any converter charger I have seen. I don't want to use victron multiplus due to size and cost.

Thank you in advance for any advice, critique and commentary regarding what I am contemplating.

 

[tenacious]

I had a similar setup/problem and resorted to removing the existing camper DC charger and running both the DC lines (straight from the LiFePO4 batteries), and the AC lines (from the inverter) to the power panel. That removes having a loop and two power sources running to the panel.

 

[Rocketman]

What you need is a transfer switch.

Because I love my Victron Multiplus I would HIGHLY recommend that - it has a built in transfer switch and charger. But you have said you don’t it.

WFCO T30 30 Amp Transfer Switch https://a.co/d/iChe683

This is an automatic switch (there are others). It will only take power from one side or the other. And automatically switches between the two.

You will also need to solve the issue of the battery charger - you don’t want the charger being ran off the inverter and creating a loop.

I always recommend posting your solar design here (unless you have already done it), you will get feedback, maybe someone gives you an idea you want to implement. I have also seen mistakes caught that saved headaches down the road.

Good Luck

 

[ibthalucky12]

I suppose I could set up the inverter with a plug for the shore power to plug into and that would prevent the shore power plug from being energized while unhooked if that was a big concern.

But on this issue, perhaps the best answer, if I am dead set on proceeding in this direction would be an AC source switch, like a battery switch that only allows one input or the other just prior to the main panel. Select source 1 or 2, shore or inverter power. This will prevent either source from back feeding into the other, which seems like a violation of some code principle right?

The reviews look like others are using this switch for the stated purpose:

https://www.amazon.com/Baomain-Universal-Changeover-SZW26-20-Exterior/dp/B07SKNMY9P/ref=cm_cr_arp_mb_bdcrb_top?ie=UTF8

Side note: The truck camper has a generator and in lieu of a transfer switch has a plug for the shore power in the cabinet where the shore power cord is stowed. This was the OEM design.

 

[ibthalucky12]

So I am approaching "substantially complete" on this project. I have slogged through and come up with what I believe are a few innovations along the way. That said I haven't finished or powered everything up yet, so some trouble shooting is a possibility, but I believe I got it all right.

With regard to powering the existing AC load center with the inverter, I have a couple of innovations to share. What I needed to do was provide two different power sources (never to be used at the same time) into a single RV AC load center. I decided to go with a 40A rated Chinese made three phase changeover switch. I don't believe there is anything like this available from other manufacturers. In fact, it is quite obvious that Blue Sea is now selling a similar model for perhaps 10x the cost, and no doubt it originates from the same factory complex in China. But I digress.

It is necessary to switch both hot and neutral because the inverter is a floating ground. Since this is an RV there isn't a true ground per se, unless connected to shore power, where if wired correctly the neutral should be bonded to ground at the pedestal. The reason I chose a three phase switch is that it has three switched contacts on each leg, and I have utilized the third contact to switch the DC converter off and on. I added a wire that acts as a switch on the oem DC converter so it is only on when my changeover switch is switched to shore power. When switched to inverter power the converter is off. I used one of the Chinese made 40A three phase AC changeover switches on Ebay that runs around $30.

That said there do seem to be some more appropriate offerings coming out of China than just this switch, which is a bear to wire because the housing is small which makes it difficult to cram 3x 3/8 cords and two wires for the converter into. It can be done but it's less than desirable. There are some other AC source switches that I bought after I had completed the install, in case it fails or I just decide to do it differently. They are larger, some are automatic , some are like a breaker that can only have one side hot at a time. Ultimately my belief is these products are or will be superior to the changeover switch for a few reasons.

I will report back again later once I get everything fired up and running. Getting close now......

 

[Bop]

Ship/shore changeover switches are EXTREMELY common in the marine industry and almost all switch all 3 lines ie Active/neutral and earth (as ground/earth loops are a nightmare in the marine world- multiple steel hulled boats at dock with shore power can literally have holes eaten through their hulls with earth loops- doesn't make you popular when your electrical fault sinks a multi million dollar boat next door at the marina...)

3 phase changeover switches are extremely common outside the US/Canada/Mexico as most of the world uses 3 phase power in the streets (many houses here in Australia have 3 phases power into the house itself ie '415v'- including my mothers lol) or a single '230v' nominal phase for smaller loads, with single phase and 3 phase manual and 'auto changeover switching' units commonplace


Most 3 phase switches here are 4 pole rather than 3- simply because the Australian electrical code requires that ALL conductors must be isolated when operating a house in 'island mode' ie during a blackout- so for a 3 phase switch, thats 3 actives/line and 1 neutral/earth