Adding an automated transfer switch

One of the most popular upgrades/mods that is done is the dual six volt batteries, instead of the regular one 12 v battery. The reasons to go with that mod are numerous but in a nutshell, for those that enjoy dry camping, or boon docking, an extended reserve capacity is the numero uno reason to go with such an upgrade.




The other upgrade that can then follow is the addition of an inverter, which basically hooks directly to your batteries, and transforms the DC 12v into AC 120v. This allows you to run different AC items, and it also allows you to plug your RV shore power  plug directly into the inverter.  The only thing you don't want to forget to do, if you do this, is to turn the converter circuit breaker off, so that you are not trying to charge back the batteries using power from the batteries. Given the losses, this would eventually drain your batteries without you realizing what is going on.




Now based on the location of your inverter, it may not always be an easy thing to bring out the shore power cable so to hook it to the inverter. In fact, based on where you are, and for how long you need AC power, sometimes it gets downright unpleasant.


That is when you think of an easier option. One that may include something a bit more permanent, easier, automated, in a nutshell, something that is called an "automated transfer switch".


These switches allow you to "switch from between shore power, when available, and inverter/generator power.




What a smart thing to do right?! Sure, but nothing is simple and easy, and you always need to do proper research. In carpenter terms, we'd say, measure twice, cut once. Same applies to just about everything, let me tell you.


The appealing idea of getting a transfer switch got me to score one on Kijiji, for a mere 100$ CAN, for a Surgeguard 41260 50 amps.




Before I hooked it, I thought I would make sure that the inverter and the automated transfer switch (ATS) would play nice with one another.




Indeed, there is this thing we call electricity, that does weird things at times, and for which you better have a plan B for when things go wrong. In this case, plan B means the bond between neutral and ground wire, that is usually found in our home electrical panels. I spare you the details of why we do have this bond there, but  the electrical code calls for only one place where such a bond with the neutral and ground wire will happen.




Could this mean there is no such bond in an RV electrical panel? Exactly! In fact, once connected to shore power, the RV electrical circuit basically uses the bond found in the home electrical panel.


Now I am saying this because some inverter have what is called a floating neutral, where there won't be a bond between the neutral and the ground wire. Knowing this, using an inverter that does not have such bonded neutral and ground wires with an automated switch to which shore power is hooked (with a bonded neutral-ground) may create a situation where some electricity is back fed from the inverter to the battery terminals, possibly energizing them, which is no good.




So what to do? Well, for starters, inquiring with the company that manufactures the ATS is a good idea. In my case, I have reached out to them and am still waiting for an answer.


I do not want to hook my inverter through the ATS to then hook up shore power and to then see my inverter go up in smoke...




I will post here as I am getting answer from the manufacturer. When I am ready to install the ATS, I will post the details of the installation here as well.




Stay tuned!




Update May 3rd 2016




Well the manufacturer was not so sure about what I was trying to do, so I ended up looking for a solution that might be a little simpler than having to hook an Auto transfer switch to an inverter, which means an inverter with an ATS built in! I have to admit that I have been keeping an eye out on classifieds so that I could eventually score a used Pure Sine Wave inverter. Why Pure Sine wave? Well, if you wanted to be able to run your microwave properly, and also to protect all of your precious electronics, pure sine wave is the way to go. It essentially produces power that is like the one you buy from the grid, oscillating in a pure sine wave form, as opposed to the modified sine wave that cheaper inverter (most are sold like that anyway) will produce.




If you have ever shopped around for a 2000 watts pure sine wave inverter, you know how expensive they can get, hence me hoping to find one on classifieds. Over the last 18 months, I have come close to getting the 2000w Go Power Pure sine wave inverter, but was never able to finalize the transaction.


To cut to the chase, I located a used Outback Inverter FX2012MT, producing a constant 2000w of pure sine wave electricity, BUT with a built in Auto transfer switch!




YES! The Nirvana of inverter with built in features. It also boosts a battery charger, so I was in heaven when I got it off Kijiji for around 400$ Canadians, when they sell for well over 2000$ new. Best of all, it works great in tandem with my Solar Charger, the Outback Flexmax 80. Can you ask for anything better? I think not!






But that thing is heavy, at 62 lbs, and is certainly built like a tank. In fact, I have the sealed version, which is meant to go on marine applications as well as mobile (RV) applications. Finding a proper spot for it won't be easy since it has to be as close as possible to the batteries (given the DC losses at high current). Design wise, you also have to take into account the fact that the two runs of AC wires from and to the RV electrical panel need to be properly sized to avoid wire heating up under heavy load. This is where things stand for now. I have located an area close to the battery but inside the trailer, so that it stays out of the elements. I am still hoping to find 8 AWG wire so that to limit the AC losses over two runs of about 22 ft (so 44ft) that will be added up to my already existing shore power cord, which is already over 20 ft in length. Even though AC losses are far lesser than DC ones, they still add up quickly when under heavy load.




The link below quickly became my new best friend in trying to identify a proper wire size to keep losses under 2 %




Voltage drop calculator




For instance, by adding the 44ft of  10 awg wire to the existing 20 ft of 10 AWG of the shore power cord, under a load of 1 amp, (120 watts) , would only generate an acceptable loss of 0.1 % where a 30 amp load would increase it to 3%. If I was able to find a bigger size wire, say 8 awg for the extra 44 ft, it would bring the loss down to 2.48%, which is much closer to the goal of 2%. Knowing I would probably never be maxed out at 30 amps for long periods of time anyway, I would be fine.


So that is the objective for now, find some good 8 AWG wire that I can use, that won't cost me 7 $ per foot.



I will update when I do.


Update May 6th 2016


I may have found the perfect wire for the job, a stranded 7 AWG 7/3 wire rated for outdoor use on Kijiji, for around a dollar a foot. This size of a wire would bring down the losses to around 2.12% under a heavy 25 amps load, or 1.27% under a 15 amps load, which is more likely.


If I am successful is buying it on Kijiji (I am still waiting to hear back from the seller) I will then proceed on to installing everything, and will provide photos and videos of the install.


In the meantime, I have been able to get confirmation from Outback that their FX2012MT inverter does have an internal auto transfer switch rated at 30 amps, in spite of the inverter itself producing only 2000 watts or 16.6 amps. I wanted to have the assurance that hooking my shore power cord through the Outback Inverter switch would not diminish the current that can pass through which I do need from time to time when hooked at a campground, for instance, where I may want to use the full 30 amps.