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Old 03-21-2023, 09:54 AM   #1
Mini-Skoolie
 
Join Date: May 2021
Location: Pompano Beach, FL
Posts: 38
Year: 2000
Engine: Cummins 5.9
Transfer Switch/Inverter Dumbness

So, I was so proud of myself that I got the transfer switch (https://www.amazon.com/gp/product/B00153EYTO/) to work, so that the solar power powers the breaker box, instead of the shore power. But then I went and did something stupid (of course: live and learn). I plugged in the shore power while the solar power was still connected (via my old 5K AIMS inverter) and turned on the heater, then promptly did a bonehead thing and walked inside the house. When I came back to the skoolie, the inverter alarm was on, and apparently fried, since it no longer indicates voltage or powers anthing. So, I learned at least three things: 1) turn off the solar feed by hand before you attach the shore power, 2) the transfer switch doesn't automatically shut off the feed from the inverter, and, 3) don't walk away when you try something new!

But, I'm wondering, why did the inverter get fried? Did I somehow mis-wire the transfer switch? The two lithium batteries are fine, and so is the charge controller. Just to be careful in case I do that stupid move again, should I have put a breaker between the inverter and the transfer box, and if so, what size?

Also, the inverter that burned out was an old one, so it doesn't "sting" as much as it could have. The new one I'm getting is a 4000 watt pure sine wave inverter by Giandel (https://www.amazon.com/gp/product/B07CTGJ46T/). I hope this is enough (seems like it should be).

Thanks!

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Old 03-21-2023, 10:08 AM   #2
Bus Crazy
 
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I think we need more info about how you wired it, because the whole point of the transfer switch is that you can have the inverter and the shore power connected at the same time...and the transfer switch will protect and isolate each from the other. There should be no need to turn off the inverter before hooking up shore power. So yes, it sounds like something was mis-wired and we can help with more info about what you did.
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Old 03-21-2023, 07:19 PM   #3
Bus Crazy
 
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Your GoPower autotransfer was probably not wired correctly. Like Ross states, when they are wired correctly they simply don't let two separate sources of power on the feed at the same time.

Inverter input is wired to the normally closed hot and common-these are on opposite sides of the switch, which is a bit counterintuitive.

Shore power input is wired to the normally open hot and common, and like the inverter input the lugs are on opposite sides of the switch, so check those. Both inputs to the autotransfer effectively 'straddle' the switch.

Also, it's super-critical not to mix up hot and common. Probably obvious, but worth repeating.

And also wicked obvious but I'll say it anyway: we're talking all 110 volt alternating current, so when you say 'via the inverter' I'm assuming your solar power inputs are actually outputs from your solar charge controller at the right voltage (12, 24, or 48 ) according to what the inverter input should be, and inverter output of 110 volts alternating current is what's going into the inverter.

Autotransfer output is what I think they call common hot and common neutral, and these lugs are on the top of the switch. This is the input for your AC panel.

The switch in its resting state (normally closed) passes power from the inverter to the AC panel. When shore power is present, the shore power juice fires an electromagnet that switches the input from Inverter (normally closed, but now open) to shore power (normally open, but now closed) with an audible click. Because shore power is often just a generator, the autotransfer doesn't happen immediately when power is present-there's a delay before it switches (they say to allow a generator to get up to speed and warm up a bit). So when you're testing, give it a minute or so to cycle between battery (inverter) and shore power or generator.

And inverters usually have pretty good input protection, like from reverse polarity, but I have no idea what, say, a voltage spike might do coming into the inverter the wrong way into its output, if that was the wiring mistake, but I can imaging it delivering out-of-phase AC, which would not be good.
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Old 03-22-2023, 08:16 AM   #4
Mini-Skoolie
 
Join Date: May 2021
Location: Pompano Beach, FL
Posts: 38
Year: 2000
Engine: Cummins 5.9
Re: Transfer Switch/Inverter Dumbness

From what you both say, it sounds like I wired it incorrectly. Actually, an electrician's "helper" did the initial wiring to the breaker panel (only), then never came back, so I tried to figure it out, and there were only two leads left, so I wired those. I will take a picture and show you the wiring and try to label it so you can see where I went wrong in life. I am NOT an electrician by any means, but did try to follow the diagram (which I will also post). I don't completely understand the acronyms and wording on the diagram. (BTW, I have been trying for MONTHS to get an electrician to do this, but they would only work on houses, and one guy wanted me to pay him to learn skoolie electricity on my dime!)

Like I mentioned, the inverter was very old (though it was working), so it likely didn't have the protection that the new one I ordered does. But I for sure want to get the wiring on the Transfer Switch right this time!

The old inverter was an AIMS 5000W inverter, and it had two light gauges on the side: one showed the voltage, and the other showed the load. It always was around 13 for volts (green), but now when I turn it on, the light goes from bottom to top (way over 13) then disappears. It's non-functional. When I came back into the bus, the siren on the inverter was wailing and I smelled smoke but couldn't see where it was coming from. Apparently, it was the inverter.

The two 300 Ah lithium batteries appear to be fine.

So, I will read your posts more closely while reading the diagram and see if I can understand what is going on, but I will indeed send pictures with indicators as to which wire is which, and hopefully I will do it right before I install the new inverter.

Thank you all so much!

Cheers,
Jim
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Old 03-22-2023, 01:00 PM   #5
Bus Crazy
 
Join Date: Jun 2016
Location: Orange County, CA
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Aha, the Curse Of The Automatic Transfer Switch has struck again! I've heard too many stories of them failing to feel comfortable having one. Even though it's far from automatic, I've used a much simpler and inherently foolproof alternative in my bus. I have three 120VAC outlets next to each other: one is fed from shore power, one from the generator, and one from the inverter. There is a plug connected to the bus's main 120VAC breaker panel, and this plug can only be plugged into one of the three outlets at one time. There is also a second plug connected to the inverter's built-in charger, but this plug will reach only the outlets from shore power or from the generator: its cable is too short to allow it to reach the inverter's outlet, so it's impossible to have the inverter's charger being powered by the inverter!

By doing this, I have absolutely eliminated any possibility of AC power going where it shouldn't. There can never be two sources of 120VAC connected at one time. Obviously it's not quite as convenient as an automatic gizmo, but it will never fail, ever, at all. Simple is good!

John

PS - was your release of the magic smoke caused by two different AC sources being connected even though their frequencies weren't synchronized?
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Old 03-22-2023, 03:40 PM   #6
Mini-Skoolie
 
Join Date: May 2021
Location: Pompano Beach, FL
Posts: 38
Year: 2000
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Quote:
Originally Posted by Iceni John View Post
Aha, the Curse Of The Automatic Transfer Switch has struck again! I've heard too many stories of them failing to feel comfortable having one. Even though it's far from automatic, I've used a much simpler and inherently foolproof alternative in my bus. I have three 120VAC outlets next to each other: one is fed from shore power, one from the generator, and one from the inverter. There is a plug connected to the bus's main 120VAC breaker panel, and this plug can only be plugged into one of the three outlets at one time. There is also a second plug connected to the inverter's built-in charger, but this plug will reach only the outlets from shore power or from the generator: its cable is too short to allow it to reach the inverter's outlet, so it's impossible to have the inverter's charger being powered by the inverter!

By doing this, I have absolutely eliminated any possibility of AC power going where it shouldn't. There can never be two sources of 120VAC connected at one time. Obviously it's not quite as convenient as an automatic gizmo, but it will never fail, ever, at all. Simple is good!

John

PS - was your release of the magic smoke caused by two different AC sources being connected even though their frequencies weren't synchronized?
Jeez, wish I had thought of that, but I guess it's not too late, considering the new inverter is on its way. Hmmmm, I guess if I just remember to turn off the inverter switch it will be less work. However, I like your thinking!
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