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Old 12-10-2007, 08:21 PM   #1
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Transfer switch

I know for most of you this bus conversion stuff mechanical, technical stuff is easy. For me, I get it all pretty much except for the 12v DC side of the equation and some of the AC/DC crossover stuff as well all the mechanical stuff. Never dealt with it before. I have to buy an rv transfer switch for my AC power to switch from shore to genset or is there something else I can use? And do I need a converter/charger? I know this is basic stuff to most of you, but this part is rocket science to me. That's why I love this forum. And by the way, I'm still holding all of you responsible for sucking me into this madness of skoolie conversion. God I love it! Just saw a 5.9 with a 5sp manual. Hmmmm.........
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Old 12-10-2007, 09:11 PM   #2
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Re: Transfer switch

what at least some of us (well at least I) do is have three regular 110 volt outlets like this one:

one that is wired direct to the generator, one for shore power, and another that runs off of your inverter. The inverter is a gizmo that changes 12 volt dc (bus voltage) to 110 volts ac (standard house voltage)

Then the entire bus (assuming no a/c) can in most cases run off of one circuit. Power for this circuit comes from a standard 110 volt plug, like this:

This system keeps things simple, and makes it impossible to accidentally connect the geni to shore power which would be disastrous.

You can select from inverter, shore, or geni power by simply choosing which outlet to plug your bus power cord into.

Remembering to keep safety third, you probably want at a minimum to have a gfci outlet that the main power runs through....and having a regular circuit breaker isn't a bad idea either. However.....i'll prob be hung for this next statement....not having a gfi or a circuit breaker is probably ok. Having a couple outlets running your tv, a light or two, etc inside your bus without the above safety devices isn't really any different than plugging your tv and related items into an x-tention cord. I have a lot of water in my bus, so i opt for the $20 gfi.

there are certianly a lot more complicated and expensive setups, but this is simple and cheap. A 110 volt outlet at home depot costs about 50 cents.

Quis custodiet ipsos custodes (who will watch the watchmen?)
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Old 12-10-2007, 09:26 PM   #3
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Re: Transfer switch

Could you put in simpler terms for me, Jason. Seriously, thanks. Safety.... what's that?
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Old 12-10-2007, 10:26 PM   #4
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Re: Transfer switch

I run a similar system to Jason.

I have three circuits within the bus which all terminate in the battery box with regular 15 amp 3 prong ends.

I have two inverters mounted in there. I also have a 20 amp box with 4 outlets that just has a 20 amp 3 prong pigtail coming out of it. Consider it a glorified power strip.

I can plug the circuits into the inverters for power off the batteries. I can also plug all three circuits into the 4 outlet box and then plug the pigtail from that into a gennie or shorepower. I can also do any combination I want...2 on shore power, 1 on inverter for example.

The system is stupidly simple, but I don't have a charger built into the inverters. I have to use that separately (it plugs into that 4 outlet box on shore power). I also lose all power to stuff in the bus when I park and change from inverter power to shore power. To remedy that situation I plan to install a computer UPS in the bus for the TV and playstation. I'm not sure how well it will jive with modified sinewave power from the inverter, but we will see.

I hope that helps somewhat...maybe?
Skooling state at a time...
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Old 12-11-2007, 01:42 AM   #5
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Re: Transfer switch

This book is an awesome reference on this subject (the image should be clickable):

(it's ISBN 978-0964738621)
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Old 12-11-2007, 11:27 PM   #6
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Re: Transfer switch

Here's a diagram of my system. The breaker panel on the left has a regular cord and plug as mentioned in the above posts so I can hook up to the generator shown or to shore power either one.

I don't know if that picture's OK, if not, here's a link to the gallery.

I did it the way mentioned in the previous posts, swapping the plug between inverter/generator, for a long time when I had a portable generator, but I got around to putting in the generator with remote start, I installed the transfer switch so that when I want to use the microwave or something I don't have to get out and futz around with the plug thing. Nice when the weather's nasty or it's dark out.
As to 12V vs. 120V, I bought an LCD TV, got it home and noticed that it ran off a wall wart. Checked the output voltage marked on it and lo and behold, 12VDC - got some parts from Radio Shack and made a cord and plugged it right into the 12V and it works fine. Then I started looking around at other things - my laptop - again, 12VDC power suply, made another cable and presto. I've got four laptops and all of them work fine off 12V - even the HP which say 18VDC on the transformer. Works fine, but doesn't charge the internal battery. I bought some low voltage lights at Home Depot, same thing, they worked off of a 12V transformer (lights don't much know the difference between AC and DC ) ). So actually I've managed to get everything but one lamp off of the inverter and onto the 12V side and I don't use that lamp, so I've pretty much elliminated the inverter all together. Just something you might want to notice when shopping for new stuff for your bus.
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