Shore + Solar = ?

[fordthomas]

So, what’s the best way to wire your skoolie so it can run off of either solar or hooked up to say a house?

 

[Rwnielsen]

Transfer switch. Wire in both inputs and output goes to your panel. You can get an automatic one that will switch, automatically, to shore power when you're plugged in to shore (house) power. I have a manual one...shore, generator 1, solar mppt.

 

[rossvtaylor]

What RW describes is the classic method and is the best way to handle powering high-draw loads, such as air conditioners, which may not run off the solar power system. Traditional RV setups require either shore power or a generator to power air conditioners and such, so they need a transfer switch to route the power to the panel.

If, however, your skoolie is set up so that you can run what you have/need off of solar then you can look at your shore power as a supplement. Ideally, a solar power system wouldn't need any shore power in the sun. If you're parked in the shade, near a house or source of AC power, then all you really need is a charger you can plug in. This is super simple and doesn't require a transfer switch. I like to keep things simple, when I can.

 

[TheHubbardBus]

Our inverter / charger has a transfer switch built in, and accepts separate inputs for both shore & generator power. Hooked up to one or both, you can charge the batteries and/or pass-through AC to the house circuits. An all-in-one unit made it much simpler, and with the inverter controlling it all you have interoperability / logic that wouldn't be possible with separate components.

 

[Rucker]

Our inverter / charger has a transfer switch built in, and accepts separate inputs for both shore & generator power. Hooked up to one or both, you can charge the batteries and/or pass-through AC to the house circuits. An all-in-one unit made it much simpler, and with the inverter controlling it all you have interoperability / logic that wouldn't be possible with separate components.

Whereas mine is not, I have separate units for inverting and charging, so I use transfer switches.

The first one has two inputs: shore power or generator (it prioritizes shore power if there is voltage on the shore power feed).

The second one has two inputs: the output of the first transfer switch (either shore power or generator if power is present) and the inverter output.

If shore power is present, none of the other power sources supply power;
If no shore power is present, the first transfer switch will provide generator power, if present;
If no generator power or shore power, the second transfer switch provides power from the inverter.

There might be better ways to accomplish this, but I wanted to have a system with dedicated receptacles that only work with either short power or generator power, namely, the NoCo charger for the batteries and the split system, which cannot be run off the battery bank.

 

[Jolly Roger bus 223]

so since this is already a discussion and i know the owner of the second skoolie i am building and wanted to keep the equipment to a minimum for simplicity.
i ran conduit and wiring into the solar battery storage area so that a battery tender can be used if the solar isnt keeping up.
if the battery charger goes dead its an off the shelf item at an auto parts store.
if she dont have shore power then its a generator she dont want so i havent bought one yet but one will probably be hidden as a gift anyway.
its all solar power and 12v the only thing it needs shore power for is the occasional lap top charging and or battery charger to keep them topped off.
of course i wired in 120v circuits that can be used while on shore power.
as a traveling lab tech trying to save per diem its hard to say where she will park for three months at a time.
she has been to some cool places and some cool freezing places and has been to some not so fun places.
she does try to avoid contracts in the big cities.
i understand she is a born and raised country girl from south texas and travelled the world until she met me and i screwed that up? now the kids are grown and gone kinda and she always missed the travelling.
now she is off again so i wanted to keep thing as simple as possible for when something broke.
she is smart but more book smart than mechanical knowledge.
so i designed around KISS. she can do anything but hasnt had to turn wrenches in the over 20 years we have been together.
i need her rig to be plug and play not when she leaves here and has a problem well i didnt leave you a multi meter so i cant ask you what this wire or that wire is reading?
oh wait a minute the multi meter i have been missing for three months is under the drivers seat?
i know because i still have that fuse box cover here because thats the last thing i worked on.
then i would have to explain how to use it.
i might get to see the rig every three months or six months at the least.
i want something simple that can be fixed in minutes from off the shelf items and not have to worry about ordering an inverter or transfer switch and the lugs are different or the wiring is different and for her it would have to have someone else to help while on the road. then i would question the quality of work that someone else did.
i want her build super simple and she has seen most of the wiring and conduit so she knows what i have done to her bus but its powered where she wants it.
there are several walls that will remain accessible just because of wiring both for adding i think she needs but dont know it yet stuff.
she will probably fill in the screw heads and paint so while i map out the wiring i will also in case i caint see them will identify screw locations.
at this point i have more wiring diagrams than i do layout diagrams?
but the electrical and the plumbing is what makes things work the layout just has to look functional.
pretty for some.

 

[rossvtaylor]

I'm 100% with Jolly Roger on this, as I approach system designs. My general thought is that a good system will run off the solar, when the rig is fully in the sun. Now, granted, I come from a perspective of boondocking preference...so I plan on not having shore power and on being self contained. In my systems, shore power is just used to run a battery charger to help keep the system topped up if you're in a shady RV park.

Of course, if the plan is to have multiple air conditioner units cranking away all day...then that would merit shore power to the AC circuits...and that's not a system I'd have. I take that back...I do have that system in our MCI bus, but that conversion was set up that way before we bought it. It's a "typical" RV-style system and that's not what I like to do.

This is not meant to criticize systems with transfer switches and big energy demands. There's a lot of merit and comfort in that style of living. I'm just explaining why I often recommend the "no transfer switch" system and 12V battery banks. Different strokes...and there's no right or wrong.

 

[TheHubbardBus]

Of course, if the plan is to have multiple air conditioner units cranking away all day...then that would merit shore power to the AC circuits...and that's not a system I'd have. I take that back...I do have that system in our MCI bus, but that conversion was set up that way before we bought it. It's a "typical" RV-style system and that's not what I like to do.

We actually did things a little different, Ross. We simply don't have the real-estate for enough panels to power a house A/C in situations where I'd consider it necessary, but I did want the ability to run one when A) anywhere we had access to 30A service, and via generator as an 'emergency' option boondocking. I also didn't want the inverter to be involved, since doing so would require a significantly larger unit that would only be required in the very rare times we were running A/C.

My solution was to use a 30A rotary switch capable of accepting 2 inputs. It's meant to switch between shore & generator power and direct what you choose to 2 separate circuits. But I wired it so it swaps the outputs, one of which goes directly to the A/C unit, the other to the inverter. When I turn it to 'shore', the A/C unit is directly powered by the shore power inlet, and the generator is routed to the inverter for charging and/or AC pass-through. When I turn it to 'generator', it's the opposite... the generator directly powers the A/C unit, and the shore input is routed to the inverter.

Another benefit of this arrangement is I don't have to have a battery bank in place to run the A/C. During the summers I plan on removing the battery bank when the bus isn't in use to keep it at a friendlier temp. If we powered the A/C through the inverter, that wouldn't work, since our inverter requires a DC power source to function, even in AC-passthrough mode. But since the A/C is essentially isolated on its own circuit, that's now a non-issue. Good for working on the bus in the hot, hot summer.

 

[rossvtaylor]

Hey TheHubbardBus, that sounds like a solid design and the perfect solution to address your needs efficiently. Nicely done!

 

[kazetsukai]

Our inverter has a built-in transfer switch, and charge integrated. We can plug in and charge / or switch between seamlessly without even interrupting power.

 

[Rucker]

We actually did things a little different, Ross. We simply don't have the real-estate for enough panels to power a house A/C in situations where I'd consider it necessary, but I did want the ability to run one when A) anywhere we had access to 30A service, and via generator as an 'emergency' option boondocking. I also didn't want the inverter to be involved, since doing so would require a significantly larger unit that would only be required in the very rare times we were running A/C.

My solution was to use a 30A rotary switch capable of accepting 2 inputs. It's meant to switch between shore & generator power and direct what you choose to 2 separate circuits. But I wired it so it swaps the outputs, one of which goes directly to the A/C unit, the other to the inverter. When I turn it to 'shore', the A/C unit is directly powered by the shore power inlet, and the generator is routed to the inverter for charging and/or AC pass-through. When I turn it to 'generator', it's the opposite... the generator directly powers the A/C unit, and the shore input is routed to the inverter.

Another benefit of this arrangement is I don't have to have a battery bank in place to run the A/C. During the summers I plan on removing the battery bank when the bus isn't in use to keep it at a friendlier temp. If we powered the A/C through the inverter, that wouldn't work, since our inverter requires a DC power source to function, even in AC-passthrough mode. But since the A/C is essentially isolated on its own circuit, that's now a non-issue. Good for working on the bus in the hot, hot summer.

Brilliant setup.

To Ross' point, first we decide what power needs we have, then we design the system.

A biggie is A/C, for obvious reasons. If you're not planning on stationary AC, the system can be designed pretty sparsely without the highfalutin' autotransfers.