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Specific products for wiring inverter, AC/DC charger & transfer switch

ekarlson

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Mar 5, 2021
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I am in the final stages of getting my solar, lithium, inverter setup going for my RV and I am having difficulty finding the products I would need to solve the shore-line/inverter to ATS to AC/DC charger wiring. I cannot be the first person to want to do this and I am hoping that someone here may have been able to find the products that I cannot find.

Here is the situation. I have PV's going through MPPT charge controllers to charge a lithium battery. There is also a shore-line that comes into my WF-8735LiS power center's main circuit breaker. That circuit breaker feeds a single power bus in the panel which is connected to a second breaker that feeds the AC/DC converter that also charges the lithium battery. I am adding an inverter which is connected to the lithium battery. The plan is to connect the shore-line and the inverter output to an ATS and feed the output of the ATS to the main breaker in the WF-8735LiS panel to power the rest of the trailer's AC circuits.

The obvious issue is that the inverter should not power the AC/DC charger. In principle, the answer is easy - the wires that feed the AC/DC charger are pulled out of the circuit breaker in the power panel and wired to a separate breaker which takes its input from the shore-line upstream of the ATS. My challenge is that I need a place to mount said breaker. I considered trying to get a small power panel (less than 5" x 8") that can take a small number of breakers and install that in the cabinet facing near the existing power panel - put my new breaker there and I'm good. Problem is - I cannot find a small power panel that I could mount in the RVs cabinet facing. Everything I can find that takes a small number of breakers still insists on putting them into a gigantic, and almost entirely empty, box - far too large to place anywhere inside the trailer. So if anyone knows of a *small* service panel (with a hinged cover) that one could mount inside a trailer, that would be helpful.

Failing the best approach of putting in a second panel with an independent breaker for the AC/DC charger, my next though is that I could put a switch/contactor, controlled by the presence of shore power, on the output of the breaker for the AC/DC charger such that power can only flow from the breaker to the AC/DC charger when the system is on shore power. I am leery of putting in a contactor that is independent of the ATS because it allows for the possibility that ATS may be passing through the inverter output even when there is shore power (which would result in the inverter driving the AC/DC charger). So my next thought was a 3-pole ATS where I use the 3rd pole to act as the switch between the breaker and the AC/DC charger - that way the switch can never be out of sync with the ATS. Problem is - I cannot find a 3-pole ATS that is suitable for installing into a trailer. Again, it has to be small and it has to be enclosed - no exposed metal tabs, spades, screws, etc that are electrified. I have found some 3-pole units, but they all have electrified bare metal sticking out in all possible directions - just begging for someone to electrocute themselves (I'm not even certain how one would use such a device - it would have to be enclosed in something to be safe, but I cannot find any sort of box that is meant to take them).

So if someone has actually built out an inverter, ATS, isolated AC/DC charger setup in their trailer, could you let me know the specific parts you found to solve the AC/DC isolation part?
 
There aren’t ready-made instant solutions but there’s many ways to do it. There’s an RV ‘adventure’ guy with a good youtube covering bypassing the factory ‘converter’ but I don’t recall the channel.

it sucks that the (attachment) small boxes aren’t readily available apparently

The simplest answer is to put in a a disconnect switch in the circuit that feeds the oem onboard “inverter” and turn it off when under solar.
side note a) RV inverters don’t generally have the ability to safely charge lithium batteries- so that is an issue in my mind
side note b) you ‘could’ eliminate the oem onboard inverter entirely and have a ‘proper’ lithium charger for optional use when on shorepower plus a decent true sine inverter.

Circuit Breaker Panels


Siemens E0408ML1125SU 4 Space, 8 Circuit, 125-Amp, Main Lug, Surface Mount, Indoor Load Center https://www.amazon.com/dp/B00002NB09/ref=cm_sw_r_cp_api_glt_fabc_Q7K9HMSSF7S0FMNS6ST0

 

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I am in the final stages of getting my solar, lithium, inverter setup going for my RV and I am having difficulty finding the products I would need to solve the shore-line/inverter to ATS to AC/DC charger wiring. I cannot be the first person to want to do this and I am hoping that someone here may have been able to find the products that I cannot find.

Here is the situation. I have PV's going through MPPT charge controllers to charge a lithium battery. There is also a shore-line that comes into my WF-8735LiS power center's main circuit breaker. That circuit breaker feeds a single power bus in the panel which is connected to a second breaker that feeds the AC/DC converter that also charges the lithium battery. I am adding an inverter which is connected to the lithium battery. The plan is to connect the shore-line and the inverter output to an ATS and feed the output of the ATS to the main breaker in the WF-8735LiS panel to power the rest of the trailer's AC circuits.

The obvious issue is that the inverter should not power the AC/DC charger. In principle, the answer is easy - the wires that feed the AC/DC charger are pulled out of the circuit breaker in the power panel and wired to a separate breaker which takes its input from the shore-line upstream of the ATS. My challenge is that I need a place to mount said breaker. I considered trying to get a small power panel (less than 5" x 8") that can take a small number of breakers and install that in the cabinet facing near the existing power panel - put my new breaker there and I'm good. Problem is - I cannot find a small power panel that I could mount in the RVs cabinet facing. Everything I can find that takes a small number of breakers still insists on putting them into a gigantic, and almost entirely empty, box - far too large to place anywhere inside the trailer. So if anyone knows of a *small* service panel (with a hinged cover) that one could mount inside a trailer, that would be helpful.

Failing the best approach of putting in a second panel with an independent breaker for the AC/DC charger, my next though is that I could put a switch/contactor, controlled by the presence of shore power, on the output of the breaker for the AC/DC charger such that power can only flow from the breaker to the AC/DC charger when the system is on shore power. I am leery of putting in a contactor that is independent of the ATS because it allows for the possibility that ATS may be passing through the inverter output even when there is shore power (which would result in the inverter driving the AC/DC charger). So my next thought was a 3-pole ATS where I use the 3rd pole to act as the switch between the breaker and the AC/DC charger - that way the switch can never be out of sync with the ATS. Problem is - I cannot find a 3-pole ATS that is suitable for installing into a trailer. Again, it has to be small and it has to be enclosed - no exposed metal tabs, spades, screws, etc that are electrified. I have found some 3-pole units, but they all have electrified bare metal sticking out in all possible directions - just begging for someone to electrocute themselves (I'm not even certain how one would use such a device - it would have to be enclosed in something to be safe, but I cannot find any sort of box that is meant to take them).

So if someone has actually built out an inverter, ATS, isolated AC/DC charger setup in their trailer, could you let me know the specific parts you found to solve the AC/DC isolation part?
I didnt read your entire post.

the main distro panel (for most RVs) has 2 sides each fed by a separate main breaker. 1 side is usually powered by inverter which does pass through or handled by an external transfer switch when shore is hooked up,. The other side is usually fed by the second leg of a 50a connection or a jumpered 50 to 30 dogbone. Perhaps you see where I’m going with this. the second (or jumpered) leg in your case would not go through a transfer switch. it would wire directly to the second (right) side of the panel and would only be energized when shore power is available, while the left side would be managed by the inverter pass-through or transfer switch (automated or otherwise).
 
I just finished converting my trailer from lead-acid to lithium/solar/inverter. The original equipment was a 100W solar panel onthe roof, a 10A BlueSolar Lite PWM from Victron Energy in the forward storage compartment and a WFCO WF-8735 for the power center AC/DC converter with the 12V from the 7-way plug wired directly up to the lead-acid battery.

What I wanted was a LiFePO battery with appropriate chargers and sufficient power form solar and tow vehicle to power a small inverter with sufficient power to run the main fridge off AC while towing.

I went with a 206Ah SOK battery, an extra 100W Renogy panel on the roof, a Victron Energy Orion-Tr Smart 18 DC-DC converter, dual SmartSolar 75/15 MPPT controllers (one for the roof panels and one for an SAE port that I installed for a moveable external solar panel) a 500VA Pheonix VE.Direct inverter (with a bluetooth dongle), a 30A ATS from WFCO (WF-30WM) a WFCO WF-8735LiS power center (as it can provide a proper lithium charging profile) and a EMS-HW30C surge protector on the shoreline. The ATS takes the inverter and the 15A circuit from the power panel that powers the fridge and 100V reciptacles so that the inverter only powers the fridge and 100V outlets. The A/C, microwave, water heater all draw too much power and for obvious reasons I don't want the inverter to be powering the AC/DC converter. I also installed an AiLi battery monitor and pulled the wires for the monitor and a remote switch for the inverter up to the side panel of the galley inside the trailer.20210516_184530.jpg

The "after" and "before" schematics and other pictures of the installation:

The after schematicSchematic-Old.jpg20210504_181541.jpg20210511_144556.jpg20210516_130428.jpg20210515_205029.jpg20210505_161208.jpg
 
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So if someone has actually built out an inverter, ATS, isolated AC/DC charger setup in their trailer, could you let me know the specific parts you found to solve the AC/DC isolation part?
I popped in a separate breaker, connected the AC/DC converter to this new breaker and leave it switched off. Has not been used in several years as the solar keeps the battery charged. Even if connected to utility power the breaker stays off. Just there to have in a difficult situation.
 
A regular ATS can be altered with a fuse or breaker to work like this ........
 

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I popped in a separate breaker, connected the AC/DC converter to this new breaker and leave it switched off. Has not been used in several years as the solar keeps the battery charged. Even if connected to utility power the breaker stays off. Just there to have in a difficult situation.
That’s how I think!
I always tend towards just running solar for everything- the batteries are handled totally automatically and it’s always ready, and plugging the house into the camper can help it pay its own way :)
About the only things that don’t go with solar well are air conditioners, water heaters, and electric stoves.
 
The wiring diagram in post #6 puts the charger solely on shore power and then the ATS routes to power the rest of the RV with the Battery/Inverter when off shore power and uses shore power when it's connected and turns off inverter. The disadvantage for me in that set up is that the connection to the AC panel goes to the 30/50 Amp general input on the AC panel; which in turn powers the Air Conditioning/Microwave/fridge circuits in addition to the outlets. I only want to power my outlets because I only have a single battery with a 120A BMS, which limited me to a 1200 watt inverter. One option was to use post #6 and remember to turn off the AC/Microwave/Fridge AC circuits when i turn on the inverter, but that defeats the whole point of the ATS. Another option was bigger batteries and a bigger BMS that would allow me to use a 2000/3000 Watt inverter, then i'd only have to turn off the AC. I'm limited on panels right now, so that did not seem viable long term.

At the end of the day, I didn't want to rewire the converter directly to the ATS and I didn't want to wire the ATS to just the breaker for the outlets, so, I decided just to add the inverter and use an extension cord to power anything that needs AC when we're not on shore power. In any event, I feel your pain about trying to figure this out. . . .
 
I hear you.
This may not be ‘right’ for you, but if it were mine I’d rewire the whole thing so that shore power/gen input only feeds one interior outlet, the AC unit, and an exterior outlet; add a lot more battery and more panels; and ditch the factory onboard converter. Get a 120V compress fridge. 1200 watt pure sine inverter: use it. That’s 10A 120VAC (unless you use microwave a lot and it’s over 10A of course. I never use a micro).
That’s my take. There’s a feeling of security not needing to run a generator or having the shakes until you get your next shorepower fix.
 
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