This site is now in read-only archive mode. Please move all discussion, and create a new account at the new Victron Community site.
I'm putting together plans to add solar to my RV and I think I have figured out what I need, but have one open question. I'll be splicing-in the the new power system to the existing AC input line.
Question is: do I need a 30A circuit breaker added to my schematic? The shore power will come out of a 30A breaker, and there's a 30A main breaker on the existing AC/DC distribution panel.
So is it necessary to add yet another breaker where I'm splicing-in the Multiplus?
One other thing: I personally have not had good experiences with DC circuit breakers. If your experience has been different then by all means go ahead with them, but in my experience the manufacturing tolerances just aren't that great. I put a 3kw inverter in my truck and initially wired it with a 300A DC breaker; it would trip at 220-230A every time, and I had a similar experience with a 60A DC breaker for another inverter install years ago. Since then I've used fuses for everything on the DC side and if I need a disconnect then I just put a switch in series and call it a day.
If I've just been unlucky and you can recommend reliable DC breakers please say so (and let me know which ones actually work), because there have been plenty of times in which it would have been advantageous to use such a device rather than a big clunky switch and fuse block but I went with the clunk just to avoid the potential for drama.
Technically, the breaker in the pedestal outside your RV will provide protection for the internal wiring, but I recommend adding a breaker inside the RV ahead of the Multi. There are times when you may hook up to a 50-amp service and the 10 gauge wire is then not protected.
Do NOT use crimp splices on romex or other solid wire. Crimps on solid wire can work loose with any vibration. A screw terminal strip or at least wire nuts provide a much better connection.
There should be a fuseor circuit breaker in the connection between your busbar and the MPPT. This is to protect the wiring should short to ground.
Not sure, but 20 amps may not be sufficient to power your DC distribution. These typically have at least a 30 amp circuit breaker at the battery. The panel should have one or more main fuses and I'd use that for your breaker size. Make sure the wire to the panel is of sufficient size.
You may get some imbalance in the current to/from each battery due to voltage drops. Taking the negative from one battery and the positive from another is perfect with two batteries but with three, there could be some imbalance. It's suggested to connect each battery to a busbar or post, then to the loads. You can probably use the shunt's battery connection for the 3 battery cables and likewise use the battery connection of the fuse for the positive battery cables.
A smaller breaker for your PV array would provide better protection. But as long as the wire is sized to handle the short-current of the array you really don't need a fuse/breaker. The difference between max power current and short circuit current of most solar panels is not significant.
You can combine the post and busbar in the negative DC path. Also, check the wiring to your existing DC distribution. It may also have a chassis connection and you should really only have one.
Have fun.
I second @Kevin Windrem's concerns about the limit on the DC loads. I think you'll need considerably more than what you've spec'd. The furnace air handler will pull about 10A; then add in some lights, etc. Individual slide-out motors can easily pull 25-30A, and if they're running simultaneously...you get the idea.
In an RV application you will often be in partial shade, so just make sure you consider that effect on the PV array. On my fifth wheel camper I installed six 200w panels -- each with its own MPPT -- to eliminate that issue entirely.
Also, this design doesn't take advantage of, or actively defeats, one of the things you're paying for with the Multiplus: power assist. The Multiplus can supplement AC input by inverting from the batteries to sustain short-duration / high-current loads. Make sure you understand this feature before proceeding with your build. I would personally recommend replacing the 30A panel in the main breaker with a 50A breaker and wiring the Multiplus to the panel with 6 AWG. The 10 AWG to the multiplus from the power inlet is fine, but -- to answer your original question -- I would put a 30A breaker between that inlet and the Multiplus, especially if you do as I recommend and wire the main panel for the 50A to capitalize on power assist.
Jersey & Kevin,
I appreciate the thorough replies and will update my plan accordingly!
I agree with Jersey about upgrading the input to the AC distribution to the max the current panel can handle. Check the manufacturer's specs. The WFCO models are rated for 30 amps max until you get to the 120/240 volt models.
Relying on power assist allows the inverter to kick in to handle additional load while on shore power however you need to manage loads when shore power isn't available to prevent overload. This includes momentary shore power dropouts.
Make sure you disconnect the battery charger in your power center. With the inverter connected ahead of the power center as you've done, the inverter will power the charger which will draw current from the batteries if not on shore power. You'll drain your batteries because the process is not 100% efficient.
Disabling the charger can be done by disconnecting the AC input to the charger. You'll find a wire from the charger connected to one of the AC breakers. Just disconnect that wire or if its on it's own breaker, just turn that one off.
Good call. I recommend switching off the breaker but leaving things intact so if something goes awry with the inverter you can bypass it and rely on the old converter for 12 VDC on shore power while you deal with the problem.
