Multiplus wiring

[alctel]

Hi,

Can anyone tell me any reason why the attached diagram wouldn't work?

The blue seas 8032 is a dual 30amp panel with a slider that locks out the one not on - so it is impossible to have both active

https://www.bluesea.com/products/803...ource_Selector

The idea is that most of the time at the marina, I would have the 'shore power' breaker active, and then whenever I want to turn on the battery charger, I'd turn on the appropriate switch on the breaker panel, which would pass through power from shore power, through the AC panel and into the AC input on the multiplus.

For inverter use, the 8032 would be switched to 'inverter' which would then energise the AC panel from the inverter.

The main thing I can see is accidentally turning on the battery charger breaker while on the inverter - but that wouldn't cause the multiplus to short or anything, would it? It would detect the incoming AC IN power (from itself) and the transfer switch would turn it off.

[hjohnson]

Why not just wire your multiplus between your shore power and panel? That’s what I did, works great.

Plus, you can then also use the multiplus and your batteries to supplement a weak shore power connection.

In my case, when I visit my friend’s dock, I can plug in, but realistically can’t pull more than 10A off of it or I risk popping the breaker. So, I set the multiplus for 10A and it will never pull more than that off of shore. If I fire up my 1700W heat gun, for example, it will pull 500W of that out of my batteries. Or, reduce the charging current when my hot water tank kicks in.

[Dockhead]

What he said.

Wire it per the instructions.

[alctel]

Originally Posted by hjohnson

Why not just wire your multiplus between your shore power and panel? That’s what I did, works great.

Plus, you can then also use the multiplus and your batteries to supplement a weak shore power connection.

In my case, when I visit my friend’s dock, I can plug in, but realistically can’t pull more than 10A off of it or I risk popping the breaker. So, I set the multiplus for 10A and it will never pull more than that off of shore. If I fire up my 1700W heat gun, for example, it will pull 500W of that out of my batteries. Or, reduce the charging current when my hot water tank kicks in.

Couple reasons:

- I will never pull more than 15 - 20amps off of my shore power at maximum - I basically have a 1000 watt hot water tank, a couple of outlets and a battery charger and that's it, so I'm actually going to disable that functionality. Almost all my stuff is DC powered - I don't have a genny even. Also that seems in general a really bad idea - if I'm pulling more than my shorepower can supply, I'd far rather trip a breaker than drain my batteries down!

- if you've wired through the multiplus and it fails, you also lose your ability to run all your AC stuff until you rewire. I know someone this happened to and it was a huge pain.

- You can't have the multiplus passing AC AND disable the charger/inverter functions and just use it as a passthrough. This is a 'really' annoying issue, as I don't want my charger on all the time - I use my solar pretty much exclusively and keep the lifepo4 at 50% when at the dock, only using the charger if I am going somewhere. Once it's switched to 'off', it stops passing through AC.

- I'd also rather not have to have the thing running all the time, just to get AC power passed through - I'd rather leave it off and only turn it on when I need charging/inversion. This also cuts down on the 'oops I forgot to turn it off once I left the dock' incidents.

[hjohnson]

Originally Posted by alctel

Couple reasons:

- I will never pull more than 15 - 20amps off of my shore power at maximum - I basically have a 1000 watt hot water tank, a couple of outlets and a battery charger and that's it, so I'm actually going to disable that functionality. Almost all my stuff is DC powered - I don't have a genny even. Also that seems in general a really bad idea - if I'm pulling more than my shorepower can supply, I'd far rather trip a breaker than drain my batteries down!

- if you've wired through the multiplus and it fails, you also lose your ability to run all your AC stuff until you rewire. I know someone this happened to and it was a huge pain.

- You can't have the multiplus passing AC AND disable the charger/inverter functions and just use it as a passthrough. This is a 'really' annoying issue, as I don't want my charger on all the time - I use my solar pretty much exclusively and keep the lifepo4 at 50% when at the dock, only using the charger if I am going somewhere. Once it's switched to 'off', it stops passing through AC.

- I'd also rather not have to have the thing running all the time, just to get AC power passed through - I'd rather leave it off and only turn it on when I need charging/inversion. This also cuts down on the 'oops I forgot to turn it off once I left the dock' incidents.

Ok, having a similar situation, I really do think you’re over complicating things. That said, what you really want is a proper bypass switch. These are reasonably common for commercial UPSs. What you’re proposing in your diagram is likely dangerous. The bypass switches ensure the input cannot be connected to the output.

As far as not using the inverter chargers for all your charging, you can always set your multiplus to a lower charging voltage, say 13.2 or something. If you’re plugged in and your solar takes you above that, it won’t push anything into the battery. By the same token, if you set the shore power limit to say 50A, and/or put it in chargers only mode, it will pass through power, but won’t actually charge because the battery voltage is too high.

That said, if you’re running a fully integrated system like I am, that’s a little more difficult. I’ve got mine set to hold the batteries at 13.5v while I’m away from the boat. While I don’t really care about what keeps my batteries charged (my slip fees include power), I do tend to leave my inverter off while away from the boat and just let my solar

As far as always leaving it on; when we’re aboard it’s always on. It only draws something like 15W to keep our 120v live and it’s super convenient for things like charging laptops and what not. What we do do is breaker off the hot water tank. If the alternator fully charges the battery, or we’re heading back to the dock the next day, making a tank of water for doing dishes is awfully nice. That and filling the shower bag.

Away from the dock, we just turn off the inverter in the summer, and let the solar do its thing. I’ve got my BMS setup to keep the testing voltage at around 13.3v which is reasonably far down the knee. There’s no real gain to going much lower.

I figure if my usage only nets me 3500 cycles, that’s probably at least 25 years. That’s good enough for my, by that point my boat will be 75 years old.

[jordanbigel]

My boat is wired very similar to what you describe, except instead of a BS 8032 feeding into the AC panel, I have a Paneltronics 4309 which has similar functionality built into 1 panel.

The AC panel has an A bus and a B bus - the A bus can only be fed from shore power. But I can set B bus to run off either shore power or off the inverter.

Each bus has 8 breakers - on the A bus I use only 2 of them, one for the the Battery Charger which feeds shore power to the Multiplus and one to the water heater (which, therefore, cannot be run off the inverter). The MP AC out is run back to the AC panel. The B bus has all the breakers for various outlets throughout the boat.

*This was set up in 2000 by an ABYC electrician. It was not originally using a MultiPlus (it was a ProSine 3.0). This setup has worked for me for 22+ years.

[alctel]

Originally Posted by jordanbigel

My boat is wired very similar to what you describe, except instead of a BS 8032 feeding into the AC panel, I have a Paneltronics 4309 which has similar functionality built into 1 panel.

The AC panel has an A bus and a B bus - the A bus can only be fed from shore power. But I can set B bus to run off either shore power or off the inverter.

Each bus has 8 breakers - on the A bus I use only 2 of them, one for the the Battery Charger which feeds shore power to the Multiplus and one to the water heater (which, therefore, cannot be run off the inverter). The MP AC out is run back to the AC panel. The B bus has all the breakers for various outlets throughout the boat.

*This was set up in 2000 by an ABYC electrician. It was not originally using a MultiPlus (it was a ProSine 3.0). This setup has worked for me for 22+ years.

So you can't accidentally have the multiplus feeding itself because it's one a different feed, correct?

[jordanbigel]

Originally Posted by alctel

So you can't accidentally have the multiplus feeding itself because it's one a different feed, correct?

That is correct, it is not possible because of two things - first, the shore power on the A Bus has the breaker to the MultiPlus - that bus is separate from the B bus. And, the B bus (which distributes power to the outlets) has a lockout switch with a slide so you can either turn on the inverter power source, or turn on the shore power source, but not both at the same time. So, based on my understanding of how current flows, it can't get there from here.

NB: I am no electrical engineer, ABYC or otherwise.

[Dockhead]

That's right.

OP would need a transfer switch -- so that connection to shore power is broken by the same switch as connects to the inverter output. Any other way is a code violation and dangerous.

But the Multiplus has a transfer switch built into it. It's much simpler and cheaper and less rewiring to simply wire it according to the instructions. On the AC side you simply cut the shore power connection wire (AFTER the RCD) and insert the Multiplus between the two sides. Much, much less rewiring.

Even if OP doesn't want to use Power Boost, the current limiting to the charger is very useful for managing weak shore power connections. This won't work unless the Multiplus is wired correctly. With the inverter off, you can still set the maximum current according to the shore power breaker size, and the Multiplus will taper off what the charger takes to stay within that limit.

There is also a separate load-shedding circuit you can connect your immersion heater and/or space heater to. This will be disconnected then automatically whenever the inverter comes on, or if the inverter is off, to keep within the set current limit. These are very useful functions.

To avoid accidentally discharging batteries, just never put it in inverter mode when you're on shore power. Simple. The inverter control has three positions: Off, Charger Only, and Inverter. If you keep it in Charger Only then Power Boost doesn't come on and you can't accidentally run down your batteries.

If the unit ever fails, it's true that you will lose AC power, but it's a trivial fix to pull input and output wires off the unit and connect them together. If you have good access, it's a 5 minute job, or less.

If OP insists on not running his AC power through the unit, then in my opinion he would be better off with separate charger and inverter, as all the benefits of the combined unit are lost.

[smac999]

The inverter in needs to come from before the Bluesea switch. So you would need a main breaker and inverter breaker before that.

You can’t have it relaying on a breaker not being on to work correctly. It needs to be wired so wrong things will never happen.

[alctel]

Originally Posted by Dockhead

That's right.

If OP insists on not running his AC power through the unit, then in my opinion he would be better off with separate charger and inverter, as all the benefits of the combined unit are lost.

That was my first choice, but victron doesn't seem to make 120V inverters in the size I wanted unfortunately.

I guess I'll wire it up through the multiplus and see if I can come up with a workaround for the charger issue.

[Dockhead]

Originally Posted by alctel

That was my first choice, but victron doesn't seem to make 120V inverters in the size I wanted unfortunately.

I guess I'll wire it up through the multiplus and see if I can come up with a workaround for the charger issue.

If you're really paranoid about losing power if the Multiplus goes down (and it's not a non-existent issues; mine has gone down twice in 10 years of ownership), then simply prewire a bypass around the Multiplus.

You will need two of these:

https://www.amazon.com/VictorsHome-C...NsaWNrPXRydWU=
or something similar. Or maybe you can find a transfer switch with enough poles that you can do it with one.

The same unit can be used to wire the unit up as you wanted at first, but like this you will have all the benefits of the combined unit, and in case of unit failure, you just switch over to direct feed.

Power Boost and current sensing tapering of the battery charger are really useful features. You might not care now, not having used them, but my bet is once you try it you won't want to go back. The Multiplus is a very cool unit; I would use all of its capabilities if I were you. Good luck!