Can someone help hammer out some details for me?

[Basement Yeti]

I want to get a pure sine inverter and battery charger combo with a built in transfer switch. Like this.
http://www.xantrex.com/power-product...prosine-2.aspx

But I am really confused about 12V. Does the inverter/battery charger directly provide power to the 12V fuse panel or does it trickle the batteries and let the 12V panel off the battery bank?

Basically I want to know if the inverter/charger will provide shore power to 12V directly like it does with 120V.

I hope this makes sense. Thanks.

[dwh]

I want to get a pure sine inverter and battery charger combo with a built in transfer switch. Like this.
http://www.xantrex.com/power-product...prosine-2.aspx

But I am really confused about 12V. Does the inverter/battery charger directly provide power to the 12V fuse panel or does it trickle the batteries and let the 12V panel off the battery bank?

Basically I want to know if the inverter/charger will provide shore power to 12V directly like it does with 120V.

I hope this makes sense. Thanks.

What it is, is an electrical bus - power flows through it this way and that.

Like the bus bars in a regular house breaker panel. Power comes to the bus from the electric company, and is pulled from the bus by the loads.

Now imagine that same thing, but you connect a battery UPS to it. If the utility power is available, it supplies the loads and charges the battery in the UPS. If the utility power goes off, the UPS supplies power to the bus. The loads never know the difference.

That's how it works. The battery is connected to the bus, the inverter/charger is connected to the bus, the fuse box is connected to the bus.

Even if you use big fat wires from the inverter/charger to the battery, and then smaller wires to the fuse box, they are still going to be connected together at the battery, and thus will become a single "12v bus".


When the charger is running, it's keeping the bus at a higher voltage than the battery (higher voltage is like more pressure), so power flows into the battery until the battery gets to the same voltage and the pressure is equalized.

If you turn on a load while the battery is charging, the load will pull down the voltage of the bus, but the charger will supply power to keep the voltage up, so power flows from the charger to the bus to the load. Loads actually because at that point, the battery is also a load.

The Prosine's charger can supply up to 100a to the bus. So if you have a 30a load pulling from the bus, only 70a would be available to flow toward the battery.

Now say you connect a 150a load. The Prosine can only supply 100a, so the load pulls the bus voltage down and the charger can't hold it up, as soon as the bus voltage gets below whatever voltage the battery is at, power will then flow from the battery to the bus. The charger will supply 100a to the bus, and the battery 50a and the 150a load won't know the difference.


When the charger is off and something pulls power from the bus, the power flows from the battery to the bus since the battery is the highest voltage supply connected to the bus.


It's sort of similar to an air compressor. The pump is the charger and the tank is the battery and the air hose is the load. Whatever you use will pull down the pressure. If the pump is running when you start using your paint gun, the air will come from the pump and the tank will stay topped off. If the pump's not running, the air will come from the tank.

If you start using your 1" airhammer and it pulls more than the pump can supply, then everything the pump can supply will get used, as well as some from the tank. When you let off the trigger, the pump is still running, only now its output is flowing toward the tank.


When the Prosine is in inverter mode, it's pulling power from the bus, inverting it and supplying its 120vac outlet.

When you supply shore power, the battery charger fires up to supply power to the bus, the transfer switch moves the 120vac outlet from being connected to the inverter, to being connected to the shore power, and the inverter just sits there waiting.

The 12v loads never know the difference as long as -something- supplies voltage to the bus.

[Basement Yeti]

That was incredibly informative, thanks. I am still a bit hazy but I have a better understanding.

That's what confused me, I assumed the 12V DC and 120V AC were completely separated. But the Xantrex Charger is providing power to the bus bar where the 12V A/C and batteries are connected, thus the 12V loads can draw power either from shore power when it's available or battery power when unavailable, either way it's coming from the bus bar where the Xantrex charger is connected to.

Right?

[dwh]

That was incredibly informative, thanks. I am still a bit hazy but I have a better understanding.

That's what confused me, I assumed the 12V DC and 120V AC were completely separated. But the Xantrex Charger is providing power to the bus bar where the 12V A/C and batteries are connected, thus the 12V loads can draw power either from shore power when it's available or battery power when unavailable, either way it's coming from the bus bar where the Xantrex charger is connected to.

Right?

Yup. It's not a bus "bar" though, it's just a bunch of wires, but they behave the same as if it was a bar. So it's a bus, but not a bus bar.

You could build it with an actual bus "bar" if you want:

http://www.westmarine.com/1/1/23678-...x-0-875-w.html


Fuse blocks usually have their own little bus bar in them - the bar is connected to the "main bus", and it supplies the fuses.

[ame="http://www.amazon.com/Fuse-Holder-Bakelite-Bar-6-Gang/dp/B002IV3GAU"]Amazon.com: Fuse Holder And Bus Bar Bakelite Fuse Holder W/Bar-6 Gang: Sports & Outdoors[/ame]

(you can see the bar that connects the bottom row of terminals)


You can also connect other supply sources to the bus, such as a vehicle alternator or a solar charge controller.

As long as -something- is supplying the bus, the loads will work. And since there is a battery connected, the supply of voltage to the bus is basically "uninterruptable".

[Basement Yeti]

Ok, cool. So the components of a breaker box is the fuse holder, the fuses, and the housing, plus wiring?

Can breaker fuses be used both for D/C and A/C boxes?

Is an A/C, or D/C distribution panel the same thing as a breaker box pretty much?

[dwh]

thus the 12V loads can draw power either from shore power when it's available or battery power when unavailable

Or both. If the load exceeds what the charger can supply, the difference will be supplied by the battery.

Whatever supplies the highest voltage will have priority to feed the bus.

Say you are connected to shore power, and the charger is supplying 14.4v to the bus and the battery is at 13v. When you turn on a load, the power will flow from the charger to the load.

Now say you start the engine, and the alternator is supplying 14.6v to the bus. Now the loads will be supplied by the alternator. Power won't flow from the charger until the voltage of the bus drops below 14.4v. That won't happen until you have more loads than the alternator can supply, or until the voltage regulator drops the output from the alternator to a voltage lower than 14.4v.

Okay, so say the alternator can supply 100a and the charger can supply 100a - you won't start pulling from the battery until the loads exceed 200a and pull the bus voltage down to where it's below the 13v the battery is at. Once the voltage falls below 13v power will begin to flow from the battery to the bus, but power is also still flowing into the bus from the alternator and the charger.


Or say it's solar. You're driving along and have good sun on the solar panel, and the solar charge controller is supplying 14.4v to the bus. But you're driving, and the alternator is supplying 14.6v to the bus. Power won't flow from the solar charge controller to the bus, because the bus has a higher voltage than the solar charge controller (more pressure).

[dwh]

Ok, cool. So the components of a breaker box is the fuse holder, the fuses, and the housing, plus wiring?

Can breaker fuses be used both for D/C and A/C boxes?

Is an A/C, or D/C distribution panel the same thing as a breaker box pretty much?

Heh. First, nomenclature...

It's just AC and DC - A/C is "air conditioning".
Breakers are reusuable - it "trips" and you reset it.
Fuses are one-time use - it "blows" and you replace it.

There are AC breakers and DC breakers. (Some, not many, can do either. Best not to think about that.)

Same with fuses.

The main components of a "breaker box" like in a house, are the box, the bus bars and the breakers.

The main components of a "fuse block" like in a car are the block, the bus bar, and the fuse holders/terminals. (And sometimes, a cover.)

When talking about automotive, a distribution panel might be built with fuses. A high quality distribution panel would normally be built with breakers.


To hook up your system, you need
A battery.
Inverter/charger.
Fuse block or distribution panel.
Wires to connect everything, and fuses to protect the wires.

So you use some big fat wire from the inverter/charger to the battery, and some not quite so big fat, but still somewhat big fat, wire from the battery to the fuse block or distribution panel.

The wire has to be fat enough to transfer the requisite amount of amperage without causing the voltage to drop too much, and the fuse has to be the right size to blow just before the wire burns in case of a short.

What happens with wire is this - say you supply 14.4v to the bus. You hook up a skinny wire and there is no load on the other end. You check the end of the wire and you see 14.4v. Now you put a 20a load on that wire and if you check it, it will have dropped to maybe 14v. That's a .4v "voltage drop".

The skinnier the wire, the more the voltage drop.
The longer the wire, the more the voltage drop.
The bigger the load, the more the voltage drop.
Combine all three and you've got a buttload of voltage drop.

Voltage drop isn't good. A little and you're okay - around 3% or less is tolerable. Too much and you've got problems, for instance your charger is putting out 14.4v, but only 13.5v is showing up at the battery. The charger will think the battery is full, but it isn't.




One thing about big inverters is that they can draw a LOT of amps from the battery, and if the wire isn't REALLY FAT, then there will be too much voltage drop.

2000 watts / 12 volts = 167 amps
2000 watts / 120 volts = 16.7 amps

So to supply 16.7 amps out the 120v side, it's got to suck in 167a from the 12v side. That's about what a Warn M8000 winch would draw if it was pulling a 1500lb load. Hoo boy... REALLY FAT wire and that's no joke.

So you need wire that can handle more than that. Say something that can handle 200a, and then you use a fuse that will blow at say 180. Then you have enough to supply the full 167a load without blowing the fuse, yet are still protecting the wire from burning in case of a short.


Now say your distribution panel can supply 100a of loads. Same deal, you need wire from the battery to the panel that can handle over 100a, say 150a, and a fuse that won't blow at 100a, but will blow before the wire burns. So say a 125a fuse.

You'll probably use fuses for the big fat wire, because they are expensive, but not horribly bloody expensive like a 12v breaker in that size.

Then, the distribution panel's bus will feed the load breakers, and you'll run whatever size smaller wire you need from the breakers to the loads.

[Basement Yeti]

Wow, really great stuff man. Thanks a lot. I feel like I have a much better understanding of what it is that goes into a system like this.

The battery, charger/inverter, and distribution panels will all be very close to each other.

I had read about wiring gauging and I understand it a lot better now.

I'll need an in line fuse from the battery bank to the inverter only? Or from the battery bank to the inverter, 12V DC, and 120V AC panel?

I also plan on going with a battery shut off switch. And I'm not sure if this inverter/charger has a surge protector from the auto transfer switch but I think I might need one.

[dwh]

Wow, really great stuff man. Thanks a lot. I feel like I have a much better understanding of what it is that goes into a system like this.

No worries. Glad to help.

The battery, charger/inverter, and distribution panels will all be very close to each other.

Excellent. Shorter wire runs means less voltage drop so you can usually save a few bucks by not having to buy the next larger size wire.

I had read about wiring gauging and I understand it a lot better now.

Good deal. Now let me drop The Bomb on you.

The Prosine 2.0 is rated to supply 2000w -continuous- output on the AC side, but up to 4500w -surge-. That means that you could potentially draw...:

4500w / 12v = 375a

...from the battery. Good god! So you gotta plug that number in when you are figuring out your wire size and voltage drop - and the fuse to protect the wire.


The Prosine 2.0 manual...:

http://www.xantrex.com/documents/Inv...1_rev-C%29.pdf

...calls for 250mcm with a 300a fuse for runs of 6' or less, and 350mcm with a 300a fuse for runs of 6'-12'. (page 3-7)


Lemme tell you something about 250mcm wire - to get it in a tight spot you might need tools to bend it to fit. A foot of it can make a nice little billy club. I'm 6'4" and I've got 14" forearms. I can bend 250mcm by hand. 350mcm...maybe. 500mcm and I'll probably need a pipe bender to work it into place (I know this, because I've had to use a pipe bender on 500mcm in the past). It's that beefy.

You are going to need to leave some room at the connection end of the Prosine for that wire since no matter what you won't get a really tight bend on it.

I'll need an in line fuse from the battery bank to the inverter only? Or from the battery bank to the inverter, 12V DC, and 120V AC panel?

Fuses and breakers protect the wire from burning up in case of a short. So wherever you have a hot wire, it must be protected by a fuse or breaker. The rule is to place the overload protection (fuse or breaker) as close to the source of current as possible. That way the maximum length of wire is protected.

Let's say you run 6' of 250mcm between the inverter and the battery. You put the fuse at the inverter end of the wire. Something (like a truck frame ) cuts into the wire -between- the battery and the fuse. Now you've got basically a very high amperage welder running out of control.

The fuse isn't going to blow because the overload isn't running -through- it. The scary monster is going to just keep arcing until either the wire or the truck frame finally burns through and breaks the connection.

Okay, so you put the fuse at the battery end. But wait...the Prosine is ALSO a source of current. What happens if there is a short between the fuse and the Prosine, while the Prosine is putting out power? That's the same deal - the fuse won't blow because the overload isn't running through it.

Fortunately, the Prosine 2.0 has built-in overload protection, so the charger will detect the overload and shutdown. Sweet.


So, on the 12v side, you need a 300a fuse to protect the wire between the battery and the inverter. You need another fuse to protect the wire from the battery to the distribution panel. The distro panel will have fuses or breakers to protect each wire running out of it to the loads.


On the 120v side you'll have a breaker box. In that box, you'll have one breaker that is for the incoming power from the inverter. So you'd run a wire from the inverter to that breaker. That breaker supplies power to the 120v bus, and protects the wire between the inverter and the breaker box.*

(But not really. If you've been paying attention, at this point you'll say, "But wait, that's not closest to the current source! It's at the wrong end of the wire!" And you're absolutely right. BUT, the Prosine can detect an overload and will shut itself down, which cuts off the current source and more or less performs the same function as a fuse or breaker...so -in this case- we can get away with bending the rule.

So why do we need that breaker? We don't really. We are required to have a disconnect and overload protection. That could just be a normal switch and a fuse, it doesn't actually need to be a breaker. But by using a breaker we get both in one, and since we're feeding a breaker box anyway...)

Then, you'll also have breakers that tap off the bus to feed the 120v loads. The size of those will depend on the size of wire you are running to the loads. Most likely, you won't use over and #12 wire and 20a breakers for those.




*So what size is that breaker and the wire from the inverter to the 120v breaker box? Well, that's a tricky question. The rule is it's supposed to be no larger than whatever breaker is feeding the 120v input of the Prosine (the shore power breaker).

Big RVs generally have 30a or 50a shore power plugs. At a developed camp site with full hookups, there might actually be 30a or 50a receptacles for them to plug into.

But there might not. There might only be 15a receptacles to plug into. So the big RVs usually carry a "dogbone" adapter that plugs into the 15a receptacle, and then they can plug their bigger plug into the dogbone. They have to watch their loads when they do that, or they can trip the shore power's breaker (and maybe have to beg the camp host to reset it).

So, you might use a 30a big RV shore power cord. Or you might use a 15a so you can plug in anywhere. (I would use a 30a shore power cord and a dogbone so I could use a 30a receptacle if it's available.)

But it would suck to limit the feed from the inverter to the 120v bus to 15a, just because the shore power is limited to 15a. That's only 1800w and you'd never be able to use the full 2000w continuous output when running off the battery.

It's a bit of a silly rule if you ask me.

We live in a litigious society and this is a public forum, so the only advice I will give you is this: "Follow the rules".

I will however tell you what -I- would do, and strenuously advise that no one should ever do what I would do. No kidding, if you break the rules then that's on you. I take no responsibility.


Personally, I would ignore the silly rule. I'd run a #10 wire and protect it with a 30a breaker. That's the max the Prosine manual allows anyway. That way, I could get full continuous output from the inverter when running on battery, and still have most (3600w) of the rated 4500w available for handling surge loads.

When on shore power, I could potentially draw more than the shore power can supply - but so what; it will have its own breaker anyway, so if I overload it that breaker will trip.

It's really no different than an RV using a dogbone adapter to plug a 30a shore power plug into a 15a receptacle. You just gotta watch your loads so you don't trip the shore power breaker.

When I'm using my 30a shore power cord and plugged into a 30a shore power receptacle, then I'm not breaking the rule anyway. I'm only breaking the rule when I use a dogbone to plug into a 15a or 20a receptacle.

I also plan on going with a battery shut off switch.

You have to anyway. The Prosine manual calls for a disconnect. You'll want that to be the very first thing connected to the battery. I.e., battery to switch, switch to fuses to whatever.

And I'm not sure if this inverter/charger has a surge protector from the auto transfer switch but I think I might need one.

It has one. From the manual, page 5-9:

"Input Voltage: The charger can operate over the range of 90–135Vac. This wide range allows the PROsine to deliver a maximum current to your batteries even when incoming AC voltage is less than ideal. A built-in surge protector protects the PROsine from surges and spikes on the AC power line."


Well...at least that protects the Prosine itself...it says nothing about if it protects things plugged IN TO the Prosine.

But it does have the ability to detect "good" shore power and it won't switch over from inverter to shore power unless the shore power is "good". (Whatever the hell "good" means...as far as I can see, the manual doesn't say.)

[Basement Yeti]

When you mentioned the distribution panel and breaker box separately you lost me.

Isn't a distribution panel a breaker box? And don't I need one distribution panel for 120V and 12v? The 12V runs from the battery, the 120V panel runs from the inverter? Does anything run from the inverter to the 12V distribution panel?

Also, I originally just wanted 1000-1,500 watt inverter. But I couldn't find a combination inverter/charger in that size. I need to find a smaller one...