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Old 09-05-2014, 02:32 PM   #21
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Originally Posted by Rossue View Post
Doug- will post ETI's response. Am still looking for input on cable length/size from any 21 owners who have installed their own inverters and connected to ETI-supplied Transfer Switch. It appears that battery/WFCO/Transfer switch are all in close proximity to each other.
Ross, I have a 2500 watt inverter and my own transfer switch and used 3 gauge wire from the batteries to the inverter (per the inverter manual) and 12 gauge from the inverter to the transfer switch.
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Old 09-05-2014, 02:38 PM   #22
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Was told in July when we visited Eti to finalize build sheet for our 21 that the transfer switch will activate all 110 outlets including outside receptacle. Battery's , inverter and transfer switch are all located In rhs (awning) side rear dinnette bench area
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Old 09-05-2014, 03:02 PM   #23
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Ross, I have a 2500 watt inverter and my own transfer switch and used 3 gauge wire from the batteries to the inverter (per the inverter manual) and 12 gauge from the inverter to the transfer switch.
Thanks Steve for the time you've taken with me over the last month or two. This is where us laymen get confused: 3 gauge or 000? Patrick at DonRowe.com has been very helpful and as he explained, 4 gauge wire is about as thick as a pencil while 0000 (4/0 or pronounced four ought) is the size of a U.S. or Canadian quarter.

For this run I will use 000 wire, and they are sending a set of two 4' length with 3/8" copper ring terminals for $63 to cover the DC side. For inverter to transfer switch he suggested 10 gauge.
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Old 09-05-2014, 03:14 PM   #24
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Originally Posted by Rossue View Post
Thanks Steve for the time you've taken with me over the last month or two. This is where us laymen get confused: 3 gauge or 000? Patrick at DonRowe.com has been very helpful and as he explained, 4 gauge wire is about as thick as a pencil while 0000 (4/0 or pronounced four ought) is the size of a U.S. or Canadian quarter.

For this run I will use 000 wire, and they are sending a set of two 4' length with 3/8" copper ring terminals for $63 to cover the DC side. For inverter to transfer switch he suggested 10 gauge.
Ross, I checked the manual on your inverter and it also suggests an 8 gauge wire to ground in RVs. (page 3-6).
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Old 09-05-2014, 03:17 PM   #25
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You can use a wire size table or calculator (such as the one at the bottom of this page) once you know your wire lengths. You only need the high current wiring between the battery(ies) and the inverter.

The Xantrex XPower 3000 can produce 3000 watts for a maximum of 5 minutes; its continuous rating is for 2500 watts. If we use the 3000 watts to determine wire size, and a nominal 12V as the source voltage, the input current to the inverter will be 3000/12 or 250 amps. If we make the assumption that the total wire length is within the recommended 10', (5' for each wire) and the 3% allowable voltage drop (which is really too high for 12V systems; 3% of 12.6 (a fully charged battery) would leave 12.2 volts at the inverter), a #1 wire would be acceptable.

Unfortunately, it isn't that simple. First, your batteries have internal resistance. If you use a pair of 6V batteries, the internal resistance is in series, which means they add together. Feeding inverters is one of the few places where a pair of 12V batteries with the same amp hour capacity will work better than a pair of 6V because the 12V batteries are wired in parallel, thus halving the internal resistance.

While many devices will work OK at a lower than designed voltage, there is a problem with an inverter. If the voltage feeding the inverter drops, and the load stays the same, the current to the input of the inverter must go up. This results in more voltage drop, both due to the internal resistance of the battery & the loss in the wiring. As the battery supplies current, its voltage drops. The combination of the two can drop the voltage to the inverter to the point where the under voltage buzzer goes off, or even worse, shuts down the inverter (most shut off at 10.5V). You can't do much about the internal resistance of the batteries, but you can produce less across the wiring.

This is why most inverter manufacturers recommend wire sizes in excess of the NEC wire table calculations. For example, Xantrex recommends a minimum of #2/0 wire for a 10' run using the XPower 3000 (PDF Manual), and states that size wire will not allow the inverter to supply 3000 watts. They recommend using #4/0 for standard installations. Longer runs than a combined 10' require even larger wires.

This is not to say that smaller wiring won't work. As long as you meet the wire size tables, you will have a safe installation (assuming you use a properly rated catastrophic fuse) but you will find the inverter shutting down earlier than it would with the recommended wire, and that it may not operate at all when you battery is not fully charged. Since most users never use the full capacity of their inverters, an undersized installation may never show up, however if at some point down the road you find you need the full capacity, rewiring may be a difficult project.

In my case, I am using Xantrex's recommended #0 wire for a 1000 watt inverter. While making a cup of coffee - a 65 amp draw at the start & with full batteries), I can watch the current increase to 70 amps (and the resulting voltage drop) over the 10 minutes it takes to brew. The voltage recovers quickly after the inverter shuts down, indicating that the drop was caused by resistance, not the 6-8 amp hours supplied to make the coffee.

Sorry to go on so long, but good installations of high powered inverters is a pet peeve of mine - I did a workshop at the last Oregon Gathering on the subject...
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Old 09-05-2014, 03:29 PM   #26
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Jon- just to be sure- the diameter of the cable increases with the number of 0's-right? So a #000 is thicker than a #0?

Thanks to you as well for taking time in helping me pick this unit.
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Old 09-05-2014, 03:51 PM   #27
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Quote:
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Jon- just to be sure- the diameter of the cable increases with the number of 0's-right? So a #000 is thicker than a #0?

Thanks to you as well for taking time in helping me pick this unit.
Yes. Wire tables can be a bit confusing in that the larger numbers are smaller diameter wires. When they reach "0", they didn't have anywhere to go with bigger wires, so they just added zeros. 4/0 (0000) is the largest AWG size, then it switches to MCM (Thousand Cross Sectional Mills) which do get larger as the # gets larger. Confusing? yes...
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Old 09-10-2014, 10:37 AM   #28
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I just talked to Reace and George.

When Escape installs the transfer switch they feed the (GO Power 30amp) transfer switch from a 20amp 120V AC breaker and the inverter output.

The transfer switch output (from the inverter or whatever the power cord is plugged in to - generator, 120V power grid, etc.) goes to another breaker box with 2 15amp breakers - which feeds the plugs. The microwave is normally NOT fed via the transfer switch, but can be if you request it. (You need to request it if you want to run the microwave from the inverter - we want to and have requested it.)
Got an email today from Reace: "with the transfer switch, all outlets except the fridge will be powered from the inverter(includes microwave)".
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