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Old 25-04-2010, 19:03   #1
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Question Wire Connection for 3000 watt Inverter - Look at My Melted Terminal Block

Just had a small electrical fire on our Xantrex 3000 watt inverter/charger today. I thought the charger had fried but after I took it apart I found the problem. Whoever did the connections used a plastic terminal block (see attached picture). The terminal block melted which caused a short and subsequently melted the wires (10 gauge) on each side of the block ( the 3rd wilre was completely removed). Fortunately after I repaired the connection (used the same block again as we are in the Bahamas and there are not parts stores here) everything seems to work fine.

I started thinking about this and was wondering if this is the correct way to do this connection? Zantrex just provides bare 10 gauge wires for the AC in and out. Not sure I would use 10 gauge crimp connectors for this connection??

Still wondering what caused this: 1) plastic terminal block melted 2) set screw came loose and shorted out or 3) incorrect wire gauge (whoever installed this didn't use marine grade wire back to the panel so it may have been a corrosion issue)

3000 watts (say 30 amps at 110) on a 40 foot round trip - what is the correct gauge of wire I should be using?
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Old 25-04-2010, 19:23   #2
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No way in Hell I would use that type of terminal block for these connections. I would use wire bugs, followed by rubber tape, followed by electrical tape. My 2500 watt Xantrex uses 10 Ga. in and out...
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Old 25-04-2010, 19:26   #3
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Definitely the wrong kind of terminal block. When using that type of block there must be a sleeve over the end of the wire or a plate in the block that presses down on the wires. The kind you have looks like the screw contacts the wires directly, ergo the damage you see to the wire strands. The damaged wires overheat and eventually lead to the kind of fire that you experienced. Bad electrical wiring is the leading cause of fire on pleasure boats.
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Old 25-04-2010, 19:30   #4
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I wouldn't use tape either. Shrink wrap is the thing to use. If by wire "bugs" you mean wire "nuts", CVH, then there is no place for them on a boat. Proper connector blocks with properly pressed on ring terminals using shrink wrap for strain relief is the best way to go.
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Old 25-04-2010, 19:31   #5
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The kind you have looks like the screw contacts the wires directly, ergo the damage you see to the wire strands.
ABYC standards say that that type of terminal must have a small plate between the screw and the conductor to spread the clamping pressure. Doubt this block has it, like you said. Also, good chance this block might be aluminum. That's a no-no too.
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Old 25-04-2010, 19:37   #6
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Sorry DeepFrz, Wire Bugs must be an Elevator repair term, as we have always called them that. Here is what I mean: Blackburn #4/0 Stranded to #2 Solid Split Bolt Connector, Copper - 30H-B1 at The Home Depot .Cover them with self-sealing rubber tape, followed by electrical tape. Xantrex ins and outs are 10 Ga. wire and these will not cause further problems. You are right too, wire nuts have NO place aboard...
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Old 25-04-2010, 20:10   #7
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Chris; Okay, I thought you meant the wire "nuts" that domestic electricians use. These should never be used on a boat.

Ideal 74B Yellow Wire-Nut Wire Connectors - 30-074J at The Home Depot

The one's you reference look a little heavy duty for this application though.
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Old 25-04-2010, 20:40   #8
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The one's you reference look a little heavy duty for this application though.
It was just an example. The ones I use are even bigger!
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Old 25-04-2010, 21:15   #9
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KevinE
I would make a very thorough check of your entire electrical system priority #1 at this point! I would not be able to sleep at night, worrying that the same guy wired other parts of the system. That connection, even before the melt down, was frightening.
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Old 25-04-2010, 21:50   #10
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Unless I’m missing something this is a factory connector inside the inverter. It came that way. I have found many of the chargers/inverters are not heavy enough in the factory wiring and terminals. I have seen a couple of chargers burn up the light nylon terminal block that a good electrician would never use. I see terminals too small and too light all the time. I don’t think they splayed the wires, just too light. This must be running high amps to do this though. Look further than this, this could be secondary failure.

Split bolt connector: I learned to call it a Kearney. A brand name from a long time ago. Good connection but bulky and must be wrapped carefully to make watertight especially if connection has a crotch. Use cambric backwards so it won’t stick then one layer of rubber then Super 33+. Did a lot of that for motor pigtails.

3000 watts is about 26 amps. #10 rated at 30 amps, so you are fine with wire size. No derating for little run like this on AC.

Non marine wire terminations can be made up with little problem if the bare copper is covered with a heavy anti-oxidant when finished. (I don’t mean a heavy coat; I mean an anti-oxidant that won’t drip when it gets hot.) This is in addition to tape and heat shrink. I have used Scotchcoat to paint individual wire too and that works well as it dries and will not run. I have spliced 480v lines with a little Scotchcoat and then 33 + that were used 100 ft below water level in a well casing and they never failed.
 
 
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Old 26-04-2010, 05:37   #11
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Unless I’m missing something this is a factory connector inside the inverter.
You would think so, but actually Xantrex inverters come with just stripped wires for both input and output. Hence my wire bug / split bolt connector recommendation. As mentioned earlier, you could also use a 50 amp screw terminal block with crimped heatshrink ring terminals. You wont get a better joint than carefully prepared bugs though... as you mentioned, they are used for big draw motors, etc. You will not have corrosion problems if you take care with the tape.
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Old 26-04-2010, 06:19   #12
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I have an email into Xantrex to see what their recommendation is. FYI the terminal block I used does have a small steel bearing plate on the ends of the screws.

Christian Van H - 'wire bug' type connectors - are you suggesting crimp style? I have these on board for 10ga wire but not sure its any better than what was there.

This circuit has a 40 amp breaker - the charger has a maximum load of 28 amps leaving me a 12 amp balance for any any other a/c I use. Is 10 ga. rated for 40 amps?
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Old 26-04-2010, 07:25   #13
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You should not have anything else connected on that circuit.

Steel is not a great conductor. Silver plated copper is what you should have in the connector block.
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Old 26-04-2010, 07:33   #14
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Kevin,

Hire someone who understands this.

This is miswired unless I am not reading you correctly. The charger should be on a 30 amp ckt. This means #10 wire. This should be on a dedicated 30 amp ckt. Nothing else on that circuit.

A 40 amp breaker is not for any general use as most all everything "else" is rated at either 15 or 20 amps and these devises will cheerfully burn up on a 40 amp circuit and you will never know until the fire spreads.

I still think another high current issue was the culprit but you need to get a professional to look at this.

So 30 amp breaker dedicated breaker to the charger. 15 or 20 amp breakers for general use.

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Old 26-04-2010, 08:34   #15
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Um Saudade,
There is a single 110 input into the inverter (shorepower or genset). This 110 provides power for the charger; house a/c has to pass through the inverter as the zantrex can automatically sense and manage power (I can leave the inverter turned on while on shore power full knowing the zantrex is not inverting 12 volt, it passes it through, when I unplug from shore power the inverter automatically picks up to deliver a/c). This is why there is a large breaker on the a/c inverter in.

BTW I have rarely had good experience with "professionals" - spend a pile of money, they solve their problem and more times than not break something else.
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