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Old 09-03-2009, 03:57 PM   #16
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Relay/contactor confusion


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The box called "convertor" is a DC power supply or a battery charger?
Both. I suspect you're worried about current draw through the switch to the converter. I will double check to see how much current it can draw before committing to the design.
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Old 09-03-2009, 04:07 PM   #17
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Relay/contactor confusion


Can you show all wires for the AC and the DC, from sources to loads? Hot, neutral and ground?
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Old 09-03-2009, 04:26 PM   #18
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Relay/contactor confusion


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Can you show all wires for the AC and the DC, from sources to loads? Hot, neutral and ground?
Sounds like an absolute mess. If I do, I'll most likely have to start from scratch in order to make it readable.

Maybe this will help for now...

All grounds connected at all times.
DC negative bonds to ground.
AC neutral bonds to ground only when NOT connected to shore power.
All metal boxes grounded.

I will need to check and see if the camper's panel has isolated neutral/ground.

Do you think I'm missing anything?
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Old 09-03-2009, 04:40 PM   #19
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Relay/contactor confusion


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Do you think I'm missing anything?
The way I draw it you can use a single hefty DPDT relay, and when you unplug shore power the coil current goes to zero and the relay armature moves to the "DC" position. The wiper of each relay pole goes to the AC and DC loads.

And, unplugging shore power unpowers the AC to DC supply.

But there might be a problem using connectors as on/off switches.

As a final test, check the voltage between your boat and the water when hooked to shore power.
There was an awful incident with a houseboat awhile back. The survivors sued.

Last edited by Yoyizit; 09-03-2009 at 04:43 PM.
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Old 09-03-2009, 04:52 PM   #20
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Relay/contactor confusion


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The way I draw it you can use a single hefty DPDT relay, and when you unplug shore power the coil current goes to zero and the relay armature moves to the "DC" position. The wiper of each relay pole goes to the AC and DC loads.
The only trouble with that, is that there's no way to be off shore power without the inverter getting power (short of taking an additional step to disconnect it). I'm going for one switch and idiot proof here

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But there might be a problem using connectors as on/off switches.
I don't follow here...

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As a final test, check the voltage between your boat and the water when hooked to shore power.
There was an awful incident with a houseboat awhile back. The survivors sued.
This isn't a boat, it's a truck bed camper; the term "shore power" seems to be universal for boats and RV's and who knows what else.

But, shouldn't a boat always be grounded to the water via the out drive, or the anodes, or whatever?
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Old 09-03-2009, 05:00 PM   #21
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Relay/contactor confusion


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I don't follow here...1

But, shouldn't a boat always be grounded to the water via the out drive, or the anodes, or whatever?2
1 connectors are connected first and then the power is switched on or off. They don't like the sparking that comes with unplugging while carrying current, especially with inductive loads.

2 yes, but a person in the water may touch energized boat metal while there is a voltage gradient in the water which paralyzes or electrocutes them. One guy couldn't release his grip on a railing, which prevented him from saving the swimmer but also saved his life.
http://ecmweb.com/ops_maintenance/ho...se/index1.html

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Old 09-03-2009, 07:44 PM   #22
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Relay/contactor confusion


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1 connectors are connected first and then the power is switched on or off. They don't like the sparking that comes with unplugging while carrying current, especially with inductive loads.
Ah. The only reasonable way to do that now would be to shut off either the breaker in the house, or the breaker inside the camper. We never do that.
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Old 09-03-2009, 07:59 PM   #23
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Relay/contactor confusion


Breakers also aren't supposed to be used as switches.
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Old 09-03-2009, 09:45 PM   #24
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Relay/contactor confusion


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Breakers also aren't supposed to be used as switches.
... unless they are SWD rated
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Old 09-03-2009, 10:12 PM   #25
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Relay/contactor confusion


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I am looking for a relay, or a contactor, or whatever it's called...

It needs to be a single pole, double throw design, it needs to switch around 30 amps at 120 volts, and it needs a 120 volt coil.

Such a thing seems illusive in my Google exploits, and I think the trouble may be the combination of double throw and high amperage. Is this thing as "weird" as I'm starting to think?
The answer is. Don't "Goooogle" for specialized, (even though I don't see what's so "Unusual" about what you are seeking) Look at the websites of major Electrical Suppliers or major manufacturers like ....(Well. I won't give free commercials. I guess, we'll leave that up to the advertizing dep't of this website! But you must be specific in your request. "Whatever..." will not do!
BTW. There's a difference (Language wise) between "ELUSIVE" and "ILLUSIVE". I don't even know if there's such a word in proper English!(Now more than ever)Don't Drink and Drive!!!
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Old 09-04-2009, 08:55 AM   #26
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Relay/contactor confusion


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... SWD rated
More Googling for me!
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Old 09-04-2009, 11:11 AM   #27
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Relay/contactor confusion


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Breakers also aren't supposed to be used as switches.
Well then, it's a good thing we never do that
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