Circuit Changeover - 12v to 240 changeover switch

scottb34300

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25 Apr 2003
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Hi,

I have a 240 volt system which runs a TV and laptop etc, but when travelling or moored on a river I connect it all up to a 12v inverter.

It’s a constant problem having to change it all over as it means taking plugs out in awkward places etc.

What I need is a changeover switch, so that when i leave the marina i can flick a switch and it will all go over to the inverter and visa versa.

Suggestions would be appreciated.

Thank you,
 

halcyon

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20 Apr 2002
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Simple solution is a 240 volt change-over relay.
Connect the inverter to the normally closed contacts, and the mains to the normally open contacts and the coil.
Plug into the marina, contacts close and connect you to the mains and isolates the inverter, disconnect the mains , relay drops out and isolates you from the mains and reconnects the inverter.


Brian
 
A

Anonymous

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A two pole relay would work fine, and be convenient, but consider the alternative of a three position manual selector switch "Inverter - Off - Shore Power". This would allow you to turn the ac off more easily, which is handy at times.

A big disadvantage of a relay is that when the shore power fails - maybe due to another boat tripping out the supply - then your power will switch over to the inverter. If you've left on a high load, on shore power, while you go ashore for a while, you might come back to a flat domestic battery bank.
 

jfkal

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Three position switch I OFF II. make sure you buy a break before make type. Otherwise you may blow your inverter.
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William_H

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You probably know but just to reiterate it would be a major disaster to have the mains connected to the running inverter (in paralell) likewise a generator of any sort. You can end up with the equivalent of connecting 2 batteries in paralell but the wrong way around so they make a 24volt shorted battery. Because the AC is going from + to- 50 times per second unless you inverter goes to + at the same instant as the mains you have a short circuit and considering that it is unlikely your inverter is running at the same frequency as the mains you get a bang in milliseconds.
So you must have a clear disconnect before connecting the new source preferably with 2 poles. Your boat is too young to smoke. regards olewill
 
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