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Magnetos, Ignition Coils and Spark Plugs Discussion about magnetos, buzz coils, spark plugs, ignitors and low tension coils.

Magnetos, Ignition Coils and Spark Plugs

12 vdc start relay mod to open vs close circuit?


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Old 09-05-2013, 07:20:59 AM
sdowney717 sdowney717 is offline
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Default 12 vdc start relay mod to open vs close circuit?

I have an onan MCCK gen in a boat along with an inverter.
I would like to be 100% certain the inverter turns off before the gen produces power or they might interconnect the 2 and burnout the inverter. I do have a 4 pole DPDT relay that switches hot and neutral. When inverter turns on, it closes 4PDT relay breaking circuit with gen. However, if load on inverter is too high, the relay will buzz and arc between the two sources and cause a short circuit.

An easy way to do it would be to open circuit the 12vdc going to inverter when gen runs using a relay. Relay would need to be like a starter relay except they when energized are closed, instead of open circuit.

Relay will not buzz with gen on if inverter is off And if someone tries to turn inverter on with gen on, inverter can not function.
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Old 09-05-2013, 07:51:54 PM
Radiomike Radiomike is offline
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Default Re: 12 vdc start relay mod to open vs close circuit?

I would repost this question in the Generator and electrical section, lots of knowledgeable people live there...

I would use two mechanically interlocked relays one for the generator and one for the inverter. No question then of a short between changeover contacts.


Mike
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Old 09-05-2013, 09:35:58 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: 12 vdc start relay mod to open vs close circuit?

Electric winches use a NO-NC relay, similar to a starter relay, just not sure if the coil is rated for continuous duty.
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Old 09-06-2013, 10:29:32 AM
sdowney717 sdowney717 is offline
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Default Re: 12 vdc start relay mod to open vs close circuit?

The start relay turned out to be a bad idea. After a few minutes it gets hot and it draws 2 amps. which is quite a waste of power.

The better idea is to do this circuit. If you saw my circuit you will understand how it works.

This will insure that the inverter can not power up the 4PDT relay ever if the gen starts up. The 12vdc signal from gen will de energize the 4PDT relay and the start up delay also helps keeping the system from joining circuits.

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Old 09-07-2013, 02:12:50 PM
Radiomike Radiomike is offline
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Default Re: 12 vdc start relay mod to open vs close circuit?

Be cautious on the specification of the four pole change over relay. If you are using the same pole of the relay for the change over there can be up to 350 volts between the inverter contact and the generator contact.

On failure of the cube relay the system will immediately change over to inverter if that is running running

How is the neutral connected, will it be grounded at some point?

Mike
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