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Safely switching between shore power & inverter


blackrose

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I have one of these type of rotary mains selector switches on my boat but mine is 0 off, 1 shore, 2 inverter, 3 not connected.

 

The instructions for my inverter (not combi) recommends turning the inverter on before turning on the AC appliances connected to it (in this case the boat's mains ring). I guess that's to ensure equipment is not exposed to any high currents or voltages at inverter startup.

 

So when switching from shore power to inverter I switch the inverter on and wait for about 15 seconds or so until the inverter fans stop running and the inverter settles before switching over from shore power (1) to inverter (2) on my mains selector switch. It's a seamless manual switchover and the TV won't even blink for example. If I want to switch back to shore power I do the reverse, switching the mains selector back to shore power first. I might leave the inverter running if I know I'm switching back soon or I might switch it off.

 

But is what I'm doing safe or is there any risk of putting shore power into my inverter, or having shore & inverter mains on the mains ring at the same time?

C26A271/GBA001E Kraus & Naimer | Kraus & Naimer, 3P 4 Position Rotary Switch,  32A | 293-7162 | RS Components

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The switch should be break-before-make, and never connect both source at the same time. I'd go further and say that it _is_ break-before-make. If it wasn't, you would have blown up your inverter and tripped your show power by now.

 

MP.

 

 

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20 minutes ago, MoominPapa said:

The switch should be break-before-make, and never connect both source at the same time. I'd go further and say that it _is_ break-before-make. If it wasn't, you would have blown up your inverter and tripped your show power by now.

 

MP.

 

 

 

As MP says, those switches are break before make to stop accidental paralleling of the mains and inverter outputs which will be out of synchronisation. There is no need to wait before moving to th next switch position.

 

Some combi units are capable of synchronising the inverter output with the mains to allow the inverter to help provide additional power to the mains where the mains supply is limitrd, for example to supply a 13 amp load from a 6 amp mains supply.

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I once saw a 750 kW generator and it's diesel engine (Paxman Ventura) after it had been unintentionally paralleled with the mains whilst about 90 degrees out of phase.  The whole kit and caboodle had gone walkabout from its mounting wrecking both diesel and generator.  The surrounding compartment was not much improved either.

 

N

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26 minutes ago, BEngo said:

I once saw a 750 kW generator and it's diesel engine (Paxman Ventura) after it had been unintentionally paralleled with the mains whilst about 90 degrees out of phase.  The whole kit and caboodle had gone walkabout from its mounting wrecking both diesel and generator.  The surrounding compartment was not much improved either.

 

N

We had the same when a pair of synced sets on a festival decided to unsync themselves…Twas impressive! A large broom was needed to sweep up the outcome. 

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4 hours ago, MoominPapa said:

The switch should be break-before-make, and never connect both source at the same time. I'd go further and say that it _is_ break-before-make. If it wasn't, you would have blown up your inverter and tripped your show power by now.

 

MP.

 

 

And the TV continues to run without a blip through the switchover as it is powered from a power supply smoothing capacitor during the short period when neither mains source is connected.

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2 hours ago, BEngo said:

I once saw a 750 kW generator and it's diesel engine (Paxman Ventura) after it had been unintentionally paralleled with the mains whilst about 90 degrees out of phase.  The whole kit and caboodle had gone walkabout from its mounting wrecking both diesel and generator.  The surrounding compartment was not much improved either.

 

N

One hand in yer pocket, wait 'til 5 to 12...

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1 hour ago, Martin Nicholas said:

I would have:

1. Shore.

2. No connection.

3. Inverter.

 

That way it sould be impossible to short the shore and inverter together, no matter how keen with the switch.

 

Yes that type is available (below). However from what Moominpapa and Cuthound have said previously there's no chance of shorting shore and inverter with the switch I have. In addition you can't switch seamlessly between shore and inverter with the switch below.

image.png.ef31f6a134e866a62c292bf675324cea.png

1 hour ago, David Mack said:

And the TV continues to run without a blip through the switchover as it is powered from a power supply smoothing capacitor during the short period when neither mains source is connected.

 

Ok I see, but the whole mains ring seems to run without a blip when I switch from one to the other 

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15 minutes ago, blackrose said:

 

Yes that type is available (below). However from what Moominpapa and Cuthound have said previously there's no chance of shorting shore and inverter with the switch I have. In addition you can't switch seamlessly between shore and inverter with the switch below.

image.png.ef31f6a134e866a62c292bf675324cea.png

 

Ok I see, but the whole mains ring seems to run without a blip when I switch from one to the other 

It looks like a Kraus and Naimer switch.

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