Inverter earth

[chris w]

This could be where I show my ignorance (again).

 

We've a Mastervolt 2000 combi and, as far as I know I wired it as per instrctions, see previous thread about surveyor's concerns over size of cables between battery and combi. We also have a shore line which we connect when we're on the boat on our marina mooring.

 

I have a battery master switch between batteries and all uses thereof, so the connection to the Mastervolt is effectively from the non battery side of the switch. That is, the Mastervolt won't work when the master switch is turned off.

 

When the shore line is connected, the charger is pumping power into the non battery side of the master switch and thus powering all the 12v circuits on the boat, even though the master switch is off.

 

Have I overlooked something in the wiring?

 

Ray

 

Possibly the master switch arrived prewired with a fuse across the main terminals. They are sometimes supplied like this for cars so that switching off the battery switch (in rally cars etc) does not disconnect the alarm and clock circuits etc.

 

If nothing else (other than the mastervolt) is connected to that side of the master switch, I can't see what else could be causing it.

 

Chris

[Keeping Up]

I seem to be missing something in the last two replies.

 

Surely if you connect any charger to the non-battery side of the master switch, as described by Ray 3 posts ago, then what he describes is exactly what will always happen: with the master switch closed (on) everything works normally, but with it open (off) the charger will feed only the on-board systems. Naturally if the mains supply is disconnected when the master switch is off, the inverter will do absolutely nothing.

 

As far as I can see, with a combi you can't use a master switch to disable the inverter, without raising the possibility that you can have the charger driving the boat circuits without the stabilising influence of a battery.

 

If you want to protect against this possibility, and yet still be able to use a master switch, the only solution I can think of is to have TWO master switches. My first thought is that the best way would be to put them in series; one switch can be used to isolate everything except the combi, and one can be used to isolate everything including the combi. The combi then connects to the short link between the two - but it would be wise to label both switches very very very carefully to avoid the possibility of making a mistake when you turn one off.

 

Allan

[chris w]

\allan

 

You're quite right of course. Age and experience triumphing over bullsh*t again.

 

Amazing how one misses the obvious sometimes (leastways I do)

 

Chris

[Ray]

Thanks. It worried me at first but I couldn't see anyway round it.

 

All I need to do when working on the 12 volt side and not wishing to find any stray volts lying around (if I accidently forget to switch the relevant circuit breaker off in the 12v master panel) is to turn the 240v off as well.