Separating Inverter and Shore Circuits

[mikereed100]

A friend has separated the inverter and shore/generator circuits on his boat such that in all the outlets the upper socket is wired to the shore/generator circuit and the lower socket is wired to the inverter. I can't think of a good reason to do this unless, for some reason, he wants to run the inverter and shore power at the same time. To me it makes more sense to just switch from one to the other using a source selector switch, but what do I know? Anybody see any advantage to separating the circuits?

[john61ct]

one is "cleaner" power than the other?

sine wave shape, or spikes/surges/brownouts

[CaptTom]

I'm with you. I'd rather throw a switch than go around unplugging and re-plugging everything. I'd also rather run on shore or genset power when available, than running some loads off the inverter all the time.

But hey, if that works for your friend, and he truly understands what he's doing and why, I'm not going to judge.

[a64pilot]

Way my Magnum inverter works is if shore power or generator power is available, its used. Inverter only gets loaded when there is no shore power, the switch over is so fast that nothing even flickers either, it is fast enough to be a UPS.
I have my generator on an automatic switch, 60 sec after the generator is on line, it is switched over to generator automatically.
No switches to throw, its all automatic.
Why complicate things?

[mikecambrai]

Fitting a rotary changeover switch is normally the easiest and simplest option. It avoids the automatic changeovers which you do not always notice. However, the reason for keeping the inverter circuit very separate is that you must not be able to have the battery charger in the circuit with the inverter. If you do you will be taking out electricity to charge the battery to feed the inverter.............. The cycle has to stop somewhere!

[noelex 77]

It would not be the best solution for many, but I can see some potential advantages, as well as the drawbacks already mentioned.

The system does add redundancy and is very KISS, both of which are valuable attributes. However, I think the main motivation may be some versatility when visiting countries with different voltages.

Many battery chargers will work with different voltages and even frequencies. By plugging in the battery charger, a different voltage of shore power can be used. The inverter can, of course, produce an alternative voltage from the shore power. By keeping both systems, appliances capable of running on any voltage can run on the shore power. Those that will only operate on a specific voltage can be fed via the inverter. In addition, this works without any switching.

The only caution I would add is that I am not sure it would comply with the codes in all countries.

[a64pilot]

A drawback is go to another country say with 220V and plug your shore power in, your battery charger may work, but now you have 220V to half of your 110V plugs

[noelex 77]

Originally Posted by a64pilot

A drawback is go to another country say with 220V and plug your shore power in, your battery charger may work, but now you have 220V to half of your 110V plugs

True, but with a "conventional" system all your outlets will be 220V (which may not be suitable for all your appliances (for example 110v power tools) or possibly you can switch all the outlets to run from your 110v inverter. In this case the maximum power is limited by your inverter and also over the longer term by your battery charger rating (so you are unlikely to be able to run a larger electric cabin heater for example).

By retaining both shore power and inverter outlets, the system outlined in the first post could run both the power tools (via the 110v inverter) and the electric heater (via the 220v shore power). This is of course providing the heater is compatable with 220v and don't forget the change in frequency.

A better solution is a multvolt isolation transformer that will do all this automatically and with no chance of mistakes, but they are very expensive and are another device that can potentially fail. An isolation transformer also reduces the risk of stray current corrosion so they are still worth considering if you can afford one.

[dsteinfeld]

Originally Posted by noelex 77

It would not be the best solution for many, but I can see some potential advantages, as well as the drawbacks already mentioned.

The system does add redundancy and is very KISS, both of which are valuable attributes. However, I think the main motivation may be some versatility when visiting countries with different voltages.

Many battery chargers will work with different voltages and even frequencies. By plugging in the battery charger, a different voltage of shore power can be used. The inverter can, of course, produce an alternative voltage from the shore power. By keeping both systems, appliances capable of running on any voltage can run on the shore power. Those that will only operate on a specific voltage can be fed via the inverter. In addition, this works without any switching.

The only caution I would add is that I am not sure it would comply with the codes in all countries.

My initial reaction was also KISS as I've just installed an inverter on our boat and was designing a new AC panel (110v shore and inverter) to accommodate switching it. However one issue that needed to be addressed may affect this split installation: the inverter installation instructions call for the green wire ground to be connected to one of the AC output wires, which, as the inverter output is floating, becomes "neutral". At first I questioned this, but realized this is the same way that electrical panels are wired (except for the "floating" bit, of course), so ok. But this assumes a single source. In this case though, while outlets usually have a tab that can be broken off on both line and neutral connections to isolate the two outlets, I haven't seen outlets where the green wire ground can be isolated (and this *isn't* what an isolated ground outlet does). Therefore the green wire is shared between the two systems, and so ultimately the neutrals of the two systems are connected together. I'm not certain of what all the risks are here, but it doesn't seem like a "good thing".

My transfer relay will switch all three wires, only connecting neutral to green wire when in the inverter position, otherwise passing all three straight to the shore power cable.

[noelex 77]

Originally Posted by dsteinfeld

I'm not certain of what all the risks are here, but it doesn't seem like a "good thing".

Yes, I agree Doug. There are potential problems complying with the various safety standards. Someone like Mainesail could answer these concerns much better than I can.

[smac999]

I recommend having a few non inverter plugs on a boat. to run your heaters etc. so if show power is lost. the heaters shut off instead of killing the battery in 30 mins. but are are compleate outets. not split that would be confusing. then rest go through the transfer switch of the inverted / charger and act automatically.

[topmast]

When I wired with 4 conductor tec cable I separated the upper /lower outlets. Lowers (2000 w inverter circuit) painted red and nobody but nobody could plug in them without consultation .Never had a problem in 40 years and was automatic switching to all shore with inverter switching to charger all on it's lonesome. Handy was vacuuming and microwave anytime and convection oven(only with engine running) Confusing? what part of red is confusing?

[buzzstar]

Originally Posted by mikereed100

A friend has separated the inverter and shore/generator circuits on his boat such that in all the outlets the upper socket is wired to the shore/generator circuit and the lower socket is wired to the inverter. I can't think of a good reason to do this unless, for some reason, he wants to run the inverter and shore power at the same time. To me it makes more sense to just switch from one to the other using a source selector switch, but what do I know? Anybody see any advantage to separating the circuits?

I do not understand why, with the system mentioned, he could not run both shore power and use the inverter at the same time. What have I missed?

[Stu Jackson]

Originally Posted by topmast

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Confusing? what part of red is confusing?

Exactly. It is simply a management issue.

[accomplice]

We have two separate AC systems -- one is direct from the genset/shore power; the other is off the inverter. The boat's larger loads, such as AirConditioning, watermaker, washer/dryer, etc. are run off the genset/shore system. All smaller loads, including all outlets, are run off the inverter. This system works well -- and according to the surveyor when we hired when we bought the bought, is perfectly compliant with ABYC.

The Victron inverter/charger we have passes through the AC to the low-load system if the genset/shore power is connected and inverts off battery power when no AC source is available.

The system does work well, with a few caveats. First, the two AC neutrals are not necessarily connected together -- one must take care when adding new circuits. Second, although the inverter/charger is supposed to pass-through the high-load AC, that feature doesn't work well when the loads have large instantaneous (inductive) demands, and wiring to use it causes an under-voltage disconnect.