Another inverter question - dedicated inverter for appliance

[sv_isara]

Hey all,
so I am slowly marching closer to ABYC setup for my electronics and inverter (renogy 3500w inverter/charger) as I am slowly mapping and rewiring some electrics. My main inverter has the neutral ground bond auto disconnect on shore power and is the main connection point of the AC line after the shorepower plug.

I also have a second 2kw inverter (inverter only - no charger) sitting around disconnected as a backup, and with my new electric oven, was thinking of using it as a dedicated oven/induction stovetop inverter, only connecting to those 2 appliances.

However the 2kw does not have the ground bond auto disconnect. The 2 AC circuits would be 100% separate, only connected on the DC side to the same battery bank:

AC Circuits
|
|
3500w inverter
|
Battery Bank
|
2000w inverter
|
fuse
|
|
Stovetop circuit

I have read countless pages on grounding etc, but I haven't run across this specific scenario with 2 inverters and 2 AC circuits. If I did do this, would I ground the case of the 2kw inverter to DC ground? Thanks for any pointers on this.

[Statistical]

Unfortunately ABYC doesn't provide an exemption for this. Most of their language assumes the only invertors used will be inverter chargers and have a link to shorepower.

They never actually address this scenario shorepower exists but it is not in any way connected to the inverter. Per the black and white letter of the regs all invertors should detect shorepower connection and disconnect neutral and ground when shorepower is connected.

The only exception listed is using an isolation transformer.

Does it make sense? Probably not. Are their edge cases which don't fit in their rules? Certainly.

Note this same edge case would apply even if you only had one inverter for example shorepower connected to nothing but a charger. No other connection to anything. Seperate from that you have an inverter which provides AC loads on the boat and has no connection to shorepower at all. Per ABYC regs even in this scenario it would need a neutral/ground bond based on shorepower connection. Again the one exception would be using an isolation transformer. It gets more dubious when you consider that some (most) marine chargers have an isolation transformer. So a charger connected to an isolation transformer is treated one way but a charger with a built in isolation transformer is treated another way.

[Statistical]

Actually I am correcting my prior posts. I found this in E-11

11.5.3.2.4 the inverter output neutral shall be grounded at the inverter; the inverter output neutral shall be disconnected from the ground when the inverter is operating in the charger or the feed-through mode(s) (see
EXCEPTION and ABYC A-31, Battery Chargers and Inverters).

EXCEPTION to E-11.5.3.2.2, E-11.5.3.2.3, and E-11.5.3.2.4: For systems using an isolation transformer or polarization transformer, both the generator or inverter neutral and the transformer secondary neutrals may be grounded at the AC main grounding bus instead of at the generator inverter,
or transformer secondaries (see DIAGRAM 5).

NOTES to E-11.5.3.2.4:
1. Inverters that function as feed-through devices and inverters/chargers may ground the neutral at the inverter when in invert mode. In that case, a separate output neutral may be required between the inverter to the inverter loads.

2. Inverters that function as feed-through devices may cause tripping of ELCI shore power protection due to the timing of their internally automated neutral to ground switching

It doesn't say disconnect just when connected to shorepower but rather when acting as a charger or pass through (transfer switch). This would seem to indicate that inverters which never acts as chargers or pass through (transfer switch from shorepower) can remain neutral-ground bonded at all times.

So it would seem your galley only inverter which is only ever inverter only with no AC input is fine to have neutral and ground bonded at the inverter and not need a shorepower switch.

[sv_isara]

Originally Posted by Statistical

Actually I am correcting my prior posts. I found this in E-11



It doesn't say disconnect just when connected to shorepower but rather when acting as a charger or pass through (transfer switch). This would seem to indicate that inverters which never acts as chargers or pass through (transfer switch from shorepower) can remain neutral-ground bonded at all times.

So it would seem your galley only inverter which is only ever inverter only with no AC input is fine to have neutral and ground bonded at the inverter and not need a shorepower switch.

Thank you! And would you ground the galley inverter's case to DC ground?

[boatpoker]

Originally Posted by sv_sharky

Thank you! And would you ground the galley inverter's case to DC ground?

Yes.
pm me an email address and Ill email a copy of the standards if you don't have them