Open neutral while on inverter

[warfdog]

I also wanted to be able to bypass my inverter and completely isolate it on both hot and neutral legs. In the prior configuration the shore power was routed to the shore/gen switch which then switched it to the panel main input. The Inverter was always in the path of shore or gen power.

I have been changing over my 30A/120V AC panel to - with an inverter bypass switch and ELCI added to provide greater safety and the ability to isolate the Inverter from the circuit when desired.

While I did a lot of reading prior to adding the ELCI and bypass switch I AM NOT AN EXPERT IN THIS AREA.

The shore/gen switch remains but an ELCI sits in front of it before the shore power input. The Inverter bypass switch which two positions (NORMAL=hot and neutral connect to/from Inverter) (BYPASS=both input and output of Inverter are disconnected and completely isolated). The Invertor can still contain 120V AC at any time since it is connected to the house DC bus.

Shore ground (green) passes thru a galvanic isolator then to the ELCI bus - Panel bus - Inverter input and output (unswitched) - Inverter and Charger chassis - Engine Ground - and house negative bus (at panel). All ground-bonding wires are appropriately sized based on the largest AC or DC connection on the device.

The Inverter bypass switch is a reversed 240V cam switch typically used in industrial applications, but sold by Blue Sea as a shore cutover switch Blue Sea 9093 (List $443.99) except it is $30 here: https://www.amazon.com/gp/product/B01G9VY1HG/. The ELCI is from Blue Sea. Model 8100.

In this configuration I get the ability to isolate the Inverter from the AC circuits, diagnose any problems with common and ground circuits, and continue to use the Inverter/Charger functions at any time. The Inverter stays in the circuit under most conditions.

Is this what you are looking to do?

 

[bglad]

See if I can explain this without a diagram.

Typically the inverter remains attached to its AC power source period. This is so it can continue to work as a charger even though you may no want it to invert.

You add a switch (barrel type or toggle with sliding interlock). This switch either connects the inverter hot & neutral to the inverter circuits or connects them to the regular AC buss. Nothing changes on the green ground (that you can see).

The reason? Sometimes an inverter will fail or go offline and not pass any AC current through it. Or, you may just want piece of mind knowing it cannot possibly munch your batteries while you are away but still charge them.

Nice to have a way to go around the inverter versus pulling the wires out of it and twisting them together...

Hey Sunchaser,

Which wires does it switch?

Thanks!

-Greg

 

[diver dave]

No one considers a “OFF, INV, GEN, SHORE” rotary switch? Seems far more logical to me.

 

[stevemitchell]

No one considers a “OFF, INV, GEN, SHORE” rotary switch? Seems far more logical to me.

I've searched for something like this in a single rotary switch and haven't been able to find one. I think I'd have to use a rotary switch for source selection (already installed/existing) and then an interlock or another rotary switch for the output to either go to the inverter, or bypass it.

 

[JDCAVE]

No one considers a “OFF, INV, GEN, SHORE” rotary switch? Seems far more logical to me.

Depends on the Inverter. I don’t believe this would work with my Magnum 2812, which has its own on-off setting on the remote panel. This unit automatically transfers the Inverter loads to shore/genny power when these are available. When these aren’t available, I leave the Inverter “off” unless running or required at anchor.

Jim.

 

[diver dave]

I agree that “automation” makes this more complex. And could envision schemes that include shore and genset in that equation.
There is also a broader idea to get the hi current/hi voltage switch out of the living space by using LV controls to a set of contactors remotely and having the high current conductors optimally placed and in a fireproof box.
Lots of ways to safely skin this cat. I, for one, want manual ON for inverter to limit idle drain when underway. But, others will want 120v always avail, and have the energy sources to permit that. Others will have 2 or even 3 gensets to alternately switch in.

 

[twistedtree]

I've searched for something like this in a single rotary switch and haven't been able to find one. I think I'd have to use a rotary switch for source selection (already installed/existing) and then an interlock or another rotary switch for the output to either go to the inverter, or bypass it.

I think the challenge is that given how you plan to set up your power system, INV, is not mutually exclusive with SHORE and GEN. And this is increasingly how power systems are being built, from what I've seen.


Certain loads, and even sometimes most or all of them are always powered via the inverter output(s).


The inverter's input is then either OFF, in which case it's running off batteries, or is being fed power from SHORE or GEN and is simultaneously passing that power through to it's loads, and charging the batteries.


I think the way your boat is set up now, assuming I remember correctly, is well suited for such an adaptation. You existing SHORE/GEN selector picks which of those power sources is fed to the inverters input. Then most/all loads are on the inverter outputs.


In this case, the by pass is strictly an emergency/maintenance switch that will infrequently used. Mine have been in the bowels of the boat next to the inverter, not on the power panel used for daily operation. The switched mine exactly once, to test it out. Otherwise it's only needed in the event of an inverter failure, both to pass shore/gen power through to the loads, and to isolate the inverter so it can be safely removed and replaced.

 

[diver dave]

Totally true if what we have is a combo “inverter/charger”

 

[twistedtree]

I agree that “automation” makes this more complex. And could envision schemes that include shore and genset in that equation.
There is also a broader idea to get the hi current/hi voltage switch out of the living space by using LV controls to a set of contactors remotely and having the high current conductors optimally placed and in a fireproof box.
Lots of ways to safely skin this cat. I, for one, want manual ON for inverter to limit idle drain when underway. But, others will want 120v always avail, and have the energy sources to permit that. Others will have 2 or even 3 gensets to alternately switch in.

This is along the lines of what I'm doing on our current build. The high power switching is done by a set of contactors in the laz, in close proximity to the power sources. It keeps the high power switching in one place, and reduces the number of high power cables that need to traverse the boat. It also provides a lot more flexibility in how you can connect things up. Control logic is in a PLC, including an interlock scheme using aux contacts on the main contactors to ensure multiple power sources can never be connected together and make sparks.

 

[diver dave]

This is along the lines of what I'm doing on our current build. The high power switching is done by a set of contactors in the laz, in close proximity to the power sources. It keeps the high power switching in one place, and reduces the number of high power cables that need to traverse the boat. It also provides a lot more flexibility in how you can connect things up. Control logic is in a PLC, including an interlock scheme using aux contacts on the main contactors to ensure multiple power sources can never be connected together and make sparks.

Yeah man. Make it nema4x !

 

[Circledog]

Hello guys,
Hoping to resurrect this thread, since there are some very smart people on this thread. First off big thanks to @warfdog for the switch pics and drawings.
I have a Magnum 2812 and am full time at a Marina in Fort Myers Florida with new electrical. When I rectified my electrical I had removed my inverter to make sure it was not an issue. Now that everything has worked for a couple of months, I’ve decided to tie my inverter back in. When I did, I found that I have to leave off my out from inverter breaker before I can power up my inverter. If I have the in and out breakers on when I go to power my Inverter, it trips the GFI at the pedestal.
Because this is occurring and can be overcome by powering up the inverter before it comes online, could it be that the neutral ground relay is slower then the pedestal breaker?
If all my items onboard are neutral and ground separate, should the inverted and non inverted sharing a neutral bus bar matter?
Thank you for any input and or ideas.
Thanks,
Paul