Splitting the A/C electrical panel into inverted vs non inverted

[Alaskan Sea-Duction]

The second outlet idea appeals to me but the color and pattern of outlets has meaning. That one is 20A vs the usual 15A, and probably hospital though I'm not sure.
You might consider adding a label even then It probably wont pass survey.

There are only two outlets and it did pass survey. Labeling is a good idea.

 

[STB]

Can someone explain the purpose (in the drawing) of the AC GRD being connected between shore and inverter loads.

One example that might be helpful is the inverter itself contains both shore power (input) and inverter power (output) AC circuits. At times they may both be in use at the same time, e.g. charging while inverting, or otherwise present at the same time (even if not in use).

One can also come up with other scenarios where invertable and non-invertable circuits may be nearby. Consider, for example, different circuits running through the same conduit, outlets which have invertable and non-invertable circuits running to different recepticles, etc.

As a result, the metal case of the inverter needs to be tied to effective equipment grouding conductor (EGC) for each of these circuits. The only way to achieve this is by bonding the two.

I have also wondered why the AC GRD and DC GRD are bonded providing a docked boat a return path to shore through water.

This is one that gets talked about a lot.

I think the most straight-forward example here is to consider a short from an 120VAC hot wire to anything electrically tied to the boat's DC negative, e.g. the metal chassis of DC devices like radios, the engines, the bonding system, etc.

This scenario, by itself, won't trip any over-current protection devices, either aboard or on shore. It just puts a high AC voltage potential on all of these devices.

Now imagine that someone touches any of this metal and anything tied to a groundin conductor, neutral conductor, or earth. This could be someone within the boat -- or a swimmer or diver. Zaaaaaaaap (especially for a freshwater swimmer or diver, this might well mean electrocution facilitated paralysis and drowning)!

As for those who complain that this arrangement might facilitate galvanic corrosion -- they are correct. No denying it. This is why a galvanic isolator or isolation transformer is important in a modern boat. We traded human safety for the safety of metal from corrosion -- and the galvanic isolator or isolation transformer help us reclaim the safety of the metal from corrosion.

Some folks ask why we need to do this if ELCIs, GFCIs, RCDs, etc are present and should protect people from harm in such circumstances. Well, first, these devices aren't universal, second having a belt and suspenders is often helpful, 3rd, adoption of such devices is being slowed by those with non-compliant, leaky electrical systems, e.g. those without separate neutral and grouding conductor buses, and finally, who trusts marina electrical distribution to be up-to-date and well maintained?

 

[catalinajack]

Coincidentally, while re-wiring my bonding system in the last two weeks, I discovered two alternating current devices that were grounded to the bonding ground system. Not good. Gone now. We have a galvanic isolator installed not long after I found a jumper wired between the neutral and safety bus bars. Anyone with an older boat would be well-advised to go hunting.

One example that might be helpful is the inverter itself contains both shore power (input) and inverter power (output) AC circuits. At times they may both be in use at the same time, e.g. charging while inverting, or otherwise present at the same time (even if not in use).

One can also come up with other scenarios where invertable and non-invertable circuits may be nearby. Consider, for example, different circuits running through the same conduit, outlets which have invertable and non-invertable circuits running to different recepticles, etc.

As a result, the metal case of the inverter needs to be tied to effective equipment grouding conductor (EGC) for each of these circuits. The only way to achieve this is by bonding the two.





This is one that gets talked about a lot.

I think the most straight-forward example here is to consider a short from an 120VAC hot wire to anything electrically tied to the boat's DC negative, e.g. the metal chassis of DC devices like radios, the engines, the bonding system, etc.

This scenario, by itself, won't trip any over-current protection devices, either aboard or on shore. It just puts a high AC voltage potential on all of these devices.

Now imagine that someone touches any of this metal and anything tied to a groundin conductor, neutral conductor, or earth. This could be someone within the boat -- or a swimmer or diver. Zaaaaaaaap (especially for a freshwater swimmer or diver, this might well mean electrocution facilitated paralysis and drowning)!

As for those who complain that this arrangement might facilitate galvanic corrosion -- they are correct. No denying it. This is why a galvanic isolator or isolation transformer is important in a modern boat. We traded human safety for the safety of metal from corrosion -- and the galvanic isolator or isolation transformer help us reclaim the safety of the metal from corrosion.

Some folks ask why we need to do this if ELCIs, GFCIs, RCDs, etc are present and should protect people from harm in such circumstances. Well, first, these devices aren't universal, second having a belt and suspenders is often helpful, 3rd, adoption of such devices is being slowed by those with non-compliant, leaky electrical systems, e.g. those without separate neutral and grouding conductor buses, and finally, who trusts marina electrical distribution to be up-to-date and well maintained?

 

[SteveK]

One example that might be helpful is the inverter itself contains both shore power (input) and inverter power (output) AC circuits. At times they may both be in use at the same time, e.g. charging while inverting, or otherwise present at the same time (even if not in use).

One can also come up with other scenarios where invertable and non-invertable circuits may be nearby. Consider, for example, different circuits running through the same conduit, outlets which have invertable and non-invertable circuits running to different recepticles, etc.

As a result, the metal case of the inverter needs to be tied to effective equipment grouding conductor (EGC) for each of these circuits. The only way to achieve this is by bonding the two.
.................

Thanks for the reply, your 2nd part I agree with the thoughts, I keep wondering why an AC hot would touch anything DC grounded, each to his own, I will not bond that, no AC leak to water.

Your reply above. I should have known to mention I have an inverter/charger combo. It has a ground bar to which you are to attach line in GRD and load out GRD (which is already on panel buss bar). Then it wants you to GRD the inverter chassis to DC GRD separately when a DC negative is already attached. (another thing that makes little sense)
When the inverter switches ON it will bond neutral/GRD which back feeds GRD to isolator.
That was the purpose of the question, why would we want to do that when the inverter does not need the AC GRD

 

[STB]

Hey SteveK,

W.r.t. your comment, "I keep wondering why an AC hot would touch anything DC grounded", one way this can happen is that an AC hot chafes or breaks loose inside of the inverter. The chassis of the inverter has to be DC grounded because it contains DC positive conductors that could break loose and touch the chassis. Without chassis tied to the battery negative, it could become hot, which would be bad.

And, since the inverter has both output/inverter-generated hot conductor(s) and supply/input hot conductor(s), the chassis needs to be bonded to each of these grounds for the same reason.

In total, all three types of ground conductors need to be bonded to the chassis in order to provide a current return path that can trip/pop the circuit interruptor if any of the associated positive/hot wires touches the chassis.

One needs to be careful that the chassis connection to battery negative is sufficient to handle all of the DC current. Sizing it for the AC current could leave it well under sized.

As for why the chassis ground is a different wire than the negative battery terminal, there are probably a few reasons. One of the big ones is that doing it this way enables it to provide protection should the inverter's connection to the battery negative wire comes loose or gets corroded.

Imagine a situation where the battery positive wire is A-Okay from the battery, through the circuit protection, and through the load, but becomes disconnected or badly corroded at the battery negative end. Now, let's consider this situation in two universes: One in which the chassis is tied to this negative. And, one in which the chassis is tied to an independent path to ground.

In the situation where the chassis is tied to the negative inside of the inverter, the chassis, like the battery negative, is no longer a (good) current return path. But, it is tied to the positive conductor through the load. So, our negative has just become a positive! The chassis is now hot.

Lean a pole or a tool or whatever against the inverter and let it touch the engine, bond wire, metal thru hull or whatever and we now have an unintended current path. If this unintended path isn't sufficient to carry the load, it can overheat from the current and become a fire hazard. Maybe the inverter is in a locker above, but the spark happens inside of an engine room with gas vapor. Pop! You get the idea.

Now, let's imagine that same scenario, except in a universe in which the chassis ground is an independent wire. In this situation, the device is still protected from a loose hot wire by the grounded chassis. Furthermore, the chassis is not hot. There is no potential to start a fire or cause sparking should something inadvertantly touch the chassis of the device and any of the many exposed metal things in a boat tied to the boat's battery negative terminal.

I'm not sure what you mean when you write the "the inverter does not need the AC GRD". It needs the AC grounding conductors in case any hot (input or output) breaks loose or chafes and touches the chassis. Without grouding the chassis, the chassis could end up 120VAC hot! With the chassis having a good electrical ground conductor (EGC), this condition would short, trip/pop the current protection device, and rapidly render itself safe.

It is true that, while inverting, the inverter is a power source and is, therefore, the source of its own grounding path for the output power. But, this doesn't take care of the input power.

Even if the inverter is just an inverter and not a charger, it still has input AC coming into it from the boat. Without these AC lines coming in, the inverter can't pass through power under normal circumstances and switch to inverting, as needed. It would have to be turned on or off manually or rely upon an exernal transfer relay. There are inverters that switch manually, but, they are almost always point-of-use inverters, not ones intended to be hardwired. As for inverters that use external relays, that really just moves where the boxes are drawn without changing the big picture.

Cheers!
-Greg

 

[SteveK]

Hey SteveK,

..............
I'm not sure what you mean when you write the "the inverter does not need the AC GRD". It needs the AC grounding conductors in case any hot (input or output) breaks loose or chafes and touches the chassis. Without grouding the chassis, the chassis could end up 120VAC hot! With the chassis having a good electrical ground conductor (EGC), this condition would short, trip/pop the current protection device, and rapidly render itself safe.
.........................
Cheers!
-Greg

Final reply as did not mean to thread highjack
when I hooked up line in/out the ground buss did not appear to have a bond to the chassis, so from that made the assumption it was just a jump off point. I will have a closer look, need to know.

 

[ranger58sb]

The relay’s in the inverter are not as fast as an ELCI switch. When you add a transformer, you have eliminated the ELCI issue, even if the dock has one.

Is that a "by definition" thing? Or are some inverters better (faster?) than others? (Fast enough?)

That is no universal spec for such things. Where it matters more is things like keeping computers from rebooting, microwave from resetting while cooking during switch overs, etc.

The spec for the transfer time is usually somewhat deeply burried.

I don’t know the answer. Have not yet heard of a relay that is as fast as the ELCI switch. Maybe the inverter people will figure it out. On the other hand because of ELIC, isolation transformers are becoming very popular.

Thanks, guys. Now that I know our boat will trip the (some?) new pedestals, I've been gathering info on how to troubleshoot. This here helps.

If an isolation transformer is the easiest solution, I'm OK with that. If there's another solution that "fixes" (?) an underlying cause that suggests installing an isolation transformer, I'd be even better with that. I think. Even if I add a transformer, too.

-Chris

 

[Stu-L]

Keeping it simple

I have a 1500 W inverter on my boat along with a generator. I like to keep things simple. Power from the inverter and generator can be accessed through any outlet on the boat. I manage my loads. If I want to run the water heater I will use shore power or generator. I can usually run a coffee maker, TV, phone chargers, Tablet chargers and Refer with the inverter.

 

[va3mrj]

Switch

Comments and guidance welcome!

I installed a Samlex 3000W inverter charger (pure sine wave) and am now ready to tap it into the house A/C panels.

My thought process- in the cutrent configuration, Pau Hana has a single 50A 125/250V shorepower feeding an isolation transformer that splits the incoming power to feed panel 1 (normal loads, including the battery charger), and panel 2 (auxiliary loads). All is breakered properly, and can be fed thru the genset as well.

Plan- relocate inverted loads (outlets, ice maker, etc) to panel 2 and rewire 1 output leg (black) from the iso transformer to pass thru the inverter/charger so only panel 2 is powered by the inverter.

The genset output to panel 2 will also be routed thru the inverter charger so when the genny is on, the internal transfer switch will shut down inverting.

Just gotta figure out the ground and neutrals...

I have done three boats now using a switch that selects Shore, Gen, Invertor.
All loads are switched to the appropriate supply. Just have to remember to shed loads when on the invertor like water heater and a/c units.

 

[DavidM]

I have done three boats now using a switch that selects Shore, Gen, Invertor.
All loads are switched to the appropriate supply. Just have to remember to shed loads when on the invertor like water heater and a/c units.

If you follow that principle rigorously you should be fine. But forget once, and you will probably have dead batteries. It is sort of like using the 1,2,all switch to protect your starting battery at anchor. Works fine, until you forget.

I think of all of the TF members who don't want to manage loads to stay withing their genset's rating or want an automatic genset starting system. Those folks want set and forget systems.

David

 

[Phyrcooler]

One possible consideration if you want a belt and suspenders approach: be sure to be able to bypass the inverter. Without this if the inverter/transfer switch fails you may not be able to get power to the items that are tied to the inverter.

Especially if it’s an inverter/charger that failed...

Or else you’ll arrive at your boat, late Friday night, for a long holiday weekend, to find your boat dark, batteries dead, no power to anything, air hot, humid and unmoving, children cranky, wife doing her best to be supportive, and then hauling everything back to the car for the 2 1/2 hour drive home. Arriving at 01:30. Or so I’ve heard. Still a bad memory 5 years later!

A big rotary bi-pass switch was added immediately after that occurrence, and I swore I’d never own another all-in-one inverter charger again!

 

[ksanders]

Especially if it’s an inverter/charger that failed...

Or else you’ll arrive at your boat, late Friday night, for a long holiday weekend, to find your boat dark, batteries dead, no power to anything, air hot, humid and unmoving, children cranky, wife doing her best to be supportive, and then hauling everything back to the car for the 2 1/2 hour drive home. Arriving at 01:30. Or so I’ve heard. Still a bad memory 5 years later!

A big rotary bi-pass switch was added immediately after that occurrence, and I swore I’d never own another all-in-one inverter charger again!

I have a all in one inverter/charger and am happy with it.

If the unit fails I turn a rotary switch (like you described) and the loads run off of shore or generator power.

Also have a backup 40 amp battery charger that will handle things in a pinch. I leave it charging my engine and gen batteries, and with the flip of a breaker it charges the house bank in a pinch.

 

[Phyrcooler]

I have a all in one inverter/charger and am happy with it.

If the unit fails I turn a rotary switch (like you described) and the loads run off of shore or generator power.

Also have a backup 40 amp battery charger that will handle things in a pinch. I leave it charging my engine and gen batteries, and with the flip of a breaker it charges the house bank in a pinch.

Sounds like a good, redundant setup.

 

[JDCAVE]

A not so small point: if you don’t have your neutrals for inverter and shore power separated, the “inverter” loads will not operate on inverter mode unless you are plugged into shore power. I discovered that with my fuel polishing system. My electrician told me that the power wire was on the neutral side of the panel, and we tested it by switching off the power and it worked. However I discovered it didn’t work while at anchor. We determined that the neutral was on the shore side of the power. So it worked when plugged into shore but not when the plug was disconnected. This was rectified when we moved the neural over to the inverter side.

Edit: I now have an isolation transformer, which probably changes things.

Jim

 

[Ka_sea_ta]

I didn't see this mentioned, The transfer relay in the inverter also switches the load as well as the neutrals. If the relay fails, depending on the failure mode it is possible to lose power no matter what the source is to the breakers that are on the inverter circuits. If this is a concern you can connect a crossover switch that takes the feed from either the inverter or shore power/genset and use that to provide power to the breakers that are normally feed from the inverter... The crossover switch would normally be selecting the input power from the inverter and only be used if the transfer relay failed....

 

[FoxtrotCharlie]

When we bought our boat it had a failed Xantrex inverter/charger - created all kinds of problems. Ripped it all out and replaced with a stand-alone 3,000 watt pure sine wave inverter. Had it wired to cover three circuits - refrig, ice-maker and all 110 outlets. There is a rotary switch that lets those three circuits get power from EITHER the elec panel (shore or gen), OR the inverter - never both at the same time. We have four 6v golf cart batteries for house bank. We have a galvanic isolator, and have had no problems at any marinas so far.