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

[Pau Hana]

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...

 

[Alaskan Sea-Duction]

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'm not a big inverter believer. I only have 6 things I power off of our inverter: Wine Cooler, Ice Machine, TV and associated equipment and 2 freezers for fish. Wine cooler and ice being the priority.

I installed a couple of outlets next to a regular outlet, except the inverter outlets are orange.

 

[rgano]

I'm not a big inverter believer. I only have 6 things I power off of our inverter: Wine Cooler, Ice Machine, TV and associated equipment and 2 freezers for fish.

LOL, that sounds like a HUGE inverter believer to me.

 

[Alaskan Sea-Duction]

LOL, that sounds like a HUGE inverter believer to me.

You could be right at least for the admiral's wine cooler!

We had a friend that wired his boat where EVERYTHING went through an inverter/charger. After a few years he started having issues. So I have a few outlets on the boat that are inverter, but I am an electric boat so I am not shy about running the genset.

 

[DavidM]

I presume that your genset is currently producing 240/120V power that is fed to the main panel 1 and 2 using the two legs of the 240V supply just like shore power through a transfer switch. If that is the case, then take one leg of the transfer switch output and run it to the inverter's 120V input which then feeds panel 2. Either shore power or generator power will then power panel 2.

This is cleaner and simpler than what you propose.

If the genset isn't currently producing 240/120V which is split to power panel 1 and 2, then how does it serve the split panel and how is it transferred.

David

 

[O C Diver]

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 may be missing something, but it should be pretty simple to take the input going to panel 2 and run that to the transfer switch in the inverter. Then run the output from the inverter to panel 2. This assumes the inverter has a transfer switch. A marine grade inverter should have the proper isolation for the ground built in. The ground from panel 2 has to run through the inverter and back to the isolation transformer when not inverting.

The battery charger also receives the 120VAC power from the inverter feed. As a result, you will need to factor that additional amp draw into wire sizing and breaker amperage.

Ted

 

[tiltrider1]

Peter, typically panel 1 is your normal house circuits and panel 2 is for auxiliary items like Heat Pumps, washer/dryer and other things we have yet to think of. Usually we would Split panel 1 into inverter and non inverter loads. This allows the boat to operate most functions when only 30 amps can be found. Now if you don’t have a washer/dryer and don’t plan to add AC then making panel 2 for inverter loads shouldn’t be to hard. It does limit your options in the future.

 

[Alaskan Sea-Duction]

I presume that your genset is currently producing 240/120V power that is fed to the main panel 1 and 2 using the two legs of the 240V supply just like shore power through a transfer switch. If that is the case, then take one leg of the transfer switch output and run it to the inverter's 120V input which then feeds panel 2. Either shore power or generator power will then power panel 2.

This is cleaner and simpler than what you propose.

If the genset isn't currently producing 240/120V which is split to power panel 1 and 2, then how does it serve the split panel and how is it transferred.

David

Great post

 

[Pau Hana]

I presume that your genset is currently producing 240/120V power that is fed to the main panel 1 and 2 using the two legs of the 240V supply just like shore power through a transfer switch. If that is the case, then take one leg of the transfer switch output and run it to the inverter's 120V input which then feeds panel 2. Either shore power or generator power will then power panel 2.

This is cleaner and simpler than what you propose.

If the genset isn't currently producing 240/120V which is split to power panel 1 and 2, then how does it serve the split panel and how is it transferred.

David

I’m back (long “essential” workday!)

The genset is producing 120v, and feeds both panels. The boat was originally configured with twin 30a inlets (1 feeding each distribution panel). I converted it to 50A as described in post #1.

 

[DavidM]

I’m back (long “essential” workday!)

The genset is producing 120v, and feeds both panels. The boat was originally configured with twin 30a inlets (1 feeding each distribution panel). I converted it to 50A as described in post #1.

Ok you have one leg of 120V of maybe 6,000 watts (50A) being produced from the genset that is tied to both panel 1 and 2 through a single pole transfer switch.

The 240V shore power is converted by the isolation transformer to a single leg of 120V that is fed to the transfer switch and then to panel 1 and 2 like the genset.

A little weird, but am I right?

David

 

[ksanders]

Since you are on the load side of a isolation transformer, bond all grounds and neutrals together.

Your boat is separate from shore power because of the isolation transformer.

 

[READY]

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.

 

[KnottyGuy]

When installing an inverter it is essential to separate inverter load neutrals from non-inverter load neutrals.

 

[DavidM]

When installing an inverter it is essential to separate inverter load neutrals from non-inverter load neutrals.

You are absolutely right. In response to a different thread (I had forgotten about this one) I wrote an article on "splitting the buss" for the Library. Go to the Library link in the upper right of this screen and click on the Misc section.

In the example I showed, the AC panel has a neutral buss which you have to split with a hacksaw like the hot buss. Most boats have a separate neutral buss so you have to saw that one in half or better yet use two terminal strips- one for inverter loads and one for shorepower only loads.

David

 

[Pau Hana]

You are absolutely right. In response to a different thread (I had forgotten about this one) I wrote an article on "splitting the buss" for the Library. Go to the Library link in the upper right of this screen and click on the Misc section.

In the example I showed, the AC panel has a neutral buss which you have to split with a hacksaw like the hot buss. Most boats have a separate neutral buss so you have to saw that one in half or better yet use two terminal strips- one for inverter loads and one for shorepower only loads.

David

Reading it now...

 

[Pau Hana]

Since you are on the load side of a isolation transformer, bond all grounds and neutrals together.

Your boat is separate from shore power because of the isolation transformer.

Kevin- should the inverted loads be bonded or separate for the non-inverted loads on the load side of the IT?

 

[ksanders]

Kevin- should the inverted loads be bonded or separate for the non-inverted loads on the load side of the IT?

Pete

On the load side of the isolation transformer you need to have your ground and neutrals bonded together.

This is your protection path.

There is ZERO practical need to separate the neutrals from your inverter loads and your non inverter loads behind a isolation transformer.

This is why isolation transformers are being installed to overcome the issues with ALCI shore power dock side breakers tripping.

You are welcome to give me a call to talk about this and catch up.

Lots of folks do not seem to understand that the isolation transformer changes everything.

There is even serious misinformation that not separating your neutrals for inverted and non inverted loads (without a isolation transformer) is somehow unsafe. Nothing could be further from the truth, but a lot of people read, and believe without actually understanding how electrical stuff works. Sometimes even good electricians simply have not thought it out.

 

[porman]

inverter

Peter, here's a simple wiring diagram for separating the inverter neutrals from the shore power neutrals. This does not include an isolation transformer.

 

[Pau Hana]

Pete

On the load side of the isolation transformer you need to have your ground and neutrals bonded together.

This is your protection path.

There is ZERO practical need to separate the neutrals from your inverter loads and your non inverter loads behind a isolation transformer.

This is why isolation transformers are being installed to overcome the issues with ALCI shore power dock side breakers tripping.

You are welcome to give me a call to talk about this and catch up.

Lots of folks do not seem to understand that the isolation transformer changes everything.

There is even serious misinformation that not separating your neutrals for inverted and non inverted loads (without a isolation transformer) is somehow unsafe. Nothing could be further from the truth, but a lot of people read, and believe without actually understanding how electrical stuff works. Sometimes even good electricians simply have not thought it out.

Will call you later today...

 

[KnottyGuy]

In most cases the fuse between the battery bank and inverter should be a Class T type fuse. Read the inverter IOM to see if the manufacturer recommends a type of fuse.

 

[tiltrider1]

When we are discussing separating inverter vs non inverter neutrals it’s all about ELCI switch’s. There is no safety issue. 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.

Bonding ground s and neutrals is always done at the power source. Inverters are a power source and most of them do this with an internal relay. Isolation transformers are a power source so bonding should be done there as well.

 

[ksanders]

When we are discussing separating inverter vs non inverter neutrals it’s all about ELCI switch’s. There is no safety issue. 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.

Bonding ground s and neutrals is always done at the power source. Inverters are a power source and most of them do this with an internal relay. Isolation transformers are a power source so bonding should be done there as well.

Well said!

 

[STB]

EDIT: Okay. I just looked back and realized this thread involves an isolation transformer, which changes things as there is no longer a return path to shore or Earth. Having said that, I didn't delete this post, just in case it is helpful to anyone who, like me, missed the earlier discussion of an isolation transformer and might misunderstand the safety issue absent it.

------------------------
I don't agree that there isn't a safety issue.

During any period of time when the boat is running on shore power and the hot and neutral are bonded on the boat, a dangerous condition exists. The situation is exactly the same as what happens ashore when a the neutral and grounding conductors are bonded in error, e.g. at a sub-panel. This is one of the reasons why a boat's "main" panel should be thought of as sub-panel from the perspective of shore power when the boat is running on shore power.

What happens is that neutral and grounding conductors end up bonded at both sides of the connection -- the main panel and the sub panel (the boat's "main" panel). As a result, the neutral and grounding conductors are parallel conductors and the current returning from the hot wire will be divided between them.

Unlike the neutral conductor, which is normally protected or insulated from interaction with, for example humans, the grounding conductor does not normally carry current and is often tied to exposed surfaces via equipment grounding conductors (EGCs), the engine, and/or the boat's bonding system, etc.

Wired correctly, this protects these surfaces from "floating" until a hot wire chafes or breaks loose or whatever and makes them into large, exposed "hot" surfaces with which humans can interact. Properly wired, if such a thing happens, it generates a short (low resistance) circuit and, with luck, blows a breaker before anyone gets hurt.

But, if the grounding and neutral conductors are tied together at the sub panel ("boat main panel"), things could turn out very badly for someone touching (directly or via a conductor) metal in the boat and any form of Earth. It could also end up badly for nearby swimmers or divers, especially in freshwater or relatively fresh brackish water. In these cases, the humans become an additional path between the current being carried by the parallel neutral conductors (neutral + miswired grounding conductors) and Earth. Since the shore power system is Earth grounded -- current is going to flow through the human.

One might thing, "Well, the inverter will only bond the neutral and grounding conductors together while it is inverting, so this won't be the case when there is shore power." And, in the typical case, that is true. But, the typical case isn't what hurts people.

Even absent failure, most inverters don't open the relay bonding the neutral and grounding conductors until sensing shore power. That amount of time represents a window of vulnerability. There is also the possibility that the relay will fail, e.g. stick in the closed position. We'd also have to consider exposure during a "brown out" when there is live shore power in the boat up to the inverter and associated failure possibilities. I could probably cook up some more scenarios, e.g. out-of-phase leakage from a nearby boat.

Ultimately, when an ELCI or RCD device ashore trips in a situation like this, it isn't a nuisance trip. At least I don't think.

 

[ksanders]

EDIT: Okay. I just looked back and realized this thread involves an isolation transformer, which changes things as there is no longer a return path to shore or Earth. Having said that, I didn't delete this post, just in case it is helpful to anyone who, like me, missed the earlier discussion of an isolation transformer and might misunderstand the safety issue absent it.

------------------------
I don't agree that there isn't a safety issue.

During any period of time when the boat is running on shore power and the hot and neutral are bonded on the boat, a dangerous condition exists. The situation is exactly the same as what happens ashore when a the neutral and grounding conductors are bonded in error, e.g. at a sub-panel. This is one of the reasons why a boat's "main" panel should be thought of as sub-panel from the perspective of shore power when the boat is running on shore power.

What happens is that neutral and grounding conductors end up bonded at both sides of the connection -- the main panel and the sub panel (the boat's "main" panel). As a result, the neutral and grounding conductors are parallel conductors and the current returning from the hot wire will be divided between them.

Unlike the neutral conductor, which is normally protected or insulated from interaction with, for example humans, the grounding conductor does not normally carry current and is often tied to exposed surfaces via equipment grounding conductors (EGCs), the engine, and/or the boat's bonding system, etc.

Wired correctly, this protects these surfaces from "floating" until a hot wire chafes or breaks loose or whatever and makes them into large, exposed "hot" surfaces with which humans can interact. Properly wired, if such a thing happens, it generates a short (low resistance) circuit and, with luck, blows a breaker before anyone gets hurt.

But, if the grounding and neutral conductors are tied together at the sub panel ("boat main panel"), things could turn out very badly for someone touching (directly or via a conductor) metal in the boat and any form of Earth. It could also end up badly for nearby swimmers or divers, especially in freshwater or relatively fresh brackish water. In these cases, the humans become an additional path between the current being carried by the parallel neutral conductors (neutral + miswired grounding conductors) and Earth. Since the shore power system is Earth grounded -- current is going to flow through the human.

One might thing, "Well, the inverter will only bond the neutral and grounding conductors together while it is inverting, so this won't be the case when there is shore power." And, in the typical case, that is true. But, the typical case isn't what hurts people.

Even absent failure, most inverters don't open the relay bonding the neutral and grounding conductors until sensing shore power. That amount of time represents a window of vulnerability. There is also the possibility that the relay will fail, e.g. stick in the closed position. We'd also have to consider exposure during a "brown out" when there is live shore power in the boat up to the inverter and associated failure possibilities. I could probably cook up some more scenarios, e.g. out-of-phase leakage from a nearby boat.

Ultimately, when an ELCI or RCD device ashore trips in a situation like this, it isn't a nuisance trip. At least I don't think.

Even without a isolation transformer there is not a safety risk having onen neutral buss, shared between inverter loads and non inverter loads.

In this case you would not have a neutral-ground jumper on your boat.
If you had the neutral-ground jumper in your boat, that would be a serious safety hazard as you described above.

Having a single neutral buss WILL trip a ALCI breaker on your new shore power feed though. That is because the instant your shore power is applied the ALCI will trip before your inverter has time to remove its neutral-ground connection. This takes time and the ALCI is faster.

Yes I suppose that the second you plugged in your shore power there are a few miliseconds of a dual path situation, but, and yes I suppose some might consider that a safety risk, but I am not of that opinion. Prior to ALCI’s becoming mandated for shore power keeping a single neutral buss when installing a inverter was pretty much a Standard Operating Practice.

 

[STB]

Hey Kevin,

What about a brown-out condition on a hot summer day with old marina wiring (or otherwise)? You've got energized shore power wires, let's say at 89VAC of potential (hot-to-neutral/grounding) and plenty of current available to fry a human, but the inverter doesn't open the bond because the input voltage isn't up to spec, so it continues to supply its load from battery. This could continue indefinitely.

Remember that delay is most likely so that the inverter can judge the quality of input power, e.g. voltage and possibly frequency. Semiconductors can switch fast enough to avoid frying a human -- ELCIs, RCDs, and GFCIs do it. What takes time is deciding if the power supplied is likely to meet spec for the load.

I really think you want those neutral buses separated for safety.

 

[ranger58sb]

In the example I showed, the AC panel has a neutral buss which you have to split with a hacksaw like the hot buss. Most boats have a separate neutral buss so you have to saw that one in half...

That's what we did.

When we are discussing separating inverter vs non inverter neutrals it’s all about ELCI switch’s. There is no safety issue. 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?)

-Chris

 

[SteveK]

Peter, here's a simple wiring diagram for separating the inverter neutrals from the shore power neutrals. This does not include an isolation transformer.

Can someone explain the purpose (in the drawing) of the AC GRD being connected between shore and inverter loads.
I have also wondered why the AC GRD and DC GRD are bonded providing a docked boat a return path to shore through water.

 

[STB]

Hey Chris,

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.

 

[bayview]

I'm not a big inverter believer. I only have 6 things I power off of our inverter: Wine Cooler, Ice Machine, TV and associated equipment and 2 freezers for fish. Wine cooler and ice being the priority.

I installed a couple of outlets next to a regular outlet, except the inverter outlets are orange.

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.

 

[tiltrider1]

That's what we did.




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

-Chris

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.