240v only system - neutral ground bond

[1201]

hi, yes I know its a dumb question but I'm still going to ask - USA system- say I want to use a 230v inverter( for example growatt 5000) to power a 240v only load. there will be incoming 240v grid power into the unit.

question is - is there still a ground neutral bond required when there is no "neutral" per se in the system, (HOT HOT GROUND) or does one hot leg become the Neutral? (HOT NEUTRAL GROUND)

thanks

 

[FilterGuy]

hi, yes I know its a dumb question but I'm still going to ask - USA system- say I want to use a 230v inverter( for example growatt 5000) to power a 240v only load. there will be incoming 240v grid power into the unit.

question is - is there still a ground neutral bond required when there is no "neutral" per se in the system, (HOT HOT GROUND) or does one hot leg become the Neutral? (HOT NEUTRAL GROUND)

thanks

I am not familiar with the GW 5000, but I assume it follows the convention of one of the two hots becomes neutral.

The G-N bond is still important with devices that do not use the neutral. If there is a short from either hot to ground, the G-N bond will create the high current to blow the breakers.

In general, I do not recomend trying to use Euro 230 inverters in the US.... Particularly if the US grid is going to be used on the AC in of the inverters. The difference in neutral between the two makes it to wonky for my taste.

 

[timselectric]

Where did you purchase the Growatt SPF-5000-ES? (Assuming that's what you have)

 

[timselectric]

Actually, I'm just going to say don't.
It can be done. (I'm doing it, myself)
But it's complicated, if you don't know what you are doing.

 

[1201]

I am not familiar with the GW 5000, but I assume it follows the convention of one of the two hots becomes neutral.

The G-N bond is still important with devices that do not use the neutral. If there is a short from either hot to ground, the G-N bond will create the high current to blow the breakers.

In general, I do not recomend trying to use Euro 230 inverters in the US.... Particularly if the US grid is going to be used on the AC in of the inverters. The difference in neutral between the two makes it to wonky for my taste.

Thanks very much. That's what I suspected but wasn't sure

 

[1201]

I am not familiar with the GW 5000, but I assume it follows the convention of one of the two hots becomes neutral.

The G-N bond is still important with devices that do not use the neutral. If there is a short from either hot to ground, the G-N bond will create the high current to blow the breakers.

In general, I do not recomend trying to use Euro 230 inverters in the US.... Particularly if the US grid is going to be used on the AC in of the inverters. The difference in neutral between the two makes it to wonky for my taste.

I have a follow up question. So in split phase systems why do we only bond neutral to ground? Why don't the hot legs get bonded?

 

[1201]

Actually, I'm just going to say don't.
It can be done. (I'm doing it, myself)
But it's complicated, if you don't know what you are doing.

Can you expound on why you say that?

 

[timselectric]

Why don't the hot legs get bonded?

That's called a dead short.

 

[1201]

That's called a dead short

So if neutral is a current carrying conductor why is that not a dead short as well

 

[timselectric]

Can you expound on why you say that?

Because it's complicated. And how it's done depends on every other aspect of the system. And making sure that nothing changes. Because then it would require a different method.

 

[timselectric]

So if neutral is a current carrying conductor why is that not a dead short as well

The definition of neutral is the grounded conductor.
If it's not grounded, it's not a neutral.
What we call a "hot" (live conductor) is an ungrounded conductor.
Two sides of a source grounded, or connected together in any other way is a dead short.

 

[1201]

Because it's complicated. And how it's done depends on every other aspect of the system. And making sure that nothing changes. Because then it would require a different method.

Your answer is so vague. What's complicated about it?

 

[CoolWill]

So if neutral is a current carrying conductor why is that not a dead short as well

Because current only flows in complete circuits. For simplicity, picture a source of electricity, like a battery. Current can flow only in circuit between the positive and negative of the battery. Connecting one pole of the battery to ground won't result in any current flowing to ground, because the circuit is not complete. If both poles of the battery were bonded to ground, like in your question, then both poles would be connected together through the ground connection, a short circuit.

 

[timselectric]

It was intentionally vague.
Because the details would take days to explain.

 

[CoolWill]

The definition of neutral is the grounded conductor.
If it's not grounded, it's not a neutral.
What we call a "hot" (live conductor) is an ungrounded conductor.
Two sides of a source grounded, or connected together in any other way is a dead short.

I know you're trying to simplify things, but that isn't really true. Neutrals don't have to be grounded to be neutrals. And not all grounded conductors are neutrals.

 

[timselectric]

I know you're trying to simplify things, but that isn't really true. Neutrals don't have to be grounded to be neutrals. And not all grounded conductors are neutrals.

If it's not grounded it's not a neutral.
It is fairly simple.

 

[1201]

Because current only flows in complete circuits. For simplicity, picture a source of electricity, like a battery. Current can flow only in circuit between the positive and negative of the battery. Connecting one pole of the battery to ground won't result in any current flowing to ground, because the circuit is not complete. If both poles of the battery were bonded to ground, like in your question, then both poles would be connected together through the ground connection, a short circuit.

Thanks for this explanation.

So then how come one at least one hot leg is not bonded?

Bonding the neutral protects the 120v circuit but what protects the 240v circuit? The same bonded neutral?

 

[CoolWill]

If it's not grounded it's not a neutral.
It is fairly simple.

But that's not true. The definition of a neutral has nothing to do with being grounded.

 

[CoolWill]

Thanks for this explanation.

So then how come one at least one hot leg is not bonded?

Bonding the neutral protects the 120v circuit but what protects the 240v circuit? The same bonded neutral?

Picture this: Let's pretend that you get 120 volts from a single battery. Putting two batteries in series gives you 240 volts. The mid point between the two batteries is called the neutral and is grounded. So if you measure from the neutral to the "end" pole of either battery, you'll see 120 volts, but if you measure between bothe end poles, you'll see 240 volts. Following? The 240 volt circuit is protected by virtue of being grounded in the middle. You can then connect any end pole to ground because that would be the same as shorting one battery.

Keep in mind this is just a simplified analogy using batteries. Here's a diagram of how a utility transformer makes the hots and neutral. The neutral is grounded and you can see why no other line can be.

 

[timselectric]

But that's not true. The definition of a neutral has nothing to do with being grounded.

The definition of neutral is "the grounded conductor".
It's called neutral because it poses no Hazzard in regards to exposed grounded metal parts.
If it's not grounded, it's just another circuit conductor.