LV6548 et Al Neutral ground bond bad for split phase?

[timselectric]

I am wondering why more than one ground connection within the house equipment is a bad idea ?
As long as the bonds and wire making those bonds are stout enough.
Now multiple ground rods outside I see the problem with voltage potential across the poor conductivity of the earth.
But across a 6/8/10 AWG copper wire inside ????

More than one N/G bond creates a parallel path on the neutral and ground. Which makes the ground conductor and neutral conductor share the neutral current. Neutral current should never be carried by the ground conductor. (Only fault current)

 

[Dona40]

I am wondering why more than one ground connection within the house equipment is a bad idea ?
As long as the bonds and wire making those bonds are stout enough.
Now multiple ground rods outside I see the problem with voltage potential across the poor conductivity of the earth.
But across a 6/8/10 AWG copper wire inside ????

I've always thought the same thing. Apparently the un bonding of a sub panel (that's any panel past the main input from the utility) whether you're using it or not is strictly for a ground fault that may occur in an appliance so that the short energy isn't transfer back though the metal bodies of all the other appliances and conduit. Making for a small chance someone could be shocked. And from what I understand of it, the inverter system, if hooked up to utility power would be an appliance. If it's a stand alone system, then a regular bonded panel would apply. At least that's how I understand it. Clear as mud.

 

[Zwy]

I've always thought the same thing. Apparently the un bonding of a sub panel (that's any panel past the main input from the utility) whether you're using it or not is strictly for a ground fault that may occur in an appliance so that the short energy isn't transfer back though the metal bodies of all the other appliances and conduit. Making for a small chance someone could be shocked. And from what I understand of it, the inverter system, if hooked up to utility power would be an appliance.

However when the inverter is turned on, it isn't an appliance but rather a power generator.

If it's a stand alone system, then a regular bonded panel would apply. At least that's how I understand it. Clear as mud.

It depends upon whether the inverter bonds N-G under inverter power. If it does, then bonding at the subpanel after the inverters will create a parallel path and objectionable current will flow on the EGC from the subpanel back to the inverter. This is really no different than having a standby gas powered generator, the N-G bonding needs to be known and wired appropriately. Another aspect is whether it is designed as a SDS system or non SDS.

My opinion has always been that if the grounding screw is removed in one inverter in a pair, any ground fault between the subpanel and the inverter may not trip the circuit breaker in the inverter. It should with one unit still bonded but I do not know of any experimentation or documentation that would indicate it would. The unit was designed this way for a reason. I'm also a strong advocate of using a 3 pole neutral switching transfer switch so the system is classified as a SDS system.

 

[timselectric]

I'm of the other mindset. I prefer a common neutral. And a single N/g bond, in one stationary location. I believe that a safety system should be a permanent system. And not passed through any type of switch.
But, either way is acceptable to the code. So, everyone will have to decide what they prefer.

 

[Grateful Ed]

I've got two Phocos PSW-H-6.5kW-230/48 which are built on the same chassis and I am hoping (pretty sure) has the same internals. I broached the subject with a tech guy, he didn't seem to think that the bonding os both was a parallel ground and then he was incredulous that I thought there was any problem and recommended I don't take the screw out as it would void the warranty. That kind of confirmed to me it was the same. I have a bonded box and have no interest in trying to mess with that. I saw that timselectric is sleeping better with them fixed and so I assume that means both with screws out. I see the review of the excellent pdf by FilterGuy that SkyPower says he also is using the both screws out approach and claims no problems. I'd love to hear that again from you guys as it only makes sense to do it this way.

 

[timselectric]

I've got two Phocos PSW-H-6.5kW-230/48 which are built on the same chassis and I am hoping (pretty sure) has the same internals. I broached the subject with a tech guy, he didn't seem to think that the bonding os both was a parallel ground and then he was incredulous that I thought there was any problem and recommended I don't take the screw out as it would void the warranty. That kind of confirmed to me it was the same. I have a bonded box and have no interest in trying to mess with that. I saw that timselectric is sleeping better with them fixed and so I assume that means both with screws out. I see the review of the excellent pdf by FilterGuy that SkyPower says he also is using the both screws out approach and claims no problems. I'd love to hear that again from you guys as it only makes sense to do it this way.

No changes here. And still sleeping fine.