Earth Leakage circuit breaker

[pjlhat]

Hi, We have a stand alone solar 1500watt system with deep cycle batteries utilising 12 v DC, 24 v DC and through an inverter 240vAC supplies. We have set the system up as a complete floating system, as in no connection to earth at all. Which I believe to be a very safe system. To be sure to be sure I entend to fit in the 240v line from the inverter an orange builders Earth Leakage Circuit Breaker with 4 x 240v outlets. I am led to believe that this unit contains two coils that will detect any uneven power draw between the Nutral and Active lines (we do not have any earth line) and will activate the circuit breaker. Can anyone confirm if this is a suitable and safe way to operate??
Regards Peter

[Sunking]

I think you might be a bit confused. While the system is not required to be grounded if below 50 volts, the equipment is required to be grounded.

[inetdog]

It would be safer than not having the Earth Current (also called Residual Current) detector. But even with it, as Sunking stated, it may not meet the electrical regulations that apply in your area.
It would not be acceptable under the US National Electrical Code, for example.

[pjlhat]

I think you might be a bit confused. While the system is not required to be grounded if below 50 volts, the equipment is required to be grounded.

Thanks but that does not answer my question regardless of regulations and they may well be different here in Australia. What I want to know will an earth leakage breaker give protection if not connected to earth in a complete floating system?
I have yet to find anyone who can point out the actual dangers of a full floating system, to me it appears safer than a graounded setup.

[pjlhat]

It would be safer than not having the Earth Current (also called Residual Current) detector. But even with it, as Sunking stated, it may not meet the electrical regulations that apply in your area.
It would not be acceptable under the US National Electrical Code, for example.

Hi Thanks for your reply I have replied to Sunking, if you are able to add any thing that would be appreciated.
Regards peter

[Sunking]

What you call a Earth Leakage Circuit Breaker we call a Ground Fault Circuit Interrupter or GFCI.

They operate by sensing the current in each polarity. If there is a difference between the to of more than 5 milli-amps they operate and need no reference to earth or anything.

But what you seem to fail to understand is the difference between a Grounded System and Grounded. You can float the system, which means none of the circuit conductors are bonded to earth. However that requires special Over Current Protection Devices and Ground Fault Indication in the event one of the polarities is faulted to ground or the chassis of any of the equipment.

A Grounded System is where you intentionally bond one of the system conductors to earth or something in place of earth, and then that conductor is called Neutral. This makes the Over Current Protection Devices very simple and inexpensive as all it requires is a Breaker or fuse on the Hot Conductors.

Now with that said, whether you have a Floating System or Grounded System, you are still required to Ground the Equipment. That means bonding all the metallic parts of the system like the chassis, frames, and raceways to earth ground or something in place of earth ground like a chassis in a car. It is a saftey issue that will prevent you from being electrocuted in the event one of the circuit conductors faults to the chassis. In short all you would have to do is touch something like the inverter, charge controller, or a solar panel frame and be electrocuted. This is why Un-Grounded Systems (Floated) are required to use a Ground Fault Indicator. If the chassis and frames are bonded to earth, you will not be electrocuted during a fault condition.

[mapmaker]

Now with that said, whether you have a Floating System or Grounded System, you are still required to Ground the Equipment. That means bonding all the metallic parts of the system like the chassis, frames, and raceways to earth ground or something in place of earth ground like a chassis in a car. It is a safety issue that will prevent you from being electrocuted in the event one of the circuit conductors faults to the chassis. In short all you would have to do is touch something like the inverter, charge controller, or a solar panel frame and be electrocuted.

In a grounded system if you touch a hot wire while also touching something grounded, you can become an alternate path to ground/neutral.

In a floating system, what is the danger of touching a current carrying conductor while you are also touching ground? The only current flow I see is capacitive. Is that the safety issue?

They operate by sensing the current in each polarity. If there is a difference between the two of more than 5 milli-amps they operate and need no reference to earth or anything.

In a grounded system the "missing" 5 milli-amps is returning through ground, rather than neutral. In a floating system how can the current in the two current carrying conductors be different? Where's the 5 milli-amps going?

--mapmaker

[inetdog]

In a grounded system if you touch a hot wire while also touching something grounded, you can become an alternate path to ground/neutral.

In a floating system, what is the danger of touching a current carrying conductor while you are also touching ground? The only current flow I see is capacitive. Is that the safety issue?



In a grounded system the "missing" 5 milli-amps is returning through ground, rather than neutral. In a floating system how can the current in the two current carrying conductors be different? Where's the 5 milli-amps going?

--mapmaker

In a truly floating system, there will not be any "missing current" if there is only a single fault connection to ground or anything else other than the circuit wires.
As a result the GFCI will not detect any fault current.
A ground detector is a different beast which works by looking for a current path to ground from the ungrounded connectors rather than checking for current balance.

Note also that when your GTI is operating, particularly for a transformerless design, the "ungrounded" array can be moving up and down with respect to ground as the GTI circuitry varies how it is interconnected to the mains wiring across the voltage cycle. The GTI requires that YOU not ground the array, but that does not mean that it is truly isolated and floating during operation.

[pjlhat]

[QUOTE=mapmaker;109534]In a grounded system if you touch a hot wire while also touching something grounded, you can become an alternate path to ground/neutral.

In a floating system, what is the danger of touching a current carrying conductor while you are also touching ground? The only current flow I see is capacitive. Is that the safety issue?

In my completly floating system I believe that the only way thati can be electrocuted is if I was to phyisiclly take hold of both active and neutral at the same time. I have actually put a screw driver in the actvive side of the the power point while standing on the concrete floor with no ill effect, though it has registered a volyage on the multimeter that I presume is some static electricity?

In a grounded system the "missing" 5 milli-amps is returning through ground, rather than neutral. In a floating system how can the current in the two current carrying conductors be different? Where's the 5 milli-amps go?

From what you say above there appears that there would be no benifit in having an Earth Leakage Breaker in a full floating system, other than to isolate the inverter in the case of an overload above say 10amps that could cause a fire?
Peter

[Sunking]

In a grounded system if you touch a hot wire while also touching something grounded, you can become an alternate path to ground/neutral.

Correct

In a floating system, what is the danger of touching a current carrying conductor while you are also touching ground? The only current flow I see is capacitive. Is that the safety issue?

Yes, and that is why the metallic chassis, raceways. and frames are required to be grounded in a Un-Grounded System. You are correct the coupling is capacities, and in a small system is insignificant. Bonding the metallic pieces shorts th ecapacitance out. In addition Un-Grounded System are prone to insulation stresses from high voltage which will eventually break down insulation resistances. That is why the NEC requires Un-Grounded Systems to only be used where trained personnel operate and maintain the system. In a UnGrounded System there has to be a ground reference with Ground Fault Indicators so in the even it alerts maintenance personnel of a fault and to schedule a system shut down to clear the fault.

And if you think a Un Grounded System is not dangerous consider this. All Utilities use Un Grounded Transmission and Distribution. I dare you to touch a 13.2 line. If you do here is what happens.

In a ungrounded system the "missing" 5 milli-amps is returning through ground, rather than neutral. In a floating system how can the current in the two current carrying conductors be different? Where's the 5 milli-amps going?

Correct and is what I am trying to make this guy understand. In a ungrounded system all conductors must must have Over Current Protection Device installed and a GFI.

[Sunking]

In my completly floating system I believe that the only way that i can be electrocuted is if I was to phyisiclly take hold of both active and neutral at the same time.

There is NO NEUTRAL in a ungrounded system. Your belief is going to get you hurt because it is false. If you have a ground fault, you will not know about. So when that happens and you touch the inverter, you are going to get educated.