GFI in a split-phase 230V system without neutral wire?

[peterpaul]

Hi, I hope this is the right place to ask this...

At our current residential construction project, the electric power company utilizes a split-phase 230V system without supplying a neutral wire to the building (only two wires). We are requesting a GFI breaker installation from our electrician, but these are still uncommon in this part of the country. That's why I wanted to ask those in the forum who are familiar with these kind of installations, if our system would work correctly? - Specifically, will the GFI still function without a neutral connector?

My father, who is an electronics engineer was concerned about the unclear grounding configuration, since the 8kV transformer is grounded 200 ft away from us, and this neutral wire will not be connected to the ground connector of the building. Do you expect any problems with this?

I'd appreciate any help with this question,
Peter


Here some additional information:
The electrical plan for the building is based on Philippine Electrical Code, which is based on the National Electrical Code of the US. The power distribution is similar to this diagram:


SPECS:

• primary voltage: 8kV
• primary Neutral (below Phase): one side of primary connected to 1/2" GI grounding rod 8 ft in soil (below electric post)
• secondary 230V between two main output wires (115V towards ground)
• secondary Neutral (in center): connected to same grounding rod below electric post
• secondary two output wires connected to building 200 ft up the street
• neutral wire is not connected to building, but termintes at post across the street
• building has its own ground connection (40 ft concrete encased electrode in foundation ground beam welded to footing rebars)

The transformer supplying the building looks like this:

 

[Dennis Alwon]

A Gfci will not work because it needs a neutral for the electronics. There may be something out there that doesn't need a neutral but I don't know about it

 

[peterpaul]

A Gfci will not work because it needs a neutral for the electronics. There may be something out there that doesn't need a neutral but I don't know about it

Well, we have 115V on each phase to ground and 230V between the two phases. Both phases are to be protected with a circuit breaker each, as commonly done here, meaning a 2-Pole joined unit. The panel will not have a neutral, but will have a building ground connector.

Would something like this work :?


The following quote from the Siemens 2-Pole GFCI datasheet is confusing to me:

Current imbalances of 4-6 milliamps or more between load conductors will cause the ground fault sensor to trip the circuit breaker.

Note: A load neutral is not required on the circuit. However, the white line neutral (pigtail) must be connected to the panel neutral for the device to function.

 

[Dennis Alwon]

With a DP gfci there is a means to connect a load neutral if the equipment has a need for a neutral. If there is no load side neutral then you do not need to connect to it however the line side is needed. So yes you can connect to ground and get 120V however that would not be code compliant

 

[GoldDigger]

You could derive a neutral just to power the breaker by connecting a center tapped control transformer between the two hot lines. Just be very sure that nobody will ever try to connect a 115V load to that neutral.
But that transformer cannot be on the load side of the breaker, so it would need its own OCPD.
Headache!

 

[Dennis Alwon]

So how are you getting 115V to ground if there is no neutral or ground????

 

[GoldDigger]

So how are you getting 115V to ground if there is no neutral or ground????

Balanced stray capacitive loads to ground would tend to do that.

 

[peterpaul]

Thanks for the replies!

You could derive a neutral just to power the breaker by connecting a center tapped control transformer between the two hot lines. ... But that transformer cannot be on the load side of the breaker, so it would need its own OCPD. Headache!

That's an interesting idea. If it only powers the GFI breakers, it would not draw much current, right? What kind of load would be on that transformer?

With a DP gfci there is a means to connect a load neutral if the equipment has a need for a neutral. If there is no load side neutral then you do not need to connect to it however the line side is needed. So yes you can connect to ground and get 120V however that would not be code compliant

Actually, we have no need for 120 or 115V circuits. It's a mystery to me why the electric power company even uses this type of transformer, as I have never seen them actually supply 115V circuits. All residential connections in this Philippine city are done with 230V.

My question is mainly regarding the use of the DP GFCI. Since I only need 230V, will it work even without the neutral wire? If the 'line neutral' from the GFCI would be connected to the house ground terminal, would it function reliably?

On the other hand, if I knew, that according to code, electric company is supposed to run the neutral wire to the building, I might be able to convince them to actually do it! I would not be surprised, if they were violating the code when supplying current without providing a neutral wire. The service drop wires they installed for the temporary construction connection literally burned up and had to be replaced, because it had only half the required cross section :slaphead:.

 

[Dennis Alwon]

The NEC requires a neutral to the service. I would think the gfci would work if you connect the neutral to the ground as I said before but it is not compliant

250.24(C) Grounded Conductor Brought to Service Equipment.
Where an ac system operating at less than 1000 volts
is grounded at any point, the grounded conductor(s) shall
be routed with the ungrounded conductors to each service
disconnecting means and shall be connected to each disconnecting
means grounded conductor(s) terminal or bus. A
main bonding jumper shall connect the grounded conductor(
s) to each service disconnecting means enclosure. The
grounded conductor(s) shall be installed in accordance with
250.24(C)(1) through (C)(4).

 

[mbrooke]

Thanks for the replies!



That's an interesting idea. If it only powers the GFI breakers, it would not draw much current, right? What kind of load would be on that transformer?



Actually, we have no need for 120 or 115V circuits. It's a mystery to me why the electric power company even uses this type of transformer, as I have never seen them actually supply 115V circuits. All residential connections in this Philippine city are done with 230V.

My question is mainly regarding the use of the DP GFCI. Since I only need 230V, will it work even without the neutral wire? If the 'line neutral' from the GFCI would be connected to the house ground terminal, would it function reliably?

On the other hand, if I knew, that according to code, electric company is supposed to run the neutral wire to the building, I might be able to convince them to actually do it! I would not be surprised, if they were violating the code when supplying current without providing a neutral wire. The service drop wires they installed for the temporary construction connection literally burned up and had to be replaced, because it had only half the required cross section :slaphead:.

It is for safety. Any hot wire will have 115 volts to ground instead of 230 volts which limits the fire and electrocution risk. 115 volts to anything grounded is far safer than 230 volts.


You need an IEC GFCI (RCD) breaker. IEC breakers do not have any 120 volt parts inside and run on straight 230 volts. Something like this:

 

[mbrooke]

The NEC requires a neutral to the service. I would think the gfci would work if you connect the neutral to the ground as I said before but it is not compliant

He said 2 wires, which would mean TT earthing. In that case a GFCI is needed, in addition to a 230 volt unit. The electronics will just energize the grounding system, a dangerous scenario.

Just to add, TT earthing is forbidden by the NEC. So if the Philippine electrical code is indeed based on the NEC instead of the IEC this would be a violation. The NEC would require a continuous grounding conductor all the way to the utility transformer neutral terminal.

 

[kwired]

He said 2 wires, which would mean TT earthing. In that case a GFCI is needed, in addition to a 230 volt unit. The electronics will just energize the grounding system, a dangerous scenario.

Just to add, TT earthing is forbidden by the NEC. So if the Philippine electrical code is indeed based on the NEC instead of the IEC this would be a violation. The NEC would require a continuous grounding conductor all the way to the utility transformer neutral terminal.

I would have to agree that if the NEC applies - a grounded conductor must run to the service disconnecting means. We would have big problems with protection from ground faults outside of low level protection like GFCI's, as you would be depending on earth impedance to carry enough current to trip overcurrent devices - not happening. Any GFCI or similar device like RCD mentioned would need 240 volt for electronic controls instead of 120 which is fairly typical for GFCI's. There are some GFCI's out there though that do run on straight 240 volts IIRC Square D has one that is a 60 amp two pole 240 volt (no neutral), but all their 50 amp and below 2 pole units all require a neutral in the supply, they can feed a load that doesn't utilize a neutral though.

 

[mbrooke]

I would have to agree that if the NEC applies - a grounded conductor must run to the service disconnecting means. We would have big problems with protection from ground faults outside of low level protection like GFCI's, as you would be depending on earth impedance to carry enough current to trip overcurrent devices - not happening. Any GFCI or similar device like RCD mentioned would need 240 volt for electronic controls instead of 120 which is fairly typical for GFCI's. There are some GFCI's out there though that do run on straight 240 volts IIRC Square D has one that is a 60 amp two pole 240 volt (no neutral), but all their 50 amp and below 2 pole units all require a neutral in the supply, they can feed a load that doesn't utilize a neutral though.

Do you have a link for the Square D unit?

Unless the OP's utility or local codes specifically want TT earthing, I would call the utility and ask for the neutral (equipment ground) to be extend to the service.


If the OP is forced to make do with only 2 hots then the main breaker or all branch circuit breakers must be GFCI. I agree, a standard breaker will not clear faults without a high current path.

 

[kwired]

Do you have a link for the Square D unit?

Unless the OP's utility or local codes specifically want TT earthing, I would call the utility and ask for the neutral (equipment ground) to be extend to the service.


If the OP is forced to make do with only 2 hots then the main breaker or all branch circuit breakers must be GFCI. I agree, a standard breaker will not clear faults without a high current path.

It is on page 1-3 of current catalog, which you can find here.

All the two pole GFCI's are 120/240 volt, except the 60 amp model, it has a footnote that says "Suitable only for feeding 240 Vac and 208 Vac two-wire loads. Does not contain load neutral connection." I guess it doesn't specify if there is a line side neutral connection, may need to look at more technical data if I can find it to know for certain. I see product data sheet for 50 and 60 amp are basically same thing with neither mentioning the neutral

 

[peterpaul]

He said 2 wires, which would mean TT earthing. In that case a GFCI is needed, in addition to a 230 volt unit. The electronics will just energize the grounding system, a dangerous scenario. Just to add, TT earthing is forbidden by the NEC. So if the Philippine electrical code is indeed based on the NEC instead of the IEC this would be a violation. The NEC would require a continuous grounding conductor all the way to the utility transformer neutral terminal.

I would have to agree that if the NEC applies - a grounded conductor must run to the service disconnecting means. We would have big problems with protection from ground faults outside of low level protection like GFCI's, as you would be depending on earth impedance to carry enough current to trip overcurrent devices - not happening. ...

... Unless the OP's utility or local codes specifically want TT earthing, I would call the utility and ask for the neutral (equipment ground) to be extend to the service.
If the OP is forced to make do with only 2 hots then the main breaker or all branch circuit breakers must be GFCI. I agree, a standard breaker will not clear faults without a high current path.

Thanks for all the insights! I will try to get to talk to a competent engineer at the electric utility and ask, if they can extend the transformer ground/neutral to the house. Physically this should not be a problem, as that wire is only 20 feet away across the street. Whether they would agree is rather doubtful, as evidently more than 200,000 residential consumers are connected with 2 wire service drop 2 phase connections, and they may not want to add another wire just for us :happysad:. I wonder, if their current connection practice contributes to the multitudes of homes in this city burning down every year due to electrical fires :?

Please let me know, if I understand your comments correctly: the lack of a continuous ground connection from utility transformer to residential grounding would make it unlikely for the regular circuit breaker to trip in case one phase is, for example, accidentally in contact with the metal roof (or metal sink) of the home. The current would have no clearly defined return path to neutral and neither the utility transformer ground 200 feet away, nor the building ground would have a low enough earth resistance to trip a 20A breaker. As a result, possibly part of the structure could pose an electrocution danger or a fault could cause enough current to flow to cause a fire without tripping the breaker, right?

American branded GFCI breakers cannot be found locally. As for locally available 2 pole GFCI/RCBO circuit breakers I found the following from CHiNT: NL1 Product Page and pdf Would this be a reasonable choice?

The Philippine Electrical Code PEC 2009 is indeed derived from the NEC 2008, thus the requirement for grounding is the same, 2.50.2.5. (c) Grounded Conductor Brought to Service Equipment (quote in image):

 

[kwired]

Thanks for all the insights! I will try to get to talk to a competent engineer at the electric utility and ask, if they can extend the transformer ground/neutral to the house. Physically this should not be a problem, as that wire is only 20 feet away across the street. Whether they would agree is rather doubtful, as evidently more than 200,000 residential consumers are connected with 2 wire service drop 2 phase connections, and they may not want to add another wire just for us :happysad:. I wonder, if their current connection practice contributes to the multitudes of homes in this city burning down every year due to electrical fires :?

Please let me know, if I understand your comments correctly: the lack of a continuous ground connection from utility transformer to residential grounding would make it unlikely for the regular circuit breaker to trip in case one phase is, for example, accidentally in contact with the metal roof (or metal sink) of the home. The current would have no clearly defined return path to neutral and neither the utility transformer ground 200 feet away, nor the building ground would have a low enough earth resistance to trip a 20A breaker. As a result, possibly part of the structure could pose an electrocution danger or a fault could cause enough current to flow to cause a fire without tripping the breaker, right?

American branded GFCI breakers cannot be found locally. As for locally available 2 pole GFCI/RCBO circuit breakers I found the following from CHiNT: NL1 Product Page and pdf Would this be a reasonable choice?

The Philippine Electrical Code PEC 2009 is indeed derived from the NEC 2008, thus the requirement for grounding is the same, 2.50.2.5. (c) Grounded Conductor Brought to Service Equipment (quote in image):

Seems that your POCO does not want to play with those that set the codes for the installers. If a POCO did that here in the US, they would have potential for lawsuits when someone gets electrocuted by their practices, so they bring the grounded conductor with any distribution equipment they provide, and do what is necessary to help installers comply with any codes they need to follow. If they don't want to pay for something - they change the location of the service point and make the owner/installer provide that equipment this helps keeping them out of the loop when something goes bad due to not following standard practices.

 

[winnie]

Question: when you say that the utility company only provides 2 wires, do you mean 2 insulated conductors supported by a bare 'messenger' cable?

In the US, a very common residential overhead service is two insulated conductors wrapped/supported by a bare metal cable. The metal cable serves as both mechanical support and the grounded conductor. The bare metal cable acts as the path for fault current back to the transformer.

-Jon

 

[kwired]

Question: when you say that the utility company only provides 2 wires, do you mean 2 insulated conductors supported by a bare 'messenger' cable?

In the US, a very common residential overhead service is two insulated conductors wrapped/supported by a bare metal cable. The metal cable serves as both mechanical support and the grounded conductor. The bare metal cable acts as the path for fault current back to the transformer.

-Jon

Good point that could be overlooked.

 

[mbrooke]

Thanks for all the insights! I will try to get to talk to a competent engineer at the electric utility and ask, if they can extend the transformer ground/neutral to the house. Physically this should not be a problem, as that wire is only 20 feet away across the street. Whether they would agree is rather doubtful, as evidently more than 200,000 residential consumers are connected with 2 wire service drop 2 phase connections, and they may not want to add another wire just for us :happysad:. I wonder, if their current connection practice contributes to the multitudes of homes in this city burning down every year due to electrical fires :?

Please let me know, if I understand your comments correctly: the lack of a continuous ground connection from utility transformer to residential grounding would make it unlikely for the regular circuit breaker to trip in case one phase is, for example, accidentally in contact with the metal roof (or metal sink) of the home. The current would have no clearly defined return path to neutral and neither the utility transformer ground 200 feet away, nor the building ground would have a low enough earth resistance to trip a 20A breaker. As a result, possibly part of the structure could pose an electrocution danger or a fault could cause enough current to flow to cause a fire without tripping the breaker, right?

American branded GFCI breakers cannot be found locally. As for locally available 2 pole GFCI/RCBO circuit breakers I found the following from CHiNT: NL1 Product Page and pdf Would this be a reasonable choice?

The Philippine Electrical Code PEC 2009 is indeed derived from the NEC 2008, thus the requirement for grounding is the same, 2.50.2.5. (c) Grounded Conductor Brought to Service Equipment (quote in image):

You are correct, a regular breaker will not trip on a ground fault. It can and will start a fire. At this point you have a TT earthed system. The GFCI breakers will work. The breakers will need to protect all circuits.

 

[peterpaul]

Question: when you say that the utility company only provides 2 wires, do you mean 2 insulated conductors supported by a bare 'messenger' cable? ..

All service drops here really only have two wires; the transformer ground/neutral is not connected to the home.

A German engineering firm made a study (pdf) of public LV-network technologies, detailed in the following diagrams:



The POCO in our city utilizes Configuration A. The comments in the engineering study:

Most LV networks of Meralco and PEPOA-DUs are according to Configuration A. This type of system corresponds to an American ?split-phase? network, but with the exception that the neutral conductor does not extend to the load. Therefore, both conductors of a Configuration A ? LV network represent a phase conductor, which is quite unique. ...
According to studies carried out by SMA Solar Technology AG the most common LV network technology is Configuration A. In these systems, appliances are with ground wire taken out usually near the 2-prong plug and then connected to ground, such as a water pipe or any means of grounding. Therefore the grounding system of Configuration A can be considered as TT but without neutral conductor (see Figure 4).

They do not mention, that this configuration violates the electrical code, only that it is "quite unique":huh:. After reading up on various earthing systems and gaining a little more understanding, this looks similar to a TT earthing system to me as well, which mbrooke already mentioned:

He said 2 wires, which would mean TT earthing. In that case a GFCI is needed, ...

Schneider electric has an informative article titled "earthing systems worldwide and evolutions" (pdf), concluding: "future evolution should favour earthing systems generating fault currents which do not exceed a few dozen amps. TT earthing systems should therefore be increasingly used."

Based on our discussion and the above info I would conclude:

1. Configuration A is the POCO's standard connection for millions of residences around the country. They are unlikely to change it just for us, even if it may violate the national code (PEC 2009). Possibly they interpret the code differently.
2. A TT earthing system is inherently unsafe when used with merely regular two pole circuit breakers, as commonly done here.
3. For safe operation, the above configuration needs the main breaker and every branch circuit to be secured by GFCI/RCD breakers, possibly using multiple levels as described by Schneider Electric for TT systems here
4. Using the correct two pole GFCI breakers, such a system, should be able to function reliably.

Do you think my conclusions are correct?