OT: 2-pole Circuit Breaker in Single Phase Supply

kamenges · Jan 28, 2019

I am designing a machine for use in the European Union. The machine will include a Ropex heat seal controller that will receive a 230VAC single phase supply derived between one of the machine 3-phase supply lines and the supply neutral. The Ropex documentation indicates that the controller should use a 2-pole breaker to supply the controller, which means the neutral will contain overcurrent protection.

For a machine in the US I would typically not put an overcurrent protection device in the neutral conductor path. Is it common practice to do this in EU installations?

Keith

Aabeck · Jan 28, 2019

You can put switches or overcurrent protection on the neutral lead - BUT - it must be switched with the hot lead. A 2 pole breaker, or switch, would be proper for this. Two single pole breakers would not be allowed.

EDIT: Yes, I have seen this on US machinery.

James Mcquade · Jan 28, 2019

you need to get with the company where it is installed.

depending on what country the equipment is going, you must deal with the following.

they use 50 hz.
230 volts is their standard house voltage, not 120 volts like the US uses.
their 3 phase power is 380 volts.

it has been several years since I shipped items to other countries, so I would double check.

I would also ask what documentation is required when you send the equipment to the customer.

james

Jonnie_R · Jan 28, 2019

Double pole protection is pretty standard in the EU for 230V 50Hz circuits.

Our standard harmonised 3 phase power is 400V 50Hz, to cover the varying voltages in the EU(UK is nominally 415V other countries can be 380V).

kamenges · Jan 28, 2019

Thanks, Jonnie_R. Looks like I have some redesigning to do.

Keith

Jonnie_R · Jan 28, 2019

The double pole system was first really pushed by Merlin Gerin in their distribution boards back in the mid to late 90s, I believe to comply with French law, and I know it definitely is a requirement in Belgium too.

I always build my panels with double pole protection on any 230V circuits.

lfe · Jan 28, 2019

For many years now I have not used the neutral in the electrical diagrams because in many modern industrial installations they do not have a neutral cable. They only supply you with the three phases and the ground.

To get the 230 V I use a 400V to 230V transformer, the primary is protected by a 2 pole circuit breaker. The secondary has one side connected to a bar of commons * and on the other side I install one or more 1 pole circuit breaker for the different supplies.

* The commons bar is naked but isolated from the metal cabinet and connected to the ground of the installation in a single point, to avoid ground loops
The common bar is not used to connect the ground wires, there is another bar for that.

kamenges · Jan 28, 2019

Follow-up question. I assume the neutral conductor will no longer be blue after the circuit breaker since you can no longer say that wire is definitely a grounded conductor. Correct assumption?

Keith

Maxkling · Jan 28, 2019

Is the neutral actually grounded?

Aabeck · Jan 28, 2019

Kamenges,

No! If the breaker trips the disconnected neutral wire is no longer neutral, it could possibly carry a voltage, so it has to have it's color changed.

Even the neutral coming off a NEMA motor over-load that disconnects the neutral to the contactor has it's wire changed. In olden times when red was 120 & white was neutral there were red wires going to both contactor terminals because if the OLR tripped that wire would give a shock from the hot going through the coil.

Maxkling,

The neutral can only be grounded in one place on a machine. Otherwise there could be the potential for the neutral current to go through the ground between 2 grounding connections.

kamenges · Jan 28, 2019

Originally posted by Aabeck:

No! If the breaker trips the disconnected neutral wire is no longer neutral, it could possibly carry a voltage, so it has to have it's color changed.

I need to stop writing in double negatives. I think we are saying the same thing. The "neutral" wire CANNOT be blue after the breaker since it might not actually be at ground potential anymore. I suspect that is what the guys in the EU will say as well but it is worth the check.

Keith

Maxkling · Jan 28, 2019

Aabeck said:
Kamenges,

Maxkling,

The neutral can only be grounded in one place on a machine. Otherwise there could be the potential for the neutral current to go through the ground between 2 grounding connections.

I’m referring to the OP if his neutral in his supply is truly grounded. If it’s an older supply using a free neutral then it wouldn’t really matter.

bkottaras · Jan 28, 2019

We do use and spec 4 wire setup (3Ph + Neutral).
A couple of images attached.

kamenges · Jan 28, 2019

Thanks, bkottaras. I should have made this part clear as soon as the questions started coming. I notice you aren't breaking the neutral like the Ropex manual would indicate. I wouldn't think this would cause any issues but they do seem to specifically indicate the neutral should go through the overcurrent protection.

As part of our installation specification to the customer we required a 5-wire supply to the machine with separate neutral and PE. The customer agreed to this and indicated this is their typical machine service type. The customer also indicate that their preferred plant-internal method of sourcing a 230VAC single phase supply is to tap the 3-phase supply conductors and the neutral conductor.

Keith

bkottaras · Jan 28, 2019

We've been using the setup for at least 10 years.
CE certifications and such.
Never had a single issue with it.

OT: 2-pole Circuit Breaker in Single Phase Supply

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