Victron isolation transformer 7000 w ~230 v installed in the US

[ELLEQUE (Miami Boat Electrician)]

VICTRON ISOLATION TRANSFORMER 7000 W ~230 V INSTALLED IN THE US

(I will refer to this device as “The TRF”)

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1…

In this case a US Marina transformer, single phase with a middle point on the output windings. It is customary to bond ( To ground) Neutral with PE Earth:
L1~L2 = 240 V
L1~N = 120 V
L2~N = 120 V
L1~PE = 120 V
L2~PE = 120 V
PE~N= 0 V

2…

What could happen if the dock PE wire is connected to the PE Input terminal of the TRF ?.. presenting:

L~N = 240 V
L~PE = 120 V
N~PE = 120 V

Are installers, leaving the PE Wire disconnected between the boat shore inlet’s receptacle and the TRF Input, using a Residual Current circuit breaker 2-pole.?

If in an input failure the TRF enclosure becomes energized, the enclosure will discharge through its M4 welded stud at the bottom of the TRF enclosure towards the dock through the boat handrails or submerged metal parts and trip.
The residual current circuit breaker may fail, and not trip killing a person?

What about active galvanic current under 20 ma continuously entering from the Dock Line to the boat bonding system?

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3…

Does the transformer contains any internal device causing similar results to the Victron Multiplus ground relay?

What is connected internally after the Input PE Terminal? The soft start internal circuit? The cooling fan? or any electronic component that could fail in a closed position creating a path to the enclosure?

ANY HOW

4…

Measured continuity (In a disconnected, uninstalled TRF on its box) with an ohmmeter, between the Input PE terminal to all other terminals and enclosure, and there is no continuity towards anywhere, concluding that “it is an isolated point”.

Probably Victron Answer is:
“The Input PE Terminal is ONLY used to install the jumper towards PE Output when the boat is hauled out of the water”.
But I am not sure that is all, or if there is more than that?

5…

EVEN WHEN THE DOCK PE WIRE IS CONNECTED TO THE TRF INPUT PE TERMINAL:

When a failure in the TRF’s input side energizes the TRF enclosure, the TRF Input PE terminal DOES NOT COME CONNECTED TO ITS ENCLOSURE FROM MANUFACTURING, so there is no a cable path for failure current to flow to the doc.
Meaning Same thing, WITH OR WITHOUT, connecting the dock PE Wire to the TRF PE Input Terminal… the discharged failure current will have to exit the M4 Stud Welded on the Bottom of the TRF.
Failure on the bonding system will endanger life

Correct?

[MikeD (Mike)]

Note this is a single transformer, not a center tapped one for a 120/0/120 system.
Scenario 1: This is normal in the US. I would also expect that the dock pilaf also contains an RCBO.
Scenario2: This seems strange. The input PE terminal of the transformer is isolated. If you have L-N of 240v, then N has been confused with L2? . In a fault free installation, there is no current path from L1/L2/N to the transformer case, nor is there any current path from the input PE to the case.
If there is a fault from L1/L2/N to the transformer case, then sufficient current will flow to trip the RCBO (GFI). - part “c” in the diagram. As mentioned above, in a fault free system, there is no current path from the Dock line to any of the boat systems.
3) In some transformers, there is a relay to open /close the output ground path between the transformer center tap (if present), and the PE connection. This is for compatibility with some 240V systems, where the L2 output would be used as the Neutral connection, and grounded in a 240V inverter.
4) yes, that would prevent touch potential from building up on the hull - assuming steel hull out of the water.
5) This situation is why these should NOT be used without an RCBO or GFI. However, as the case stud is connected to the local ground - ie the hull, then there is no touch potential to a person wholly inside the hull. The only hazard would come to a person outside touching the hull, or a person inside touching something connected to an outside ground.
Failure of any bonding system can endanger life.

[ELLEQUE (Miami Boat Electrician)]

Thanks very much for answering.
I am attaching a screenshot of a diagram indicating real measured voltages… FOUND 360 V between input and output connectors on the transformer.

All equipment is working well in the boat
Here are some clarifications:

This Victron Isolation Transformer 7000W, 230V, is Installed in a European Wired Boat, Fiberglass hull, Docked in USA (All appliances and devices were replaced with US 60 hz devices ), still the wiring is original.

The engine propellers, Generador, inverter, Seacocks and rudders underwater are connected to a in hull bonded system, AND TO ZINK PLATES ( I wonder the results if zincs were depleted, or disconnected?)

Out of the 4 wires coming from the doc into the boat inlet receptacle; only 3 wires continue from the receptacle toward the transformer: L1, L2 and PE ( PE is bonded on the dock side with the dick Neutral “N”).

The dock has a standard 2 Pole circuit breaker, not a RCBO.
I have two Residual Current curcuit breakers installed, one in the input , and one in the output of the transformer.

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SEE ATTACHED DIAGRAM EITH READINGS

Are PE input and PE output really isolated ?

Why is the reading 363 Volt N(input) ( Same as L2) vs ~ L( output) ?

Would it be better to leave permanently disconnect the PE INPUT? (Actually is bonded/same as dock Neutral “N”)

[MikeD (Mike)]

Are PE input and PE output really isolated ?
Yes they are (or should be! if all is good). Voltage measurements from input to output while wired to the yachts systems will then include stray voltages from the input PE to actual ground potential. Also series resistance of the grounding system.

The 363V reading is the 118V input (Ni ) plus the 244v L out voltages. You are measuring from the -180Phase L2 (in this case wire is the “neutral” wire) to the output 244 In phase volts. PE-s are effectively coupled together by the water and grounding systems(0v top reading). The out of phase voltages add.

No, it’s best to leave the PE input terminated in the PE input connector. This secures the wire from wandering around, and it is effectively isolated / insulated.

Your 2 pole breakers and residual current circuit breaker together give the function of an RCBO, which opens both poles either on over current or ground leakage. So that’s ok.
BTW in case you missed this, the PE out is connected to N out by the J5-J7 link.

[ELLEQUE (Miami Boat Electrician)]

Thank you !!
It is quite uncomfortable and risky having 360 V aboard,
PUCK ISOLATION TRANSFORMERS.pdf (434.2 KB)

“…PE-s are effectively coupled together by the water and grounding systems(0v top reading)…”

Coupled together?

Before installing, I measured continuity from PEi to enclosure and it shows isolated.
What is the reason for the terminal PEi to exist? if it is connected to nothing…

I did disconnected PEi temporarily and verified all measured voltages remain the same, and found no changes.

As a curiosity, I attach a document related to PUCK TRANSFORMERS, where they recommend not to connect the PEi.
Any opinions regarding that ?

[MikeD (Mike)]

once the transformer is installed, and the output PE connected to the anodes (Zincs), that couples the transformer output PE to the dockside PE THROUGH the CONDUCTIVITY of the water.

The input PE is connected to a terminal block, but that is not connected to anything else. It merely provides a secure anchor for the PE cable. it MAY, if a JUMPER is installed, be coupled to the output PE for when the yacht is hauled out. This should only be done by a qualified electrician, and removed before the yacht is re-launched. With the GFI’s in the circuit, this is an optional step that prevents potential shocks should someone touch the hull / anodes at the same time as an internal electrical fault occurs (extreme low probability).

Having 360V on the yacht is no big deal, as it is only accessible inside the protective case of the transformer. We had 415V 3 phase on our small 48’ yacht with no issues.