AC DC common ground

[pdqsailor]

Thank you very much for this..

[s/v Jedi]

Originally Posted by pdqsailor

Thank you very much for this..

For a 3.6kW transformer, which is the correct model for a 120V/30A shore power that you have, as well as a 230V/16A shore power in the EU, can be smaller and lighter when they use a toroidal transformer. It’s still 23kg but I think it’s manageable, similar to a start battery.

Here is a link: https://www.victronenergy.com/upload...formers-EN.pdf

[pdqsailor]

Thank you...

[goboatingnow]

Originally Posted by s/v Jedi

For a 3.6kW transformer, which is the correct model for a 120V/30A shore power that you have, as well as a 230V/16A shore power in the EU, can be smaller and lighter when they use a toroidal transformer. It’s still 23kg but I think it’s manageable, similar to a start battery.



Here is a link: https://www.victronenergy.com/upload...formers-EN.pdf

I can buy my transformer with 110 vac primaries so I can accept both 110 step up. Equally I can configure it as step down frequency remains unchanged of course

[goboatingnow]

Originally Posted by s/v Jedi

I have a request and a question:



R: can someone pm/email me the ISO document about shore power, RCD and isolation transformers?



Q: under ISO and when using an isolation transformer: is the RCD between inlet and isolation transformer mandatory or does it allow an exception because of the isolation transformer?



For the thread: you can improve on the RCD and removing any jumpers between AC and DC by utilizing an isolation transformer. Not only does this eliminate all risk for swimmers but also for people on board. It is the clear winner for safety and that is added to the galvanic protection for the boat.



I added the diagram, which shows a standard 2-pole breaker after the inlet.

The relevant iso spec doesn’t have lot to say


galvanic isolator
device installed in series with the a.c. protective conductor of the shore-power cable to block low-voltage d.c. galvanic current flow, but permit the passage of alternating current normally associated with the protective conductor
4 General requirements
4.1 The protective conductor insulation shall be green or green with a yellow stripe. Neither colour shall be used
for current-carrying conductors.
NOTE The equipotential bonding conductor of the d.c. electrical system (see ISO 10133) also uses green, or green with a yellow stripe, insulation and is connected to various exposed conductive parts of direct-current electrical devices, other extraneous conductive parts and the d.c. negative ground/earth.
4.2 The protective conductor shall be connected to the craft's d.c. negative ground (earth) as close as practicable to the battery (d.c.) negative terminal.
NOTE If an RCD (whole-craft residual current device) or an isolation transformer is installed in the main supply circuit of the a.c. system (see 8.2), the negative ground terminal of the d.c. system need not be connected to the a.c. shore ground (protective conductor).
4.3 For craft with fully insulated d.c. systems (see ISO 10133), the a.c. protective conductor shall be connected to the hull of a metallic hull craft, the craft external ground (earth) or the craft lightning-protection ground plate, if fitted.
4.4 Metallic craft hulls shall not be used as conductors.
4.5 The protective conductor shall be connected to metallic hulls at a location above any anticipated water
accumulation.
4.6 Individual circuits shall not be capable of being energized by more than one source of electrical power at a time. Each shore-power inlet, generator or inverter is a separate source of electrical power. The transfer from one power-source circuit to another shall be made by a means which opens all current-carrying conductors, live and neutral, before closing the other source circuit, prevents arc-over between contacts and is interlocked by mechanical or electromechanical means. Both current-carrying conductors, live and neutral, shall be broken simultaneously when changing power sources.
4.7 Energized parts of electrical equipment shall be guarded against accidental contact by the use of enclosures of at least IP 2X type, in accordance with IEC 60529, or other protective means which shall not be used for non- electrical equipment. Access to energized parts of the electrical system shall require the use of hand tools or have a protection of at least IP 2X, unless otherwise specified. A suitable warning sign shall be displayed (see 5.2).
4 [emoji767] ISO 2000 – All rights reserved

4.8 The neutral conductor shall be grounded (earthed) only at the source of power, i.e. at the onboard generator, the secondary of the isolation or polarization transformer, or the shore-power connection. The shore-power neutral shall be grounded through the shore-power cable and shall not be grounded on board the craft.
4.9 A galvanic isolator or other suitable device may be fitted in the protective conductor to resist imported stray galvanic current flow while permitting the passage of a.c. current, if present. Galvanic isolators shall be designed to withstand the application of power from a short-circuit test from a source capable of delivering 5 000 A r.m.s. symmetrically to its output test terminals for the time required for the circuit-breaker in the test circuit to trip. After three applications of the short-circuit test, the electrical and mechanical characteristics of the isolator shall be unchanged.
5 Marking
5.1 Shore-power inlets shall be marked to indicate voltage, current, shock hazard symbol and read owner's
manual symbol .
5.2 A permanently mounted waterproof warning sign shall be located at the panel-board on the craft. The sign shall include the information shown in Figure 1a) or 1b).
Warning Electrical shock hazard Fire hazard Read owner's manual
a) Suggested warning sign using symbols
ISO 13297:2000(E)
WARNING — To minimize shock and fire hazards:
1) Turn off craft's shore-power connection switch before connecting or disconnecting shore-power cable.
2) Connect shore-power cable to craft's inlet before connecting to shore-power source. 3) If polarity indicator is activated, immediately disconnect cable.
4) Disconnect shore-power cable at shore-power source first.
5) Close shore-power inlet cover tightly.
DO NOT ALTER SHORE-POWER CABLE CONNECTORS.
b) Suggested warning sign with text in language appropriate to the country of use
Figure 1 — Suggested warning signs
NOTE In Figure 1 b), item 3 is required only if a polarity indicator is installed in the system and items 2, 4 and 5 are not required for permanently connected shore-power cable installations.
5.3 Switches and controls shall be marked to indicate their function, unless the purpose of the switch is obvious and if operation of the switch could not, under normal operating conditions, cause a hazardous condition.
[emoji767] ISO 2000 – All rights reserved 5

ISO 13297:2000(E)
5.4 Electrical equipment shall be marked or identified to indicate:
a) manufacturer's identification;
b) model number or designation;
c) electrical rating in volts and amperes, or volts and watts;
d) phase and frequency, if applicable;
e) ignition protected, if applicable, by ISO 8846.
6 Ignition sources
Electrical components installed in compartments which, in normal operation, may contain liquefied petroleum gases (LPG) or petrol vapour, e.g. petrol tank, engine compartment and LPG lockers, shall be designed to be compliant with ISO 8846 or in accordance with IEC 60079-0, and shall be located in accordance with ISO 9094-1.
7 Overcurrent protection 7.1 General requirements
7.1.1 In unpolarized systems, double-pole circuit-breakers that open both live and neutral conductors are required.
7.1.2 Fuses shall not be installed in unpolarized systems.
7.1.3 Overcurrent protection devices for motor loads shall have a predetermined value of current flow that is
consistent with demand-load characteristics of the protected circuit.
7.1.4 All a.c. motor installations and each motor of a motor-operated device shall be individually protected in accordance with 7.1.3 by an integral overcurrent or thermal protection device.
An exception may be made for motors that will not overheat under continuous locked-rotor conditions.
7.1.5 The rating of the overcurrent protection device shall not exceed the maximum current-carrying capacity of the conductor being protected. See Table A.1.
7.2
7.2.1
7.2.2
7.2.3 Overcurrent protection shall be provided for isolation and polarization transformers, including a bank of transformers operating as a unit. Each transformer shall be protected by an individual overcurrent device on the primary side, rated at not more than 125 % of the rated primary current of the transformer.
Main supply circuits
Double-pole circuit-breakers shall be installed in conductors to the shore-power supply circuits.
A manually reset trip-free circuit-breaker shall be installed within 0,5 m of the source of power or, if impractical, the conductor from the source of power to the panel-board circuit-breaker shall be contained within a protective covering, such as a junction box, control box, enclosed panel-board, or within a conduit or cable trunking or equivalent protective covering. If the location of the main shore-power inlet circuit-breaker exceeds 3 m from the shore-power inlet connection or the electrical attachment point of a permanently installed shore-power cord, additional fuses or circuit-breakers shall be provided within 3 m of the inlet or attachment point to the electrical system in the craft, measured along the conductor.
6 [emoji767] ISO 2000 – All rights reserved

7.3 Branch circuits
7.3.1 The live conductor of each branch-circuit in a polarized system shall be provided with overcurrent
protection, i.e. a fuse or circuit-breaker, at the point of connection to the main panel-board bus.
7.3.2 Both conductors of each branch circuit in unpolarized systems shall be provided with overcurrent protection by double-pole circuit-breakers and double-pole switches, if used, at the point of connection to the main panel-board bus.
8 8.1 8.2 a)
b)
8.3


In essence primary and secondary rcbo is recommended no earth connections on secondary or primary.

Where do you see problems.

[goboatingnow]

In my case RCBOS on the primary no electro static shield , RCBOS on the secondary. No common neutrals no grounding no neutral bonding. ( but can easily be done but unnecessary with RCBOs protection ABS plastic box. No shore earth connection on board except to metal shore power receptacle. Dual pole breakers , most shock risks are therefore neutralised one would presume this is your approach.

My reading is it’s ISO compatible too

[s/v Jedi]

I see no mention of RCD’s being mandatory anywhere? I thought they were just like in ABYC?

Can you email me the PDFs?

[goboatingnow]

Originally Posted by s/v Jedi

I see no mention of RCD’s being mandatory anywhere? I thought they were just like in ABYC?



Can you email me the PDFs?

Link https://xanthiona.files.wordpress.co...ac-current.pdf

This is not the most current but it’s closed enough.

Why in the name of god would you not fit RCBOs anyway. There as cheap as chips €16 fron garo

[s/v Jedi]

Originally Posted by goboatingnow

Link https://xanthiona.files.wordpress.co...ac-current.pdf

This is not the most current but it’s closed enough.

Why in the name of god would you not fit RCBOs anyway. There as cheap as chips €16 fron garo

Because they serve no purpose with an isolation transformer. They should be in the dock pedestal, so that the shore power cord, which often hangs in the water, is protected.

Is it mandatory in shore power pedestals?

Anyway, my reference diagram is good as it is for ISO compliance.

[Jolly Roger]

Originally Posted by pdqsailor

So like I had to become educated .. so do you and you also have to think critically and get your information from MULTIPLE sources to arrive at a well rounded and informed bigger picture and make up your OWN mind as to the best way to proceed...

How can one possibly become well rounded and informed about a technical electrical subject like this, when hardly any of the so-called experts can't even agree between themselves, with some disagreeing vehemently.
We sure have plenty of multiple sources here.
I also posed a simple question, which has been completely ignored by the pundits, who are clearly much more interested in impressing each other with their profound knowledge, instead of giving a simple answer to a pretty simple and logical question, that is relevant to the OP's original inquiry.

[s/v Jedi]

Originally Posted by Jolly Roger

How can one possibly become well rounded and informed about a technical electrical subject like this, when hardly any of the so-called experts can't even agree between themselves, with some disagreeing vehemently.
We sure have plenty of multiple sources here.
I also posed a simple question, which has been completely ignored by the pundits, who are clearly much more interested in impressing each other with their profound knowledge, instead of giving a simple answer to a pretty simple and logical question, that is relevant to the OP's original inquiry.

I think I answered PDQ’s question just fine, sorry if that is not good enough for you, but he seemed happy with it and keep in mind that our answers are free of charge so complaining about it is a bit weird.

About your question: pdq answered it: you need to study and learn about it. Your question shows a lack of understanding on the subject which makes it impossible to answer.

If your installation is original or had modifications done by a qualified person, it should just be fine. If you want to improve on it, compare with my reference diagrams: I post them for that reason and they are free to use. These diagrams show the best way for you and your boat to do this.

In this case you can see that shore power ground doesn’t get connected at any busbar in the boat, because it stops at the transformer. And for good reason.

[team karst]

Originally Posted by s/v Jedi

I have a request and a question:

R: can someone pm/email me the ISO document about shore power, RCD and isolation transformers?

Q: under ISO and when using an isolation transformer: is the RCD between inlet and isolation transformer mandatory or does it allow an exception because of the isolation transformer?

For the thread: you can improve on the RCD and removing any jumpers between AC and DC by utilizing an isolation transformer. Not only does this eliminate all risk for swimmers but also for people on board. It is the clear winner for safety and that is added to the galvanic protection for the boat.

I added the diagram, which shows a standard 2-pole breaker after the inlet.

I'm confused. Are you not polarizing the output of the iso xfrm by grounding the neutral?

[pdqsailor]

Originally Posted by goboatingnow

Your last paragraph is indeed correct blind faith in so called largely “ advisory “ standards are no substitute for clear thinking and informed decision making

Ultimately you make your vessel safe.
In my view therefore. I do not bond anything to seawater if at all possible and I rely on RCBO to ensure my vessel is safe. I am however fitting an isolating transformer to improve my vessels safety and recently orders a toroidal one of suitable ratings. I will have to add soft start to this unfortunately and I will protect it with RCBOS as necessary

Guess what I had sitting on the shelf in my garage.. a Hammond isolation transformer 3840 VA. 32 amps at 120 volts..

[s/v Jedi]

Originally Posted by team karst

I'm confused. Are you not polarizing the output of the iso xfrm by grounding the neutral?

I am not. My output is 240V which is never grounded because there is no Neutral, just L1 and L2. Like a household 240V outlet like this one: https://www.amazon.com/Leviton-107-0..._df_B000FPDKOI

Only after the inverter/chargers I create a new Neutral using an autotransformer but even there I do not ground the Neutral. I use double pole breakers instead.

[team karst]

Ok. Floating scheme. Safer and unusual. It is the best for small designs. Although navy ships also do it. Its a good idea to monitor it for accidental grounding.