Interested minds ... (boat electrical systems, the 'Big picture').

[T_i_m]

Hi all, (and thanks for the add to the mods) first post here and I hope here is the right place for it.

 

I'm an ex electronics / datacomms / network systems field support tech who has built a couple of small boats and a kitcar and restored many machines (mainly cars and motorbikes), designed, built and raced an electric motorcycle (alongside Cedric Lynch that some of you may have heard of) etc.

 

I have also grown up in and around boats, mainly small cruisers and dinghies, courtesy of Dad, an EX Merchant Navy skipper.

 

I am friends with a guy who lives locally on a narrow boat and nowdays needs little, often electric things sorted out and because of mobil/flexibility issues, can't easily do them himself every time.

 

Whilst I understand and have worked with 'mains' and 12-48V DC, batteries of all different chemistries, alternators, inverters, solar panels, MPPT / PWM chargers, IC engines, motors and the like, I'm not sure how all these interrelate when on a narrowboat. Is there / should there be some clever central switching unit that handles the synchronisation of the Travel Pack AC with Inverter ac and both are switched out when connecting shore power etc?

 

He's had a new Beta engine fitted a while back (I've seen / heard it running <g>) and it has a Travel Pack of some sort that isn't currently (excuse the pun) wired up but it may be that it wasn't wired back up for a good reason (read of damaged crankshaft keyways etc). I had worked out that it was a mains level thing from an info-thin telephone conversation earlier. 😉

 

So, I was interested to learn if there was a good site that covers this sort of stuff at a level that I might appreciate please? 

 

My dream would to be handed a boat wide wiring diagram and a wodge of datasheets for each of the bits to sit down and absorb with a brew and him filling in any details but I'm not sure if that is being too hopeful?

 

Thanks for your time in advance. 😉

[Alan de Enfield]

The UK canal system is a very small market for boats, and in particular Narrowboats (and no where else in the world is daft enough to have boats under 7 feet wide).

 

What you need to understand is that narrowboat building is a 'cottage industry' and no two will ever be the same, even from the volume' (I use the term loosely) manufacturers the customer will have differing requirements with a variety of appliances and that variety can be placed anywhere in the steel shell. Galley (Kitchen) for example can be at the stern, in the middle or at the bow so the wiring for the domestic appliances can be 'anywhere'.

 

As you may be aware- on the low voltage side the choice of wiring size is not based on current rating but on volt drop, so the 12v cable from the battery to the fridge (2 metres away) will be much much smaller than that for a fridge 20 metres away. I had to use 8mm2 wiring to get a fridge to run correctly when it was only about 4 metres from the power source.

 

You may wish to aquire and read the ISO standard for wiring 'small craft' as it details all you need to know (ie NO twin & earth allowed) and specifies things like the maximum numer of terminals on a post etc etc etc.

 

 

ISO 13297:2020

This document specifies the requirements for the design, construction and installation of the following types of DC and AC electrical systems, installed on small craft either individually or in combination:

a) extra-low-voltage direct current (DC) electrical systems that operate at nominal potentials of 50 V DC or less;

b) single-phase alternating current (AC) systems that operate at a nominal voltage not exceeding AC 250 V.

 

Edited September 3 by Alan de Enfield

[T_i_m]

Thanks very much for the reply Alan,

 

I appreciate boats are likely to be different layouts and have different kit but I was wondering more about the 'core' solutions used for managing say all the electrical power sources? That might range from fairly automatic to mostly manual and it would be the former that I might like to understand re what might be 'fairly typical' etc.  I am aware some of the Mains <> Battery <> inverters <> Solar controllers can deal with simultaneous multiple inputs and load types but wasn't sure how say a Travel Pack might fit in? That might be just another input on a suitable controller or just a two way isolator switch?

 

eg, 'You currently have shore power then run up the engine' sort of thing.

 

As for voltage drop, Ohms law will generally deal with most (especially DC) situations. 😉

 

The electric motorcycle I built I measured the voltage drop over the longest traction conductor and used that into a small LCD voltmeter calibrated to read amps drawn. The A/B/ total voltage was easy (just potential dividers into the voltmeter) but for the speed I fitted a magnetic sensor over the final drive gear and then some F to V electronics, also fed into said LCD display (via some suitable switching etc). I calibrated it on my bench with a frequency generator and the wheel rolling radius and so had the frequency / mph. According to the RADAR beside the track at the TRRL, it was spot on. 😉 

 

Thanks for the heads-up on the relevant ISO doc. I don't predict I would be adding any wiring and certainnly not the 240V stuff but it would still be good to know what is supposed to be there.

 

I've picked up some stuff about Travel Packs here and will have a rummage about on Youtube etc.

 

Cheers.

[MtB]

13 minutes ago, T_i_m said:

I've picked up some stuff about Travel Packs here

 

I suspect "Travel Pack" is a misnomer for "Travel Power".

 

Or are both a thing?

Edited September 3 by MtB
Missing word

[blackrose]

This old website has some examples of typical AC & DC boat wiring systems if that's what you were looking for?

 

http://www.smartgauge.co.uk/nb_ac_sys.html

[T_i_m]

55 minutes ago, MtB said:

 

I suspect "Travel Pack" is a misnomer for "Travel Power".

 

Or are both a thing?

I may well have forgotten what he said or he may have forgotten what it was called but hopefully someone will clear it up for me. 😉

49 minutes ago, blackrose said:

This old website has some examples of typical AC & DC boat wiring systems if that's what you were looking for?

 

http://www.smartgauge.co.uk/nb_ac_sys.html

Thanks very much for that Blackrose, yes, that's very much the sort of thing (and further linked info) that I was thinking of (especially all the galvanic stuff) and would be a good grounder to it all.

 

'A picture speaks 1000 words', well, it does for me anyway. 😉

 

Thanks again.

[Alan de Enfield]

1 hour ago, T_i_m said:

'A picture speaks 1000 words', well, it does for me anyway. 😉

 

 

Just be aware that not everything you read on the smartgauge site is totally correct.

 

For example it states :

 

 The installation must include one or more RCDs that protect all circuits.

 

However, in the Boat Safety Scheme (boaty equivalent to the MOT) it states that for privately owned boats it is advisable but NOT mandatory. (It is only mandatory in commercial boats [hire boats etc] where customers are at risk).

 

Extract from the BSS :

Guidance for owners – there is no BSS Requirement for a Residual Current Device (RCD) to be
incorporated within the main consumer unit or otherwise installed. However, it is strongly
recommended that a Residual Current Device (RCD) is installed to provide appropriate electric shock
protection on AC systems.

 

Smartgauge has some very good information, but it should always be read along side the legislation so an informed decision can be made.

 

Edited September 3 by Alan de Enfield

[nicknorman]

On the mains AC side, a lot of modern boats have a Combi inverter charger. These devices are connected to 12v (or whatever) DC by fat cables. They have at least 2 and often 3 sets of mains ac connections. Typically one mains input and 2 mains outputs. One mains output is just a “pass through” for the mains input and would therefore only be powered when connected to shore power or Travelpower. This might be used eg for an immersion heater that you didn’t want to run from the batteries.

 

The other output is the continuously-on output. This is internally fed either from the inverter circuitry or from the incoming  shore power etc, or both.

If shore power is present, this is passed through and powers the battery charger circuitry. In the background the Combi is tracking the phase and frequency of the shore power. If the shore power is unplugged then the inverter takes over virtually instantly at the correct phase etc. When shore power is plugged in again, the Combi inverter takes a few seconds to synchronise with the shore power frequency and phase, then switches over to the shore power and shuts down the inverter circuitry, so that again, there is no jump in phase or break in supply.

 

You can set a maximum AC current input limit for the case when the shore bollard has a smaller than normal breaker, and if the boat demands more ac power than is allowed by this limit, the inverting section starts up and merges with the shore power to supplement it (at the expense of draining the battery, obviously). This comes by various names such as “power support”. So whilst the standard shore bollard and boat plug/socket is rated at 16A, with power support you could turn on appliances totalling say 24A, 16A from shore and 8A from the inverter.

 

If you have a Travelpower you need some means to select between it and shore power because it is verboten to connect 2 ac sources together unless they are phase matched! A lot of people have a simple break before make rotary switch for that, but we have an automatic switch which defaults to shore power, unless there is power on the Travelpower input in which case it switches over to that. It is important that the travelpower can’t make the prongs of the shore power socket live.

[David Mack]

32 minutes ago, nicknorman said:

It is important that the travelpower can’t make the prongs of the shore power socket live.

Don't you mean 'mains inlet'? Technically a plug not a socket , although the term is often misused.

[nicknorman]

57 minutes ago, David Mack said:

Don't you mean 'mains inlet'? Technically a plug not a socket , although the term is often misused.

Probably. Or not.  I’d say it is a bit more complicated than that as you have male and female plugs, and male and female sockets. I think the shore lead plugs into the boat’s socket, although of course the shore lead plug is female and the boat’s socket is male.

Edited September 3 by nicknorman

[blackrose]

7 hours ago, Alan de Enfield said:

 

 

Just be aware that not everything you read on the smartgauge site is totally correct.

 

For example it states :

 

 The installation must include one or more RCDs that protect all circuits.

 

However, in the Boat Safety Scheme (boaty equivalent to the MOT) it states that for privately owned boats it is advisable but NOT mandatory. (It is only mandatory in commercial boats [hire boats etc] where customers are at risk).

 

Extract from the BSS :

Guidance for owners – there is no BSS Requirement for a Residual Current Device (RCD) to be
incorporated within the main consumer unit or otherwise installed. However, it is strongly
recommended that a Residual Current Device (RCD) is installed to provide appropriate electric shock
protection on AC systems.

 

Smartgauge has some very good information, but it should always be read along side the legislation so an informed decision can be made.

 

 

Surely if the Smartgauge recommendations exceed the safety standards shown in the legislation then if one questions it's correctness you'd have to say it goes beyond the requirements of the legislation. 

 

The Smartgauge site represents the views of its author and I'm pretty sure he'd argue that it's the legislation that's wrong in not making protection on all AC circuits mandatory. 

[Alan de Enfield]

5 hours ago, blackrose said:

 

Surely if the Smartgauge recommendations exceed the safety standards shown in the legislation then if one questions it's correctness you'd have to say it goes beyond the requirements of the legislation. 

 

The Smartgauge site represents the views of its author and I'm pretty sure he'd argue that it's the legislation that's wrong in not making protection on all AC circuits mandatory. 

 

I was simply pointing out that it is incorrect to say that an RCD MUST be used.

 

It is certianly an advisory, and gives you additional protection, but a compulsory installation it is not.

 

It's like a tyre manufacturer saying you must change your tyres when the tread depth gets to 5mm, when the UK legal requirement is 1.6mm.

5mm does give you better road holding, but it is not what the requirements / laws say.

[MtB]

11 minutes ago, Alan de Enfield said:

 

I was simply pointing out that it is incorrect to say that an RCD MUST be used.

 

It is certianly an advisory, and gives you additional protection, but a compulsory installation it is not.

 

It's like a tyre manufacturer saying you must change your tyres when the tread depth gets to 5mm, when the UK legal requirement is 1.6mm.

5mm does give you better road holding, but it is not what the requirements / laws say.

 

 

It never ceases to amaze me how much trouble so many people have distinguishing between mandatory requirements, and things which are optional but actually very good practice and well worth doing. 

 

 

 

 

 

 

[Alan de Enfield]

16 minutes ago, MtB said:

 

 

It never ceases to amaze me how much trouble so many people have distinguishing between mandatory requirements, and things which are optional but actually very good practice and well worth doing. 

 

 

 

 

 

 

 

Yes - you'd have thought that "Smartgauge" would have been savvy enought to know this, they could simply have written, "it is not a mandatory requirement but we recommend it, as it is good practice" rather than you "must"

 

Maybe they were just 'saving ink'.

Edited September 4 by Alan de Enfield

[nicknorman]

50 minutes ago, Alan de Enfield said:

 

I was simply pointing out that it is incorrect to say that an RCD MUST be used.

 

It is certianly an advisory, and gives you additional protection, but a compulsory installation it is not.

 

 

I’m surprised by your major faux pas! Whilst it is not compulsory in order to satisfy the BSS, it is of course mandatory to be compliant with your favourite thing the RCD/RCR. ISO 13297 says 

The craft shall be provided with earth-leakage protection in the main supply circuit by
a double-pole RCD having a maximum nominal trip sensitivity of 30 mA and 100 ms maximum trip time located in accordance with 7.2.2, or
each receptacle located in the galley, toilet, machinery space or weather deck shall be protected by a GFCI (RCD) having a maximum sensitivity of 10 mA.

[MtB]

51 minutes ago, nicknorman said:

 

 

I’m surprised by your major faux pas! Whilst it is not compulsory in order to satisfy the BSS, it is of course mandatory to be compliant with your favourite thing the RCD/RCR. ISO 13297 says 

The craft shall be provided with earth-leakage protection in the main supply circuit by
a double-pole RCD having a maximum nominal trip sensitivity of 30 mA and 100 ms maximum trip time located in accordance with 7.2.2, or
each receptacle located in the galley, toilet, machinery space or weather deck shall be protected by a GFCI (RCD) having a maximum sensitivity of 10 mA.

 

Which illustrates the thing I usually point out but forgot to this time.

 

When wanting to know if <something> is mandatory, first one must establish which set of regulations one is needing to comply with.

[David Mack]

1 hour ago, nicknorman said:

Whilst it is not compulsory in order to satisfy the BSS, it is of course mandatory to be compliant with your favourite thing the RCD/RCR. ISO 13297 says ...

Although as has been pointed out on the forum numerous times before, the RCD/RCR does not require compliance with ISO standards; just that meeting ISO standards gives deemed compliance with RCD/RCR requirements, but a boatbuilder/fitter is still free to do it other ways that meet the essential safety requirements.

[nicknorman]

6 minutes ago, David Mack said:

Although as has been pointed out on the forum numerous times before, the RCD/RCR does not require compliance with ISO standards; just that meeting ISO standards gives deemed compliance with RCD/RCR requirements, but a boatbuilder/fitter is still free to do it other ways that meet the essential safety requirements.

But in this case not fitting an RCD would not be a justifiable alternative means of compliance. The only justifiable reason for not having an RCD would be if there were no mains electricity on the boat, in which case the ISO is not applicable.

[Alan de Enfield]

1 hour ago, nicknorman said:

 

 

I’m surprised by your major faux pas! Whilst it is not compulsory in order to satisfy the BSS, it is of course mandatory to be compliant with your favourite thing the RCD/RCR. ISO 13297 says 

The craft shall be provided with earth-leakage protection in the main supply circuit by
a double-pole RCD having a maximum nominal trip sensitivity of 30 mA and 100 ms maximum trip time located in accordance with 7.2.2, or
each receptacle located in the galley, toilet, machinery space or weather deck shall be protected by a GFCI (RCD) having a maximum sensitivity of 10 mA.

 

 

 

Yes the RCR does require RCD installation - but as MTB so frequently points out ' which specification do you work to' ?

To get your C&RT licence the BSS is the minimum,

 

 

I am surprised that you would quote an out of date specification which was withdrawn in 2014 !

 

Whilst the technical criteria are the same the wording in the current issue of the specification  is somewhat different (no mention of toilets etc)

 

 

 

13.3.2 Both current-carrying conductors of each branch circuit in unpolarized systems shall be provided with overcurrent protection by double-pole circuit breakers and double-pole switches, at the point of connection to the main panel board bus.
NOTE Use of a reverse polarity indicator presumes compliance with 13.3.1.

 

14 Ground-fault protection/earth-leakage protection, AC systems
14.1 RCDs shall be of the trip-free type.
14.2 The craft shall be provided with earth-leakage protection in all AC (e.g. shore power, inverter, generator) sources by one or more double-pole RCDs having a maximum nominal trip sensitivity of 30 mA and 100 ms maximum trip time.
NOTE Common standards for RCD construction are IEC 60898-2:2016[7], IEC 61009-1:2010[8] and IEC 61543:1995[9].
14.3 The RCD device shall have an internal circuit for manually testing the trip function.

 

15 Panel boards (switchboards), DC and AC systems
15.1 The front side of panel boards, i.e. the switch and circuit breaker operating face, shall be readily accessible. In DC systems, the rear side, i.e. the terminal and connection side, may be readily accessible, in AC systems the rear side shall be accessible.

[nicknorman]

43 minutes ago, Alan de Enfield said:

 

 

 

Yes the RCR does require RCD installation - but as MTB so frequently points out ' which specification do you work to' ?

To get your C&RT licence the BSS is the minimum,

 

 

I am surprised that you would quote an out of date specification which was withdrawn in 2014 !

 

Whilst the technical criteria are the same the wording in the current issue of the specification  is somewhat different (no mention of toilets etc)

 

 

 

13.3.2 Both current-carrying conductors of each branch circuit in unpolarized systems shall be provided with overcurrent protection by double-pole circuit breakers and double-pole switches, at the point of connection to the main panel board bus.
NOTE Use of a reverse polarity indicator presumes compliance with 13.3.1.

 

14 Ground-fault protection/earth-leakage protection, AC systems
14.1 RCDs shall be of the trip-free type.
14.2 The craft shall be provided with earth-leakage protection in all AC (e.g. shore power, inverter, generator) sources by one or more double-pole RCDs having a maximum nominal trip sensitivity of 30 mA and 100 ms maximum trip time.
NOTE Common standards for RCD construction are IEC 60898-2:2016[7], IEC 61009-1:2010[8] and IEC 61543:1995[9].
14.3 The RCD device shall have an internal circuit for manually testing the trip function.

 

15 Panel boards (switchboards), DC and AC systems
15.1 The front side of panel boards, i.e. the switch and circuit breaker operating face, shall be readily accessible. In DC systems, the rear side, i.e. the terminal and connection side, may be readily accessible, in AC systems the rear side shall be accessible.

But if you are going to build a new boat, surely you should aim to comply with the RCD/RCR?
 

I am not at all surprised that I quoted an out of date version, since the up to date versions are very expensive and I am not building a boat!

[Eeyore]

This is quite an interesting read.

https://www.theiet.org/media/2734/practical-considerations-for-dc-installations.pdf

Quite specific (by standard) of what can and can not be used in shore based dc systems.

Many of the "can not" items are frequently found in use for dc on canal boats, everyones favourite being the old round pin plugs and sockets.

Interesting that ac standards are very similar shore side and onboard, but dc standards not so much.

[Alan de Enfield]

34 minutes ago, Eeyore said:

This is quite an interesting read.

https://www.theiet.org/media/2734/practical-considerations-for-dc-installations.pdf

Quite specific (by standard) of what can and can not be used in shore based dc systems.

Many of the "can not" items are frequently found in use for dc on canal boats, everyones favourite being the old round pin plugs and sockets.

Interesting that ac standards are very similar shore side and onboard, but dc standards not so much.

 

 

It would be an interesting exercise to compare the IET document "Electrical Installations For Small Boats" with the above and with the ISO 13297:2020 but bearing in mind that a 'guide' cannot replace or overide a specification.

 

 

Edited September 4 by Alan de Enfield

[Eeyore]

26 minutes ago, Alan de Enfield said:

 

It would be an interesting exercise to compare the IET document "Electrical Installations For Small Boats" with the above and with the ISO 13297:2020 but bearing in mind that a 'guide' cannot replace or overide a specification.

 

 

COP for comparison. 

 

Looks a lot like thread drift, but actually shows that someone with this type of shore side DC experience will be far less qualified to work on your boat than their AC counterpart!

Of course we mustn't forget

 https://bmeea.co.uk/2023/06/30/bmeea-code-of-practice-edition-6-has-been-published-get-your-copy-now/

A bit on the pricey side for fireside reading, but very much what @T_i_m asked for.

 

Edited September 4 by Eeyore

[T_i_m]

23 hours ago, Alan de Enfield said:

<snip>

Smartgauge has some very good information, but it should always be read along side the legislation so an informed decision can be made.

Understood and thanks for the heads up.

23 hours ago, nicknorman said:

On the mains AC side, a lot of modern boats have a Combi inverter charger. These devices are connected to 12v (or whatever) DC by fat cables. They have at least 2 and often 3 sets of mains ac connections. Typically one mains input and 2 mains outputs. One mains output is just a “pass through” for the mains input and would therefore only be powered when connected to shore power or Travelpower. This might be used eg for an immersion heater that you didn’t want to run from the batteries.

 

The other output is the continuously-on output. This is internally fed either from the inverter circuitry or from the incoming  shore power etc, or both.

If shore power is present, this is passed through and powers the battery charger circuitry. In the background the Combi is tracking the phase and frequency of the shore power. If the shore power is unplugged then the inverter takes over virtually instantly at the correct phase etc. When shore power is plugged in again, the Combi inverter takes a few seconds to synchronise with the shore power frequency and phase, then switches over to the shore power and shuts down the inverter circuitry, so that again, there is no jump in phase or break in supply.

 

You can set a maximum AC current input limit for the case when the shore bollard has a smaller than normal breaker, and if the boat demands more ac power than is allowed by this limit, the inverting section starts up and merges with the shore power to supplement it (at the expense of draining the battery, obviously). This comes by various names such as “power support”. So whilst the standard shore bollard and boat plug/socket is rated at 16A, with power support you could turn on appliances totalling say 24A, 16A from shore and 8A from the inverter.

 

If you have a Travelpower you need some means to select between it and shore power because it is verboten to connect 2 ac sources together unless they are phase matched! A lot of people have a simple break before make rotary switch for that, but we have an automatic switch which defaults to shore power, unless there is power on the Travelpower input in which case it switches over to that. It is important that the travelpower can’t make the prongs of the shore power socket live.

Thanks very much for your time and trouble on that Nick. I'm going to have to read it a few times to fully absorb it but it all made sense etc.

 

When you stated the Combi units typically had one ac input I immediately thought 'so how to we deal with 'shore'  and 'Travel-power' but then you answered that at the end. 😉

 

One further question if I may ... do I read you right that there could well be at least a couple of ac outlet circuits, like where you see raw mains and UPS > generator outlets in hospitals / datacentres?

[Eeyore]

A quick reminder for some, and maybe news to others:

In a world full of standards there is no such thing as standard. 😉