mains The Mains Electrical Thread

[TheQ]

I'd been thinking about how to start this thread over the weekend, since Vaughan's offer to discuss my electrical set up.  Since then other electrical questions have appeared in the CO thread, so I've started this thread to discuss Mains electrical problems open to anyones questions.

If the Mod's or original posters of the electrical questions would like to move them to this thread, then please do. Once they are dealt with, I'll post the proposed layout of electrics for my boat and we can tear that apart.

[ChrisB]

I can't comment as I don't know enough about the subject but would just like to say that  I would never hire, buy or anything else a boat that I had to plug in at night.

But then the perfect night for me before age got my joints was a small lidded boat like a Drascombe Coaster on the mud of an estuary like Breydon with my chain leading to an anchor in deeper water.

Lifting off the mud is a superb alarm clock and off you go, the magic morns is when that happens as the sun comes up.

As modern youth say "I just don't get this plugging in bit"

[JennyMorgan]

I have often considered spending the night on Breydon Flats but can you imagine the furour? Would have to take ground outside office hours otherwise the SOB would be dashing around and at any hour Hemsby Pie & Co might come dashing to the rescue! 

[BroadScot]

Hi TheQ,

I don't see any reason to move your new thread, and being a retired spark, shall read with interest. There are several other lecky members may also show interest.

Iain

[TheQ]

Since no one else has posted anything about electrickery, here's something that is taken from SHORELINE MARINE ELECTRONICS page on Earthing, which is relevant to Vaughans' and my posts on the CO thread. This is what I intend to be working from, with reference to the regulation liinks, shown further down this post. 

On another (non broads web site) it was interesting to note the USA regulations say, their mains Earth and DC earth must be bonded together.

Earthing Guidance Notes...    Information about earthing in marinas, small boats, houseboats     ............................................................................................. Earthing and electrical safety The practice of omitting the AC earth to craft earth connection (commonly referred to as equipotential bonding) is only allowed for small pleasure boats in the EU area (EN ISO13297). This practice is not permissible on houseboats in the UK, which are covered by a more stringent electrical safety standard (BS7671, which also applies to electrical installations on dry land). In the USA completely different regulations regarding RCD usage apply. A recent study of RCD reliability published in 2007 by the UK Electrical Safety Council found that about 3% of RCDs they tested did not work. (In this context 'did not work' translates to 'unable to protect against lethal electric shock'). Other studies find consistent results. The UK Electrical Safety Council report on RCD reliability is available here... RCD reliability It is simply not safe to rely on an RCD as the sole means of protection against electric shock; especially in a high-risk area such as a boat in a marina. Equipotential earth bonding is also required; just like in our homes on dry land. The safest option is to connect the AC earth to the craft's earth and fit a robust galvanic isolator or isolation transformer to mitigate any galvanic corrosion. ............................................................................................. Conflicting Philosophies for electrical safety There is some controversy as to why ISO 13297 allows the use of RCDs as the sole means of protection against electric shock without any other safeguards such as equipotential bonding (i.e. connecting AC protective earth to craft earth). All other electrical safety standards expressly forbid the use of RCDs as a sole means of protection against electric shock, and insist on equipotential bonding, especially in high risk areas. Here is the relevant paragraph from EN ISO 13297 (which applies only to small pleasure craft in the EU area) ISO 13297 section 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 isolating transformer is installed in the main supply circuit of the a.c. system (see Section 8.2), the negative ground terminal of the d.c. Systems need not be connected to the a.c. shore ground (protective conductor) This particular part of ISO 13297 puts electrical safety totally in the hands of the RCD, but RCDs are not 100% reliable. Using an RCD alone without protective earthing is not acceptable on dry land or in a houseboat. For example BS7671 section 415.1.2 states that; The use of RCDs is not recognised as a sole means of protection and does not obviate the need to apply one of the protective measures specified in Sections 411 to 414 The only measure that can realistically be applied here is Section 411 which requires that fault protection is provided by protective earthing, protective equipotential bonding and automatic disconnection in case of a fault... (BS 7671 411.1) Note that BS 7671 is the UK version of the international standard EN 60364 electrical installation for buildings which covers the EU area. It has sections applicable to marinas and houseboats but is not applicable to small pleasure boats. However, the general philosophy of how to use mains electricity safely is consistent throughout the EU area; a) use good quality earthing and Equipotential bonding. an RCD provides additional protection, particularly in high risk areas. c) RCDs are not allowed as a sole means of protection. ............................................................................................. Seems inconsistent ? Why ? The reason behind this earthing inconsistancy where EN ISO 13295 is different from all other advice is to reduce galvanic corrosion by preventing galvanic current flow from boat to shore through the (nonexistent) earth connection. However in the case where an RCD is the sole protection it does this at the expense of safety. There is a perfectly simple way to have a safe protective earth connection without increasing corrosion and that is to connect the AC protective earth to the boat earth (battery negative, engine block, any underwater metalwork etc.) and fit a galvanic isolator. or an isolating transformer which will be safe and will not increase galvanic corrosion. ............................................................................................. What are the consequences of a faulty RCD when there is no equipotential bonding ? Let's say you are in the engine room, perhaps doing some maintenance work using an electric drill or a lamp powered from the AC mains. Your boat is correctly wired in accordance with the electrical regulations for small pleasure craft (ISO 13297 etc). In order to save money on a galvanic isolator or isolating transformer your AC mains earth and the boat's earth (engine block etc) are not connected together... this is OK according to the applicable regulations, but... A fault develops in the drill or lamp and a live wire touches the engine block. This type of fault should trip the RCD on the shore power inlet, but the RCD has a fault of it's own and doesn't trip (see below for info about RCD reliability). The engine block and anything connected to it is now live. That means the DC system is now live, the prop shaft and propeller and sacrificial anodes are now live, and so the water near the boat is also live. The water around the boat will tend to conduct the live to earth but the connection is not reliable (especially on a plastic or wooden hulled boat) and is unlikely to be good enough to blow the main fuse or circuit breaker quickly enough (or at all) to protect anyone who happens to be in the water near the boat. Or a person on board who is touching the AC earth and the craft earth at the same time, maybe somebody is in the galley touching the sink (boat earth) and the fridge (AC earth)... This type of fault might kill immediately or it may go unnoticed for a long time, minutes, hours, days. Fire or electric shock are real possibilities and the longer the fault goes unnoticed the greater the chances of a serious outcome... ............................................................................................. So what's the difference when equipotential bonding (earthing) is fitted ? Go back to the previous scene in the engine room... if the AC earth was bonded to the boat earth (engine block etc) as soon as the live wire touches the engine block a fuse will blow (or the main circuit breaker in the shore power outlet). This disconnects the power immediately. ... No danger... This has at least two valuable consequences, the first is that it immediately removes any dangerous voltage from the faulty item and therefore the engine block etc don't become live. The second is that it lets you know something is wrong... mmm drill doesn't work... why ? Even if the RCD and all the fuses or circuit breakers were faulty and the main earth connection at the shore power outlet is faulty as well, there is a much reduced danger when equipotential bonding is fitted because all the exposed metalwork and the water around the boat are at the same potential. ............................................................................................. How reliable are RCDs ? There have been at least three recent studies on RCD reliability. The following is quoted from a 2007 report on RCD reliability from the Electrical Safety Council in the UK. These studies were all done in domestic houses and all produced a failure rate of about 3 per hundred units tested. The Electrical Safety Council's own survey during 2006 of approx 600 RCDs in domestic properties showed a failure rate of 2.8 per hundred tested. (ref The Reliability of RCDs in Domestic Properties, ERA Report Number: 2007-0274, produced for the Electrical Safety Council 2007) From research published in Italy in 1996, electromechanical RCDs in Italian residential properties had an average failure rate of 7.1%. When the RCDs were subject to regular testing, the figure fell to 2.8% From the available evidence, the primary mode of failure of the electromechanical RCDs tested in Italy was ingress of fine particles of dust and moisture causing the moving components within the RCDs to stick or to operate more slowly than intended. (Ref. Cantarella G., Caressin V., Tammasini R., Quality of Residual Current Operated Circuit Breakers, ETEP. Vol. 6, No. 3, pp 149-156, 1996) Electronic RCD manufacturers claim that their products are more reliable than electromechanical RCDs,. However, research carried out in the US in 2001 suggests that the reliability of electronic RCDs may be similar to that of electromechanical RCDs, The RCD failures in the US were attributed to the failure of electronic components. The failure rates were higher in cities with conditions of high humidity, which may not be relevant to conditions found in the UK. (Ref. GFCI Field Test Survey Report, NEMA, Rosslyn, USA, Jan 2001) Note that the above failure rates where in nice dry houses, increased failure rates are noted due to humidity and moisture ingress. There is no data for marinas available however it seems reasonably to assume failure rates will be the same as or higher than in domestic properties on dry land. The UK Electrical Safety Council report on RCD reliability is available here... RCD reliability ............................................................................................. Notes on the electrical regulations which apply to boats/P> Earthing on small craft up to 24 metres in the EU area is covered by ISO 13297. Earthing on houseboats in the UK is covered by the IEE wiring regulations (BS7671). The BMEA code of practice for electrical and electronic installations on small craft incorporates ISO 13297 and many other standards which are relevant to small pleasure craft (up to 24 metres) in the EU area. The code of practice is available from BMEA The Institute of Engineering and Technology (IET) have written a number of articles explaining BS7671 wiring regulations applicable to marinas, houseboats and pleasure craft... houseboat regulations IET article marina regulations IET article for a full list of articles on the IET website... IET articles index also... IET home page also see the... boat safety scheme For copyright reasons we cant reproduce the full text of the regulations, however here are interpretations of some of the relevant points. BS7671 (the IEE wiring regulations) applies to the marina wiring, socket outlets etc, and also to the internal wiring of houseboats (i.e. permanently moored residential boats supplied from a shore power socket outlet). Mains power outlets in UK marinas will normally have a 30mA RCD fitted in accordance with BS7671 section 709. This is because marinas are considered areas of increased risk of electric shock (ref BS7671 section 709.512.2). BS7671 sensibly requires that all exposed metalwork of a houseboat, including metal parts in electrical contact with the water, be bonded to earth with a specified minimum impedance. This is just as in a land-based residence where all exposed metalwork (e.g. gas, hot water, cold water, central heating pipes metal sinks and any structural metalwork) must be connected together. This is known as protective earthing and protective equipotential bonding. (BS7671 chapter 41 and Fig 709.1). Equipotential bonding in conjunction with an RCD and fuse or circuit breaker provides the best protection against electric shock or fire hazard to people in and around a building or boat. This is particularly relevant in wet areas and in the case of a boat/marina it will afford protection to anyone in the water near the boat as well as people on the boat or jetty. The anomaly where small craft covered by EN ISO 13295 are exempt from equipotential bonding (provided an RCD is correctly fitted) is a point of controversy with some electrical engineers who believe the relatively small cost saved by not fitting a galvanic isolator does not justify the reduction in safety.

[Vaughan]

Sorry to be late replying Q, but I have been having a day off after a slight contretemps on a different thread. Never mind!

Point 1/. I am not an electrician.

In my experience however, I think the big danger is that people seem to regard shore power as a sort of extension lead, and that they are protected by the trips on the shore power point, as they would be if they plugged a lead into the wall in their own home.

I was going to recommend the European Recreational Craft Directive (ERCD) as this was always my bible, but I see you have already found the appropriate ISO numbers.

Again, in my experience, I know that the most important thing is the earth. Not sure if our fittings were bonded to the DC negative but I don't think so. They were all protected by a bi-pole voltage trip on both sides, as well as an automatic polarity changer, as you cannot rely on the polarity of shore power supplies. It was also regarded as vital that all AC circuits should be independent of anything else in the boat, and all wiring runs were in protective conduits. 

A good piece of maintenance is to do a regular continuity test of the three pins in the shore cable. These are pulled on and off a lot and they can easily come loose inside, so you think you are earthed but you might not be!

I think you can guess what I am going to say - this is not a job for an amateur, which includes me. You would want your house to be wired by an electrician, for peace of mind, and the same should apply to your boat. I know that one of the main pleasures of boating is doing your own work on your own boat but I do not think of this as a DIY job.

Peachments in Brundall make what I think are the best shore power panels and they will advise you as to a recommended boatyard, if they don't fit it themselves. They make the panels according to your own requirements.

For an electrician, there is John Spruce, who has been mentioned on another thread. He was the chief engineer of Crown Cruisers and has fitted a lot of shore power in his time! If you contact him you will be in safe hands and please give him my kind regards. Andrew Peachment also!

 

[BroadScot]

22 minutes ago, Vaughan said:

A good piece of maintenance is to do a regular continuity test of the three pins in the shore cable. These are pulled on and off a lot and they can easily come loose inside, so you think you are earthed but you might not be!

This plug is very good for such applications. If there is an earth fault or leakage, it will show on the lights.

Iain

[TheQ]

As a rough outline my System, is planned to be, ( plug = Male exposed pins, Socket= Female concealed recepticles)

32A Plug--- 16Amp Fuse-  16A Socket  (this adaptor if required)

or

13A Plug--- 16A Cable- 16A Socket ( this adaptor if required)

16A plug to 16A cable to 16A Socket --- to 16A plug ( there will be 1 16A Plug each side of the boat)

16A Socket to 3 Position switch,  Port input --- OFF --- Starboard input.

From Switch to the equivalent of  this on a Panel.

followed by

From the polarity change over switch to the double pole RCD and mains Breaker.

And from there to the next unit, which isn't quite decided yet as I haven't yet chosen the inverter, many, but not all, have pass through and automatically switch themselves off when mains is present. So I may or may not need a mains selector switch to choose inverter or shore power.

From there to the ring main, I have considered a star mains system but for where I want sockets a Ring is more convienent.

[TheQ]

Ha!!!  BroadScot, Great minds think alike!!

 

 oops missed the Galvanic Isolator Just after the 3 postition switch.

Vaughan your concern over Battery chargers is correct, some have their output Negative bonded to Mains earth. 

This would not work in my situation, so I have 4 12V CTEK battery chargers to charge each battery bank in the 48V System, they DO NOT have their negative outputs bonded to earth, so therefore have floating outputs and can be used in such a manner.

[BroadScot]

9 minutes ago, TheQ said:

Ha!!!  BroadScot, Great minds think alike!!

Mine is over 30 years old ! Has saved me a few rattles over the years. One of the SSEB meter lads had a spare one and kindly gave it to me. That looks like a converted IP46 Box with a switch cut into it. I have found that slicing in a cross with a pocket knife  ensures it gives a good fit to flexible cables. However, a stuffing gland gives the best water tight fit.

Iain

[Vaughan]

Actually I was thinking of the standard European shore power plugs, similar to those fitted on camper vans. All marinas are (or bloody well should be) fitted with this type of fitting. The problem is that you have to pull rather hard to un-plug them and so the wires can come loose inside. 

 

[MauriceMynah]

Thank you Vaughn, I had been starting to think that I would like shore power on Nyx, and had wondered if it was a DIY project. I am more than happy to take your word for it (that alone must come as a great surprise to you ) that this is one for the professionals, though that does put the job on the back burner for a while.

[BroadScot]

1 minute ago, MauriceMynah said:

that this is one for the professionals,

Correct MM !!!

Iain

[TheQ]

I've just realised another oops on my rough description, in that, you need an RCD after the Inverter as well.

If you look at the Change over switch you have a couple of Lights, a waterproof Junction Box, a suitable Mains switch for which they charge £50 at most a tenners value in parts. Similarly Galvanic Isolators only have at most £20 worth of parts in them yet cost £100+.

Luckily with my 40 years of playing with tronics and trickery. I shall build my own, so all live equipment that is the wrong side of the RCD, will be in a waterproof control panel, that would need a screwdriver to open and will be labelled with the necessary warning signs.

[TheQ]

37 minutes ago, Vaughan said:

Actually I was thinking of the standard European shore power plugs, similar to those fitted on camper vans. All marinas are (or bloody well should be) fitted with this type of fitting. The problem is that you have to pull rather hard to un-plug them and so the wires can come loose inside. 

 

Naughty people you should always pull by the plug not by the cable...

I spent a while, repairing radio equipement where this sort of thing kept happening!!

[JanetAnne]

Does the 240v earth not automatically become bonded to the 12v negative through the engine, gearbox, engine bed assembly. That would be bonded and carry the 12v negative connections for starter motor etc?

[TheQ]

39 minutes ago, JanetAnne said:

Does the 240v earth not automatically become bonded to the 12v negative through the engine, gearbox, engine bed assembly. That would be bonded and carry the 12v negative connections for starter motor etc?

Not necessarily. it is the decision of the builder, whether to make the connection between 12VDC earth and 240V(230V) earth. If you read the long post I put up earlier,  in the section, Conflicting Philosophies for electrical safety.  You'll see there are fors and againsts for tieing the two together.

 This is of course in a wood or GRP boat, if you have a metal boat then yes the earths will automatically connect through the hull but you should properly make the connection somewhere for safety.

[LondonRascal]

I found this guide most helpful in understanding the concept - of installing mains electric on a boat.

I am not qualified so it might be a terrible example of how to do it, but then again it might be just right - and certain if you wish to understand matters more in a simple way this is the document to take a look at.

It is a PDF so you will need to click the link and download.

shore_power.pdf

[Vaughan]

1 hour ago, TheQ said:

Naughty people you should always pull by the plug not by the cable...

I am (naturally) talking about hire boats, where things must be "hirer-proof" if at all possible. In the case of shore power this is difficult, especially if the plug has been left lying on the quay, and then been run over by a customer's car!

What I do is remove the cable, bring the two plugs together and touch across the three pins (live, return and earth) with any old DIY ohm meter. If it don't beep, you ain't connected.

I also tell hirers on trial runs to always plug the boat in, before you plug in the bank. That way, if you drop the cable in the river on your way down the side deck, you won't blow all the fuses in the boatyard! The reverse is true when un-plugging.

That is if you remember to unplug. In this case you will cast off your moorings, climb up to the flying bridge and select ahead gear, having looked carefully both ways. You get about 25 metres off the quay and then POINK!

Sure enough, when we installed shore power in St Gilles, the first one to do this was me, to a round of applause from all my staff who were watching.

[MauriceMynah]

If I do hasve shore power put in Nyx, I'd like the 'boat socket' to be through the helm, so I cant turn the wheel with it plugged in. Does that make sense and is it a reasonable thing to do?

[TheQ]

That explanation, linked to by LondonRascal, I don't think is too far out. I dislike the pattress (back box) shown with the picture of the mains socket, as it has open gaps in it's top surface which would allow the odd drip of water to fall in. I wouldn't expect waterproof sockets / backboxes to be used, but open tops are not needed.

Personally I would go for MK brand plugs and sockets of any type where possible.

Some years ago On a Open university residential course, we dissected and tested MK plugs and sockets and compared them against those bought cheap of a market. Absolutely everything on a MK plug is better quality from the plastic been much harder to melt, to the quality of the metal in the contact for conduction. Also they are generally of better design in the first place.

 I would add, that I am approaching this thread as someone who has fitted electrics for technical Electronic test stations, wiring in my model railway shed, and house. I have since read up on marine installations, but would bow to the experience of Vaughan or any other boatbuilder / marine electrician on this site.

 SInce my boat is electrically driven, I can probably fit an interlock, so I can't drive off plugged into the mains, though I can guess what will happen the day before I fit the interlock!

[grendel]

Just one thought occurs to me, the 16A plugs and leads are not fused (I had to think about this yesterday when constructing an extension lead to connect to a camping electrical outlet, and run to a standard mains extension socket. a 13A extension lead is protected by a fuse in the plug - the equivalent 16A blue plug has no fuse, so the extension cable from the electric post to the boat, has no fuse. there should be a trip on the post, which might or might not protect you, but if your extension cable were to be damaged, or the outer sheath of the cable be damaged and accidentally dipped into the water, where would that leave you.

Another reason the cable should be inspected carefully before use, the bare minimum is careful inspection of the cable along the whole length before you plug it in.

[TheQ]

13 minutes ago, MauriceMynah said:

If I do hasve shore power put in Nyx, I'd like the 'boat socket' to be through the helm, so I cant turn the wheel with it plugged in. Does that make sense and is it a reasonable thing to do?

It would be quite possible to do, depending on whether there was room for a surface mount Plug between the wheel and Bulkhead OR if you have a flush  / Slightly protruding  Plug on the wheel side, whether you had room on the other side of the bulkhead for the rest of it. I've not come across this idea before Neither have I read anything in the regs that would stop it.

Ah I see your picture / Avatar, if that is the boat and it's a later Elysian/ Bounty 27 then there would be room for a flush mount plug to be mounted behind the wheel in the console. (I've done away with my console, as I wanted more room in the Centre cockpit).

[ChrisPZ]

A lot of good points above - especially bonding.

I refitted the AC control panel in Princess Zena a couple of years ago and wanted to add a couple of things for you may want to consider for your design (whether competent DIYer or giving a spec to a professional) - or not.

We have have separate socket and lighting circuits for fore and aft, as it made running radial circuits easier (they could be protected with a relatively small cb, didn't need to be run in large cable and could be isolated separately) - although this was mainly due to layout and the original 60s 240v generator installation which was still partly in use.

The charger and immersion heater are on their own individual circuits - these are behind an interlock so that they are only energised when the shorepower is connected - meaning there is no chance of the inverter mistakenly running the charger/immersion.

Perhaps most important - Vaughan's post about using Peachments to build a panel: After pricing up a diy solution using a mixture of domestic consumer unit parts and manual changeover switches, I went to Brian Ward with a spec and panel design of what I would really like - they made an engraved panel to spec. with auto changeover, all the contactors for the interlocked circuits, wired to a short loom and termination panel, for around £60 more than my DIY solution.  The end result is far better.

 

[TheQ]

Reading Grendels, notes on fuses, I Would also hope that the Electricity posts are fitted with RCDs as a fuse will not stop you being electrocuted. It's also worrying reading the post, I put almost on the top of this thread, and they report 3 in 100 RCDs do NOT trip when they are supposed to!! I must go and Investigate an Electricity post, I'll need to use one soon!!!