mains The Mains Electrical Thread

[TheQ]

ChrisPZ.

I hadn't got as far as 240V Immersion heaters, I will need some system to ensure My immersion heater is on only when the generator is on or shore power connected although my battery pack supplies a 10Kw electric motor and could run the emersion heater, it would be unnecessary use of battery cycles..

The chargers will need taking from the Mains input Before the Inverter, so that they only come on, on shore power.

 I'm fairly happy with the 12v lighting onboard, when they have LEDs, fitted and a couple of small LED spots are also fitted they will not have enough drain to worry my batteries. 

I must admit your Idea for going to Brian Wards may be a solution, as a nice engraved panel is something I would have to buy anyway, it will depend on how the costings finally work out, once I'm happy with the design.

[BroadScot]

Just as a side issue, MK are not as good a quality as they use to be, and overpriced for what they are, indeed I returned more of their accessories than any other make. I would never use VOLEX, but their items have improved. CONTACTUM are much improved, Marbo and BG from Screwfix are a good price also. So shop about is my advice.

Iain

[ChrisPZ]

The reason for the including contactors to control the non-inverter circuits is that they can be controlled after the RCD, meaning we only need one RCD main switch.

The mix of 12v and 240v lighting we have is a throwback to the generator originally fitted, but it is quite useful when doing work on one system or the other.

[Vaughan]

Well Q, we came a bit late to this thread, but we are making up for lost time!

There is a lot to discuss here, so let me take a point at random.

 "EARTH". I would just like to clarify the use of this term as it may help to understand our discussions. 

DC circuits are positive and negative, but there is no "earth". Furthermore, the negative side is not necessarily the return. Many old American vehicles and boats are wired "positive earth". The use of negative earth in DC circuits on boats has become the norm, owing to electrolytic action in salt water. If a boat is wired "negative earth" this will mean that electrons will eat away the skin fittings in the hull rather than the prop shaft, inboard bearings, or the rudder, since the skin fittings are cheaper to replace. This is also why steel hulls have to have ALL of their fittings electrically bonded.

The 12 volt (or 24) circuits in a boat are similar to a road vehicle and are known as "earth return" or insulated return". Earth return means that the engine and chassis are being used as a convenient return for the negative, which then needs just one cable, back from the engine to the battery. In a steel hull the circuits must be "insulated return" and separate from the engine. Hence you will see things like temperature gauge senders, with two wires instead of one.

 

What I hope I have explained, is that a 220 volt AC circuit does not mix well with all this and must be kept separate. If this circuit is not well earthed to shore (and here is the real meaning of "earth") then it will find its own way, through somewhere "nasty" in the boat, such as the domestic water system.

Imagine a circuit where where only the live side is protected and is feeding an immersion heater in the hot water tank. After a couple of years the heater gets corroded (which they do) and starts leaking current. If the polarity from the shore has been reversed, then the new "live" side is not protected, and if there is not a good earth to shore, the current will find its own way out of the boat through the skin fittings and turn your domestic water system into a giant electric kettle. Believe me, I have seen it happen.

And don't forget of course, that if you are working on the engine at the time, or even have your hands on the steering wheel, or a water tap, it might find its way to earth through you!

[MauriceMynah]

I think I'll stay 12 volt DC alone

[Bound2Please]

5 minutes ago, MauriceMynah said:

I think I'll stay 12 volt DC alone

Thats what we are MM and I was Senior Tech for Britsh Rail CS&TE dept in a former life...

Charlie

[ranworthbreeze]

6 hours ago, BroadScot said:

Just as a side issue, MK are not as good a quality as they use to be, and overpriced for what they are, indeed I returned more of their accessories than any other make. I would never use VOLEX, but their items have improved. CONTACTUM are much improved, Marbo and BG from Screwfix are a good price also. So shop about is my advice.

Iain

Hi Iain,

Agreed on the MK, but I still always fit them, an option in the past used to be Crabtree, I have seen far many of the cheaper sockets with signs of overheating around the outside of the live connection.

With regards to leave it to the professional, that is down to how forgetful the professional is, seen yet again far too many lapses in concentration, fitting the wrong breaker, getting the cable the wrong side of the connection resulting in arcing, burnt out connectors etc.

Regards

Alan 

[BroadScot]

1 minute ago, ranworthbreeze said:

Agreed on the MK,

Hi Alan,

G E T till taken over were bullet proof, especially their 45amp pull switch for showers. Never returned anything made by G E T.

I had trouble with the MK 45amp DP switches used for double ovens, the silver contacts melted know matter how tight the terminals were.

The joys of our industry ! Basically dear is not always best, but using cheaper brands can prove a bargain, when in doubt, always use a qualified Electrician. You know it makes sense.

Iain

[HemsbyPie]

On 15 August 2016 at 9:23 AM, JennyMorgan said:

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! 

I doubt you could afford us... 

[JennyMorgan]

49 minutes ago, HemsbyPie said:

I doubt you could afford us... 

Not if you all want breakfast!

[Wonderwall]

Hi all

im a sparky to trade. Though marine electrics is something I have had very little dealing with.

My take on the info so far is really not to mess about with it unless you totally understand what is going on. A little knowledge is a very dangerous thing.

RCDs , when tested by the test button regularly are very reliable, branded ones of course. I would imagine the vibration on a boat could play havoc with terminations which then would require continual assessment.

Water and electricity is obviously a dangerous mix which needs some particular respect.

Id be tempted to stick at 12 volts. It is boating after all and most things will easily run on this.  I'm a bit of a dinosaur though 

[Viking23]

If you have say an immersion on board connected to shore power, and you loose the neutral connection, anywhere between the electric post and the heater, then any neutral wire on the boat will be at live potential, as it is fed through the low resistance of the immersion heater. 

So wiring of ALL components must be wired correctly, and in accordance with the wiring regs. They are not a fit and forget item either, unfortunately there are no yearly or 4 yearly inspections of the wiring or cables.

The hook up cable is vulnerable, it can act as a third mooring line, be a trip hazzard, run over with trolleys, obtain gravel and concrete rash as it rubs over harsh surfaces.

When was the last time you checked the hook up cable? are all connections sound, and is the cable strain relief doing the job at both ends.

On standard 13A plug tops I usually leave the earth wire longer, and the live as short as possible, so if the cable is snagged, the live pulls first, and the earth hangs on till the bitter end.

On hook up cables, and many portable appliances, drills, hedge trimmers etc,  they are vulnerable to breaking at the point of entry to the plug socket or point of entry to the appliance, sometimes just cutting off 4" is enough to reterminate them.

 

[Bound2Please]

19 minutes ago, Viking23 said:

On standard 13A plug tops I usually leave the earth wire longer, and the live as short as possible, so if the cable is snagged, the live pulls first, and the earth hangs on till the bitter end.

 

 

Isnt that the way a standard 13a plug top was designed to be wired up????????

Charlie

[Vaughan]

Perhaps we are beginning to realise why I don't like immersion heaters on boats. A good calorifier can provide adequate hot water for the day, after only about 2 hours running, provided the engine has come up to optimum temperature (85-90 degrees).

You may also notice that I seem to be telling disaster stories about shore power, when I am the one who is strongly pushing for its use on a different thread. This is because I have a lot of experience in using it, so I know the pros and cons. It makes an enormous difference to the use of a modern boat and if it were widely available for modern Broads boats, it would cure the problem of running engines on moorings. However, it needs to be used sensibly and most important, it needs to be installed properly.

Another thought - what about these modern boats with all their gadgets, most of which, even the TV nowadays, are running on AC, through an inverter? This means you already have 220v circuits on board, with all the potential problems that go with them. Where do these circuits find their earth? Perhaps an electrician can answer that?

[MauriceMynah]

I know when I'm out of my depth, and I sure am here, so a question.

The only use I have for 240 volts will be the running of a vacuum cleaner, and a jet wash. I was thinking of buying one of those camping leads with the blue round end at one end and a line of four 13 amp sockets at the other.

Basically my question is, Does that make a safe way of using the power posts available?

My battery charging and hot water come from the engine, which provides sufficient for my usage.

[BroadScot]

39 minutes ago, MauriceMynah said:

I know when I'm out of my depth, and I sure am here, so a question.

The only use I have for 240 volts will be the running of a vacuum cleaner, and a jet wash. I was thinking of buying one of those camping leads with the blue round end at one end and a line of four 13 amp sockets at the other.

Basically my question is, Does that make a safe way of using the power posts available?

My battery charging and hot water come from the engine, which provides sufficient for my usage.

Use one of these on your extension MM, that way any faults with the appliance, it will trip.  http://www.safetyshop.com/rcd-adaptor.html?gclid=CjwKEAjwltC9BRDRvMfD2N66nlISJACq8591h8Os8lRO7YPr7TuZeEyhf-fjF9RdD0vwdUgphhcrrRoCDk_w_wcB

[Vaughan]

1 hour ago, MauriceMynah said:

 

I know when I'm out of my depth, and I sure am here, so a question.

The only use I have for 240 volts will be the running of a vacuum cleaner, and a jet wash. I was thinking of buying one of those camping leads with the blue round end at one end and a line of four 13 amp sockets at the other.

Basically my question is, Does that make a safe way of using the power posts available?

My battery charging and hot water come from the engine, which provides sufficient for my usage.

 

I'm out of my depth on this as well, except that it amounts to the use of power tools on a mooring, which any boatyard will tell you must not be done. But then any boatyard will also tell you that they often do it anyway. The danger, of course, is if you drop it in the river. The distribution board cable that you describe is also not water resistant - nothing is water "proof".

My first job on leaving school was in a shoe factory in Norwich, where there were huge mechanical machines which could take your hand off before you knew it. They didn't have total protection as shoe making is a craft and the operation has to be "hands on". So safety policy was half involved in the protection and guarding of machinery. The other half was the training and awareness of the operator.

I think that this also applies to the craft of boatbuilding and I have always borne this in mind when thinking of safety.

By the way your idea of leading the power cable through the steering wheel is a good one. Never thought of that! In theory you could also fit a relay, so that the key is de-activated when the shore power is plugged in. But then we are mixing voltages again - perhaps not!

 

[TheQ]

Most modern electrical Equipment such as TV's, Radios, and even hoovers etc that have internal PSUs are double insulated and do not require an earth on board or at home (they dont even have an internal connection for it). They are classed as Class 2 when I get my PAT tester out.

 Even some toasters,  electric kettles, and many power tools are now built this way.

They are indicated (or should be) on the permanant label by the double box symbol.

[Vaughan]

5 minutes ago, TheQ said:

 

Most modern electrical Equipment such as TV's, Radios, and even hoovers etc that have internal PSUs are double insulated and do not require an earth on board or at home (they dont even have an internal connection for it). They are classed as Class 2 when I get my PAT tester out.

They are indicated (or should be) on the permanant label by the double box symbol.

 

Thank you, I had a feeling that might be the answer. But what about about the circuits in the boat, that supply the equipment? Modern hire boats have a 220v socket in each cabin, for all the plug-in goodies, and powered from an inverter which also supplies microwaves, etc. This is comprehensive circuitry but how is it  protected, when the boat is not connected to earth?

[TheQ]

While BroadsScots solution will work, it would be better to fit one of these.http://www.ahctools.co.uk/products/show/id/133#.V7RC8eRTGUk

or https://www.edwardes.co.uk/en/products/powerbreaker-j62t-240v-dp-16amp-max-30ma-40ms-inline-rcd-orange-body

 imediately after the 16A Plug as it protects the whole cable and anything attached to it.

 they aren't cheap though, you could use the 13A equivalent, if you don't need 16A.

http://www.ebay.co.uk/itm/Masterplug-In-Line-Safety-Circuit-Breaker-RCD-Adaptor-Garden-Power-Trip-Switch-/400702145471?hash=item5d4bb583bf:g:LF8AAOxyuR5TYMDo

 

[TheQ]

8 minutes ago, Vaughan said:

Thank you, I had a feeling that might be the answer. But what about about the circuits in the boat, that supply the equipment? Modern hire boats have a 220v socket in each cabin, for all the plug-in goodies, and powered from an inverter which also supplies microwaves, etc. This is comprehensive circuitry but how is it  protected, when the boat is not connected to earth?

Apart from the fact you should still be running the output of your inverter through a contact breaker of the appropriate value and an RCD.

This is where some authorities say, you should have the Boat 240V earth line connected to the On board earth, so giving you an earth via a sacrificial anode or the boat metal work.

[Bound2Please]

16 minutes ago, TheQ said:

While BroadsScots solution will work, it would be better to fit one of these.http://www.ahctools.co.uk/products/show/id/133#.V7RC8eRTGUk

or https://www.edwardes.co.uk/en/products/powerbreaker-j62t-240v-dp-16amp-max-30ma-40ms-inline-rcd-orange-body

 imediately after the 16A Plug as it protects the whole cable and anything attached to it.

 they aren't cheap though, you could use the 13A equivalent, if you don't need 16A.

http://www.ebay.co.uk/itm/Masterplug-In-Line-Safety-Circuit-Breaker-RCD-Adaptor-Garden-Power-Trip-Switch-/400702145471?hash=item5d4bb583bf:g:LF8AAOxyuR5TYMDo

 

that still hasnt answered Vaughans question has it?

Charlie

[TheQ]

7 minutes ago, Bound2Please said:

that still hasnt answered Vaughans question has it?

Charlie

Give me a chance, I'm answering (if I know the Answer) , between measuring electronic equipment between 100mv and 1000V, or 100uA  to 10A, I have to work some time!!!

 

Ps I'm going for dinner break now...

[LondonRascal]

Just to add something to the mix...Since there are some in the know so far as electrons and all that go:

If you have for example a 16Amp shore connection coming into the boat - but, you worked out at times you might need, for example 25Amps to run all your equipment (like an air-conditioning system while all your other loads were in use taking you up to this loading.)

Could a generator be used to provide the additional current to the boats electrical system - and could it have some current sensing to 'call for the generator' and provide the boost when required I wonder.

Or, maybe I am wishing for too much and instead should either think about just a larger generator or a 32Amp shore power connection.

 

[Vaughan]

37 minutes ago, TheQ said:

Ps I'm going for dinner break now...

Bon appetit!