Earthing/Bonding/Grounding

[leechy]

Hi Everyone

Havn't logged on for a bit ,been busy on the boat.Anyway blew up my 1500 w cheapo inverter last week,put the willys up me actually as it banged smoked and banged again.I isolated everything then opened it up and found the five internal fuses were fine .so then tried it again and sure enough bang smoke and bang.Have read all the other threads on inverters and earthing but still puzzled .old inverter will be carefully stored in the bottom of my bin but iam going to buy a new 2000va victron phoenix inverter (not combi ).i dont have an rcd at the moment but think i need one( or two)Could any one advise of the safest earthing for my boat as i dont seem to have one of those either .also does both the 12v and 240v need earthing or bonding or whatever you call it?.The shell is all steel,don't have (won't have )shore power.Can any replies be suitable for some one who shortens wood for a living and not an astro physacisty person.and by the way does anyone know why the internal fuses didn't blow.

 

Many thanks Leechy

[Guest]

I dont know about Victron, but Mr Sterling told me how to earth one of his inverters. There is an earth terminal on the inverter that connects to the steel shell. The 240 Volts from the unit pass through an RCD (or whatever they are called this week), and circuit breakers to fuse the circuits. We actually used a "garage consumer unit" from Screwfix. He said DO NOT connect neutral and earth together as some people seem to do. The 12 Volt input is via 80mm cables from the battery via a 250amp fuse and battery isolator. The seemingly ridiculously large cables are to minimise volt drop of which there is plenty when you pull in excess of 200 amps off the battery bank. I have bonded (earthed) steel pipework and steel sink top to the shell also.

[Cafnod]

Hi Stan.

I think the bloke could do with a bit of help on the earth bonding front if you could explain it.

[bottle]

Bonding:

 

The idea of bonding all metalwork is to make it all, the same potential.

 

To give a simple example, two metal pipe running alongside each other, if there was an electrical fault one of these pipes could become 'live', if the other pipe is 'earthed' and you touched both of them you will make a circuit, with the probability of receiving a potentially fatal shock**

 

If all the metal fittings are 'bonded' together by cable/straps then that will take the fault and you will be safe.

 

** This applies to the 230 volt

Edited May 10, 2006 by bottle

[ChrisPy]

frankly I think that nobody should be considering doing or modifying electrical installation and wiring if they do not understand the basic principles. Giving a brief answer on a thread like this could be misleading.

 

Leechy, I suggest as a start you read up the TBTraining notes <http://www.tb-training.co.uk/> and buy a good book on the subject, like Nigel Calder's electrical and mechanical handbook.

[Alastair]

.also does both the 12v and 240v need earthing or bonding or whatever you call it

 

You are scaring me. There is no such thing as an 'earth' for 12V systems.

 

I suggest you do a bit of study on general electrics - the Nigel Calder boat maintenance book has a good introduction into basics - including the difference between DC and AC.

 

Electricity can be just as lethal as gas - please take care.

[NB Willawaw]

Leechy,

 

I fully understand your dilemma.

I think you have to look at it in the context of the AC wiring in your house.

Would you attempt to rewire your house on the strength of what strangers

told you on the internet ?

 

RCD - yes, definitely

Bonding - I would. Normally, I bond both the negative from the battery and

the AC earth to the steel hull.

 

How to do it is a bit more tricky.

 

If you are really not confident with mains electricity, get a friendly electrician to

help you (not over the internet) or do it for you.

It might cost you money, but its better than electrocuting yourself or others.

 

Mark

[DHutch]

You are scaring me. There is no such thing as an 'earth' for 12V systems.

So if you take the -ve terminal of the battery, and conect it to the hull with a stout lenght of 35mm2 cable, is that count as "earthed or bonded" ?

- Bearing in mind also that the hull is steel, sitting in the canal, and bonded to the earth of the 240vac system?

 

 

Im still not nesserally saying that anyone without suitable knowlage should attemt to dable in highvoltage electrical work (or lowvoltage for that matter) without supervision from some more competant.

- We dont know how able leechy is, from exprence, even people who have worked all there life as a electrician can be totaly stumped by a boats wiring system.

 

 

Daniel

Edited May 11, 2006 by dhutch

[leechy]

frankly I think that nobody should be considering doing or modifying electrical installation and wiring if they do not understand the basic principles. Giving a brief answer on a thread like this could be misleading.

 

Leechy, I suggest as a start you read up the TBTraining notes <http://www.tb-training.co.uk/> and buy a good book on the subject, like Nigel Calder's electrical and mechanical handbook.

 

Chris

Many thanks for your concern.To try and calm your worries i do have a basic comprehension of 240 v wiring being a joiner in the building trade for 20+ years ,im not saying i havn't had a whack or two but this inverter blowing seriously worried me and made me glad i was there when it happened due to the potential fire it could have caused. I know the regs on earth bonding on terra firma and how RCDs operate ,which in turn made me look closer at the boats wiring.I know i need an rcd out going from the inverter and a 240amp maga fuse is supplied with the inverter for the incoming,i think the cables are supplied form victron but if not i appreciate they will need to be in the region of 70mm2.The point im trying to make Chris im doing this out of neccessity and not pleasure and i think that anyone like me should be encouraged to visually probe their own electric systems to ensure they are the best and safest possible which like mine with no 240 rcd obviously isn't

 

Many thanks

Leechy

[Alastair]

So if you take the -ve terminal of the battery, and conect it to the hull with a stout lenght of 35mm2 cable, is that count as "earthed or bonded" ?

 

Daniel

 

That's not earthing - because it doesn't provide the function of an earth in any way whatsoever (in the event of a short, the short should travel via the earth, etc).

 

The BSS requires all DC wiring to be wired out and return - so you shouldn't ever have a need to bond the -ve to the hull. I know that mostly the engine -ve will not be isolated from the hull, but that is a special case.

 

Dan, I suspect you are just having a troll, because I think you know more about these technical matters than I do!

[Gary Peacock]

You know there is a very easy solution to this. Read the regulations or if you don't want to then ask someone else to do the job who did.

 

I know that sounds negative but mains voltage can and does kill, low voltage mistakes cause fires but mains voltage can be far more instantaneous/terminal if your home brewed theory goes wrong!

 

So I would personally suggest were regulations and guidance are in place you are far better to follow them for every bodies sake.

 

 

Most people wouldn't dream of messing with their household wiring if they didn't know what they were doing but that same person given a boat will quite happily make it up as they go along! I have always found this strange but we regularly see potentially lethal DIY jobs and when you question of the owners about who did it you find a total lack of even fundamental understanding of the work they have undertaken.

 

Forums like this one are a great asset to those that use them but if some of the advice given was ever to find it's way into a court room or coroners inquest the authors would find themselves in a very uncomfortable position.

 

The RCD, ISO's, BMEA code of practice and BSS might have faults but at the end of the day if you comply with these you can sleep comfortably in the knowledge you have simply done what you are required to do and no one can point the finger of blame at you if it all goes pear shaped.

 

Anyway end of todays rant! (Sorry)

[ChrisPy]

 

Anyway end of todays rant! (Sorry)

well said, Gary.

[Cafnod]

I was in a branch of City Electrical Factors today, waiting to be served. The guy in front of me was being sold what he needed to wire up outside lights, he knew nothing about electrical installation, but they sold him the bits and even wrote down the colours for him.

I was with a friend at a branch of BOC about twenty years ago. He was getting a large bottle on contract for his mig welder. He asked them if he could rent oxy/acetylene (as a windup) they said fine. He asked if it made any difference that he lived in a council flat. They said that was between him and his landlord he said it was a tower block the guy said did it have a lift.

Seen some horrific escapades on rock climbs where people have just bought their gear (on one occassion that morning) and "wanted to try it out."

The point I am trying to make here is that to me a lot of the blame rests on the people who will sell/rent/lease this stuff with no responsibility for what or how it is used, these people are grey box shifters for the most part. When I had my garage I saw lots of apalling work, I had a lad bring in a car with the brake pads in backwards. I rectified the fault and showed him what he had done wrong. Had a lot of business off his family after that.

Mate of mine has an outdoor shop, wont sell people kit for climbing unless they know how to use it, sends them to the local club. Reckons that live climbers buy more gear than dead beginers.

Not sure if ranting at people to read and follow regulations really achieves anything other than to make them feel alienated, inferior and resentful.

[lymmranger]

Hi Everyone

Havn't logged on for a bit ,been busy on the boat.Anyway blew up my 1500 w cheapo inverter last week,put the willys up me actually as it banged smoked and banged again.I isolated everything then opened it up and found the five internal fuses were fine .so then tried it again and sure enough bang smoke and bang.Have read all the other threads on inverters and earthing but still puzzled .old inverter will be carefully stored in the bottom of my bin but iam going to buy a new 2000va victron phoenix inverter (not combi ).i dont have an rcd at the moment but think i need one( or two)Could any one advise of the safest earthing for my boat as i dont seem to have one of those either .also does both the 12v and 240v need earthing or bonding or whatever you call it?.The shell is all steel,don't have (won't have )shore power.Can any replies be suitable for some one who shortens wood for a living and not an astro physacisty person.and by the way does anyone know why the internal fuses didn't blow.

 

Many thanks Leechy

 

Whilst agreeing with everyone else, If I were in your position I would be more worried about having a 240v AC system without an RCD!

 

This alone would offer you a greater level of safety....

 

Whilst your boat is in the water you should "earth" your AC to the hull at the same common point as the 12v DC system. If done logically it is one of the more comprehensible wiring tasks......

 

Earthing is an extremely emotional topic that has seen some very heated discussions (even violent!).

 

I was advised by a BSS examiner to physically disconnect the incoming earth (from landline) and to just earth via the "boat earth"..... In fact I seem to remember suggesting this on a previous thread.. ??

 

Like you Leechy I am perfectly capable of wiring a domestic property (17 now - all passing inspection) I took 85% of a course once, but boats are a peculiar animal which seems to sap all confidence out of me???????

 

Dare I mention galvanic isolators????? .....Errrr OK I`m off

[John Orentas]

The question is about the wiring of an inverter. The first priority is to consult the wiring instructions for the inverter, different manufacturers' instructions will vary slightly but general all the metallic major components of the boat should be bonded to the hull and the neutral in the absence of instructions to the contrary should be bonded to the same point.

 

Doing things this way will ensure that the RCD when fitted will function correctly. It is unwise to confuse the issue with other matters, whether low voltage DC systems or anything else.

 

The fuses of any system or appliance will blow only if the fault causes a current flow greater than the rating of the fuse and in the case of an inverter the 12 volt input AND the 230 volt output should be protected. In this particular case I suspect the high voltage circuit was busy blowing itself to bits but leaving the input side relatively unaffected.

Edited May 13, 2006 by John Orentas