Earthing on boats

[davew]

Hi,

A friend that's just boaugh a canal boat is 'doing' it up and is worried
about the
electrics and has heard that boats use positive earth so he's asked me for
advice.
I know about electronics & house wiring (well a bit anyway) but have never
considered this on a boat where he'd like to have a computer TV etc....

Now considering I was going to help him sort the electrics out what else
should I know that's differant from 'Land' electrics I tried searching for a
helpful
UK website but none found.

Any pointers

thanks

 

[Dennis Pogson]

Hi,

A friend that's just boaugh a canal boat is 'doing' it up and is
worried about the
electrics and has heard that boats use positive earth so he's asked
me for advice.
I know about electronics & house wiring (well a bit anyway) but have
never considered this on a boat where he'd like to have a computer TV
etc....

Now considering I was going to help him sort the electrics out what
else should I know that's differant from 'Land' electrics I tried
searching for a helpful
UK website but none found.

Any pointers

thanks

Usually, a boat has no "earth return", so the engine and electrics need a
separate connection to the battery negative. The usual system is to have a
distribution panel on which the positive is on the switch, indicator-lights
and fuse (or contact-breaker) side, and all the negatives are fed back to a
negative bus bar whic is connected to battery negative. The main switch is
usually positioned close to the battery or batteries, and if a 2-battery
system is used, a blocking diode is used so that the domestic battery can
run down to almost zero, whilst you still have a full battery for starting
the engine.

If you can get hold of a copy of "The 12-volt Doctor's Handbook", this is a
great starting point. Also Reading University's website used to have some
great stuff on marine electrics, but I don't know if this is still the case.


Dennis.

 

[Gordon Wedman]

You might also want to try uk.rec.sailing for an answer.

 

[[email protected]]

Hi,

A friend that's just boaugh a canal boat is 'doing' it up and is worried
about the
electrics and has heard that boats use positive earth so he's asked me for
advice.
I know about electronics & house wiring (well a bit anyway) but have never
considered this on a boat where he'd like to have a computer TV etc....

Now considering I was going to help him sort the electrics out what else
should I know that's differant from 'Land' electrics I tried searching for a
helpful
UK website but none found.

Any pointers

thanks

Steel Canal boats should be wired with all switching in the positive
line, an insulated negative return,but with battery negative bonded to
the hull at one point..
Blocking diodes for split charging are best avoided.
Bear in mind that all wiring will be 12 or 24 volts and conductor
cross sectional area is important and should be fully assessed based
upon the length of the run.
Methinks that you have not searched very much! There is a wealth of
info out there on the web..
uk.rec.waterways is the best group for asking questions.
12v (typ) electrics on a boat are VERY easy to get wrong!!!!!!
Your friends best bet is to get a good marine electrician to spec the
system, then you could wire if you wish.
Just my 2 pennorth

Richard

Nb "Pound Eater" Glos+Sharpness Canal UK

 

[davew]

Steel Canal boats should be wired with all switching in the positive
line, an insulated negative return,but with battery negative bonded to
the hull at one point..

This sounds like normal land electrics.

Blocking diodes for split charging are best avoided.
Bear in mind that all wiring will be 12 or 24 volts and conductor
cross sectional area is important and should be fully assessed based
upon the length of the run.
Methinks that you have not searched very much! There is a wealth of
info out there on the web..

I had a quick surfer a while ago but some info conflicted with
other sites and what seemed to make sense.
My fisrst confusion was the idea of positve earth and what happens when
you tie up at one of those sockets along the canal.

uk.rec.waterways is the best group for asking questions.

Cheers for that.

12v (typ) electrics on a boat are VERY easy to get wrong!!!!!!

Yes that's why I've done nothing, hands in pockets and all that.
12V, lots of amps, water, diesel.... oil.......

Your friends best bet is to get a good marine electrician to spec the
system, then you could wire if you wish.
Just my 2 pennorth

Well the boat ( I wish I understood more of) is around 53ft wooden
boat made in the 1960s (not a narrow boat) and is still floating just.

We got side tracked reading about the creatures that can eat away
at the hull and getting the polarity wrong could mean losing the
screws/nails
holding the thing together and how things differ depending whether you're
in sea water or on the canel, fascinating stuff , I'd no idea of such
things,
bit different to what I'm used to such as wiring computers together.


In the next few weeks it might be ready to be re-wired and/or checked
before plugging anything in that's my plan but wasn't sure what I may face.
I was hoping of a hayes type manual that they have for cars.

I'm also hoping there's a free wi-fi hot spot somewhere along the regents
canel unlikely I guess.

Thanks for replying

 

[Dennis Pogson]

This sounds like normal land electrics.


I had a quick surfer a while ago but some info conflicted with
other sites and what seemed to make sense.
My fisrst confusion was the idea of positve earth and what happens
when you tie up at one of those sockets along the canal.

"one of those sockets along the canal" would presumably be 240v AC?

Cheers for that.

Yes that's why I've done nothing, hands in pockets and all that.
12V, lots of amps, water, diesel.... oil.......


Well the boat ( I wish I understood more of) is around 53ft wooden
boat made in the 1960s (not a narrow boat) and is still floating
just.

So you can forget the hull for earth return.

We got side tracked reading about the creatures that can eat away
at the hull and getting the polarity wrong could mean losing the
screws/nails
holding the thing together and how things differ depending whether
you're in sea water or on the canel, fascinating stuff , I'd no idea
of such things,
bit different to what I'm used to such as wiring computers together.


In the next few weeks it might be ready to be re-wired and/or checked
before plugging anything in that's my plan but wasn't sure what I may
face. I was hoping of a hayes type manual that they have for cars.

The only suppliers of "the 12-volt doctor's practical hanbook" seem to be
in the US, but you could have a Google yourself. It is exactly what you
need! http://www.landfallnavigation.com/bbe12.html

I'm also hoping there's a free wi-fi hot spot somewhere along the
regents canel unlikely I guess.

Thanks for replying

Dennis.