Electrically grounding a Narrowboat.
Jonathan Stafford
include the grounding (negative side of the batteries) to the Hull, is there
a reason for this, can it increase corrosion ??. The engine and gearbox are
insulated by rubber so it doesn't get to ground this way.
Any thoughts appreciated,
Jon
simon gray
--
just spending a day or so with the luxury of a real toilet
http://www.star-one.org.uk/ http://www.mp3.com/simongray
su4704
the hull and the negative supply but the hull must not be used as a
conductor as the chassis is in a car. A negative conductor must be run out
from the supply to each appliance but I am sure that this is already the
case on your boat.
Hope this is of some help,
Kind regards,
Steve.
"Jonathan Stafford" <j...@me.bigfoot.com> wrote in message
news:9i2clp$kki$1...@epos.tesco.net...
Ron Jones
Using the hull as a "wire" - like a car - is liable to accelerate
electrolytic corrosion. Anyway, why ground the negative? Neither the
positive or the negative are at the same potential as the hull. It's *not*
like AC mains where the neutral is at (almost) zero volts (because it's
earthed at the substation). While we're mentioning earthing, don't forget
that if you connect up to a AC land line, and therefore earth the hull, you
will also increase corrosion of both your boat and any adjacent steel piling
(I've seen the results - *not* on my boat I hasten to add).... But then you
need to earth it to avoid dangers of electrocution - can't win with AC on
boat (unless you go down some sort of isolation transformer route or just
make 12V from the shore mains.).
Ron (the mad scientist)
[Currently renting a house with the Lancaster canal at the foot of the
garden and wishing the ribble link was finished]
nb Betsy Trotwood
mc Kingfisher
Halligbury Mill
Kevin Hollis
the boat and the metal in the ground, scaffold poles or whatever, due to a
difference between the local earth potential and that of the earth at the
substation which is connected through to the boat by copper.
Would directly connecting the metal hull of the boat to the scaffold poles
using thick wire stop electrolysis, since it would eliminate the voltage
difference, or at least give a route for the current that wasn't through
water, an electrolyte ?
Is this done ? Has anyone tried it ?
Kevin
Kevin Hollis
connects to the boat ?
Kevin.
Kevin Warrington
Kevin Hollis <kho...@mpc-data.co.uk> wrote in message
news:9i4bbd$8c6$1...@lion.mpc-data.co.uk...
indicate that I am supposed to have some vague knowledge about this
electrickery stuff - even though I am allowed by law to sign serstificates
of safety and appear in court as an expert witness, most of my family will
not allow me to wire up a 3 pin plug).
I think that you'd need to bond all the scaffold poles to a decent earth
AND ensure that all the boats in the vicinity were also bonded with a hefty
great length of wire. There is some interesting stuff on the Mastervolt
website (can't remember address) that discusses electrolysis and potential
cures (accidental pun there, sorry), ranging from disconnecting the earth to
buying a (Mastervolt) isolating transformer.
From memory of college days, "neutral" is connected to earth at the
substation. Therefore, there should be no PD between neutral and earth.
There often is, though.
--
Regards,
Kevin J. Warrington, IEng MIIE
su4704
it was with . My fault I think because I did not express myself well enough
for them to understand but I agree with this totally. The problem with
shore lines is that the electricity board earth connection is remote from
the local earth. Stick a meter probe in the soil and connect the other side
to the green wire in your plug. Set your meter to A.C. volts ( better do
this first !) and you will get a reading of between 2 and 4.5 V depending
how far away the local 'earth ' point occurs.
I quite agree, so as I see it if you are on a permanent mooring, buy an
earthing rod from your local electrical shop and drive it in to the bank and
connect the earth supply to this as well as your boat. I argue that a
scaffold pole will be equally as good as long as you maintain a low
resistance contact with the zinc covered pole and your copper wire.
Well that is my opinion for what it is worth.
Steve.
"Kevin Hollis" <kho...@mpc-data.co.uk> wrote in message
news:9i4evc$9er$1...@lion.mpc-data.co.uk...
Andrew Royal
which occurs where two dissimilar metals, which will have different voltage
potentials, are immersed in an electrolyte (canal or sea water) and
connected electrically externally to the electrolyte. (Its a sort of
battery effect!)
Although a boat hull is generally made of one metal (steel or iron), due to
various factors including heat stress, mill-scale and differences in paint
surface, it will still have different voltage potentials over its surface,
and therefore corrosion will occur.
This may be prevented either by cathodic protection, that is applying a
voltage potential to the metal (as used on metal gas pipelines for example),
or by applying anodes of a suitable metal, often zinc, to the structure, so
that the anodes corrode rather than the structure. The latter is the method
normally used in boats.
Galvanic corrosion will be exacerbated by electrical currents flowing
through the hull of a vessel, or voltage potentials applied to the hull.
It is therefore preferable to avoid any connection to the hull, and ideally
all the electrical equipment should have both positive and negative poles
insulated from the hull. True marine alternators and starter motors are
constructed with an insulated negative, i.e. no electrical connection to the
metal case, but practically this makes those parts much more expensive, and
many engine manufacturers therefore use standard auto equipment, where the
negative pole is electrically connected to the Metal casing.
Even engines on rubber mountings are unlikely to provide total insulation,
due to the presence of oil and grease, and also potential electrical paths
through fuel pipes etc., or indeed the drive shaft to the propeller.
In essence, it is standard accepted practice to rely on anodes to minimise
the damage to the hull, and to insulate both poles of the electrical
installation from the hull.
All of this is fine for 12 or 24 volt DC systems, but when a shore mains
supply is used then earthing is required for safety reasons.
Any shore mains supply should be protected by an earth leakage circuit
breaker (usually referred to as an RCD - residual current device) on the
shore side, which will detect any leakage to earth and if necessary
automatically disconnect the supply.
It is further advisable to install an RCD on the boat as well, and to
connect the shore earth conductor to the boat hull. This will not effect
corrosion when the shore line is disconnected as it will not be connected to
anything else.
I hope these comments are of some help, although rather protracted.
Unfortunately it is not a simple subject and I am sure that someone has
written a book on the subject (if only aimed at sea-going craft).
If in any doubt I would recommend you seek professional advice from a marine
electrical engineer.
Andrew Royal
Nb JOSEPH
simon gray
> In essence, it is standard accepted practice to rely on anodes to minimise
> the damage to the hull,
Would these be the anodes which protect an area of the hull about a
square foot around them, & which the boatyard will charge you an
exhorbitant amount for ?
Graham Ridgeway
from "su4704" <su4...@eclipse.co.uk> contains these words:
> I quite agree, so as I see it if you are on a permanent mooring, buy an
> earthing rod from your local electrical shop and drive it in to the bank and
> connect the earth supply to this as well as your boat. I argue that a
> scaffold pole will be equally as good as long as you maintain a low
> resistance contact with the zinc covered pole and your copper wire.
> Well that is my opinion for what it is worth.
> Steve.
Do not waste your money on a labelled ;'earthing rod' please.
'Copper' water pipe is just as good. Buy one 8ft/3m length or whatever
fits in your car. Cut into 3 with a hacksaw. Or go down the local tip
and 'hijack' some old offcuts.
Use a block of wood between yer 'ammer and the top of the pipe when
banging in to the ground to prevent mushrooming
Use 'jubilee' clips to attach some chunky cable.
Jobs a good 'un
I agree that if you can effect a low resistance connection to scaffold
pipe - then this will also be fairly effective.
Just remember that 1 ohm in the path of 1 volt = er..... 1 amp !!! [
I = E/R ] so that resistance needs to be LOW !!!
IIRC there used to be 'trickery' circuits available to power a receiver
using the small PD between Earth and Neutral [Just measured here and I
have 3.6v at the moment] although the current available is very small.
Graham
Ian & Hilda Dedic
hope), so a few volts AC between the mains earth and local ground shouldn't
cause corrosion.
If there's any DC potential difference that's a different story -- so
measure the DC voltage not AC if you want to see whether accelerated
corrosion is likely.
Ian
"su4704" <su4...@eclipse.co.uk> wrote in message
news:9944528...@ananke.eclipse.net.uk...
Alastair
<andrew...@cwcom.net> wrote:
<snip>
>
>It is further advisable to install an RCD on the boat as well, and to
>connect the shore earth conductor to the boat hull. This will not effect
>corrosion when the shore line is disconnected as it will not be connected to
>anything else.
>
Be wary of connecting RCDs in series, especially if they use a test
button to switch off the socket. A story:-
I had a rig at work which had a mains socket mounted on it for the
control box. This must have an RCD so we fitted a socket with integral
RCD. The off switch on the socket simply connected live to earth
through a resistor, and thus tripped the RCD.
The electrician switched off the power at the socket and opened the
back of the box (yes he should have pulled out the plug, he knows that
now). A few minutes later there was quite a spectacular bang and a big
flash - the power was back on!
The rig power came from the shop mains which had an RCD. When my mate
pushed the button the RCD in the plant room tripped, not the one on
the rig. When someone noticed that all the power had gone off in the
shop they switched it back on!
Oh, and it was a live to neutral short with a spanner, so teh RCD
still didn't trip, but the fuse did blow.
--
Alastair
Andrew Royal
couple of anodes at the front and back? Does anyone have any experience of
the effects, or indeed has anyone tried not putting anodes on their boat?
As the problem is worst in sea water, I wonder how important the anodes are
in canal water, which in some places may be more aggressive due to chemicals
that electrolytic action!
I can only say that when I first reblacked the hull of my boat, after about
three years, there was no sign of a variation in the level of corrosion,
which was minimal in any case. There was evidence of corrosion taking place
at the anodes, which is as it should be.
I guess if you have a new boat you are unlikely to risk not putting anodes
on to save a few pounds, it can't be wrong.
Andrew Royal
Nb JOSEPH
Paul E. Bennett
andrew...@cwcom.net "Andrew Royal" writes:
> Any shore mains supply should be protected by an earth leakage circuit
> breaker (usually referred to as an RCD - residual current device) on the
> shore side, which will detect any leakage to earth and if necessary
> automatically disconnect the supply.
>
> It is further advisable to install an RCD on the boat as well, and to
> connect the shore earth conductor to the boat hull. This will not effect
> corrosion when the shore line is disconnected as it will not be connected to
> anything else.
Actually, the earth connection to shore should have a galvanic isolator
inserted in it or you should be using an isolation transformer where the
earth from shore is not connected. All the other advice was good, though,
from an electrical point of view. Earth galvanic isolators can be made
from two large diodes connected in opposing directions in parallel.
However, connecting the negative side of the battery to the boat hull
will provide a shielding to all your electronic equipment and prevent
the radio frequency emissions (inherently emitted by all electrical and
electronic equipment) from becoming a nuisance. However, do not use the
hull as a conductor. Separate negative supply wiring should accompany the
positive wiring and twisting up as pairs will help.
> I hope these comments are of some help, although rather protracted.
> Unfortunately it is not a simple subject and I am sure that someone has
> written a book on the subject (if only aimed at sea-going craft).
There are the "Regulations for electrical and electronic equipment
of ships" which is published by the IEE.
> If in any doubt I would recommend you seek professional advice from a marine
> electrical engineer.
Absolutely.
--
********************************************************************
Paul E. Bennett ....................<email://p...@amleth.demon.co.uk>
Forth based HIDECS Consultancy .....<http://www.amleth.demon.co.uk/>
Mob: +44 (0)7811-639972 .........NOW AVAILABLE:- HIDECS COURSE......
Tel: +44 (0)1235-814586 .... see http://www.feabhas.com for details.
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
********************************************************************
Malcom Nixon
>In article <3b46...@news-uk.onetel.net.uk>
> andrew...@cwcom.net "Andrew Royal" writes:
>
>
>> If in any doubt I would recommend you seek professional advice from a marine
>> electrical engineer.
Yes indeed. Does anyone know if there is a recognised professional
body for marine electrical engineers or perhaps qualified electrical
fitters - and those working around the canal system.
And how many boatyards, boatbuilders use professional electricaly
qualified staff I wonder
--
Malcolm
nix...@surfaid.org and mal...@duplin.org.uk
http://www.users.surfaid.org/~nixonm/index.htm
P & Q Brown
>The problem which you are trying to avoid is known as "galvanic" corrosion,
>which occurs where two dissimilar metals, which will have different voltage
>potentials, are immersed in an electrolyte (canal or sea water) and
>connected electrically externally to the electrolyte. (Its a sort of
>battery effect!)
>
Eve', the world's last surviving steamer drifter, which was moored
against a steel quayheading in the tidal river at Great Yarmouth. Now
it needs something like £750,000 of repairs.
--
Peter Brown
Kevin Hollis
corrosion,
> which occurs where two dissimilar metals, which will have different
voltage
> potentials, are immersed in an electrolyte (canal or sea water) and
> connected electrically externally to the electrolyte. (Its a sort of
> battery effect!)
Does this mean that earthing both metals to the same earth will have no
effect ?
> This may be prevented either by cathodic protection, that is applying a
> voltage potential to the metal (
Tell me more.
> Galvanic corrosion will be exacerbated by electrical currents flowing
> through the hull of a vessel, or voltage potentials applied to the hull.
So should I earth the boat to an earth spike ?
Kevin.
Kevin Hollis
> from two large diodes connected in opposing directions in parallel.
>
Is this to reduce corrosion, or as a saftety feature ?
How does it work ? And since current can flow each direction through one or
other diodes how is that different from an open cable ?
Are we still talking about 240v AC ? And what is large for a diode ?
Kevin.
Paul Jerome
It needs 0.7 volts to turn a diode on. Therefore a small fluctuation in
voltage will not cause a current to flow, but a serious fault will.
Paul Jerome
Paul E. Bennett
kho...@mpc-data.co.uk "Kevin Hollis" writes:
It provides galvanic isolation while maintaining a safety earth path.
The two diodes will conduct forward at about 0.7V (if they are silicon
types) and will be high impedence isolating barriers below that level.
This will stop the current flow that erodes the hull and/or metal
fittings. However, any fault earth leakage current will tend to exceed
the 0.7V level and thus you get a conduction path to the real earth
when you need it.
John Lee
Graham Ridgeway <m5...@zetnet.co.uk> wrote
>
> IIRC there used to be 'trickery' circuits available to power a
receiver
> using the small PD between Earth and Neutral [Just measured here and
I
> have 3.6v at the moment] although the current available is very
small.
I've seen 50 volts between neutral and earth.
John.
Kevin Hollis
>
> The two diodes will conduct forward at about 0.7V (if they are silicon
> types) and will be high impedence isolating barriers below that level.
> This will stop the current flow that erodes the hull and/or metal
> fittings. However, any fault earth leakage current will tend to exceed
> the 0.7V level and thus you get a conduction path to the real earth
> when you need it.
I think I'm starting to get it. Please correct my argument where it may fall
over.
Since there is a potential difference (perhaps 3 or 4 volts) between
cable/hull earth and 'ground next to the boat' earth, a current flows
through the water to metal scaffold poles etc. This promotes electrolysis
and metal is scavenged from one metal to the other, leaving shiny metal
patches on the hull and significant metal thinning. (Still a bit confused
how the battery effect between the two metals, Fermi level etc.. is linked
with this.)
So the obvious solution seems to be to connect the cable/hull earth directly
to the 'ground next to the boat' earth thus eliminating the voltage
difference.
However, this will provide a very low conductance path between the two
earths and will increase the current flowing through the hull, even though
it must virtually eliminate the current flowing through the water.
A compromise is to use a 'galvanic isolator' which will not permit current
flow at very low voltages (<0.7V). This will cause some current flow through
the water at these low voltages but we don't mind since the galvanic
corrosion at this voltage is very low. However, when the voltage difference
increase to above 0.7 Volts the diodes will allow current flow thus reducing
the current through the water, which would be more significant at these
voltages.
Phew!! This is nasty physics !
I'd really like to get to the bottom of this one since I am moored next to
scaffold poles and do get some galvanic corrosion.
Kevin.
Kevin Hollis
> I
> > have 3.6v at the moment] although the current available is very
> small.
>
> I've seen 50 volts between neutral and earth.
Hmm, just realised I've been slightly confused .
In fact 'neutral' is earthed at the local substation and 'earth' is locally
earthed to an earth spike/plate. Now since 'Neutral' should come nowhere
near the boat hull, any voltage difference between cable/hull earth and
local earth must be due to a voltage difference between the local earth
spike (e.g.near the distribution point for all the boats) and the earth
potential near the boat, a distance of maybe 100 metres at most.
I think I need to get my voltmeter out.
Kevin.
Brian on Harnser
news:3b476b54...@news.clara.net...
> On Fri, 6 Jul 2001 23:07:04 +0100, "Andrew Royal"
> <andrew...@cwcom.net> wrote:
>
> <snip>
> >
> >It is further advisable to install an RCD on the boat as well, and to
> >connect the shore earth conductor to the boat hull. This will not effect
> >corrosion when the shore line is disconnected as it will not be connected
to
> >anything else.
> >
> Be wary of connecting RCDs in series, especially if they use a test
> button to switch off the socket. A story:-
>
A long time ago the company I worked for sent me on a Safety Course on a
boat (on topic) in St Catharines Dock, London.
One of the lectures was on "Electrical safety" with a demonstration of the
effectiveness of a RCD. To show just how good it was at saving life the
lecturer grabbed the Live conductor to make the trip operate before he was
electrocuted. He then asked for questions. My hand shot up and I asked "What
are you going to do the day that trip goes wrong and fails to operate?"
--
--
Brian from sunny Suffolk by the river Hundred
BevanLewis
>From: "Brian on Harnser" brian...@harnser.fsbusiness.co.uk
>Date: 10/07/2001 08:28 GMT Daylight Time
>Message-id: <9ifl9p$2jr$1...@newsg3.svr.pol.co.uk>
<Snip>
>
>A long time ago the company I worked for sent me on a Safety Course on a
>boat (on topic) in St Catharines Dock, London.
>One of the lectures was on "Electrical safety" with a demonstration of the
>effectiveness of a RCD. To show just how good it was at saving life the
>lecturer grabbed the Live conductor to make the trip operate before he was
>electrocuted. He then asked for questions. My hand shot up and I asked "What
>are you going to do the day that trip goes wrong and fails to operate?"
>
A coincidence, I also did a first aid course on board a boat on St Kaths
organised by the British Safety Council. It was in 1983 so I assume my
certificate is out of date now, In fact I attended a WRG refresher course only
a few weeks ago but didn't finish it because one of the partipants fainted and
I had to accompany him to hospital !
***********************************
Tim Lewis
Home e-mail: t...@timlewis.org.uk
Web Page: http://www.timlewis.org.uk
Home phone: 020 8367 6227
Mobile phone: 07802 518094
*************************************
Paul E. Bennett
kho...@mpc-data.co.uk "Kevin Hollis" writes:
Nearly.
> Phew!! This is nasty physics !
>
> I'd really like to get to the bottom of this one since I am moored next to
> scaffold poles and do get some galvanic corrosion.
The water, containin various mineral salts in suspension, acts as an
electrolyte and, with disimilar metals of scaffold poles and hull steel,
you get a weak battery effect between shore and boat. This can be of
the order of 0.01V to about 0.4V (although in some circumstances maybe
higher than this) so the diodes would tend to be a block to the current
flow (although it will do so wakly due to minor leakage at PN junctions).
Kevin Hollis
OK. I'll try again.
Different voltage potentials between boat and scaffold poles causes current
flow through the water and so increases corrossion (because of the increase
ionic contect of the water when current flows, or perhaps because the
current flow draws reactive ions to the surface of the boat.) So it seems to
make sense to connect the boat to the scaffold (or earth spike) by a big
chunky low resistance wire. But this then creates a battery due to the
difference between the chemical voltage potentials of the metals, and you've
just connected the two terminals of the battery with very few ohms, causing
galvanic corrosion. So to cure the problem insert a galvanic isolator which
will block the very low voltages associated with the battery effect while
allowing conduction of current due to teh difference between the earth
potential and the boat potential.
(Hmmm! I'm not convinced by the last point. Surely current either flows or
doesn't and the diodes will spend most of their time in open state if a
voltage difference of >0.7V exists between boat and land.)
Nearly there, I can feel it in my water.
Kevin.
Ron Jones
> I quite agree, so as I see it if you are on a permanent mooring, buy an
> earthing rod from your local electrical shop and drive it in to the bank
and
> connect the earth supply to this as well as your boat. I argue that a
> scaffold pole will be equally as good as long as you maintain a low
> resistance contact with the zinc covered pole and your copper wire.
>
Ah, You've all fell in the trap! Put a dozen copper poles / rods in if you
like and the boat will *still* corrode faster! Once you've eliminated any
effect from the mains (like floating earths, etc.) then you have *made* a
battery! With one electrode as the copper rod, the other as the steel boat,
the electrolyte is the canal/wet ground, and your shoreline is the load!
Copper being lower down the electrochemical series will not corrode, so
goodbye steel....
For the brainy ones, I guess we'll have the following...
Fe = Fe++ + 2 electrons
Cu + 2 electrons + Water = CuO + hydrogen (so don't smoke near your
earth rods)
If you connect a meter in the earth lead, you should be able to observe a
weak current flowing.
--
Ron (the mad scientist).
Anthony Matheson
<j...@me.bigfoot.com> wrote:
>I am in the process of rewiring a Narrowboat. The current wiring does not
>include the grounding (negative side of the batteries) to the Hull, is there
>a reason for this, can it increase corrosion ??. The engine and gearbox are
>insulated by rubber so it doesn't get to ground this way.
>Any thoughts appreciated,
>
>Jon
>
>
What about a visit to Colin Marsh's Power Pages boat electrics site?
It even has a Q & A section:
<http://www.geocities.com/cmmarsh2001/index.htm>
--
Anthony Matheson
http://www.amath.co.uk
To reply by email, remove footwear
Ed. Harris
Andrew Royal <andrew...@cwcom.net> wrote:
> That is an interesting point! just how much of the hull is protected by
> a couple of anodes at the front and back? Does anyone have any
> experience of the effects, or indeed has anyone tried not putting anodes
> on their boat?
> As the problem is worst in sea water, I wonder how important the anodes
> are in canal water, which in some places may be more aggressive due to
> chemicals that electrolytic action!
When we had Guinevere out the other month you could see where the ?zinc?
?magnesium? had been laid down on the exposed steel of the shell in
places. Some of these spots of corrosion were half way down the boat.
--
Ed. NB Guinevere on the Nene
==
Adrian Stott
Matheson) wrote:
>On Thu, 5 Jul 2001 19:50:19 +0100, "Jonathan Stafford"
><j...@me.bigfoot.com> wrote:
>
>>I am in the process of rewiring a Narrowboat. The current wiring does not
>>include the grounding (negative side of the batteries) to the Hull, is there
>>a reason for this, can it increase corrosion ??. The engine and gearbox are
>>insulated by rubber so it doesn't get to ground this way.
>>Any thoughts appreciated,
My understanding (from The Bible, i.e. Nigel Calder's "Boatowners
Mechanical and Electrical Manual) is that negatives from all DC
devices should return individually to a single point (typically most
will go to the negative side of the DC breaker box which is then
connected to the single point) which is welded/bolted to the hull.
The battery negative should go to this point as well. This is to
ensure that there are no differences in potential in the negative
wiring, which could cause current to flow where you don't want it to.
For AC, the grounding wire should also go to the common point. The
neutral should not -- UNLESS you have an isolation transformer, when
it should.
You *should* have an isolation transformer. This is installed on the
boat end of the shore power line. It is the only device which truly
prevents stray AC currents between the shore and the boat. Galvanic
isolators are not as good. Without any isolator, there are lots of
ways unwanted current return through the water can occur, which eats
away at your hull a treat. The transformer also makes you immune to
shore power sockets which are wired up wrong.
Read the book. Even at 30 quid, it's well worth it.
Adrian