narooma
Well-Known Member
Any electricians out there? I need advice please. The earth bonding is in need of replacement/repair. What items should be bonded to earth and should the anode be bonded to the copper strip which is fixed to the hull?
earth bonding
- Thread starter narooma
- Start date
roly_voya
Well-Known Member
DO NOT bond to the copper strip if it is attached to the chain plates, it is the lightening earth and should ground seperatly to the keel.
You only need to bond things that are metal, underwater and conected to the boats electrical system (unless its a metal boat) so yes to the engine seawater intake because salt water is conductive so conects it to the engine but know to the sink outlet because even if the sink is grounded the plastic wast pipe insulates the fitting from it. Also check that the DC neg and AC grounds are seperately grounded but also bonded to the zinc.
There are some ecellent books on this and it is worth having a read up as it can get quite complex and potentially lethal either to you or the boat!
You only need to bond things that are metal, underwater and conected to the boats electrical system (unless its a metal boat) so yes to the engine seawater intake because salt water is conductive so conects it to the engine but know to the sink outlet because even if the sink is grounded the plastic wast pipe insulates the fitting from it. Also check that the DC neg and AC grounds are seperately grounded but also bonded to the zinc.
There are some ecellent books on this and it is worth having a read up as it can get quite complex and potentially lethal either to you or the boat!
Benbow
Well-Known Member
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Also check that the DC neg and AC grounds are seperately grounded but also bonded to the zinc.
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Also check that the DC neg and AC grounds are seperately grounded but also bonded to the zinc.
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vyv_cox
Well-Known Member
"yes to the engine seawater intake because salt water is conductive so conects it to the engine"
Do you really imagine that electrons pass around a right angle bend into the seawater inlet, up a bendy plastic pipe, through the raw water pump impeller and into the engine? Where they will do useful work transferring charge between it and an anode outside the boat?
If so, can I interest you in this money-making scheme based in Nigeria, whereby you will make thousands of pounds at no risk to yourself? Just send me a few grand and I promise to treble it.
Do you really imagine that electrons pass around a right angle bend into the seawater inlet, up a bendy plastic pipe, through the raw water pump impeller and into the engine? Where they will do useful work transferring charge between it and an anode outside the boat?
If so, can I interest you in this money-making scheme based in Nigeria, whereby you will make thousands of pounds at no risk to yourself? Just send me a few grand and I promise to treble it.
jfkal
Well-Known Member
Well well. the bonders for bonding sake are out again. There are plenty conflicting standards and requirements out there. Unless you pepper your hull with plenty of anodes and keep them clean constantly you are better off not to bond what is isolated in the first place i.e. through hulls. The added advantage is that they are not getting blown out of the hull (with the usual consequences) during a lightning strike.
BTW whether you keep DC and AC seperated or not is immaterial since they enjoy each others company anyway sitting in the same saltwater.
Keeping your lightning side of things seperately is only good for your peace of mind, however after having travelled a few hundred meters through air, lightning would not see great difficulties jumping a few feet over to your DC and/or AC side of things and checking out what damage could be done there before fizzling out in seawater.
BTW whether you keep DC and AC seperated or not is immaterial since they enjoy each others company anyway sitting in the same saltwater.
Keeping your lightning side of things seperately is only good for your peace of mind, however after having travelled a few hundred meters through air, lightning would not see great difficulties jumping a few feet over to your DC and/or AC side of things and checking out what damage could be done there before fizzling out in seawater.
boatmike
Well-Known Member
You make a very good point regarding lightning conductors. Intentionally or not GRP boats often have things bonded internally to an earth that is connected to a through hull fitting, seacock, anode, or keelbolt beneath the WL. If there is no EXTERNAL lightning conductor to provide a better route to ground this is asking for lightning to blow a hole in the bottom of the boat in my opinion. Anyone disagree??
roly_voya
Well-Known Member
The piont about seperating AC/DC earths is not an electrical one its machanical. If you use something like a common block or stud for both and it comes adrift for any reason you have both earths connected but NOT grounded which could result in all the dc kit going 230v live if you get a fault - it has happened! If you have mechanicaly seperate grounds the worst that can happen is you loose one earth.
Cox is probably right that in normal circumstances you wont get a problem with the sea water intake if it is well seperated from other fittings and any anodes but if you includ it you definatly won't even under fault conditions so why not
Cox is probably right that in normal circumstances you wont get a problem with the sea water intake if it is well seperated from other fittings and any anodes but if you includ it you definatly won't even under fault conditions so why not
Benbow
Well-Known Member
[ QUOTE ]
The piont about seperating AC/DC earths is not an electrical one its machanical. If you use something like a common block or stud for both and it comes adrift for any reason you have both earths connected but NOT grounded which could result in all the dc kit going 230v live if you get a fault - it has happened! If you have mechanicaly seperate grounds the worst that can happen is you loose one earth.
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OK, that makes more sense. Thanks for clarifying.
The piont about seperating AC/DC earths is not an electrical one its machanical. If you use something like a common block or stud for both and it comes adrift for any reason you have both earths connected but NOT grounded which could result in all the dc kit going 230v live if you get a fault - it has happened! If you have mechanicaly seperate grounds the worst that can happen is you loose one earth.
[/ QUOTE ]
OK, that makes more sense. Thanks for clarifying.
