ground fault from shore power

[SGIDAVE]

All 3 of those points deal with inproperly installed systems. Do it right in the first place and ALL those issues are avoided, accept for the lightening of course, in that case, your screwed anyways, if air is conducting electricity, so is damn near everything else your boats made of, a simple bond wont really matter.

Hello Bin,

When you say

The Bond is for safety, it should NEVER be electrically tied to anything, doing so defeats its purpose.

Your argument is really with the ABYC standard E11, specifically E11.5.5.1 and following where it states: The main AC system grounding bus shall be connected to the engine negative terminal or the DC main negative bus on grounded DC systems

dave

 

[Binare]

All 3 of those points deal with inproperly installed systems. Do it right in the first place and ALL those issues are avoided, accept for the lightening of course, in that case, your screwed anyways, if air is conducting electricity, so is damn near everything else your boats made of, a simple bond wont really matter.

Hello Bin,

When you say

The Bond is for safety, it should NEVER be electrically tied to anything, doing so defeats its purpose.

Your argument is really with the ABYC standard E11, specifically E11.5.5.1 and following where it states: The main AC system grounding bus shall be connected to the engine negative terminal or the DC main negative bus on grounded DC systems

dave

The problem is that laymen read code and think they understand that code.

The DC grounding system, including your grounding bus is a non-current-carrying system. It is the exact same as the bond system in AC.

You need to understand the difference between a grounded conductor and a grounding conductor in order to understand the code, whether its in AC or DC, you do not.

Tying it in at the negative side of the DC maintains its non-current-carrying as its not part of any actual circuit unless there is a fault, it is the same potential as the AC bond system and is there as SAFETY.

If the positive side of a DC circuit fails and touches the metallic case of a piece of equipment, the grounding bus is there as safety to ensure a path of low resistance, low resistance equals high current equals tripped breaker. EXACTLY the same in an AC system.

Assuming you know these things and tying in DC equipment to the grounding bus, instead of the grounded (negative) bus is wrong and defeats the purpose of that safety, now the normally non-current-carrying metal parts of that dc system is carrying current it shouldn't be.

I am well versed on both ac/dc systems, my comment

The Bond is for safety, it should NEVER be electrically tied to anything, doing so defeats its purpose.

Is 100% correct.

I suggest you read the code you are quoting and look for the definition of grounding, you will be surprised given your misunderstanding of the topic.

The 3 points you mentioned state tying in the AC bonding system with the DC negative connection, that is completely incorrect and misleading, and the code you mention agrees with me.

The AC bond system shall be tied into the DC grounding(bond) system, which is than tied into the negative side main bus. If I tie in the AC or DC bond into any other part of DC negative, and do not maintain it as a grounding system(tie in a negative conductor from equipment), it has become part of the negative bus and you no longer have a non-current-carrying grounding bus.

 

[JeffE]

There are [potentially] three sources of AC power on these boats: shore power, the genset, and the inverter. The relationship between the neutral and ground bus for each varies with the source. For shore power, you "just" carry the forward ground and neutral from the shore power connector. However, for the inverter and the genset, the ground and neutral need to be tied together on the boat...which *must* not be done for the shorepower.

For a genset, it's generally done when the source is switched. This may be as simple as tieing the ground into the genset neutral, since the neutral is switched (from disconnected to the boat's neutral bus).

For an inverter, it depends if the inverter automatically switches from source to DC (inverting) and if it automatically switches when it does. I've had inverters that automatically switch the source/DC (a Trace SW2512) but not the ground (we had to install a relay), and those that switched both (a Trace SW4024). I actually don't know what the one I have now does -- maybe someone from Ranger could chime in here.

The DC system also has 3 busses -- the positive, the negative, and corrosion ground. The positive bus is totally isolated from all the others. The negative bus should have *exactly* one tie to the corrosion ground -- on some boats, the tie is done in multiple spots, but Nigel Calder makes the point that multiple tie-ins may result in stray current corrosion (due to the slightly different voltage potential at the various tie-in points). The corrosion ground is also tied into the AC ground. If this is done without an isolation transformer and without a galvanic isolator, you may be impacted by stray current corrosion, either from a source on your boat (bad) or from another boat's faulty wiring (really bad). Our boats don't have a galvanic isolator installed by default, but you can add one.

Generally, you don't need to thinks/worry about any of this. Ranger appears to me to have done a conscientious job of design/installation of their AC and DC systems (at least on my boat. I've been very pleased with it as I've tinkered, I just wish they provided service loops and better strain-relief).

Isn't all this fun?!

Jeff