In all such installations it is important to maintain the separation of grounded and ungrounded systems, which is sometimes not easy to do. And almost all electric propulsion systems above 50 volts are installed as isolated ground systems while the rest of the boat’s DC systems are typically grounded. Some bow thrusters, with their own battery that is not connected to other batteries on the boat are installed as an isolated ground system while the house batteries are grounded. Conversely, an engine cranking circuit may be installed as a grounded DC system while the house batteries on the boat are installed as an isolated (ungrounded) DC system. For example, some high-pressure common rail diesel engines (see our forthcoming diesel lessons) require isolated cranking and battery charging circuits while the house batteries and circuits may be grounded. Note that it is possible to have both grounded and ungrounded DC systems on the same boat. System in which both positive and negative poles remain isolated from the ground (earth), e.g., not connected to the water through a metallic hull, the propulsion system or earthed through the AC protective conductor.’
#Abyc positive ground isolator iso
In this case we have what the ABYC sub-committee calls an isolated DC system and what the ISO calls a fully insulated two-wire DC system. In some circumstances, primarily for corrosion control, it is desirable to isolate the negative side of a DC system from source ground. We cover the various grounding circuits in this module of our Advanced Marine Electrics program and provide a more detailed explanation of the reasons for these circuits in our two AC modules, and the corrosion and lightning modules. This is done to prevent potentially dangerous voltage differences arising between different metal objects on the boat (e.g., given a fault in an AC circuit or a lightning strike), or to connect submerged metal objects to a sacrificial anode, or to mitigate against stray current corrosion, or to minimize radio frequency interference, or for all these reasons. The connection to source ground holds these circuits at a common potential. These will include the AC grounding circuit if we have ABYC-compliant AC circuits, any bonding or lightning protection circuits, and perhaps electronic grounding circuits.
We may have various other circuits also connected to source ground. The ABYC also calls earth ground source ground we will use this term. Most of our DC systems have the negative side of the system, what we have called circuit ground, connected to earth ground – i.e., the water surrounding the boat.
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