Re: [Amel Yacht Owners] Upgrading all electronics
Bill Kinney <greatketch@...>
Kent,toggle quoted messageShow quoted text
It is not as simple as saying it is "OK as long as you don't connect the ground [of the charger] to the bonding system”
You can not, and should not, remove all connections between the bonding system and the AC safety ground. Those connections are there by Amel design—not by accident and are shown on Amel’s electrical drawings. See Olivier’s comments on this matter. Because of the connections between them, the bonding circuit and AC safety ground circuits really are all part of the same system, in normal operation carrying almost no current, but equalizing voltages.
Because there are always going to be connections between the AC safety ground and the bonding system, ANY connection between the DC negative and the AC safety ground is the same as connecting the DC negative to the bonding system. This should NOT be done--anywhere--on an Amel.
The apparent problem with some battery chargers is that they make such a connection between DC negative and AC safety ground internally. These are the kinds we need to avoid. On a proper marine battery chargers this connection would not be part of the design. It would be bad practice on any boat to have multiple connections between DC negative and AC safety ground scattered around the boat and always bad to have the charger case be part of the DC negative circuit. I am pretty sure that such a piece of equipment would not be considered ABYC compliant.
An important point to remember is that the AC Safety ground—in normal operation—should not carry any current at all. It is only there to drain off hazardous voltages caused by short circuits to equipment cases. Almost always, when this happens the current draw is enough to trip the circuit breaker, shutting down the faulty circuit.
Recommending that the case of a battery charger (or inverter, or any piece of equipment connected to AC line voltage) should not be grounded should not be done lightly. Most of the time, that ground is an important safety issue. If there was an internal short the case of the charger could become “hot” at full line voltage. If the case is not grounded that condition can continue until the next thing to touch it (You?) carries 220 volts to ground.