Re: [Amel Yacht Owners] Alternator and Masse leak detector
Hi Bill,toggle quoted messageShow quoted text
As I understand it, the Isolated ground system on an Amel is no different to other yachts with Isolated ground systems, and is quite simple namely that the negative of the DC system (and indeed the AC system) is not connected to the rest of the equipment in the boat. So every piece of 24v equipment is connected to the battery bank with a +ve and negative wire via the switch panel and or busbars or indeed directly to the batteries. The battery bank negative is not connected to the engine block or anodes. Then all the equipment and metal on the boat is linked together and earthed to the sea independent of the battery bank.
With this system the alternator for example has to be an isolated ground alternator. That is the -ve terminal is not electrically connected to the alternator frame as on some alternators. So there are two terminals on the back of the alternator, one +ve and one -ve and there is no electrical contact between them and the alternator frame.
If the +ve or the -ve on the battery system is connected to the ground system a fault light appears on the “Masse” detector.
If any sensor or piece of equipment on the engine is not isolated ground rated then its -ve will make an electrical contact with the bonding system.
It is, to my eye, likely that the 24v charging alternator has a fault such that the negative terminal is leaking to the frame of the alternator and thus to the engine itself which is connected to the bonded system and to the sea. By disconnecting the 24v negative cable from the faulty alternator there is no longer a contact between negative 24v and the bonding system, which is why the fault light goes off then. Thus we have found the fault.
Furthermore I suspect that within the faulty 24v alternator we will discover that it is one of the diodes within the rectifier that is leaking to the frame, but that remains to be seen.