Posted: Sun Mar 07, 2021 10:16pm

I'm in the process of buying an Airlink Isolation Transformer to protect my narrow boat from galvanic corrosion whilst it is connected to shoreline. Tests showed that there was some electrical leakage, which was prevented with an isolation transformer. However, since placing the order, I've been told that my Victron Multiplus 12 | 3000 | 120, which was fitted at the time of the test, might already act as an isolation transformer, meaning that I don't need to buy the Airlink. Please, would someone let me know if that's correct, so that I have the option of cancelling the order in time. Thanks Here's the link to the Victon datasheet ... https://www.victronenergy.com/upload/docu ments/Datasheet-Multiplus-inverter-charger_2kVA- and-3kVA-120V-US-EN.pdf

Posted: Mon Mar 08, 2021 8:19am

An isolation transformer fits into the INCOMING mains earth conductor. An inverter like the Multipus that I think can add its output to that supplied by shoreline goes into the line and neutral. I don't know what it does with the earth but in no way is it an isolation transformer. Any electricity generated onboard the boat, so that includes from an inverter, can not normally cause hull corrosion. It is only when the supply comes from a shore based source and there is a connection between hull and the soil (mains earth lead) that corrosion can occur. I think the inverter must connect the mains earth to the hull otherwise it would not be safe when the boat is connected to the shoreline. I think whoever told you that you don't need the Airlink does not understand the subject well enough to advise. However, if you got that from Victron then I happily accept it because they know what's inside it. I have never heard such a statement before. Your link is for a 120V unit, you need a 240V one for UK use and it does not work. The manual I found does not suggest what you have been told is true.

Posted: Tue Mar 09, 2021 12:17am

Thanks, for your reply. The person who suggested that the Multiplus might act as an isolation transformer wasn't entirely sure, so I'll continue with the order of the Airlink.

Posted: Tue Mar 09, 2021 7:12am

For safety the mains earthing needs to be wired so there is protection with the inverter in use and out of use so even if you set it up as recommended with an internal relay in the earth circuit there may be times when the shoreside earth is connected to the boat hull, that means to avoid potential corrosion you need and isolation transformer.