Jedi AC power system (English)

When we bought Jedi back in 2002, it was mostly a 12V DC powered boat. The only AC power was to come from a Trace inverter/charger and shorepower. The installed genset was a Fisher-Panda which was 12V output only and the cylinder was seized. We got rid of it, like anyone should get rid of this junk, and were presented with the choice for either a DC or AC genset. We ended up ordering a Northern Lights 120V AC 6kW genset. At the same time we ordered an AC watermaker and air-conditioner. There wasn't much thought about the design and wiring of the system as we wanted to go out sailing. Over the years, we made small and not so small changes and we finally ended up with the following diagram (click it for full picture in seperate window):

The system is configured around a Freedom 30 inverter/charger which has two internal automatic transfer switches. We installed this 3000W inverter / 140A charger combo in Trinidad because we could not start the watermaker from the Trace 2500W inverter and we wanted to be able to make water in the event that the genset breaks down. We can generate power with the two big alternators on the main engine (210A each) and feed this to the inverter.

Another nice feature of the Freedom 30 (also on the Freedom 25) is the dual automatic transfer switches. You can use one AC input for shore power/genset and the other for a second inverter. We installed a small 600W true-sine inverter which handles most tasks. As can be seen in the logic-table in the diagram, when power is applied to the 2nd input of the Freedom 30, it will be switched to the 2nd output only, never to the 1st output. This way, you can design automatic overload protection for a small inverter by not allowing loads that are too big to try to run from the small inverter. For this to work, we divided the AC busbar in the main switchpanel into 3 busbars. The first one is only powered from genset or shorepower, not from the inverters (for airco and waterheater). The second busbar can be powered from genset, shorepower (using 1st transfer switch) or the 3000W inverter. This is for the big loads which can (and we wish) to be handled by the big inverter. The 3rd busbar is for all the AC outlets around the boat which can also be powered from the small inverter. We can still overload the small inverter by trying to power the 1200W coffeemaker from it and sometimes we accidently do. We can happily report that the internal overload protection of this 600W inverter works ;-)

Last but not least is the isolation transformer. Yes, this is a big and heavy item but we wouldn't want to do without. We can take any shorepower voltage in use around the world and make 110-120V from that for use aboard. At the same time, the isolation feature protects us from severe electroshock therapy and protects the boat from galvanic corrosion.

Over the last couple of days, we installed two additions to the system. First was a new digital meter from Blue Sea Systems which can show AC voltage, current, power consumption in Watts and the frequency in Hz. The frequency was the main reason to install it because we want to keep an eye on the frequency from the genset (is directly related to the engine rpm). The second addition is a small 120V fan which starts running when either genset or shorepower is available. It ventilates the cabinet where the Freedom 30 is installed which gets quite hot when charging the batteries. We used to open the cabinet door during charging but the cats like that too much . . .

When I look at our system I think it's pretty much a perfect system. We loose a lot in case the big inverter fails but we have outlets on the small inverter we can use in that case. The only problem left is the watermaker during a failure of the big inverter or from a burned out main switch panel. To deal with that I will install some emergency AC outlets which connect directly to the genset and a by-pass switch to power the watermaker directly from the genset. The watermaker is the only peace of equipment that I can think of which I would like to run after such a failure; the emergency outlets are for anything else I might overlook. If you think of anything else or just want to comment on our system, please click the "Reacties" link below.

ciao!
Nick.

Comments

[Geplaatst door: Scott Whitfield]

Thank you for posting this. Your setup here is nothing short of brilliant. I had to read the last pages of the Xantrex Freedom 30 manual to understand how the transfer function worked. Great thinking!

[Geplaatst door: Scott Whitfield]

Would you be kind enough to share what isolation transformer you are using? I'm interested in that it will accept both 220 and 120 voltages and transform them to 120. How much current does it accept in either mode? Thanks!

[Geplaatst door: Nick Vermeulen]

Hi Scott,

We just replaced the transformer with a 3,600W version made by Victron. This will allow a full 30A on 120V or 16A on 220V.
These units have easy jumpers for step-up or step-down mode so that you can use it for any combination of shore- and boat-voltage.
Keep an eye on the frequency, 50/60 Hz. Some equipment made for one might get damaged on the other. A transformer doesn't change the frequency of the input.

Sorry for replying so late ;-)
ciao!
Nick.