Inverters on A55

Joerg Esdorn

On my boat, I have the 2.5 KW Mastervolt Mass Sine inverter.  There was an option when I bought the boat to get a 5KW inverter.  As MV makes no 5KW inverter, I believe this was 2x 2.5KW inverters hooked up in parallel.   I am now thinking about adding a second 2.5KW inverter and wonder whether I could run the watermaker or AC with it.  These inverters can supply up to twice the rated output which should get over the needed additional power for startup of the watermaker or AC. But I wonder whether these inverters will supply a sufficiently good sine voltage to make the watermaker operate.  I asked Dessalator and they said I’d have to try it out.  Does anyone with a A55 have the second inverter and can answer my question?

Joerg Esdorn 
A55 #53 Kincsem
Currently in La Rochelle

Billy Newport

Arno Luijten


There is a omission in the English version of the Mastervolt website:
This is the Dutch page for the Mass Sine 24/5000. The page does not exist in English.

Second of all the actual continues power from the Inverter is not 5kW but 4kW and for the 2,5 kW it is 2 kW.

Third (to answer your question), the Mass Sinewave inverters cannot be set in parallel as that would require a synchronization across the inverters (Alternating current, inverters need to be in phase with each other). These models do not provide that facility.
The Mass series of inverters is a fairly old design and cannot even properly integrate with the Masterbus system as they are not made by Mastervolt (3rd party manufacturer, I forgot the name).
The Mass Pro and Ultra models are more modern and allow setting them in parallel and have Masterbus as well. You could consider replacing the existing one with a Mass Sine Ultra 24/4000. This one is 4kW continu
In my case I replaced the 24/2500 with the Mass Combi Ultra 24/100/3500 (3,5 kW cont.) so I can run the washer and other stuff even when connected to 60Hz shore power. (let me know if you want details).

Arno Luijten
SV Luna,

Joerg Esdorn

Very helpful, Arno!  Your point about Masterbus integration explains why the MV technician didn’t connect my inverter to the Masterbus system he installed!  It looks like 4KW will be enough to run the water maker.  The specs say 15A continuous draw and there is apparently a “soft” startup.   I’m not sure it’s enough to run the AC but that’s something I can find out.  Cheers. Joerg