charger failure - excess incoming voltage

[jimrosbe]

Problem: When connected to shore, excess incoming voltage causes charger failure

I have a steel Dutch-built motorsailer built in 1990, that I bought in 2011. From May to September, when connected to shore power, we never noticed any problems. Last month I connected my boat to shore power in Norway, and my Mastervolt 24/40-3 charger (installed new six months ago) registers “FAILURE 266U” and the voltmeter on the boat’s main electrical panel is at the very top of its scale (>250v).

We measured voltage of 238v at boat end of shore cable...and taking off the cover of the charger, measure incoming voltage to the charger at 251v.

When connected to shore power, I can hear a humming sound buried somewhere in the cabinetry...and according to the boat’s wiring diagram there is an isolation transformer.

When running the boat’s Onan 6.5kw generator, the charger works fine.

Any suggestions? Is it possible that the isolation transformer is stepping up the voltage?

[donradcliffe]

There are isolation transformers with taps which can increase the voltage 10% or so--they are used where there are problems with marina voltage supplies sagging.

[CharlieJ]

+1 for Don's comment although all electrical devices operate on the general spec of acceptable voltage being +/- 10%. If the IT is fitted, and if it has taps, my guess is that the tap setting is for > 10%.

You need to dig into the cabinetry and find the nameplate data for the "hummer" before we can be much more helpful.

[smac999]

some have a switch so you can boost voltage with the flip of the switch. as needed or not needed at different marinas. may be that easy to fix. may require some rewiring.

[jimrosbe]

Thanks for your comments. Unfortunately I will have to wait until returning to Norway in April to uncover the isolation transformer, but if (as I expect) it is a Victron, here is what they emailed me:

"There Is no voltage control in the transformer. its so that the transformer voltage is always (10-15 volts)higher than the input voltage. If you will put a heavy load on it the voltage will drop.
With small loads the voltage will not drop much and if your input voltage is higher than normal , then you could measure higher voltages on the output, this cannot be adjusted."

I will contact Mastervolt to see if there is an adjustment on the charger to safely accept higher voltage.

[smac999]

if possible move the boat further down the dock away from land. the voltage will be less at the ends of the dock.

if you have a meter. go measure the plugs further down the dock and see what happens first.

increasing the load of your own boat will likely not effect much. as you move down the dock, you have the loads of all the boats added.