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Old 20-06-2019, 11:36   #1
HIP
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Shore Power Causing high voltage, I知 🤔

Hopefully some electrical geniuses here can help me.

I have a 30 amp smart plug shore power plug on my boat. I have that going through a 40 amp breaker, then a Victron 3600W isolation transformer and then to my mastervolt 12/2500 (230 v) inverter.

My Alternating current system sits at 230 volts on the boat voltage meter either on the generator or just running off the batteries. I知 in the US now and my isolation transformer jumpers are in the right configuration for going from 120 to 230 volts. I measure the 30amp plug at my shore power pedestal and it says 120volts on my volt meter. Then I plug it in to my smart plug 30 amp receptacle on the boat and my voltage meter on the boat jumps from 230 volts to 256 volts and the inverter starts clicking periodically like a relay is going on and off. No shore power light is on at the panel. None of the shore power systems work like air conditioning or water maker, but they will work off the generator.

Anyone have any idea why my voltage would jump up like that? Is the inverter going bad? I知 at a loss for ideas. Thanks for any suggestions.
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Old 20-06-2019, 12:52   #2
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Re: Shore Power Causing high voltage, I知 🤔

HIP-
Not totally a WAG but IIRC in the US utilities are actually required to provide 117 VAC plus or minus 10%, and exactly what you get varies with which provider you have as well as how the equipment is set up. If you are close to a transformer, you get higher voltage than if you are not, etc. So my first thought would be to stick a proper voltmeter in that dock power, and see if perhaps the shore power is at 117VAC plus 10%, which could be 128 volts, which is then being boosted to 256VAC by your transformer. It *might* be that simple. If that's the problem, the best way to fix it would be to disconnect from shore power or find another way to step in down, after placing a call to the power company to ask them to check their line.
In the US, power companies have an obligation to "Make the light bulb light up" and that's about all they bother with. Anything more precise is left as an option for the customer to deal with.
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Old 20-06-2019, 15:05   #3
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Re: Shore Power Causing high voltage, I知 🤔

Just a WAG, but could it be because US power is 60Hz and your transformer is expecting European 50Hz AC.
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Old 20-06-2019, 15:26   #4
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Re: Shore Power Causing high voltage, I知 🤔

I don稚 think so. The transformer should be able to handle either frequency according to the literature.

When I measure the outlet with my volt meter it comes in at 120 volts. So the transformer should go to 240 unless there is some voltage drop in the reading of my volt meter.
The inverter says it should be able to handle up to 265v so I知 not sure why this high voltage would make it act up.

The bad thing is my Air conditioners won稚 power up now. I hope I didn稚 fry them.
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Old 20-06-2019, 21:09   #5
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Re: Shore Power Causing high voltage, I知 🤔

I have seen a victron iso transformer put out really high voltage as well. like 250+ from a 120v input. I replaced it and the new one did the same thing. victron told me it was within the tolerance levels....

you'll have the find a setting in the mastervolt to allow the higher voltage to pass through. that is likly what is turning off and stoping power. either that or the mastervolt does not like the 60hz.
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Old 20-06-2019, 21:11   #6
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Re: Shore Power Causing high voltage, I知 🤔

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Originally Posted by StuM View Post
Just a WAG, but could it be because US power is 60Hz and your transformer is expecting European 50Hz AC.

the transformer shoudln't care but the inverter /charger probably does

some things on the boat will also care if / once you get it working through the mastervolt.
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Old 21-06-2019, 08:58   #7
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Re: Shore Power Causing high voltage, I知 🤔

We have a very similar situation on our boat. She was built for Asia power(230v, 3 wire, 50Hz). When we arrived at US power (Puerto Rico) we, too, bought and installed a Victron Auto Isolating Xfmr. When we plug into shore power, we see anywhere from 230v to 255v AC. I've checked the shore power pole, and seen 110v up to 124vAC. I just assumed the Xfmr has a fixed winding, and just stepps up the incoming by that fixed ratio. So far....everything keeps on working OK on our boat. But it does concern me-what is the voltage beyond the 230v the motors are designed for(aircons, watermaker, refer, etc) where things are likely to fail? I've never seen specs on that, and have no idea where to find that info. If the Xfmr puts out 230v at 110v input, it puts out 261v at 125v input....both within limits for incoming power!
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Old 21-06-2019, 10:29   #8
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Re: Shore Power Causing high voltage, I知 🤔

No one has asked, so I will. Why do you have a breaker on the inlet rated for 33% MORE than the smart plug is rated for? If anything I would go 20 amp or if you really want to be safe, 25amp.
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Old 21-06-2019, 13:35   #9
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Re: Shore Power Causing high voltage, I知 🤔

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No one has asked, so I will. Why do you have a breaker on the inlet rated for 33% MORE than the smart plug is rated for? If anything I would go 20 amp or if you really want to be safe, 25amp.
Good call. Sorry that痴 a typo. Should say 30 amps.
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Old 21-06-2019, 13:36   #10
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Re: Shore Power Causing high voltage, I知 🤔

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Originally Posted by sailcrazy View Post
We have a very similar situation on our boat. She was built for Asia power(230v, 3 wire, 50Hz). When we arrived at US power (Puerto Rico) we, too, bought and installed a Victron Auto Isolating Xfmr. When we plug into shore power, we see anywhere from 230v to 255v AC. I've checked the shore power pole, and seen 110v up to 124vAC. I just assumed the Xfmr has a fixed winding, and just stepps up the incoming by that fixed ratio. So far....everything keeps on working OK on our boat. But it does concern me-what is the voltage beyond the 230v the motors are designed for(aircons, watermaker, refer, etc) where things are likely to fail? I've never seen specs on that, and have no idea where to find that info. If the Xfmr puts out 230v at 110v input, it puts out 261v at 125v input....both within limits for incoming power!
Thanks for the feedback. My inverter says it should handle these loads but it is 10 years old. Maybe it痴 crapping out.
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Old 22-06-2019, 08:32   #11
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Re: Shore Power Causing high voltage, I知 🤔

We have a similar setup, and own the same Victron Auto isolation transformer. I don't recall if it's in the manual, or in some other Victron documentation somewhere, but I learned that the Victron iso transformer is intentionally designed to boost incoming voltage by approx 10%. This is to compensate for low incoming voltage that you might see at the end of the dock when everybody else is running their aircon. But consequently, if incoming shore voltage is on spec (~120v) when plugged into US shore power, you will see ~260 volts inside the boat.

This isn't ideal, but it's exactly what we see when plugged into US power in our current marina, and everything still seems to work as it should. The 230v Victron inverter still syncs up just fine -- matching the ~260v / 60hz that it sees on the input -- and our aircon units also run fine (though they are 60hz spec units).

I agree with smac99 that it's probably your Mastervolt inverter that doesn't like either the higher voltage or the 60hz frequency. The clicking sound you're hearing from the inverter is presumably the Mastervolt's shore-power input relay closing and opening because it can't stay synced.

Another possibility, although less likely, would be an incorrectly wired ground (earth). Our Victron inverter has an automatic ground relay that closes, connecting ground and neutral, whenever there is no A/C input power connected. But as soon as it senses an A/C input, the ground relay opens (ground and neutral are no longer connected at the inverter), and earth and neutral MUST be bonded at the source (either generator, or iso transformer in our case). We had a situation where a broken ground connection in the generator terminal box would prevent the Victron inverter from staying synced when running the generator... the inverter's A/C input relay would close and open repeatedly, like it sounds like yours is doing. So it's possible that the earth-neutral connection isn't wired correctly in your Victron transformer, and that's what's preventing your Mastervolt from staying synced. The Victron manual details out the proper wiring pretty clearly (it varies depending on whether the boat is floating, or on the hard). You might also check with Mastervolt to confirm what your existing inverter "expects" wrt earth-neutral connection.

Good luck.
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