5000W water boiler from 3000W Multiplus - AC Out 2?

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d-h asked Feb 10, '23

5000W water boiler from 3000W Multiplus - AC Out 2?

Hi all,

I have wired up my inverter to supply the 240v breaker board from AC-Out 1 that has the boat sockets and the water boiler on, both on independent breakers.

The sockets all work fine but when I turn on the water heater on, which has a peak draw of 5000W (and am connected to the shore supply) it trips the marina shore supply (and the breakers in the boat).

My question is two part:

1. I assumed that when on shore power that the 3000w limit would not apply?

2. If I connect the water heater to AC-Out 2 (only avalable when shore power is connected) then will 5000w output still be accepted by the mutliplus and pass through the power or does the load still need to be below 3000W?

P.S The water boiler was working fine when the shore supply went direct to it before I installed the inverter (two days ago) so the power demand is fine for the shore supply.

Thanks in advance!

Dudley

inverter current draw

1

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pwfarnell commented · Feb 11, 2023 at 09:22 AM

Do you have power assist turned on in the settings so that the Multiplus boosts the shore power.

Secondly, is it definitely tripping on overload or could it be an earth leakage if you have combined MCB / RCD type breakers (RCBO).

0 ·

pwfarnell answered · Feb 11, 2023 at 07:18 PM

As you have just installed the inverter my guess would be that the rewiring has introduced a n error, live and neutral shorted out somewhere or live and earth. Turn off the inverter and disconnect the shore power. Then check to see if you have got continuity between live and neutral or live and earth. The immersion will have a 50 ohm resistance between live and neutral when switched on, test it switched on and off. Check all wiring that was disturbed or modified to make sure everything is connected correctly and that there are no loose strands sticking out of wire ends making rogue connections. This sounds like a basic wiring error, nothing to do with the Victron kit.

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d-h answered · Feb 13, 2023 at 05:23 PM

Good evening all,

Problm solved now thanks very much for all the input, helped me massively in tracking down the fault to the water heaters element. Turns out it had shorted inside the unit so replacing the thermostat and the element has solved the problem. The inverter now runs it perfectly should it be required when off the shore power.

Thanks again all.

Dudley

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Answer 1 · 2023-02-11T06:50:43Z

JohnC answered · Feb 11, 2023 at 06:50 AM

Hi @D H

You don't say exactly which model Multiplus you have, but presumably one that can handle what you're doing. Your questions..

1) That 3000W is actually 3000VA, inverter power, and doesn't apply to passthrough from shore.

2) Without looking through specs of all the Multi models, you may find ACOut2 has a lower limit. Leave the heater on ACOut1.

Your real issue though is tripping the shore breaker. What size is it, maybe 20A? So you might get by (only just) drawing 5000W alone from it, but your Multi may be also charging batteries too, so overload results.

You could limit the Multi's Input Current via settings, and that should always ensure you never trip the shore breaker.

In the washup though, a 5000W water heater seems a little out of place with limited power. Maybe a smaller element?

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Answer 2 · 2023-02-11T17:49:10Z

d-h answered · Feb 11, 2023 at 05:49 PM

Thanks both for the input, much appreciated.

Slight correction - the heater is 1200W so it shouldn't be an issue.

It seems to be tripping the 40A main breaker on the boats breaker panel (I'm a bit of a newbie so i'm not exactly sure if its an RCBO) . The heater itself is on a 10A breaker but it trips the main instantly on power on before getting to that one - AC In->Multi->Boats breaker panel with 40A as the main breaker and then two individual breakers for the sockets/boiler)

I'm not too sure but it's instantly tripping it as soon as I turn it on - when you say earth leakage, is there a way of chasing down if that's the issue?

Thanks in advance, if i get this nailed then I'll be a victron convert for life! So far the rest of it is perfect!

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Answer 3 · 2023-02-11T19:27:01Z

d-h answered · Feb 11, 2023 at 07:27 PM

Great thanks Farnell, I'll check those tomorrow and let you know how I get on. (Also I definitely wasn't blamng the victron kit, I absolutely love it, boiling a kettle off grid for the first time was game changing!)

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Answer 4 · 2023-02-12T01:01:36Z

Al answered · Feb 12, 2023 at 01:01 AM

It might be worth measuring the immersion element resistance if your tripping all your breakers.

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Answer 5 · 2023-02-12T01:17:48Z

JohnC answered · Feb 12, 2023 at 01:17 AM

On a boat it's especially important you seek out and remedy the cause of any issues earthing related. Some info in here.. https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

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Answer 6 · 2023-02-13T17:43:21Z

philippem answered · Feb 13, 2023 at 05:43 PM

Hi, a water boiler is stressing a lot any solar installation, even some disagree I recommend to downgrade 50% all the specs. By doing this you will reduce a lot the stress on the electronic components, extend the lifetime and seriously reduce the risk of fire by overheating.

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