hobohome avatar image
hobohome asked

Quattro 5k 48v Overload / short circuit

My off-grid system consisting of a Quattro 5k 48v inverter did some weird stuff for the second time last night.

I suddenly lost all power. The inverter LEDs were showing Low Voltage and Overload.

The Venus GX reported a warning :

Low voltage - 49.59v (which is far from low)

And an error - Overload

This is the second time I have seen this, the first time was over six months ago.

Turning the inverter off and back on resolved the issue.

Here is what I’m thinking (and I’m really only guessing):

If there was a dead short on a house 240v circuit you would of course expect this to trip a distribution circuit breaker, but what if the inverter can not supply enough current to exceed the trip point?

Does anyone know what the inverter will do when presented with a dead short on the output?

Any other ideas what might be causing this?

MultiPlus Quattro Inverter ChargerSOC
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jacko avatar image jacko commented ·

What batteries do you have this might determine the amount of current they could provide in a short circuit situation and if that would be enough to trip an mcb, do you have rcd protection aswell. I had been having overload problems with an attached generator shutting down do you have a generator in the installation?

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hobohome avatar image hobohome jacko commented ·

Yes, I do have a generator, but this was not running at either time.

The battery bank is a flooded LA of 32Kwh (675ah)

Yes RCD's are fitted to every circuit - but of course they will not trip in a phase->neutral short situation.

The largest MCB's are 16amp (@240v) and I am a little surprised if the 5kva inverter attached to that battery bank can not exceed 20 - 30 amps or more. But who knows what it will do when presented with a dead short.

The reason why I thought that it may be a dead short is that I have a much smaller system in a motorhome (2kva inverter) and I have seen this inverter just stall without drawing enough to trip an MCB when a washing machine motor developed a near dead short.

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5 Answers
hobohome avatar image
hobohome answered ·

I just wanted to follow up on this issue now that I am confident that it has been resolved. It may help someone else in the future.

The symptoms listed above continued and became more frequent. I contacted the state Victron service agents (located in Cairns Australia), who were just fantastic! It is all too rare these days to find a service agent who really cares AND has the expertise to help resolve a serious problem.

Henk recommended that the inverter ribbon cables be replaced , and sent me a set (I am an electrical tech, so can do the work myself).

With the inverter apart, I found a fairly significant layer of dust on most of the boards and carefully cleaned these and replaced the three ribbon cables. (The inverter is adjacent to my workshop, so the dust probably contained some conductive grinding material).

The inverter has now been back in operation for over two weeks and the issue has not reoccurred. I don't know if the problem was the cables or the dust on the boards, but I am very happy to have the inverter back up and running and performing as it should.

A massive thanks to @Henk from Pasma Electrical, Victron service agent in Cairns!

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boekel avatar image boekel ♦ commented ·

Good solve!

Dust + condensation due to temperature changes can also do a lot of bad things.

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Anil Ghatikar avatar image
Anil Ghatikar answered ·

I my case a 5 KVA Quattro when presented with the accidental connection of phase and neutral (while working by electrician - few seconds) actually carried the current with Overload warning and gave a generator start command ( programmed to start the generator on loads more than 3 KW) but the 16 AMP MCB located 30 meters away did not trip

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hobohome avatar image hobohome commented ·

That’s interesting. Thank you.

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Paul B avatar image
Paul B answered ·

I would test my batteries and see if they can deliver the said current, How old are they

load the invert up with a few kettles and see what happens to the battery voltage. at max load they should give around 100 amps and at max overload around 200amps and hold the voltage about the low voltage settings you have set, baut anyway over 40 volts the higher the better

if you have a ccgx or venus connected you would be able to trace and check this on the VRM site

good luck and I hope thus dust was the issue

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Charlie Johnson avatar image
Charlie Johnson answered ·

@Anil Ghatikar: You have highlighted an interesting and not widely understood phenomenon. First off, let's look at the trip curves for fuses and circuit breakers. Here is one for Class T fuses:

As you can see, it will take >500% of the rated capacity (a reasonable approximation of a dead short) to open the fuse in about 0.01 second. If the impedance of the conductor on the load side of the fuse is so high that 5 x rated capacity cannot be passed, then the fuse will not open at that current.

Marine Electricians in the USA use a SureTest Circuit Tester to test AC electrical circuits. One of the tests is to determine the Available Short Circuit Current (ASCC) which is found by measuring the impedance of the circuit. A good rule of thumb is to have an ASCC of 5 to 10 times the fuse or circuit breakers rated capacity. This ensures that if there is a phase to ground or phase to neutral short circuit that the conductor impedance will not hinder the operation of the over current protection device.

So, your 16A circuit breaker 30m away probably did not trip because the circuit impedance did not allow enough current to flow to trip in accordance with the breaker's trip curve.

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youssefpjd avatar image
youssefpjd answered ·

I have a quattro 5 kw, and I have a problem of overload and the phase and the neutral are short-circuited ... the problem always perciste ... there is a solution please

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boekel avatar image boekel ♦ commented ·

Hi @Youssefpjd

Please go through the support channels for your system:

If you've checked all options (like disconnecting all users) and you still have this problem, you'll need an installer / distributor to help you further.

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