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desperatedan avatar image
desperatedan asked

Problem with dump loads on an off grid system

Off grid system, nice big bank of batteries powered with a 6kW wind turbine and backup generator.

We've had a new lot of kit installed which is run by a Victron Quattro inverter/charger and colour control.

Our old system (Outback inverters) worked by feeding the power into our bank of batteries and then, when there was excess wind power, dumping that power to storage heaters which were hard wired into the system. It worked well. Power would only be dumped to heat when the house's needs were all met and the batteries were fully charged.

The new system dumps power whenever wind speeds are high which sounds ok, but in practice it's not working well for us. We've had several low-wind days and our batteries are therefore low, and now the wind speeds are picking up: so power is being dumped even though our batteries are still on a relatively low charge (last time I looked we were at about 58% according to the colour control) and with the washing machine running (nothing else) the level of charge in the batteries was actually dropping, despite the wind turbine belting round, because so much power is being dumped.

The batteries rarely get above 80% charge, and are frequently below 50%. We live in an area with very good wind speeds and relatively little turbulence, so the turbine is very efficient for us. Or at least, it was, before we had this new kit installed.

In addition we've realised that whenever our diesel generator is put on (the remote start no longer works since the new installation--we'll get round to that later) all the dump loads come on. We're paying for the generator to run, in order to dump 6kW of heat we do not need before our batteries are charged.

We've queried this all with our installer and he says the new system is working as it should. I am not convinced. I do not want to pay to run a generator to produce mostly heat--I don't want to dump any power when the generator is making it, because I want to minimise the hours the diesel generator runs. And I want to be able to run the washing machine, tumble dryer, and a few other things too, especially on high-wind days, but the dump loads mean I don't have the power to do that.

This can't be right, surely.

Advice?



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6 Answers
Chris avatar image
Chris answered ·

I feel your pain - and the devil is in the detail (and assistants! - often)

What is managing switching on the dump loads?


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desperatedan avatar image
desperatedan answered ·

Installer says it's all controlled by the Quattro, and that the dump loads respond to increasing frequency as the wind speeds pick up. I am losing confidence in him, though, as he's now contradicted himself several times about how this all works.

With our previous system we could change everything using the control panel, but the Colour Control doesn't give us many options.



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Chris avatar image
Chris answered ·

ahh yep - suspected this might be the case.

Generators often have a higher off load / low load frequency - up to 53hz or more. And also be unstable!

Also assuming they have configured the "PV inverter" assistant on the quattro .There are frequency thresholds that can be changed. It all has to match up and be carefully choreographed.

The quattro starts to ramp the grid frequency as the battery "approaches" being fully charged. This could be causing the dump loads to come in too early - if their frequency controlled switches are set too low. (unfortunately ive never been able to find any actual documentation for the %'s and what is meant exactly by "approaching" and have recently seen on a lithium battery system that it only happens actually at 100% SOC and not before)

Turbine output and quattro charge capacity is critical for avoiding over volt issues on the AC. But you may already be aware of that... just throwing it in there....

Its also best having the Colour Controllers internal relay managing the generator (it may or may not be?) As it has far more functionality (just a dump volt free relay for "run / dont run" control though)

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desperatedan avatar image desperatedan commented ·

So with this system there’s no way to avoid dumping power when the generator’s running? If that’s true (and I don’t doubt you) then the system is not fit for purpose.

We don’t have PV, just a wind turbine—does that matter with regard to the “PV inverter assistant” you refer to?

You suggest that we should be able to change the point at which the frequencies change, and therefore the points at which the dump loads kick in, but we can’t find a way to do this using the Colour Control, which is how our installer told us we should change settings.

The generator’s remote start isn’t functioning. It hasn’t since the new kit was installed, so we can’t use the Colour Control to manage the generator at the moment. We’re trying to find out what the installers changed on the gen set to see if we can change it back, but they’re just insisting it’s all working fine and that we need to “get used to the new system”. Which isn’t very helpful.

This new system has resulted in us having less usable power, having to run our generator a whole lot more than we used to, and in our having to mess around with plug-in dump loads instead of them being hard-wired things we could forget about. It’s a disaster, and right now I cannot recommend Victron products—not to anyone who lives off-grid, as we do. From what I’ve now learned, here and elsewhere, it’s a major step backwards for us, compared to the set up we had before. And there’s little we can do about it, as the installer persuaded us to have our wind turbine rewired to a different set up which our old kit won’t work with. So we can’t revert to our previous set up. It’s such a mess.



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mikeb avatar image
mikeb answered ·

Hi


Just a question we’re they outback inverters or outback charge controllers?

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desperatedan avatar image desperatedan commented ·

Inverters. But it's immaterial here, as they were used on our old system and it's the new one we're having problems with.

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mikeb avatar image mikeb desperatedan commented ·

Was just trying to understand how the wind turbine was controlled


So I could advise how to incorporate it on to the Victron kit


Regards

Mike

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desperatedan avatar image desperatedan mikeb commented ·

The wind turbine was controlled by the wind turbine controller that was supplied with it from Proven. That sent power to our house, our batteries, then the dump loads in that order, and it had three different relays which controlled those dump loads, so we had three dump loads! Then we had the Outback inverters as well. However, that's the old system, not the new one. The new one has done away with the wind turbine controller and replaced it and the inverters with the Quattro we now have.

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mikeb avatar image mikeb desperatedan commented ·

So have you the AC version of the wind turbine ?

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desperatedan avatar image desperatedan mikeb commented ·

Was just trying to understand how the wind turbine was controlled


So I could advise how to incorporate it on to the Victron kit


Sorry, I thought I'd explained but perhaps I wasn't clear. The turbine needed new blades and some other bits so while it was being refurbished the installer had it rewired to work at a different voltage, in order to make it compatible with this Victron kit. That means it's now not compatible with our old kit, so we've not got the old controller, or inverters, anything--just new Victron inverter/charger and some other bits.

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desperatedan avatar image
desperatedan answered ·

I've just read up the description of the Quattro inverter charger on the Victron website, and saw this:

"it can accept two AC inputs "

The installer told us we'd be able to add PV to our system with this kit, as it could handle multiple inputs. We've already got our wind turbine feeding into it, and our back up diesel generator, that's its two AC inputs used up, isn't it? So we can't add PV. So unless I'm missing something, that's another thing he told us that turns out to not be true.

I despair.

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mikeb avatar image
mikeb answered ·

Hi

Do you think you require a installer to rectify the issue ?



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