Multiplus II 48/10000 external fan control

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question

iand asked Sep 22, '22

Multiplus II 48/10000 external fan control

Does anyone know under what conditions external fans (if connected via the relay and an assistant) are switched on?

The internal fans are variable-speed temperature controlled (noisily!) but any external ones are just on/off. Do they only turn on when the internal ones have reached maximum speed, or at some other point controlled by an internal temperature sensor?

I can imagine the case where with the external fans off the enclosure warms up, then the external fans switch on, which blows cold air in so the temperature drops, so the internal fans slow down and the external fans switch off, and then this repeats.

A (better?) alternative would presumably be to connect the (24V) external fans in parallel with the fans inside the unit so the speeds track -- the internal fans on the 48/10000 draw about 20W total and the external ones would be less than 5W so this shouldn't cause a problem with the driver circuit.

Filtering would be needed for the external fans (2 x Noctua NF-A14 IndustrialPPC-24V-2000) to stop them being as noisy as the internal ones. I'm surprised nobody has tried an LC filter instead of RC because this would avoid the resistor voltage drop -- any reason for this?

Multiplus-II quattro 10kva fan

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Rob Duthie commented · Sep 22, 2022 at 10:31 AM

See the blog about noisy fans this explains all about the issues and fixes.

Regards

Rob D

NZ

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iand Rob Duthie commented · Sep 22, 2022 at 11:19 AM

Thanks Rob -- I'd already read that (and all the others...) but I couldn't find a clear description of exactly how/when external fans are turned on and off (e.g. when internal fan comes on, or only when it reaches maximum speed, or something else) -- I'll have another look.

(assuming you mean these threads...)

https://community.victronenergy.com/questions/46137/victron-multiplus-ii-485000-noisy-fan-replacement.html

https://community.victronenergy.com/questions/20665/external-cooling-multi-plus-123000-how-to-setup.html

https://community.victronenergy.com/questions/47486/temperature-at-which-multiplus-fan-cuts-in.html

I'm still surprised nobody has tried an LC filter to remove the noise due to the low-speed PWM but without lowering voltage and rpm due to resistor voltage drop...

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sharpener iand commented · Sep 22, 2022 at 03:38 PM

Conceptually it's a nice idea but as an electronics engineer I have a big variety of Rs and Cs in the junk box but very few Ls so it's less easy to experiment. Also they tend to be comparatively expensive, and bulky enough to require proper mountings.

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iand sharpener commented · Sep 22, 2022 at 06:02 PM

Inductors (especially for low current) are easily available off-the-shelf or simple to wind yourself on a ferrite or metal powder core -- loudspeaker crossovers use them all the time. But they do need fastening down to something...

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Rob Duthie iand commented · Sep 22, 2022 at 08:58 PM

The LC filter does not work that well and is bulky to fit, my fix is simple and very effective. The problem is Victron very course PWM control is to low a frequency.

Regards

Rob D

NZ

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iand Rob Duthie commented · Sep 23, 2022 at 09:27 AM

I'm well aware what the PWM problem is :-)

What is your "simple and effective" fix for the 48/10000, because for this model it's been reported that just adding a capacitor doesn't work (or not very well), and adding a resistor reduces fan speed and therefore cooling effectiveness?

(and doing any of this for the internal fans will void the warranty which I can't risk, which is why I'm only asking about external fans)

Still no reply about exactly *when* the external fans are turned on by the assistant, though... :-(

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Rob Duthie iand commented · Sep 23, 2022 at 10:58 AM

I changed the fan to another brand and rubber mounted to stop the noisy vibrations.

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iand Rob Duthie commented · Sep 23, 2022 at 04:42 PM

I saw that, but didn't you also add a resistor as well as the capacitor, and the new fan plus resistor has lower airflow? Also IIRC this was the 48/5000 model, and others have reported that the same fix doesn't work as well on the 48/10000?

And the guarantee problem remains -- I really wish Victron had thought about this, a quieter cooling solution with proper PWM control (and maybe 140mm fans instead of 120mm) would have cost them next to nothing if they'd designed it in from the start... :-(

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Rob Duthie iand commented · Sep 23, 2022 at 09:49 PM

Hi

No resistor used, only a small cap and fan change, with a very small airlow change not worth worrying about, this is what i do for my clients installs who complain about it. Have they istalled the rubber dampners?

It is a much quiter unit than before.

Is Victron listning?

Regards
Rob D

NZ

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iand Rob Duthie commented · Sep 23, 2022 at 09:51 PM

But is this the 48/5000 or the 48/10000? Others have said this doesn't work with the higher-speed fan on the 48/10000...

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Rob Duthie iand commented · Sep 23, 2022 at 09:56 PM

I use this mod on the 48/500 models

Fitting rubber dampers will help a lot.

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iand commented · Oct 25, 2022 at 08:42 AM

I never got any answer to this question about when the external fans turn on (using an assistant and the relay). I can't see any need to keep this secret, it would actually be useful information for anyone needing an external cold air feed to keep the MP II cool and reduce temperature derating.

Simple question -- are the external fans turned on as soon as the internal ones start (at minimum speed), or only when they reach maximum speed, or somewhere in between?

Maybe @Guy Stewart (Victron Community Manager) can help?

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Modifications Space

Node Red Space

Answer 1 · 2022-09-24T05:06:18Z

raymiller answered · Sep 24, 2022 at 05:06 AM

I've also added some stick-on sound deading sheeting to the inside cover of my MulitiPlus 2 which also reduced the sound levels. I used this because it was very simple and quick to install and reduced the front panel vibration which is also part of the problem.

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Answer 2 · 2022-11-01T20:51:49Z

Margreet Leeftink (Victron Energy Staff) answered · Nov 01, 2022 at 08:51 PM

The external fans, via relay and relay assistants, will turn on as soon as the fan in the MultiPlus turns on. It does not look at the internal fan speed; it just looks if the internal fan is on or off. But a time delay can be programmed; for example, turn the external fan on 30 seconds after the internal fan has switched on.

Do not forget that if you use the relay assistant, you will need two assistants, one to close and one to open the relay.

I would not suggest adding an external fan parallel to the internal fan. Doing so will void the warranty.

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iand commented · Nov 02, 2022 at 05:00 PM

Thanks @Margreet Leeftink (Victron Energy Staff) but this contradicts what was said (from @Johannes Boonstra (Victron Energy Staff) on another thread which is that they only turn on when the internal fans reach full speed.

https://community.victronenergy.com/questions/164953/multiplus-ii-quattro-ii-external-fan-control.html

This makes a big difference, because for a 48/10000 the internal fans can come on at low speed at quite a low output power (maybe <1kW?) which can happen at night (bad for external fan noise), but they won't reach maximum speed until a high output power (maybe 5kW?) which is OK.

Which one is correct?

I was going to use the fan assistant and relay, not connect in parallel with internal fans.

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Answer 3 · 2024-03-11T14:45:00Z

offgridvoltage answered · Mar 11 at 02:45 PM

A simple answer is to use the K1 programmable relay via an ESS assistant. You can set the relay to activate when the internal fans are on and de-activate after the internal fans have turned off..... The usual configuration is to use the output of K1 to trigger an external relay and external power source to the fans.

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