Multiplus II hum/buzz - hoe much is too much

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nicov asked Aug 20, '20

Multiplus II hum/buzz - hoe much is too much

My Multiplus 2 is making a constant hum/buzz. I expect that - sort of normal with toroidal transformers. However, in the evenings the grid AC becomes a bit high (240-245 V), and the humming becomes louder. When should I start worrying?

Measuring with the NIOSH SLM app the buzz is about 38.6 dB(A) when the grid is connected (V_ac_in= 243 V), and 33 dB(A) when the grid is disconnected.

Using an app creatively called “Spectrum”, it seems like the buzz is at 200 Hz. Why would that be (I expected 50 Hz, which is the grid frequency)? My knowledge of toroidal transformers is lacking, so I’m mostly curious. I guess it could be a limitation of the app.

Multiplus-II MultiPlus Quattro Inverter Charger

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Modifications Space

Node Red Space

Answer 1 · 2020-08-20T20:08:18Z

Rob Duthie answered · Aug 20, 2020 at 08:08 PM

Hi

They do buzz depending on what loads you have etc, water heater control system from lines companies can make it buzz very nosily. As in here NZ they do, mine does at certain times of the day.

Certain loads if they have high harmonic loads will make the Mulitplus buzz, due to its internal transformer etc.

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Answer 2 · 2020-08-20T20:12:23Z

H.W.Oelofse answered · Aug 20, 2020 at 08:12 PM

@NicoV given that the average noise level fora living room is stated as 40db I do not think that this is an abnormal sound. what is interesting is that the sound is at 200hz as you said, i suspect that this may be a harmonic frequency that may be a result of the kind of loads that may be running at the time. I have observed similar behaviour on my system at home and it appears to be normal. hope this helps?

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Answer 3 · 2020-08-20T21:44:09Z

trip-tracks answered · Aug 20, 2020 at 09:44 PM

With the mains available, you will find the buzz is due to the load when the charger is working. Try turning the charging off, at least during those noisy times, while maintaining the inverter features.

If your solar manages to fill your system, you don't really need the mains charging the system all the time, perhaps only when it has fallen behind due to inclimate weather?

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Answer 4 · 2020-08-21T00:57:00Z

daryl answered · Aug 21, 2020 at 12:57 AM

I have 3 in a 3-phase configuration. 1 buzzes a lot even under very low load, the other 2 never, I'm confused.

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