Do all inverters hum when on?

[Kevin Warnock]

My Trace SW 4024 inverter makes a buzzing sound when on. I've always assumed this is totally normal. But the sound is loud enough I could not have the inverter in the living part of the bus with me. However, if it were silent, I would keep it in the living part of the bus so that it could remain cool since the bays can get super hot on a super hot day. The buzzing is not obnoxious, but there is no mistaking it. It's about as loud as a running refrigerator heard from ten feet away.

So, my question is... are there silent inverters out there? In particular, it would be great if there were a tiny 24 volt inverter, say 200-400 watts, that is completely inaudible. Then I could use it to power dimmable CFL lamps, which to my knowledge are not available in DC versions. I use dimmable CFLs at home, and they are totally fantastic, as they are quieter when dimmed than normal incandescent bulbs, and of course they use much less power. Also, the light color when heavily dimmed is more neutral and pleasing than a heavily dimmed incandescent bulb.

As it is now, I use DC lighting, so the big inverter is rarely on long term. It's on for things like the microwave or hairdryer, but the noise isn't a problem for these short term uses.

If anyone knows of dimmable CFLs that run on 24 VDC, please let me know.

Thanks!

[buswarrior]

FWIW, have you tried pressing on parts of the case when it hums?

Maybe just a harmonic between parts you might suppress with a shaved matchstick wedged in or a tightened screw?

Yes, I'm reaching...

happy coaching!
buswarrior

[JohnEd]

BW,

You aren't reaching all that far.  With the huge transformers in those things any errus metal will really try to move at a 0 cycle freq.  If it were the windings that were making a loud noise I think they would short out quickly.

Get a stethascope and place it on all the metal surfaces and find the one that is really making a racket.  Or, as BW said, really press down with your thumbs on the various metal panels and see which one stops singing.   Mostly I think you will find that the entire thing vibrates due to the transformer.

If you ake 3/8 rubber mat and cut out pieces that will fit on each panel and then you glue those pieces of rubber to those panels you will have made the assembly as quiet as possible. Tighten all the screws, for sure.

John

[Sam 4106]

Hi JohnEd,
I agree with all your comments except the part about "glue those pieces of rubber to those panels". He already mentioned how hot the inverter gets so if he follows your advise he will soon have smoke to go with the heat. Then he can get an inverter that doesn't hum.
Good luck, Sam MC8

[white-eagle]

We've been fulltiming with a lot of boondocking for the past year.  My inverter hums.  i can hear it well when i open either door of the bays.  It may be getting hot, but not that hot.  i have a board on top of it, and a few things sitting on it.  no vents were on top. 

i suppose you could reduce the charge rate.  if we are on light electric, like 20a, i set the charge rate to 5a.  when we use the genset, we set it to 30a so it charges faster.

mine's a 2012, so maybe not as hot as yours for that reason, and i'm hard of hearing, (especially at female pitch).

[JohnEd]

You need a good supply of cooling air.  NEED IT.  I have installed a push fan to augment the "pull" an on my inverters.   Running just a little hot will shorten the life of tronics.  How much is determined by the design and HOW HOT.

I have never seen an air filter on any f the inverters I have come across. Cooling is critical and that layer of dus inside on te heat syncs is pushing you towards disaster.  Open theinverter and blow it out as needed.  With my two dogs I "need" to do that every year if we spend more than a few months camping.

As well as installing a aux fan I have taped a piece of cheese cloth over the air nlet.  I vac it off everymonth and it is definatly catchig crud.

HTH

John

[JohnEd]

if he follows your advise he will soon have smoke to go with the heat.

If the inverter can ignite rubber that is  contacting the sies you have a whole set of other problems.

[John316]

Both of our 4KW Trace inverters hum. FWIW

God bless,

John

[Sam 4106]

Hi JohnEd,
I wasn't expecting the rubber to cause the smoke. Just like the dust, the rubber would insulate the inverter causing the inverter to get hotter by reducing heat dissipation, and the electronics would cause the smoke. Sometimes there are unintended consequences when you try to fix one problem and create another.
Good luck, Sam Mc8

[JohnEd]

Sam,

I can see where you are correct.  I had not considered that consequence.  I think most of the heat rejection in the unit occurs in the heat syncs for the rectifiers.  The skin has to contribute something...for certain.  If the unit is that sensitive I would opt to add fan capacity as I have done in every case as all mine got very warm to the touch under full load.

Thanks for your comment,

John