Hi. Newbie here. Hoping someone can please help me?
Had our system installed last week. The inverter gets noisy and extremely hot to the touch? Has anyone else experienced this?
Everything was working great until the first fully sunny day. At peak production the inverter got extremely hot and started making a loud humming noise - sounds like an internal fan going into overdrive. You can imagine how shocked we were!
Our installer is coming back in a couple of days to double check over the install but they have suggested that it is common for Fox inverters to become hot and noisy when working at capacity. I won’t accept this.
We haven’t yet contacted Fox support but obviously will do this if the installer can’t find any physical issues.
Here’s a pic with the details of our inverter model. It is sited in a garage so well sheltered from direct sun.
Is the firmware out of date? Will updating that sort the issue?
Any inverter (not just Fox) when working hard will produce heat, it's a by product in the energy exchange, the whole back of the inverter is a heat exchanger designed to get rid of that heat and it's not that unusual on a very sunny day for the inverter fins to be at 40C or 50C.
Is the Inverter mounted indoors ?, normally they would be mounted in a garage, roof space or outside where there is plenty of air circulation to take the heat away.
I can't comment on the noise other than to say inverters do make squeeks, pops and buzzing noises when working - they are not normally that intrusive when compared to normal ambient noises but if it's mounted in your kitchen or somewhere like that it could be irritating - i'm not aware of any inverter that runs totally silently.
Is the Inverter mounted indoors ?, normally they would be mounted in a garage, roof space or outside where there is plenty of air circulation to take the heat away.
I can't comment on the noise other than to say inverters do make squeeks, pops and buzzing noises when working - they are not normally that intrusive when compared to normal ambient noises but if it's mounted in your kitchen or somewhere like that it could be irritating - i'm not aware of any inverter that runs totally silently.
As Dave has said .. they get hot when generating ... I have added a few fans on top, pulling the heat away from the unit. I actually have these connected to a "smart" plug .... and Home Assistant to automate so they come on when temp reaches a certain limit. You can see on my graph, where the fan has kicked in
It's surprising just how effective a couple of computer fans is at reducing the heat.
I got a pair of 140mm computer fans on USB, the total power draw is only 4W on high, but it drops the inverter temp down to below 40c even in this heat. KH7. Have to say that I have never noticed it making any noise, however. Quite a bit more effective than the 50W pedestal fan which I programmed to go off at 45c. It hasn't turned on ever since I added the computer fans, but when it did turn on, it doesn't reduce the temps as much as the computer fans.
Keeping the temp low is good - they derate if it gets too hot, and the components should last better. Personally I didn't put that one on a smart plug, on the basis that it's only 4W. Also thermal cycling can be an issue for some electronics.
I got a pair of 140mm computer fans on USB, the total power draw is only 4W on high, but it drops the inverter temp down to below 40c even in this heat. KH7. Have to say that I have never noticed it making any noise, however. Quite a bit more effective than the 50W pedestal fan which I programmed to go off at 45c. It hasn't turned on ever since I added the computer fans, but when it did turn on, it doesn't reduce the temps as much as the computer fans.
Keeping the temp low is good - they derate if it gets too hot, and the components should last better. Personally I didn't put that one on a smart plug, on the basis that it's only 4W. Also thermal cycling can be an issue for some electronics.
Are you using the USB connector on the inverter itself to power the fans?WyndStryke wrote: ↑Sat Jun 21, 2025 11:47 pm I got a pair of 140mm computer fans on USB, the total power draw is only 4W on high ...
No, I think that USB connector is for firmware updates and similar. It's using wall power.
Hi,
Just searched for this exact same issue and saw your post. My inverter today for the first time of me noticing it, is making a lot of noise and very hot as well. But the outside temp is also very warm and the solar is generating nearly 90% of peak production so the inverter is in over drive at 14.28kW. I checked and its very warm but will be installing some fans as per the previous post with PC fans and linking them to my home assistant as its mounted in the garage and was concerned when I first heard it today.
I assume its just like being near a Power substation, the invertor is doing all the work to convert the Solar DC to AC etc so will get hot doing this work.
Will keep an eye on it, was a loud humming that made me go check but seems to be the "norm" for the FOX inverters under high load.
Just searched for this exact same issue and saw your post. My inverter today for the first time of me noticing it, is making a lot of noise and very hot as well. But the outside temp is also very warm and the solar is generating nearly 90% of peak production so the inverter is in over drive at 14.28kW. I checked and its very warm but will be installing some fans as per the previous post with PC fans and linking them to my home assistant as its mounted in the garage and was concerned when I first heard it today.
I assume its just like being near a Power substation, the invertor is doing all the work to convert the Solar DC to AC etc so will get hot doing this work.
Will keep an eye on it, was a loud humming that made me go check but seems to be the "norm" for the FOX inverters under high load.
Fox ESS H3 Pro 15kW 3-Phase Hybrid Inverter
34 x 440W (3 strings 12+12+10) - Jinko Tiger Neo 440W N-Type All Black Mono Panels
Fox ESS EC2900 - 14.4kW Li-ion Battery (1 x Master + 4 Slaves @2.88kWh each)
3-Phase Export
HomeAssistant - To be configured
34 x 440W (3 strings 12+12+10) - Jinko Tiger Neo 440W N-Type All Black Mono Panels
Fox ESS EC2900 - 14.4kW Li-ion Battery (1 x Master + 4 Slaves @2.88kWh each)
3-Phase Export
HomeAssistant - To be configured
Thanks everyone for the replies to this thread. Really reassured me that our inverter is operating correctly. Also a good idea to install additional fans if concerned about it getting too hot.
Just in case anyone else comes to this thread in future, the key point that emerged is that our inverter has a built in fan which is obviously what makes the noise. However some other Fox inverters don’t have built in fans so run near silently.
By good fortune we had our inverter installed in the garage so the noise is not a problem. However we discussed having it in the house and I’m so glad we didn’t. My advice is definitely don’t get one of these inverters installed in the house as the noise is sufficiently loud that it would be very irritating.
Just in case anyone else comes to this thread in future, the key point that emerged is that our inverter has a built in fan which is obviously what makes the noise. However some other Fox inverters don’t have built in fans so run near silently.
By good fortune we had our inverter installed in the garage so the noise is not a problem. However we discussed having it in the house and I’m so glad we didn’t. My advice is definitely don’t get one of these inverters installed in the house as the noise is sufficiently loud that it would be very irritating.
My installer asked the question about noise for me and received this reply from Fox
" This is normal for the high pitch sound when its running at Max capacity "
This is from fox-ess tech site and may help those of a nervous disposition -
"This is known as coil whine and is perfectly normal in modern inverters, especially when the system is working hard (charging, discharging, or exporting to the grid). It happens when electronic components like coils or transformers vibrate slightly as electricity flows through them at high frequencies.
It’s not a fault and doesn’t affect performance or safety — just a harmless byproduct of efficient power conversion. In quiet environments, it can be more noticeable, but rest assured it’s common in many types of electrical equipment.
Why Does It Happen?
Magnetic Vibration
Inverters use switching components (like MOSFETs or IGBTs) that rapidly turn power on and off — often at frequencies from 4 kHz to 20+ kHz.
These signals pass through inductors and transformers.
The magnetic fields inside these components expand and collapse rapidly, causing mechanical vibration of the core, windings, or surrounding parts.
Resonance
When these vibrations match a natural resonance frequency of the component or PCB, they can amplify, making the noise louder and more noticeable.
Load-Dependent Behavior
Under higher loads (like peak charging, discharging, or grid export), current flow increases, and switching dynamics change — making coil whine more likely or more audible.
You’ll often hear this during battery charge/discharge, grid-feed, or high PV production.
Is It Normal?
Yes — this is typically normal for inverters and other power electronics, especially:
When pushed harder under higher loads.
If switching frequencies fall in the 7–14 kHz range (audible to most people).
In quiet environments where even faint noise is noticeable.
It’s not a sign of a fault, provided:
There are no other symptoms (like heat, failure, error codes).
The noise isn’t suddenly louder than usual or accompanied by crackling or irregular sounds.
Why It’s More Noticeable Sometimes:
Human ears are very sensitive between 8–12 kHz — we evolved that way to detect subtle threats.
If the inverter is mounted to a wall that resonates (e.g., plasterboard or wood), it can amplify the vibration like a speaker.
Some people are more sensitive than others — especially younger users or those with no hearing loss."
" This is normal for the high pitch sound when its running at Max capacity "
This is from fox-ess tech site and may help those of a nervous disposition -
"This is known as coil whine and is perfectly normal in modern inverters, especially when the system is working hard (charging, discharging, or exporting to the grid). It happens when electronic components like coils or transformers vibrate slightly as electricity flows through them at high frequencies.
It’s not a fault and doesn’t affect performance or safety — just a harmless byproduct of efficient power conversion. In quiet environments, it can be more noticeable, but rest assured it’s common in many types of electrical equipment.
Why Does It Happen?
Magnetic Vibration
Inverters use switching components (like MOSFETs or IGBTs) that rapidly turn power on and off — often at frequencies from 4 kHz to 20+ kHz.
These signals pass through inductors and transformers.
The magnetic fields inside these components expand and collapse rapidly, causing mechanical vibration of the core, windings, or surrounding parts.
Resonance
When these vibrations match a natural resonance frequency of the component or PCB, they can amplify, making the noise louder and more noticeable.
Load-Dependent Behavior
Under higher loads (like peak charging, discharging, or grid export), current flow increases, and switching dynamics change — making coil whine more likely or more audible.
You’ll often hear this during battery charge/discharge, grid-feed, or high PV production.
Is It Normal?
Yes — this is typically normal for inverters and other power electronics, especially:
When pushed harder under higher loads.
If switching frequencies fall in the 7–14 kHz range (audible to most people).
In quiet environments where even faint noise is noticeable.
It’s not a sign of a fault, provided:
There are no other symptoms (like heat, failure, error codes).
The noise isn’t suddenly louder than usual or accompanied by crackling or irregular sounds.
Why It’s More Noticeable Sometimes:
Human ears are very sensitive between 8–12 kHz — we evolved that way to detect subtle threats.
If the inverter is mounted to a wall that resonates (e.g., plasterboard or wood), it can amplify the vibration like a speaker.
Some people are more sensitive than others — especially younger users or those with no hearing loss."