Noisy Inverter Driving Me Mad

[spillenger]

Hello.

I have a small off-grid cabin on Cape Breton Island, Nova Scotia.

For more than five years, I got by with a 1500W xantrex inverter that I bought, like many people up here, at Canadian Tire. We don't come close to putting that much of a load on it, so it worked fine. It ran completely silent. Then, this year it just died. And this model didn't have any breakers, fuses or even a reset button, and it's got no user-serviceable parts. So it's dead. RIP.

So, my solar guru picked up a newer model of the same basic inverter for me at Canadian Tire, this one going under the brand "Eliminator." It was rated at 2000 watts, had a nice LED readout, several breakers and even a remote on-off switch. The price was right -- about C$250. Looking good. But when we installed it inside the cabin, the noise it made (which we decided was the two fans being on all the time) was intolerable. I mean, I come up here for peace and quiet. So, we moved it under the cabin, under the floor so it would be protected from the elements, and that was better. But it's still generating this humming noise that I can hear all day long when there's even a minor load on it. For example, I keep my internet antenna and router on all the time, and they pull next to nothing, but it's enough to get those fans going. When I turn them off, the noise stops.

Here are my questions:

1. WHAT DO I DO???

Let me be more specific.

2. Is this a problem other people have experienced with inverters? Do all inverters have this issue? Do these fans really have to run 24/7?
3. Is it definitely the fans? That's what the guru said it was.
4. Am I right to think that enclosing the inverter in some kind of sound-proofed plywood box would kind of defeat the purpose of it having fans that keep the unit well ventilated? And that doing so would cause the inverter to quickly burn out?
5. Is a C$250 inverter of this kind thought to be a cheapo-cheapo inverter and would a higher-quality one be quiet? If so, any recommendations that wouldn't break the bank? And that I could find in, say, Halifax, the largest city in Nova Scotia, where I have to go anyway in a few days? Or that my wife could buy and bring up with her from Washington, DC, when she flies up this Saturday?

I know these are hard questions to answer remotely, but any light you could shed would be much appreciated. This noise is making me feel like I'm back in the city!

Many thanks,
Paul

[bcroe]

Noisy Fans

That unit may have a couple tiny fans that rev to max every time there is any load. Possibly you could add a much larger fan & ducting. Running at lower rpm for the same flow, it could be a lot quieter. Probably just run it all the time the inverter is on, to avoid control problems. Some fan systems use variable speed fans, but that gets a lot more completed. DC fans (electronically commutated) are easier to speed control. Check exit air temp rise under heavy inverter load, to see if the fan is doing the job. Bruce Roe

[inetdog]

For more than five years, I got by with a 1500W xantrex inverter that I bought, like many people up here, at Canadian Tire. We don't come close to putting that much of a load on it, so it worked fine. It ran completely silent.
So, my solar guru picked up a newer model of the same basic inverter for me at Canadian Tire, this one going under the brand "Eliminator." It was rated at 2000 watts, had a nice LED readout, several breakers and even a remote on-off switch. The price was right -- about C$250. Looking good. But when we installed it inside the cabin, the noise it made (which we decided was the two fans being on all the time) was intolerable. I mean, I come up here for peace and quiet. So, we moved it under the cabin, under the floor so it would be protected from the elements, and that was better. But it's still generating this humming noise that I can hear all day long when there's even a minor load on it. For example, I keep my internet antenna and router on all the time, and they pull next to nothing, but it's enough to get those fans going. When I turn them off, the noise stops.

Here are my questions:

1. WHAT DO I DO???

Let me be more specific.

2. Is this a problem other people have experienced with inverters? Do all inverters have this issue? Do these fans really have to run 24/7?
3. Is it definitely the fans? That's what the guru said it was.
4. Am I right to think that enclosing the inverter in some kind of sound-proofed plywood box would kind of defeat the purpose of it having fans that keep the unit well ventilated? And that doing so would cause the inverter to quickly burn out?
5. Is a C$250 inverter of this kind thought to be a cheapo-cheapo inverter and would a higher-quality one be quiet? ...

I know these are hard questions to answer remotely, but any light you could shed would be much appreciated. This noise is making me feel like I'm back in the city!

A. Ten years ago, Xantrex was a top of the line brand. I would not necessarily have the same confidence in their private label brands today.
B. If you really are hearing a hum or buzz rather than a higher pitched air/fan noise, that is the the basic 60 Hz inverter circuit you hear. That noise is likely to be conducted through your cabin frame, so putting it under the house but not using vibration isolation will not eliminate the problem.
C. The fact that it comes on immediately with a low load also tells me that it is not the fans but the inverter (probably transformer) itself.
D. What happens when you set it on some plastic on the ground under the cabin instead of screwing it to the wood? If that makes a big difference, you need a vibration isolating mount for it.
E. If that is not the problem, look at running your internet antenna and router off DC or on a much smaller separate inverter.

[bonaire]

PowerOne inverters have no fans but have some crazy clicking sounds from the anti-islanding circuitry which could be maddening.

Micro-inverters mounted on the roof under the panels? That would be silence, I think. I doubt any string inverters are silent.

[thastinger]

The fans on my Cotek do not come on until I put about a 600 watt load on it. It runs the fridge in total silence all day long but when I turn on the 500W worth of overhead lighting, the fans come on and stay on until I turn off the lights.

[bcroe]

Noise

I have been worried about electrical noise interfering with radios, etc. Inverters (or
any kind if switcher) have the potential for huge noise generation. They can be fixed,
with elaborate shielding & good filters on all the leads into the inverter.

Looking at a 7.5 KW inverter today, I did spot a standard RFI filter on the AC line
output. However, it remains to be seen, how effective the overall filtering & shielding
actually is. Besides a shield cage, I would need 2 AC and 2 DC filters to add another
layer of EMI containment. A quick search indicates filters that size start at around
$100 apiece. Been doing this all my life...... Bruce Roe

[SunEagle]

I have been worried about electrical noise interfering with radios, etc. Inverters (or
any kind if switcher) have the potential for huge noise generation. They can be fixed,
with elaborate shielding & good filters on all the leads into the inverter.

Looking at a 7.5 KW inverter today, I did spot a standard RFI filter on the AC line
output. However, it remains to be seen, how effective the overall filtering & shielding
actually is. Besides a shield cage, I would need 2 AC and 2 DC filters to add another
layer of EMI containment. A quick search indicates filters that size start at around
$100 apiece. Been doing this all my life...... Bruce Roe

Maybe look into military grade shielding since they are designed to block an EMP.

[bcroe]

Shield

Maybe look into military grade shielding since they are designed to block an EMP.

Not worried about EMP here. More about my radio tower that is close by; the DC feed goes between the base and a guy anchor. It would start as 1/2" hardware cloth (soldered at every intersection, very important), which should provide plenty of ventilation. Making a walk in door seal could be a problem. Bruce Roe

[SunEagle]

Not worried about EMP here. More about my radio tower that is close by; the DC feed goes between the base and a guy anchor. It would start as 1/2" hardware cloth (soldered at every intersection, very important), which should provide plenty of ventilation. Making a walk in door seal could be a problem. Bruce Roe

Ok. you lost me there with the "hardware cloth" and ventilation.

I believe you indicated that you want to block RF being generated by your radio antenna and equipment.

Are you talking about shielding the RF from sensitive equipment in your "Shack" but worried about openings and pathways for the RF to enter?

[bcroe]

Ok. you lost me there with the "hardware cloth" and ventilation.
I believe you indicated that you want to block RF being generated by your radio antenna and equipment.
Are you talking about shielding the RF from sensitive equipment in your "Shack" but worried about openings and pathways for the RF to enter?

If I have the name right, "hardware cloth" is like a very coarse square weave metal screen. The pattern might be 1/4" or 1/2" openings, and apparently run through a solder bath to solder all cross points.
The solder guarantees the largest radio "hole" size, 1/2" should be effective to 10 hole wavelength or 5" or below 2360 MHZ. Just how to maintain that contact spacing for an access door isn't clear just now.

The concern, is inverter switching noise will interfere with reception of weak radio signals. No worries about interfering with inverter operation. Any AC or DC line filters will be mounted penetrating the shield boundary.

At the same time, the mostly open 1/2" squares should allow plenty of air flow. Bruce Roe

[SunEagle]

If I have the name right, "hardware cloth" is like a very coarse square weave metal screen. The pattern might be 1/4" or 1/2" openings, and apparently run through a solder bath to solder all cross points.
The solder guarantees the largest radio "hole" size, 1/2" should be effective to 10 hole wavelength or 5" or below 2360 MHZ. Just how to maintain that contact spacing for an access door isn't clear just now.

The concern, is inverter switching noise will interfere with reception of weak radio signals. No worries about interfering with inverter operation. Any AC or DC line filters will be mounted penetrating the shield boundary.

At the same time, the mostly open 1/2" squares should allow plenty of air flow. Bruce Roe

Ahh. Got it. The metal mesh pattern stops the RF but allows air flow. And you want to create a doorway without reducing the effectiveness of the shield.

[inetdog]

Ahh. Got it. The metal mesh pattern stops the RF but allows air flow. And you want to create a doorway without reducing the effectiveness of the shield.

Small holes, like window screen, have a disproportionately high resistance to air flow. A screen that blocks only 50% of the light could have air resistance 8 times as great as open space would. For the hardware cloth sized holes, the effect is much closer to just the reduction in area.
"Weather stripping" of metal fingers is often used for bridging the gap in doors that have large clearances but still have to block RF.