Converting a household space heater to DC

In summary, the speaker uses a portable electric space heater to keep their room warm during winter, but it makes a loud hum that keeps them awake at night. They cannot use their electric baseboards and believe the hum is caused by the 60Hz AC power. They are considering installing a bridge rectifier to turn the AC into DC and eliminate the hum. However, there may be issues with heat sink requirements and it may be cheaper and easier to just buy a new heater. Another suggestion is to try to locate and fix the source of the hum by tapping or shaking the heater.
  • #1
Garbus
3
1
Hello,

Basically, I use a portable electric space heater to keep my room warm during the winter, and it works quite well, except it makes a very loud hum that keeps me awake, so my options right now are poor sleep due to hum or having my room drop to about 12 C over night if I turn the heater off. For a number of reasons I can't use my electric baseboards, otherwise this would be a non issue.

Now, I assume the awful humming is because of the 60Hz AC power going through the heater (its a simple convection heater, so no fan or anything to cause noise), so my line of thinking is to install a bridge rectifier between the wall socket and the heater, thus turning the AC into DC and hopefully eliminating the hum. Theres no electronics on this heater, as far as I can tell, there's just a power control that switches more or less banks of heating elements on, so it should work on DC right?

If I get a proper spec rectifier that can handle the voltage current, should this work to eliminate the hum? Are there any issues I am overlooking with turning AC into DC?

Thanks!
 
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  • #2
I hope you don't spend a lot on a rectifier that can handle that load and find out that it hums.
 
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  • #3
Can you provide heater make and model number?

Have you attempted to determine exactly where the sound is coming from? The noise source could be as simple as a loose section of sheet metal guarding.
 
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  • #4
It will probably be ok. You will get 120Hz ripple in the DC but with much lower amplitude than the original 60Hz. I'm assuming you mean a full wave rectifier, of course. Make sure you put the rectifier after any switches, fuses etc. those parts probably can't handle switching DC current.
Also pay attention to the heat sink requirements of the rectifier, the current rating is usually a proxy for operating temperature, or they have specified the temperature or heat sink requirements for the current rating. Diodes usually fail from getting to hot from the current, not from the instantaneous current value. Recognize that the place you may want to mount the rectifier might already be hot from the heating element thus requiring a better heat sink than you might expect.
However, I wonder if it wouldn't be cheaper and easier to buy a different heater.
[edit] No! not between the wall socket and the heater, between the heater element and everything else. Or, replace the switches and fuses with DC rated parts.
 
  • #5
Be careful about insurance cover/liability if you modify it.
 
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  • #6
I think your present hum is at 120 Hz, so the rectifier will make no difference.
If we suppose the hum is caused by the wire expanding and contracting over the cycle, then it receives two maxima per cycle, giving 120 Hz.
On the other hand, if we assume the hum comes from the magnetic attraction between wires, then it will be maximum at current peaks. As both wires involved in this have the same alternating current, there are two maxima per cycle. Further, the pull is dependent on current squared.
If you reduce the current by half, then the thermal variations will be only a quarter. The magnetic variations depend on current squared, so will also be a quarter. If the sound amplitude is a quarter, then that is a sixteenth acoustic power. This is 12dB, so it will sound about half as loud.
 
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  • #7
I like @Asymptotic's suggestion. You have many 60 Hz appliances that don't make an annoying hum. The difference between those that do and those that don't is something vibrating, probably something loose.

I also use a 60 Hz space heater. It makes no hum that I can hear.
 
  • #8
Perhaps then it might be best to just buy a new heater then. Ah well.
 
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  • #9
Garbus said:
Perhaps then it might be best to just buy a new heater then. Ah well.
Or unplug it and tap it or shake it to find the offending piece; then, if applicable, bend the offending piece to shut it up. If you can't find the problem, take the beast apart and see what you can find; after all, it's no good the way it is and maybe you'll learn something for the next time.

Cheers,
Tom
 
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What is the purpose of converting a household space heater to DC?

The purpose of converting a household space heater to DC is to enable it to run on direct current (DC) power instead of alternating current (AC) power. This can be useful in situations where only DC power is available, such as in an off-grid or emergency scenario.

Can any household space heater be converted to DC?

No, not all household space heaters can be converted to DC. Only space heaters that have a built-in AC to DC power converter or that are specifically designed to run on both AC and DC power can be converted.

What equipment is needed to convert a household space heater to DC?

The equipment needed to convert a household space heater to DC includes a power inverter, which converts DC power from a power source (such as a battery) to AC power, and a battery or other DC power source. Some space heaters may also require a special adapter or converter to connect the inverter to the heater.

Is converting a household space heater to DC safe?

Converting a household space heater to DC can be safe if done properly and with the right equipment. However, it is important to note that altering the power source of a space heater may void its warranty and could potentially cause damage or malfunctions. It is recommended to consult a professional electrician before attempting to convert a space heater to DC.

Are there any benefits to converting a household space heater to DC?

There are a few potential benefits to converting a household space heater to DC. These include the ability to use the heater in situations where only DC power is available, potentially lower energy costs if using renewable energy sources such as solar panels, and the elimination of potential safety hazards from using an AC power source.

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