EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: ricko_uk on May 24, 2023, 08:41:04 pm
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Hi,
I assume that infrared sauna heaters are just resistive loads like normal sauna heaters, is that correct?
If so I also assume they can be driven with 220V DC are are there specific reasons for that not to be a good idea?
The reason I'm asking is to see if the rather high electric field can be lowered. My assumptions are:
1) with AC you get a peak of 311V (or possibly twice that 622V if the peak to peak is the value that "affects" the user in the sauna). With DC you get only 220V
2) AC might affect people more than DC. But not 100% sure, if someone knows about this I would appreciate feedback on this too.
Thank you :)
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220V, DC is a deadly supply which would require special DC rated switches. DC if it draws an arc will not tend to self extinguish as AC will, because AC goes to zero each half cycle, (I know that is a generalization). You would be creating an unexpected hazard for electricians etc. which could be deadly.
P.S. If an electrician with his meter set on AC measures the DC voltage he will read 0v and think it is safe.
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It will work fine during "normal conditions", the resistive IR heater does not care, but DC beyond some 50V or so requires you are absolutely mega giga sure the circuit never ever fails open circuit. No switches, no fuses, nothing that can break open. Then you would add a 220VDC rated fuse.
If the filament ever breaks, there is a significant risk of a nasty arc event causing fire.
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What electric field are you trying to reduce? Infrared ceramic heaters don't emit an intentional electric field more than regular cables.
In fact, running it on DC may even "make it worse", because you'd either need rectifiers or AC/DC converter. Both add some "noise".
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If you want to play the new age electromagnetic hypersensitivity bullshit game, how about a traditional sauna where you burn wood to heat up the stone thing on which you throw water. This is what I have. It has a certain atmosphere and feeling to it, given the flames, noises and smell of burning wood. Although for your health, even the small amount of particulate emissions from wood that bypass the chimney (when adding wood, for example) or circulate back from outdoor air, are far worse than any electric field.
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Use aluminum window screen as a shield.
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Hi,
I assume that infrared sauna heaters are just resistive loads like normal sauna heaters, is that correct?
correct
If so I also assume they can be driven with 220V DC are are there specific reasons for that not to be a good idea?
Yes, circuit protection is much harder with DC
The reason I'm asking is to see if the rather high electric field can be lowered. My assumptions are:
1) with AC you get a peak of 311V (or possibly twice that 622V if the peak to peak is the value that "affects" the user in the sauna). With DC you get only 220V
2) AC might affect people more than DC. But not 100% sure, if someone knows about this I would appreciate feedback on this too.
Thank you :)
Your assumptions are baseless. The only effect that has any effect on people is the heat from the infrared.
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Assuming this has some controls. Switching power supplies work just fine on DC. If heater turns on with relay, that will not work long with DC on contacts and a triac control will never turn off.
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Oh not this again.
I had a boss with this same thing, buying $$$ earbuds with small air tubes transmiting the sound, to avoid the "Damaging radiation".
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One question: why?
DC is actually less deadly than AC, given the same voltage, but that's no reason to do this. An RCD/GFCI will protect against earth leakage and electric shock.
As mentioned above, the problem with DC is it's more difficult for switches, circuit breakers and fuses to interrupt he current, because there's no zero crossing point when the arc extinguishes.
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Frankly, if you are concerned about the electric field, DC is not necessarily safer than AC. Many electrically induced phenomena are much reduced with AC because the average (not RMS) field is zero. For things with time constants on the order of 10s of ms (which include many biological phenomena), the effect of AC is reduced, but DC can have a strong effect. The safety issues of arc faults mentioned previously is one aspect of this. Corrosion is another, which you might want to pay special attention to in a hot, damp environment.
The other posters have it covered, though. 220 VDC with a lot of amps behind it, like you would need to drive a heater, is a huge safety hazard that is really difficult to mitigate. The DC induced corrosion in a sauna is going to make the chance of arcing a when, not if, question. When it fails, the arc will likely burn the whole thing down, including those inside. This is far more hazardous than any line-frequency AC fields.
Electrocution hazards are also worse with DC, though Edison tried his damnedest to show otherwise.
John
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Electrocution hazards are also worse with DC, though Edison tried his damnedest to show otherwise.
John
You've got that backwards. Electrocution hazards are worse with mains frequency AC, than DC, given the same current.
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You've got that backwards. Electrocution hazards are worse with mains frequency AC, than DC, given the same current.
I stand corrected.
John
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Frankly, if you are concerned about the electric field, DC is not necessarily safer than AC. Many electrically induced phenomena are much reduced with AC because the average (not RMS) field is zero. For things with time constants on the order of 10s of ms (which include many biological phenomena), the effect of AC is reduced, but DC can have a strong effect. The safety issues of arc faults mentioned previously is one aspect of this. Corrosion is another, which you might want to pay special attention to in a hot, damp environment.
With DC, there will be no sustained electric field. Would still be easier to just use shielding to shunt away AC electric fields.
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2) AC might affect people more than DC. But not 100% sure, if someone knows about this I would appreciate feedback on this too.
The electromagnetic emissions from an electric heater on 240VAC 50/60Hz (including this IR glowing type) are not that much different to the emissions from in-house wiring carrying the same current or on-street wiring carrying the same current. The glowing elements are just wires of a different resistance.
Big, hot glowing things are scary (and rightly so); so it's natural for the human mind to associate other negative things to them.
If you don't care for the opinions of people here that say not to worry about EM radiation then please at least don't fall for scams where people spend crazy $$$$$ on things that claim to shield you against it. Ordinary chicken wire (grounded) is a highly effective reflector, fancy materials and items are scams. If you can still receive a phone signal then by definition you are still receiving EM waves.
Fun fact: Some scam devices even broadcast massive amounts of EM to interfere with (eg) phone signals (very illegal) and make you think you have succeeded but actually do the opposite. These are called cell-phone jammers, but might be rebranded as EM protection.
It's also worth understand the wide range of frequencies we call EM radiation. On the low end (VLF): it's almost impossible to block, it's a part of life and the planet itself generates it. At the very high end: light itself is EM radiation, you need it to see at night (or at all).
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Near IR is probably the most dangerous form or radiation emitted from sauna heaters, but only to the eyes and can be mitigated by not staring at it, or using eye protection.
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With DC, there will be no sustained electric field. Would still be easier to just use shielding to shunt away AC electric fields.
With a DC voltage, there will be a sustained electric field by definition. In fact, you can even shield it similarly. If one were concerned about magnetic fields, the shielding is a different story.
However, in any case, the direct effect of AC vs DC from a coupled field standpoint on someone in the sauna is likely negligible, but the safety implications are real enough. And, there is always the belief effect, which might strongest of all.
John