Hello,

My wife and I are doing a remodel of our master bathroom and would like to add radiant floor heating.  For better or worse, we are a bit paranoid about EMF's.

Thermosoft and SunTouch seem to be the most used, zero/low EMF manufacturers.  We'd like to go with a mat product.

Thermosoft claims "zero" EMF, though some have found that hard to believe.  SunTouch claims something slightly more fuzzy.  .13x the average daily exposure (which they list as 1mG).  Not sure if that means they say they output .13mG, but that's what we assume they are saying.

It's unclear to us what the true and actual EMF output is for these products on a finished floor.

Has anyone actually measured either product with an EMF reader?  We would love to know what the true readings are on a finished floor (magnetic and electrical fields).

Also of major importance is a product that will not stop working after a few years.

Has anyone had the mats (or in SunTouch's case, even just the WarmWire cables) installed for 5 years or more?

Thanks!
-James

There is no such thing as zero, (even solid crystals carrying no electric current have a magnetic field.) The DC magnetic field at the surface of the earth is ~0.4G, give or take ~0.2G depending on where it's measured.

I've measured many things with VLF/ELF field survey meters, but never resistive electric heating products. Products that use non pulse-width modulated DC current will have much lower ELF/VLF than AC output with thyristor-dimmer or rectified diode waveforms, but the power supply that's delivering the current could be a real VLF/ELF blaster similar to fluorescent ballasts, with significant VLF/ELF emissions on the control cabling to the thermostats, etc, even if power to heater elements is "clean".

In Thermosoft's statement #4 on their website:

" ThermoTile radiant floor heating systems are manufactured, unlike any other heated floor system, with both a current return wire AND an inner foil wrap to eliminate EMF risk."

...belies a misunderstanding of what it takes to mitigate low frequency EMF. A foil wrap does next to nothing against EMF/VLF emissions due to woefully insufficient skin depth at the wavelenghts/frequencies of interest. While foils can mitigate radio frequency stuff, they're worthless at sub-megahertz frequencies, let alone 60Hz/120Hz and the single digit harmonics thereof, which comprised the vast majority of the emitted power in powerline EMF. The drain wire is similarly useless. The picture on their web page (http://www.thermosoft.com/radiant-floor-heating/ )may or may not be accurately depicting the actual product, but it shows un-twisted wire inside the foil shield, and twisting the conductors would be EXTREMELY effective for making the emissions fields self-cancelling at ELF/VLF frequencies beyond some minimum distance (determined by the tightness of the twist.

Their statement:

"This eliminates interference with telephones, radios, pacemakers, hearing aides and television. Without these features, other electric floor heating systems can act as a huge static-causing antenna under your heated floor."

...makes me believe the thing is actually PWM or cheap thyristor dimmer output, a sewer of emissions from 60Hz-500MHz. The foil will mitigate some of the emissions the 10+ MHz issues related to communications RF, but as stated, nothing much in the sub-1MHz region, and absolutely nothing at power line frequencies.

Bottom line, request independent 3rd party field test data of the ELF and VLF from the manufacturers. (Get a spectrum with decibel milli-gauss, if they will provide it.) It may in fact be as low as stated in the powerline harmonic spectrum, but there's nothing in their promotional statements on the topic that leads me to believe they have better than a 5-th grader's understanding of the problem.

If you really care about this, use a hydronic (pumped hot water) solution, and place all pumps, power wiring and hot water heating devices in a location well away from the floor being heated.

Yet another reason to be a wet-head! I love it.

Please tell us more about the deciblel mill-guass spectrum and what it means to a person donning the standard Al head gear?

What they don't have to deal with dB-mG in the wet head world? :-)

Logarithmic scales can be more useful than linear when looking at electromagnetic field strength, ergo decibel power or decibel field strength are common in the measuring instumentation. When looking at powerline EMF it's useful to look at the spectrum to know at what frequency most of the power is being emitted rather than just a raw composite power number, because that affects what you would need to do to shield or attenuate the bulk of the power. If most of the emissions are above 1megaherts it's a different cat than if it's all under 1kilohertz. Hand held field strength meters are filtered, but the output number is an composite of the instrument's filter output, not broken down by frequency. Being a 'lectrical enginerd with some EMI experience down to the powerline EMF bands, prefer to see the spectrum rather than a lumped number, if available. Al headgear is a heluva lot cheaper than u-metal headgear, so it's good to know if you really need the exotic alloy (and which version would be more appropriate.)

Resistance electricity is such a source-fuel efficiency dog I shy away from it in most apps, but from an EMF point of view it's a no brainer to move onto something that doesn't involve voltage conversions and electrical current. No voltage + no current=no EMF, problem solved.

So no EMF induced mutagenisis from low-voltage radiant floor dogs?

Am I safe in my corrugated steel building from high voltage transformer just outside?

Posted By BadgerBoilerMN on 02 Mar 2013 10:24 AM
So no EMF induced mutagenisis from low-voltage radiant floor dogs?

Am I safe in my corrugated steel building from high voltage transformer just outside?

If it's grain-oriented silicon steel of sufficient thickness and magnetically coupled to similar steel flooring it does a surprizingly good job of shunting the line-frequency EMF of the transformer, around rather than through the space.  Carbon steel at typical corrugated thicknesses may make measurable dent in the peak field readings, but not as much as you'd like.

There's also safe/safer/safest field strengths to consider.   If you happen to have an old CRT computer monitor or tube-TV, (particularly a monochrome CRT or black & white TV) set it up on a table near the wall next to the transformer, and put up a static image, or if you can, adjust the width & height of the raster area so that you see both the top & bottom as well as side sync areas.   The magnetic deflection yokes of CRTs and old-school displays are both a significant source of, and susceptible to line frequency EMF.  If the image has a lot of visible up/down jitter (more likely with a computer monitor), or a static or slow-scrolling distortion that changes shape when you turn the unit 90 degrees on the table, you probably don't want to make that area your lunch table or "power-napping" lounge.

But see if it also happens elsewhere in the building too.  I've previously managed to ferret out illegitimate connections between neutrals on strings of high-bay lighting that resulted in fairly high line-frequency EMF anywhere in the building, (peaking near the 208V 3-phase wiring runs) that dropped more than 10dB when the neutrals were properly separated so that the return currents followed the same paths as the associated phase currents.  (The lighting ballasts ran measurably cooler after that too.)

You know, I was pulling your leg...but your answer was intriguing and it makes me want to be physicist and ask more questions. Alas, I have a snow melting system to install and must pursue more base elements of the physical universe.

I am going to ground the steel siding and roof to the 6-6, 10-10 flat wire in my radiant slab and hope that will help.

I thank you, my friend.

Grounding the steel doesn't do much at line-frequency, but is pretty good at shunting the EMF from pulsed currents from lighting strikes, etc, which tends to run in the megahertz range. The building is a small but real fraction of a wavelength at 1MHz, but it takes the whole state of MN to be a similar fraction of wavelength of 60Hz.

Do the math, wavelength=velocity/frequency. The velocity is the speed of light, which is about billion feet per second (order-of magnitude only.) The entire width of the lower 48 of the US is about 1 wavelength at 60Hz, which makes any shielding and protection issues for line frequency EMF a near-field magnetic issue, more comparable to static magnetic fields in many respects. But at a megahertz and above inductances of the dimensions of human-scale (or at least building-scale) objects begin to matter.

Don't have much on the mutant-dog question for ya though! :-)