Humming floor 3

[Skogsgurra]

I got a question about heated floors yesterday. It was a simple question: Why do floors hum?

The obvious answer, of course is that they do not know the Words. But this guy wasn't satisfied. "Must be harmonics" he said. "do you Think that a snubber could work?"

"OK, so it is a heated floor?" I asked.

It is a heated floor. With a thin resistive foil, no dimmer no thermostats. Just DOL, 230 V 50 Hz. The foil is covered with an insulating layer somewhere between 3 and 6 mm thick. And on top of that the floor as such. The foor hums so that people cannot sleep in the room where the floor is.

My take on this is that there is an electrostatic attraction between resistive foil and insulating layer (with an epsilon around 5). Force is voltage squared, so the dominating frequency should be 100 Hz. So far, Everything computes.

But this has never happened before. Anywhere. At least not in this guy's experience. And he works a lot with heated floors. Question: Do floors hum a lot? Or is this one a rare exception?

If they do hum - what do you do to silence them?



Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[MikeHalloran]

My guess, given zero experience with resistively heated floors, is that there's an air gap somewhere, so the floor is buzzing like a cheap transformer.

An acoustic spectrum analysis might reveal something.

First thing I'd try is run a heavy-ish roller all over the floor, in an attempt to (re)bond the constituent layers.
... after reading the heating system manufacturer's installation instruction, to see if that voids a warranty, or supplies an overlooked process step.





Mike Halloran
Pembroke Pines, FL, USA

 

[msquared48]

Alter the mass.

I am wondering if it is behaving like an antenna, amplifying a specific frequency range.

Mike McCann, PE, SE (WA)

 

[Skogsgurra]

Tin foil ear plugs do not seem to help.
Problem owner now follows this thread.
Waiting for more input...

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[VEBill]

How about magnetic attraction from the conductors carrying the current and a nearby metal object, such as a nail?

Some of the heated floor systems used balanced wiring to eliminate concerns about electromagnetic fields. The hot and returns are kept very close to each other, to reduce the area of the loop and almost entirely eliminate EM radiation.

Anyway... If push comes to shove, then procure and install a suitable DC power supply. Many such floor systems are in the high 100s of watts, not out of reach. If it's kilowatts, then it might get expensive.

 

[msquared48]

Just a thought, but transformers humm too...

Mike McCann, PE, SE (WA)

 

[Compositepro]

All heating elements will have a 120 Hz vibration due to the AC current causing temperature variation at that frequency. The higher the heat flow, and the lower the mass of the heating element wire, the high this vibration will be. Bare wire space heaters are often audible. Add a sounding board and a resonance, and it will get worse by orders of magnitude.

 

[Skogsgurra]

This is a rather low power resistive foil - not wire/wires. So I have ruled out any magnetic forces (we have to be realistic, don't we?)

I was not asking for thoughts - that, we already have had enough locally. I was asking for similar experiences. Se OP: "Do floors hum a lot? Or is this one a rare exception?"


Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[VEBill]

OP asked several questions, including "If they do hum - what do you do to silence them?"

DC. If feasible, it would certainly silence the AC humm.

"All heating elements will have a 120 Hz [100Hz?] vibration..."

No, not all. DC.

"...transformers humm too..."

If that was in regard to humm from a possible DC power supply, then it can be designed or selected to be silent, and/or it could be installed in the basement, far away from the bedroom.

I'm assuming that it's not simple to tear up the floor to redo the entire installation. And pouring a concrete slab over the floor is probably not ideal.

Thus my suggestion of DC, if feasible (depending on power level). A DC power supply in the basement. If it's kw, no.

Or get a white noise generator, or run a fan. Pure silence is very difficult to maintain.

 

[OperaHouse]

I have a Morningstar SL-10 solar charge controller. The PWM rate ia about 100hz, there are no inductors, the case is aluminum and it is epoxy potted. Operating at 5A it hums. By all sense of reason, it shouldn't make a noise.

 

[Skogsgurra]

And, the Solar Panels are on the roof - I presume?

That shows us that the humming problem, which I thought was limited to floors and certain fish species (Porichthys notatus and relatives), now also has invaded roofs.

I think that the problem owner is following this thread. Magnus: any new findings? It's getting cold outdoors and I guess that the guy is eager to return to his bedroom?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[KENAT]

Is there a structural element or furniture item or ... with a resonant frequency such that it is being excited by the heated floor?

With the equipment I work with we'd tell you that all floors hum!

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Skogsgurra]

Do they really?

That is exactly what I asked about - someone that had experience with humming floors. You seem to be the guy. What Equipment is that?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[KENAT]

Sorry Skogs, we build Atomic Force Microscopes's they will pick up very small vibrations etc. as 'noise' in the data. We usually have to isolate them from vibration and acoustic excitation and even then have limits of how much acoustic noise or vibration can be in the environment.

So we will detect 'hums' not audible to the human ear.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Skogsgurra]

Haha, Kenat. You never disappoint! But, remember - I am meaner!

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[MikeHalloran]

I used to work with blood cell counters. They are probably not quite as sensitive as AFMs, but their front ends do respond to normal human speech.

Is it possible that all of your friend's prior installations were in relatively noisy environments, and this one is in a particularly quiet location?

Has anyone actually measured the hum?
Recorded a sample?
Done a frequency analysis? (smartphone apps exist for this)



Mike Halloran
Pembroke Pines, FL, USA

 

[Skogsgurra]

Not to my knowledge, Mike.

The floor hums away just South of Stockholm. It is 160 miles away. Not much, but there's no incitament to go and do the measurements as long as no one says so. The problem owner (responsible for the materials and installation) is situated in Gothenburg.

I guess that he has field guys that can do the measurements. Or that the room inhabitant or his parents can do it.

If he doesn't lurk, I shall contact him about that. Any idea what the app is called? We are going do port our ARCUS to an Android anyhow, but a simple prêt à porter is quicker.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[MikeHalloran]

I have SpectraView Analyzer Free and Spectrum Analyzer on my Android.

Mike Halloran
Pembroke Pines, FL, USA

 

[itsmyjob]

I do have a humming floor here, not heated floor per say, but humming. Should teach him the words...

small 12v transformer on a basement beam (no silent block)... I could silence the floor by unplugging the transformer, which will turn off my thermostat preventing the furnace the keep the house warm.

Eric N.
indocti discant et ament meminisse periti ​

 

[VEBill]

My house has electric heat, with a similar low voltage thermostat system. I built the transformers, required two, into a nice metal box. But I instinctively installed the metal box onto the plywood electrical support panel with rubber washers to help isolate any possible humming noise. Seemed like a very obvious noise mitigation strategy.

Of course some of the old baseboard heaters make TICK TICK TICK sounds when they change temperature.