Electric heater noise problem... - Page 1
Forum section: electronics / beginners

author: sam1275
author_rank: Frequent Contributor
timestamp: November 06, 2014, 06:46:35 pm
content: Hello everyone, I have a electric heater in my living room, it has noise when working, the noise is not 50hz(the electric frequency in country I am living), but a much sharper sound, it makes me feel like it's just near my ears. The higher power I set, the loader it will be, although it's not very load even at the highest power, but it's really annoying to hear it all day, the heater uses resistance wire so I don't even know how it makes the noise, but I think maybe I can solve the problem by giving it DC instead of AC, so I plan to use 4 diodes to make a rectifier bridge, then use 2 capacitors as filter, can anyone help me to decide the specification of the capacitors? The utility power is 220 volts, 50HZ, and my electric heater is 2200 watts. Thank you for any help!

author: denelec
author_rank: Regular Contributor
timestamp: November 06, 2014, 09:42:03 pm
content: Does your heater have an electronic circuit to modulate the power?Sometime, a light bulb will buzz when on a dimmer. Dimmers can introduce a lot of high frequency harmonics in the voltage and current. This could explain your noise.But I've never seen an electric heater with a dimmer circuit.Usually electric heaters modulate power by varying the number of elements or by cycling the power like a slow pwm.These methods avoid creating harmonics.Generating high amount of harmonic currents can lead to problems (neutral, transformer and motors overheating, various electronic equipment malfunction, etc...) so that why it should be avoided.Do you have an oscilloscope to view the current waveform?

author: sam1275
author_rank: Frequent Contributor
timestamp: November 07, 2014, 07:24:51 am
content: Quote from: denelec on November 06, 2014, 09:42:03 pmThank you for your reply, I remember it change power level by turn on or off different set of resistance wire(from the user manual, I had a quick look when I bought it), it have 2 sets of resistance wire, one is lower power and another is higher power,(for example 600w+1600w, I forgot), on the lowest power level only 600w wire is working, the medium is 1600w only, and the highest full power mode makes those two sets of wire working together to archive 2200w.

author: Whales
author_rank: Super Contributor
timestamp: November 07, 2014, 07:52:48 am
content: Have you had a look around inside at the heating wire recently? A mounting might have aged/broken (allowing it to rattle from the 50hz irregularly -> generate non 50 hert sounds) or some debris might be floating around in there. Worth a try

author: sam1275
author_rank: Frequent Contributor
timestamp: November 07, 2014, 08:26:07 am
content: Quote from: Whales on November 07, 2014, 07:52:48 amThank you, it have this noise since the first day I had it, I even changed one due to this problem, but no luck.

author: IanB
author_rank: Super Contributor
timestamp: November 07, 2014, 08:36:10 am
content: Does the heater have a fan or is it a convection heater?I honestly can't think of why it would make such a high pitched noise. Maybe some photos would help? Without knowing what is making the noise, trying to run it on DC is not likely to help.

author: sam1275
author_rank: Frequent Contributor
timestamp: November 08, 2014, 01:40:40 pm
content: Quote from: IanB on November 07, 2014, 08:36:10 amIt's a convection heater, I don't know how the noise happen neither, but I think it's the easiest way trying to stop it by run it on DC.

author: IanB
author_rank: Super Contributor
timestamp: November 08, 2014, 06:10:50 pm
content: Quote from: sam1275 on November 08, 2014, 01:40:40 pmIf AC doesn't cause the noise, DC won't stop the noise.

author: Zero999
author_rank: Super Contributor
timestamp: November 08, 2014, 06:46:57 pm
content: Running off DC may stop the power controller from working and even if it is the AC which is causing the noise, unfiltered DC would still have an AC component so would still make a noise.

author: Jeroen3
author_rank: Super Contributor
timestamp: November 09, 2014, 12:04:29 am
content: You would probably kill it unless you reduce the DC voltage to the ac equivalent. If you bridge rectify it with some (huge) capacitors the voltage will be higher than ac rms.And the current/power is continuous, not sure if it will like that.

author: Yago
author_rank: Frequent Contributor
timestamp: November 09, 2014, 11:04:44 am
content: I have am oil filled heater that "sings" as it warms up too!Much higher in pitch than 50Hz, does a ringing that seems to drift in pitch, amplitude and harmonics(don't say timbre!:P), a little like Cpt Kirk on the transporter.It's a monocoque construction and the "cells are interconnected at the top and bottom.It think these structures act like bells and resonate from the energy of 50Hz (higher harmonics), frequency shifting as the heat changes tensions in the "bells"??Not sure, a guess, if I get change I'll record the sound but it would be a good while before I can play with my toys!

author: Kaptein QK
author_rank: Regular Contributor
timestamp: November 09, 2014, 12:54:05 pm
content: It is probably the harmonics on the 220V.The magnetic fields generated makes the resistance wire vibrate.

author: sam1275
author_rank: Frequent Contributor
timestamp: November 09, 2014, 01:34:44 pm
content: Thank you everyone, so I want to try DC first, could any tell me the specification of the capacitors I should use?

author: denelec
author_rank: Regular Contributor
timestamp: November 09, 2014, 01:50:27 pm
content: Quote from: sam1275 on November 09, 2014, 01:34:44 pmIf you rectify the AC and put a filtering capacitor, you will get more than 300V DC. You will burn the elements.

author: BradC
author_rank: Super Contributor
timestamp: November 09, 2014, 03:09:42 pm
content: Quote from: sam1275 on November 09, 2014, 01:34:44 pmI would skip the capacitor at first and just feed it with a bridge rectifier. If it's a mains related noise it'll likely double in frequency when you do that. Be aware the bridge will be dissipating in excess of 10W when the thing is at full noise, so make sure its properly heatsinked.