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WikiProject Electronics (Rated C-class)
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When a contactor develops a buzzing sound, do they usually need to be replaced? I have that problem in a breaker box attached to my hydrokinetic heating unit. My contractor has consistently told me the buzzing sound is irrevalent. Since winter is upon us with cold temperatures and I have an off peak/on peak system depending on these contactors doing their job to heat the auxilary water tanks for on peak heat when temperatures lower than 30 for a heat pump, I think the contactors are beginning to fail. Reason being.....every few days the heat temperatures in our house begin to drop about 3 points. Am I right on my inclination and am I being scammed by the electrical installer????

Wikipedia is the last place to look for fix-it information. Why don't you trust your contractor? Try another contractor? --Wtshymanski 18:35, 1 February 2007 (UTC)
Use a DC rectified coil in the contactor, this will reduce any noise (also called chatter) 00:15, 25 April 2007 (UTC)

Mention buzzing[edit]

How can Contactor not mention noise? Relay clearly says

Contactor relays can be extremely loud to operate, making them unfit for use where noise is a chief concern.

therefore how could it be that the Contactor page itself not mention noise, and what, if anything, one should do about it?! (One supposes the noise they are referring to is buzzing.) Jidanni (talk) 01:14, 28 February 2008 (UTC)

Wikipedia should explain how things work and what they are used for, but not provide detailed instructions for designing or repairing things. Both relays and contactors make a noise when the contacts open or close. The noise level is proportional to the size of the device and the number of contacts. A small relay makes a soft click that may be difficult to hear. A large contactor makes a thud. I would not say that it is extremely loud, but you will certainly hear it if it is nearby and there is not a lot of other noise in the area. Contactors and large relays may hum or buzz when they are energized with AC power, but they can not ordinarily be heard very far away or in the presence of significant background noise. The buzzing of a contactor that energizes a nearby motor shold not be heard over the noise of that motor. It may not fail anytime soon, but it is not a good quality product either. -- C J Cowie (talk) 02:22, 28 February 2008 (UTC)

Yes, but a contactor, when first installed, makes a tiny buzz, but as the years go by, the buzz gets louder. The consumer wonders which of:

  1. normal, live with it
  2. dust off with forced air
  3. time to replace
  4. pending disaster

Jidanni (talk) 03:13, 28 February 2008 (UTC)

EV conversions?[edit]

The article has an image with the caption; "Albright SPST DC contactor,sometimes used in EV conversions." What are EV conversions? Best Regards. DynamoDegsy (talk) 14:58, 24 April 2014 (UTC)

Electric vehicle Andy Dingley (talk) 16:43, 24 April 2014 (UTC)

Conversion to American English?[edit]

Recent edits have "tidied up" this article to convert it to US English [1] [2] and tag it as such [3]. Yet this article was created in British English [4], "specialised".

What is the basis for making this change? Contactors are not a US-specific device. Andy Dingley (talk) 08:00, 1 July 2016 (UTC)


This article is exclusively about electromagnetic contactors but contactors can also be operated by pneumatics, hydraulics or camshafts. Is this already covered somewhere else or shall I add a section? Roberttherambler (talk) 11:02, 11 September 2017 (UTC)

Well, if you can source it, then go for it. It's an obscure term and I feel it's maybe a bit archaic. Electric locomotives (and their relations) are the only places I can think of where the term was at all commonplace in that sense. Certainly HV switchgear on them that used pneumatics for a degree of isolation was one. Andy Dingley (talk) 11:08, 11 September 2017 (UTC)
Yes, many EMUs had electromagnetic contactors (one could often hear them chattering) but I think British Railways used camshaft-operated contactors powered by air/oil motors. I will look into it. Roberttherambler (talk) 11:25, 11 September 2017 (UTC)
Do you have the per-class driver's handbooks? They're sometimes quite good for this. As is the bigger driver's manual for all types in general (I have the various editions of that, as it changes over time - but the diesel one is better). Andy Dingley (talk) 11:30, 11 September 2017 (UTC)
No, I haven't. Roberttherambler (talk) 11:47, 11 September 2017 (UTC)
It's briefly mentioned here[5] about 4 REP units: "Camshaft control was fitted, with separate camshafts for the resistance and weak field notches". Roberttherambler (talk) 12:01, 11 September 2017 (UTC)
OK, I've added a section. Roberttherambler (talk) 13:20, 11 September 2017 (UTC)