Silent(humfree) contractors not suitable for 24/7 use

[mikehammer69]

Only just noticed this on a Hager spec sheet
Was about to order one for myself , not sure if applies to all brands

 

[ebee]

Interesting

 

[SUNRAY]

OO'er.

I remember the days when contactors didn't hum.

 

[bernardgreen]

I remember the days when contactors didn't hum.

some one had taught them the words.

Some "hum free" AC contactors are in fact a DC contactor with a built in bridge rectifier and capacitor to feed the coil with a "smooth" DC This enabled the use of a simple magnetic arrangement.

The bridge rectifier and the capacitor are the weak points which can shorten the life expectancy of a contactor

 

[SUNRAY]

I supposed I should be looking at what 'hum free' actually means.

To my mind if I opened a control panel and heard anything humming; I'd start looking to see which device had a problem. however any wire wound device has the potential to 'hum' if you get close enough to it -at some stage I'm sure we've all put our ear to something to see if it's powered.

 

[mikehammer69]

Its for under/overvoltage protection so presumably the main contactor needs to be n/o

Don't think there's any way round it.

Afaik some of the shower controllers use a relay /contactor combination so main contactors aren't energized ,but that wouldn't fail-open I don't think

My vacuum cleaner almost ground to a slow halt as I was using it one day so I decided to fit it

 

[SUNRAY]

Why not use the detector device as a safety circuit and then use a contactor only when required?

 

[mikehammer69]

Why not use the detector device as a safety circuit and then use a contactor only when required?

Explain that operation for me ?

The detector needs to de-energize the n/o contactor almost immediately to cut the supply