A whining contactor on Economy 7 supply

[salisbury spark]

A 100a single phase Contactor(HR55) on a 24 hour timer supplying 4 E7 storage heaters (55amp max)

When contactor is energised it regularly has a varying pitched whine(vibration)
This changes when i turn off the heaters one by one or wiggles the contactor/cables.

It does it on a new generic hr55 contactor aswell (i did clean the faces on both)

Tried allsorts of things 'packing out' the core and stopping as much free play as i can.

I know they are prone by there inherent design to this but any ideas on stopping it. If i push the 'moving parts tighter when they are engaged this helps.

I wonder if it the actual contacts vibrating as packing the core tightly doesnt help.

Would a capacitor accross the coil help? Thanks

 

[Knobhead]

First off check the voltage across the coil with the heaters turned off. Then check the voltage as each successive heater is turned on.
With you saying it’s quiet with no load it sounds like a volt drop problem.
A capacitor will make it worse.