Thermal Magnetic Breaker Settings

[Mike Lamb]

This main disconnect has adjustable dials. What are they for and does a homeowner need any knowledge about their settings? Or do I for that matter?

I suppose they are for some sensitivity response to over loads but I'm guessing.

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[Jim Katen]

Perhaps an adjustable time delay?

[Marc]

I think the adjustment on the left is there for the factory to set the magnetic trip I(m), characteristics of the breaker to whatever it's supposed to be for that particular panel. This particular adjustment seems capable of reaching values of anything between 5 and 10 times the value of the thermal trip, I(n). I don't think it's there for the homeowner or even the electrician to play with. If you look at the label, it might tell you just what value of I(m) the adjustment is supposed to be set at.

I don't know what the adjustment on the right side is for. A better view might help.

Marc

[inspector57]

I've never seen it but then at 400 amps, that in itself would be a rareity.

[Bill Kibbel]

They are breakers manufactured for industrial equipment. The dials are to make adjustments to the breakers to match the characteristics of industrial motors. In other words, to minimize nuisance tripping on motor start-up.

[Mike Lamb]

This is in a house with nothing electrically special going on.

100 amp main panel would be just fine.