Question on comparing DC amps to AC amps please

You would have to ask the manufacturer, IMHO. Things like contact material, contact wiping and clearing path and arc suppression strategy typically vary between manufacturers and even between contactor designs from the same manufacturer.

Yes the manufacturer will have design models that are used to predict the performance of particular designs - but it isn't just a case of saying so much at 240vac equates to so much at 12v dc.

It also depends on the dc load and whether it is highly reactive and, if inductive, whether it has a fast diode across it. Thus there will be a resistive load rating and a much lower rating for reactive loads.

I concur with all Sue Said,

with the added point that when we use small AC Contactors to break DC with Inductive Loads, we usually add in a few contacts of the same device in series, This way there are multilple breaks in the Circuit at the time the contactor opens. this helps in extinguishing the DC Arc.

If you have 4 contacts available, use all four contacts, the more the merrier, as long as the load is enough that contact resistance is not a problem.

Tom Grayson

Thanks to both of you.