When contacts are rated for DC can they carry the same AC current? Need a 70+ amp set of continuous duty contacts from a DC relay to carry a 120 VAC with a max 70 A. The relay will be activated with 12 VDC so the coil will be fine, just looking for thoughts on the use of the contacts for this carrying ability.

 

As a general rule, the contact conditions required for switching DC are more stringent than AC so they are often rated slightly higher capacity when used on AC.
Max.

 

If you think about alternating current, it breaks the arc with every cycle as the polarity changes. So a DC rating will usually be MUCH lower than the AC rating (eg. 1A DC 24V, 20A AC 300V).

 

Yes most DC rated relays and contactors will handle AC switching without issie.

 

As a general rule, the contact conditions required for switching DC are more stringent than AC so they are often rated slightly higher capacity when used on AC.
Max.

So if a 200 amp dc relay was used for a 70 amp ac contact do you feel this would be adequate? Thank you for your assistance and input.

 

Yes most DC rated relays and contactors will handle AC switching without issie.

If you think about alternating current, it breaks the arc with every cycle as the polarity changes. So a DC rating will usually be MUCH lower than the AC rating (eg. 1A DC 24V, 20A AC 300V).

So if a 200 amp dc relay was used for a 70 amp ac contact do you feel this would be adequate? Thank you for your assistance and input.

 

Yes most DC rated relays and contactors will handle AC switching without issie.

Thank you

 

So if a 200 amp dc relay was used for a 70 amp ac contact do you feel this would be adequate? Thank you for your assistance and input.

I would say so with some certainty.
Max.