Estimating VAC rating from VDC rating

Question

I have encountered several terminals, sockets, cables, and similar components which are rated in either DC or AC voltage, but not both. I sometimes want to use an AC rated part with DC or vice versa. Is there a way to identify when this is obviously unsafe?

For example, I know not to use something rated for 12VDC with 125VAC.

To give a specific case, I want to know if I can use this https://www.grote.com/electrical-connections/trailer-connectors/heavy-duty-7-way-connectors/82-2145/ 40a @ 28 VDC rated socket with a 10a @ 125 VAC load. Thank you.

Answer 1

You can not estimate an AC rating from a DC rating, a DC rating from and AC rating or estimate any other "rating." The rating is what is published by the manufacturer. What you are asking for is an estimate of the risk involved with using a component outside of its rating. It is really a bad idea to leave anything unattended if you are not certain that is will be operated within its ratings. It is probably not a good idea to operate anything above 50 volts if that is outside its rating. The risk also goes up with increased current. You are always on your own when you take the risk of using something outside of its rating.

Answer 2

In the absence of other information, I don't think it is safe to exceed the manufacturer's specifications. If the manufacturer says that the maximum voltage is 28 V dc, then I would assume that some insulator somewhere or some air gap somewhere would break down if you apply 125 V ac.

You may get someone to say that it will "probably" work. If you are comfortable knowing that you "probably" won't have to explain the fire to your insurance company, go right ahead.