Contact Ratings

[justlearnen]

If I have contacts rated for 110 VAC/28 VDC, can I run 12 VDC thru the contact? My miniature pump is 12vdc and I want to activate it thru the mentioned contact. What can I do to use the 110vac/28vdc?

 

[melone]

As a first order approach, yes. Since 12 is less than 28, it sounds like it would work. However, if you are trying to pull 100A, even at 12V, I don't think your switch will work.

 

[BrianG]

The reason the a.c. voltage rating is much higher than the d.c. rating is because an a.c. circuit has a lower tendency for sustained arcing when the contacts open. However as Melone says, the current must be considered as well as the operating voltage. The d.c. rating given will be for a non-inductive, i.e. resistive, load - your pump motor will be inductive - and you also need to consider the startup current surge to stay within the overall d.c. rating. If the motor inductance is significant you will probably need to consider an R-C "snubber" circuit to prevent the contacts arcing.

 

[justlearnen]

I believe that my motor and a timer will require 36-40 watts

 

[advidana]

yes it can be used if the ampere rating is sized correctly.
What is the current rating of the contacts and are they horsepower rated.