relay power ability

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pts760

Copper - Posts: 403

Joined: December 11, 2009

Location: United States

Posted: July 02, 2013 at 3:36 PM / IP Logged

I want to use relays to break the speaker output on a amp that puts out 100 watts a channel at 4 ohms. I'm building a speaker selector for a customer with a house boat.

According to my calculations a SPDT 30A/40A relay can handle up to 576 watts at 14.4 volts at 40A(Power= voltage x current)and 432 watts at 14.4 volts at 30A. Are my calculations correct? Should I be okay to do this? Has anyone done this?

I drink current, eat ohms, and bleed voltage

soundnsecurity

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Joined: November 10, 2008

Location: Louisiana, United States

Posted: July 02, 2013 at 4:05 PM / IP Logged

amps equals the square root of power divided by resistance, so 100watts divided by 4 = 25, square root of 25 is 5amps, well within the range of a 30A relay

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itsyuk

Silver - Posts: 505

Joined: February 23, 2010

Location: United States

Posted: July 02, 2013 at 5:09 PM / IP Logged

radio shack sells a little 4PDT relay that is rated 7 amps. i have used these many times in the past for this very purpose. the largest amp i have used these on is a JL 300/2. no problems.

yuk

quiet rural missouri, near KC.

If your system moves you physically and not emotionally, you have wasted your money.

pts760

Copper - Posts: 403

Joined: December 11, 2009

Location: United States

Posted: July 04, 2013 at 12:33 PM / IP Logged

Awesome. Thanks for the info

I drink current, eat ohms, and bleed voltage

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relay power ability

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