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I'm building a magnetic stirrer. I wanted to add a heated bed and I've been looking at peltiers as a heat source. To control the temperature I've identified the "WH7016K", a Chinese-made temperature control system designed specifically for direct peltier control and it's only about 20 bucks.

However, the data sheet for the device says the max load of the relay is 8A/30VDC or 2A/220VAC. If I'm using a 12VDC peltier is it safe to use one that draws 5A? Am I correct in assuming that the relay has a max load of 240 watts and the 60W load of a 12V/5A peltier should be fine?

Manual for the device is available here, ‎but it is fairly sparse. It's also a word document so heads up if that rubs you the wrong way.

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If the relay is rated at 8A/30VDC then it should be OK at lower DC voltages and lower DC currents such as 12V/5A. If in any doubt use an external relay triggered from the one in the controller.

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  • \$\begingroup\$ figured as much but wanted to make sure before i spent money. thanks! \$\endgroup\$
    – quixotic120
    Mar 4, 2014 at 15:46
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The relay will not burn out immediately, it is within its ratings, however note that the life of the relay may only be a 100,000 or 150,000 operations at close to full current. That means that if it cycles every 2 seconds, it could die in a couple months of 24/7 operation.

If it works for you, you may wish to supplement the relay output by using it to control a DC SSR of suitable rating. When operated with almost no load, the relay life will typically be at least 10x longer, and an SSR should last "indefinitely".

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  • \$\begingroup\$ good point! I will add in an SSR, I'm pretty sure I have one around that will work actually. \$\endgroup\$
    – quixotic120
    Mar 5, 2014 at 23:07
  • \$\begingroup\$ @jon Just be careful that it's a DC output type. The AC output type will not turn off. \$\endgroup\$
    – Spehro Pefhany
    Mar 5, 2014 at 23:17

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