I have two water loops, one to dissipate heat and one that cools water. Both are closed loops. I have four 12706 Peltier modules connected to a switching power supply that can deliver 12 V and 30 A. I’ve connected the peltier a in parallel. I would expect the system to consume around 24 A, however all I see with the power meter on the wall is 4 A. I’ve used 12 gauge wire from the power supply to the peltiers. I even tried two sets of wires so that two peltiers would share one cable. Cooling the peltiers works, you can see the massive radiator. Temp on how side is about 27C. Cold side is negative with no water block and about 16C with it. two water blocks and four peltiers

copper radiator Why aren’t the Peltier getting more current? Is it the power supply? Are the Peltiers bad? But 4 of them together even if bad should consume more than 4 A, right?


EDIT: adding two pictures. One of wall meter and one of amp meter on positive wire feeding four peltiers. I see 20 A on the cable, and that makes more sense as it’s closer to the theoretical 24 A that the Peltiers should consume. As you see in the other picture, wall meter reads almost 8 A. So I guess that reading is bad? wall meter amp meter no voltage sensing

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    \$\begingroup\$ Is the "power meter on the wall" measuring the AC input to the power supply or the 24V DC output current of the power supply? \$\endgroup\$ Commented Jul 15, 2023 at 19:06
  • \$\begingroup\$ It’s measuring the total amps consumed the the switching power supply connected to it. PSU is 12 volts. Thanks! \$\endgroup\$
    – acanessa
    Commented Jul 15, 2023 at 19:10
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    \$\begingroup\$ Sorry - 24V was a typo. It is still not clear if the ammeter is measuring the AC input current of the power supply or the DC output current. \$\endgroup\$ Commented Jul 15, 2023 at 19:16
  • \$\begingroup\$ Just edited the post. Do we think the issue is the wall meter? \$\endgroup\$
    – acanessa
    Commented Jul 15, 2023 at 19:28
  • \$\begingroup\$ Both readings are correct, but the high voltage supply requires less current. Remember, 120W at 120V is 1Amp, but at 12V is 10A. \$\endgroup\$ Commented Jul 15, 2023 at 19:36

1 Answer 1


A power supply passes power (voltage times current), not just voltage or just current.

If the power supply is delivering 12 V at 20 A, I would exepect it to draw a bit more than 2 A at 120 V (some power will be used in the power supply itself).

The meter shows a poor power factor, which will increase the current drawn by the supply above what a simple power calculation suggests.

  • \$\begingroup\$ Thank you. That make sense. Can you clarify the comment about the power factor? \$\endgroup\$
    – acanessa
    Commented Jul 15, 2023 at 19:51

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