Wires become very hot when supplied with 12VDC6A

Thread Starter

caje

Joined May 2, 2020
9
Today I was prototyping an upcoming hobby project of mine (wine fridge). I had the following components:
- 12V 3A PSU (2x) (link)
- 12V 6A Peltier module (link)
- Inkbird ITC-1000 Thermostat 220V (link)

I connected the 2 PSU's in parallel to obtain the 6A current, and connected common ground to negative of the Peltier module. Then I connected the common positive to entry 7 on the thermostat, and connected entry 8 on the thermostat to the positive of the Peltier module. I then connected by 220V AC to the power supply of the thermostat. For wiring from DC to the Peltier I have used jumper wires that I normally use for my Raspberry Pi.

I observed that everything was working fine, but that the positive wire connecting the thermostat to the Peltier became very hot! The plastic around the connectors began melting, so I turned off the power.

My guess is that the jumper wires are not able to withstand 6A current. Is this true? Which wires should I look for to support this setup?
 

SamR

Joined Mar 19, 2019
2,126
For wiring from DC to the Peltier I have used jumper wires that I normally use for my Raspberry Pi.
Which puts out ~200mA max, and do you think they might have a problem with 6A? I am assuming you are using 22AWG wire with PVC plastic jacket.
Here is a chart, I would cut the ampacity for chassis wiring in half to give a safe overhead: YMMV
1589487287980.png
 

Thread Starter

caje

Joined May 2, 2020
9
Right, thank you. So if I read your chart correctly I would go for at least 0.8 mm diameter wires. Looking at wires available in local shops I see the H05V-K, and looking at the data sheet the 1mm2 (d=1.13mm) version has a current rating of 10A. This seems like a safe choice then, I would assume.
 

SamR

Joined Mar 19, 2019
2,126
It also depends on the jacket materials heat resistance. I am more used to Industrial THHN wire which is NEC (US National Electric Code) rated. Me, for 5A, I would shoot for 18AWG stranded with a silicone rubber jacket. Flexible and heat resistant. That is assuming it is a relatively short run. I tend to be very conservative about wiring towards the safety side. Hot wires mean you are losing energy as heat and not using it in powering the circuit. Besides, wire is relatively cheap. You haven't posted your wiring diagram but I would double and triple check for a short to ground or any other reason that may be causing the wire to get hot other than sizing.
 
Last edited:

MisterBill2

Joined Jan 23, 2018
6,071
Today I was prototyping an upcoming hobby project of mine (wine fridge). I had the following components:
- 12V 3A PSU (2x) (link)
- 12V 6A Peltier module (link)
- Inkbird ITC-1000 Thermostat 220V (link)

I connected the 2 PSU's in parallel to obtain the 6A current, and connected common ground to negative of the Peltier module. Then I connected the common positive to entry 7 on the thermostat, and connected entry 8 on the thermostat to the positive of the Peltier module. I then connected by 220V AC to the power supply of the thermostat. For wiring from DC to the Peltier I have used jumper wires that I normally use for my Raspberry Pi.

I observed that everything was working fine, but that the positive wire connecting the thermostat to the Peltier became very hot! The plastic around the connectors began melting, so I turned off the power.

My guess is that the jumper wires are not able to withstand 6A current. Is this true? Which wires should I look for to support this setup?
Some of those jumper wires are so very thin that they make good low current fuses. For 6 amps I would suggest no smaller than #18 wire, if the goal is no heating of the wires and not much voltage drop.
That table is rather optimistic in stating that #18 is good for 16 amps.
 
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