<p>The <a href="https://reprap.org/wiki/PCB_Heatbed#MK2b_Dual_Power_Technical_Details" rel="nofollow noreferrer">PCB heatbed Mk2B</a> has a reported resistance between 1.0-1.2&nbsp;&ohm;. The current that is drawn from the power supply equals about 12/(1.0 or 1.2) = 10-12&nbsp;A. Note that this amount of current requires cables that can carry that load, too thin cables heat up. </p>

<p>Note that you have wired the bed correctly for 12&nbsp;V (see image below), the wires might have a too-small cross-section, try thicker wires. Personally I use AWG 12-14 silicone wires depending on the bed resistance.</p>

<p><a href="https://i.sstatic.net/QJT2em.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/QJT2em.png" alt="Mk2B heatbed connections"></a></p>

<p>AWG 12-14 size silicone, multiple threads (these are the best for the bed because they are more flexible), should be able to handle the load fine. Note that cables also have resistance; if there are heat spots in the cable or the connection, this indicates that the cable may be broken or the connection has too much resistance.</p>

CC BY-SA 4.0
2020-03-17T01:57:39.763Z
Yes, the heat spots were indicated in the cable. I will replace its with a thicker ones. Thanks for your help
DrPortgas
CC BY-SA 4.0
2020-03-17T12:38:46.957Z
@DrPortgas, don't use that machine again until you replace that cable.
user77232
CC BY-SA 4.0
2020-03-18T09:29:32.367Z
yes, i had replaced the cable and its works very well. Thank a lot
DrPortgas
CC BY-SA 4.0
2020-03-16T07:28:07.737Z
2020-03-16T15:19:17.840Z
2020-03-16T15:19:17.840Z
0scar
<p>Check the diameter of the cable. The smaller the diameter the higher the resistance, thus the heat. AWG14 seem a bit small.</p>

CC BY-SA 4.0
2020-03-17T01:58:32.267Z
Sure, i will check again the diameter of the cable
DrPortgas
CC BY-SA 4.0
2020-03-17T12:37:14.280Z
14 awg should be sufficient. Moving to 12 awg won't really reduce the heat.
user77232
CC BY-SA 4.0
2020-03-16T13:29:04.767Z
2020-03-16T13:29:04.767Z
Wolfram
<p>I'm using a 200x200&nbsp;mm PCB Mk2B which connects to the MOSFET of the D8 pin on a RAMPS 1.4 shield. I used 12&nbsp;V power source for heat bed so I connected positive to pin 1 and negative to both pin 2 &amp; 3 of the bed. Heat bed worked properly. But the wires that connects power source to power supply pin on RAMPS were being heated badly. I think the problem is come from heat bed because when I unplugged heat bed, wires were cool down instantly. </p>

<p>Can someone helps me with this problem. I'm just a newbie in this area.</p>

CC BY-SA 4.0
2020-03-16T15:34:25.243Z
Its normal for the wires in a 12v system to get hot. What was the bed temp? how long was the print?
user77232
CC BY-SA 4.0
2020-03-18T09:33:23.557Z
The bed temp is 60 degree. The wires were getting hot just after the print begun. But replaced the wire with a thicker ones had solved the problem
DrPortgas
CC BY-SA 4.0
2020-03-18T12:39:45.577Z
What AWG did you use? (NB: it supposed to be printed on the cable)
user77232
<heated-bed><heat-management><power-supply>
Heat bed wires get hot (12 V connected to RAMPS 1.4 shield)
DrPortgas
# Heat bed wires get hot (12 V connected to RAMPS 1.4 shield)

(Asked by: username_0 on 2020-03-16)

I'm using a 200x200 mm PCB Mk2B which connects to the MOSFET of the D8 pin on a RAMPS 1.4 shield. I used 12 V power source for heat bed so I connected positive to pin 1 and negative to both pin 2 & 3 of the bed. Heat bed worked properly. But the wires that connects power source to power supply pin on RAMPS were being heated badly. I think the problem is come from heat bed because when I unplugged heat bed, wires were cool down instantly.

Can someone helps me with this problem. I'm just a newbie in this area.

**Tags:** heated-bed, heat-management, power-supply

> **Comments:**
> **username_1**: Its normal for the wires in a 12v system to get hot. What was the bed temp? how long was the print?  
> **username_0**: The bed temp is 60 degree. The wires were getting hot just after the print begun. But replaced the wire with a thicker ones had solved the problem  
> **username_1**: What AWG did you use? (NB: it supposed to be printed on the cable)  

---

## 2 answers

### Answer by username_2 on 2020-03-16. Score: 1 | Accepted answer

The [PCB heatbed Mk2B](https://reprap.org/wiki/PCB_Heatbed#MK2b_Dual_Power_Technical_Details) has a reported resistance between 1.0-1.2 &ohm;. The current that is drawn from the power supply equals about 12/(1.0 or 1.2) = 10-12 A. Note that this amount of current requires cables that can carry that load, too thin cables heat up.

Note that you have wired the bed correctly for 12 V (see image below), the wires might have a too-small cross-section, try thicker wires. Personally I use AWG 12-14 silicone wires depending on the bed resistance.

[![Mk2B heatbed connections](https://i.sstatic.net/QJT2em.png)](https://i.sstatic.net/QJT2em.png)

AWG 12-14 size silicone, multiple threads (these are the best for the bed because they are more flexible), should be able to handle the load fine. Note that cables also have resistance; if there are heat spots in the cable or the connection, this indicates that the cable may be broken or the connection has too much resistance.

> **Comments:**
> **username_0**: Yes, the heat spots were indicated in the cable. I will replace its with a thicker ones. Thanks for your help  
> **username_1**: @username_0, don't use that machine again until you replace that cable.  
> **username_0**: yes, i had replaced the cable and its works very well. Thank a lot  

---

### Answer by username_3 on 2020-03-16. Score: 1

Check the diameter of the cable. The smaller the diameter the higher the resistance, thus the heat. AWG14 seem a bit small.

> **Comments:**
> **username_0**: Sure, i will check again the diameter of the cable  
> **username_1**: 14 awg should be sufficient. Moving to 12 awg won't really reduce the heat.  

---

