overhating 12 heatbed

[Shsims]

hey have an I3V that I just upgraded to the 12" from 10" and I'm having an over heat problem, 1st j2 relay melted, fixed it, now it looks like wires from headbead are starting to burn (very hot) and relay may be melting again, what do I need to check, did not have this using 10" bed

[sniffle]

I had this problem... here's how i fixed it.

I replaced the relay provided with a 40A automotive relay, and i replaced all heat bed wiring with 10AWG high temp silicone wiring. While I was at it, I moved the heated bed to its own 30A power supply and now run the hotend and electronics off of an old PSU. The wiring now gets warm but never hot.

The reason that the wiring is beginning to melt is that it can't handle the load the heated bed pulls, and as a result generates heat. To be safe you should probably use a minimum of 12AWG wire, I just went with 10AWG to go for overkill... :-)

Good luck
hope this helped

[Shsims]

Can you tell which relay you got so i can pic one up

[printbus]

Speaking up for Sniffle, just go to an auto parts store and look in the electrical area for accessory relays. They might be marked for use with horns, lights, etc. The typical ones are cubes about 1-inch in size.

The typical meltdown is with the terminal block, and not the relay itself. FWIW, here's my analysis of the meltdown problem - http://3dprintboard.com/showthread.p...ll=1#post48172

EDIT: That thread also has pics of an automotive relay retrofit.

[Shsims]

can ya send a pic on how you wired relay, I just bought a 12v 40amp relay with 4 connections, dont wanna screw it up, also got 10awg wire so let me know