12v pcb heatbed on 24v

[dcaron]

I have a 12v PCB heatbed. If I fed it 24v directly it would run at about 15-16 amps. From a hardware perspective, would the board be able to sustain this load if I limited the pwm to 66% giving me an average 10A or is the peak current too high? I don't want to get a 24v pcb bed because they often have too high resistance values limiting the power output to measly 100-125w. I should probably invest in a silicone AC heat pad, but I don't seem to find reasonably priced SSR that can be trusted. Had a bad experience with ebay ones…

Thanks for your advice.

[dc42]

I don't recommend relying on PWM to reduce the heater power.

What sort of PSU do you have? If it is a CCTV/LED type then you can probably turn up the voltage to around 14V.

[DjDemonD]

As an alternative perspective, I run a 300x200 PCB heater though its 12v connectors using a 250W 24v PSU. What happens is the PSU runs maxed out so I fitted a fan to it, but the heater works fine. I am not running it via the controller but via a fused mechanical relay. So no its probably not the ideal arrangement but when I hooked it up initially via its 24v connectors it would only draw 4A from the same PSU and wouldn't get up to ABS temperatures. Maybe consider a thermal fuse also. If you have a much more powerful PSU this might be unwise. So I'd say modest PSU and a relay and its doable.

I have no experience with using PWM to effectively run 12v devices on 24v so if David thinks its a bad idea I'd be inclined to believe him.

[haleyp]

DjDemonD good to know you can run a 12V heater at 24V. It makes sense. A typical 12V PCB heater is 12v^2 x 1.2 ohms = 173 watts. At 24V, 24v^2 x 1.2 ohms = 691 watts. As long as the copper traces and the PSU can handle it, why not?

I always use a 12V hot end heater on 24V. It heats up wonderfully fast!

[dc42]

@haleyp said in 12v pcb heatbed on 24v:

I always use a 12V hot end heater on 24V. It heats up wonderfully fast!

And if the heater mosfet fails short circuit, you will have melted heater block and probably a fire.

[T3P3Tony]

@dc42 I think @haleyp was referring to a heated bed not a heater block

@haleyp what is the max temp the heated bed can reach at 24V? that could be dangerous or not. PCB heated beds are generally made using FR4 PCBs which is rated to 140C before the resin holding the glass fibres could go soft.

[dc42]

@t3p3tony said in 12v pcb heatbed on 24v:

@dc42 I think @haleyp was referring to a heated bed not a heater block

Possibly, but he did say "hot end heater" in the line that I quoted.