Limit heatbed PWM value

[shadow axle]

Hello,
I want to limit my heatbed PWM value to 50% I have a 500x500 ratrig, and the heatbed needs 1.5kW power at 100%. My breaker doesnt like it. However if I could limit the PWM value to maximum 50%, then it would need less power (I know, slower heating but thats fine for me).
Tried to look up in the config.cfg, but I only found the [heater_bed] control: pid and pid values, and in the v-core3-cfg: [heater_bed] pwm_cycle_time: 0.02 # 50hz for european AC, to avoid flickering lights.

Any other option to limit the heatbed PWM? Thanks!

[hoary moat]

That's not quite how PWM works. 50% means it's 100% but 50% of the time. So you'd still be drawing 1.5kW peak.

However it might be enough to satisfy your breaker.

[hoary moat]

What you want to do is:

[heater_bed]
max_power: 0.5

in user overrides, like everything else.

As usual, look up the options in the klipper config reference: https://www.klipper3d.org/Config_Reference.html#heater_bed

As you can see it says " It uses the same heater settings described in the "extruder" section."

That means all parameters under https://www.klipper3d.org/Config_Reference.html#extruder can be used under [heater_bed] as well.

[stone mason]

Also keep in mind failure modes. SSR can fail open - meaning regardless of what the software is telling it, it will be as if the bed is directly connected to the outlet. So if your breaker can't handle the bed I would long term think about getting a different bed heater (kenovo will make custom ones)

[hoary moat]

Probably actually an advantage that the breaker trips in that case 😄

depending on what else is connected to it

[stone mason]

Yeah - I have a house built in the 80's and those breakers aren't the best so I try not to rely on them

[echo kite]

you either swap the house wiring/breaker to make do with the power draw or you install a lower power bed.
Not sure where you got your kit from but RR actually swapped to a 1200W bed instead for this reason

https://us.ratrig.com/3d-printers/keenovo-heater-pad-and-ssr-relays-multiple-sizes-configurations.html
they sell it extra here as well

as the other said, relying on software to limit the power draw can be fatal in case of a fault.
if you are lucky your breaker would catch that but if you aren't something might start to burn

[shadow axle]

Of course this is just a temp solution until the main problem is solved, but I just dont want to wait and not use the printer until it is done.