Is it possible to limit the maximum power output of an element to achieve the two following use cases:
If I have a heating element that has a maximum power higher than what the circuit can handle, eg. a 6000W element on a 16A circuit, can I limit max output to 50%
If I have an HLT that uses 12500W that is max of my circuit, but have a RIMS at 3500W, can I throttle them so both can run at the “same” time, but limit the Max current draw is no more than what the circuit allows? Maybe the simple mutex will achieve this? I’d like to grant the RIMS as much power as it needs to keep mash temp where it should be, and the rest to heat the MLT sparge water. Basically, the RIMs should have priority over HLT.
For the first use case, you’d need some electrical/physical solution. In software, you can run an element at 50%, but this does not reduce peak draw: it uses PWM to run the element at full power 50% of the time.
A mutex would work for your second use case. To avoid one of the clients hogging the mutex, we also implemented the Balancer block.
You can add a maximum constraint on the PWM block. This would limit the average power, but not the instantaneous power. PWM is repeated ON/OFF so during the ON period, which is 50% off the full period, it will still run at max power. This period is probably longer than the time it takes to trip your fuse.
A mutex combined with a balancer will ensure that they are not turned on at the same time and that the power is shared fairly. We have not implemented actuator priorities, but in my experience, it works well without priorities.
Mash tun is near setpoint and needs 10% power
BK is far from setpoint and wants 100% power.
Total requested is 110%, so MT gets 10*100/110 = 9% and BK gets 91%.
To make the balancer and mutex work well, use the same PWM period for both.
I don’t know what kind of elements you have, but our 3-phase elements are basically 3 single-phase elements in a single flange. You could toggle them separately.