load management

[Barry Fields]

If I had a 2000watt resistive PWM DUMP load, and the average pwm signal (10 minutes) was over 50%, would that not indicate that I have approx 1000watts of available PV power that I should use for and opportunity load?

[boB]

At 50% duty cycle, a 2000W load should be dissipating 1000 watts *IF* the voltage you are applying to that load is at the voltage required to dissipate 2kW in that resistor.

I'd also use a fan.  Maybe.

[Barry Fields]

Where am I going here is as follows:

An opportunity load would be engaged based on the PWM% (last 10 min avg) indicating that excess PV power is available.
That load would stay engaged during a minimum run timer MRT (say 20min) .

When MRT =0 then if PWM%avg >0% and SOC >90% the load would continue for 5minutes and rechecked.

If the PWM%avg <0% or SOC< 90% the load would disengage.

A delayed restart timer DRST (5min) would prevent premature re-engagement.

The system would recheck PWM%avg and SOC every 5minutes for possible re-engagement.

This approach would work even without an actual PWM load.


My planned DUMP LOAD would be a rewired hot water heater run my primary inverter. shown below.

[ClassicCrazy]

I  bypass the pv input  around the controller to the resistance heater load. An SSR or DC contactor can be used to switch the PV input. I use a contactor now with it just being on off controlled by Aux . But I guess it could be pwm using a ssr or igbt depending on pv voltage.
Larry

[Barry Fields]

I  bypass the pv input  around the controller to the resistance heater load. An SSR or DC contactor can be used to switch the PV input. I use a contactor now with it just being on off controlled by Aux . But I guess it could be pwm using a ssr or igbt depending on pv voltage.
Larry

Thanks for your input. I hate to correct myself twice in the same week but I found an error in the schematic. corrected one below.

My primary Aims 6000w inverter runs continuously for my water pump and fridge and other little stuff I can manually switch from grid. There is room for it to handle another 2kw.
Therefore I chose to use that 220v to run the DUMP. As the DUMP LOAD requires approx 10a @220 it enabled me to use 14-2 wire to that load with a 15a breaker.

How do you trigger opportunity loads?

regards Barry

[ClassicCrazy]

The Aux contacts on the Classic have lots of different ways to turn on or off or pwm based on voltage, soc, etc . That is what I have been using.
I have a video on how I used the PWM of Waste Not to send extra power to water heater.
But switching the load using PWM might be difficult for the inverter depending - on mine it would make my LED lights flicker though didn't have effect on other loads.
https://youtu.be/s7trVpHLts4?si=gOzi8TAL_mV9fwJO
Larry