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

[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.

On disengagement, For lead acid batterys it is necessary to ensure that they be fully charged at least every 3days. There should be a flag for that being true. And a modification to the line above to this

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