Guru
Joined: 13/10/2014
Location: AustraliaPosts: 2260
| Posted: 10:45pm 06 Jun 2025 |
phil99 has eloquently answered the IGBT question, and most of your questions are answered in the thread.
The capacitor bank, charged by Solar, is the power source for the heater, pulse power discharge of a 5000uf capacitor into an 18Ω HEAT-BANK, which is what an insulated HWS is, in good solar that switches at between 10hz to 45hz.
In my old system of panels, PWM was charging caps to 220v and discharging to around 155v, as there is always PWM switching, the existing thermostat in the hot water system was used without any problems. (Obviously the thermo must never switch DC)
However I no longer use this.
The solar panels are now connected to a BIG off Grid inverter, the SMALL size HWS works beautifully in this situation, it's run time is around 10 minutes at 2.8kW with normal usage and a run time of 40 minutes with long showering (my Wife) at night in winter.
If you have small Solar and/or Battery power, then set it to disable the HWS at low battery state. This is better utilization of the solar panels and more efficient use of solar "most of the time" !!
Obviously if you are just trying to run a small HWS off grid with a few panels then the PWM (cap charge) controller works pretty well, no "LONG" showers at night though, unless you like warm (not hot) water in the morning.
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Edited 2025-06-07 10:06 by KeepIS