I don’t see having hot water as an optional load, I see it as a necessary load.
You know when you’re likely to have the best chance of solar doing the heavy lifting, but if there is no sun at that time, well you have to use the grid.
Doing without hot water isn’t an option and a timer will achieve this.
If you have multiple geysers, you can use that CBI (ECU) so that they don’t all come on at the same time, but if 1 is already hot, it doesn’t occupy a prime production slot.
There is also no time wasted between heating a geyser and heating the next one. It only allows a second circuit to get supply if the load has dropped off on the first circuit.
The only thing I do dynamically is the geyser which maintains 45 degrees from 12pm to 6am. The reason being, that I don’t want it to start heating straight away after the shower in the morning should the water temp drop below 45. Then the thermostat raises to 70 anytime the batteries are over 99% for 10min plus. That way I can store a few extra kw of energy in the geyser.
If I have a sunny day where the geyser heats to 70 I can ride through the next overcast day without it having to use any energy to maintain the low limit of 45.
I tried to do something similar with the AC too, but I dont find it provides much value. Temp bounces back as soon as the AC is off, so why cool a room for the whole day.
How are you doing that? External temp sensor with the built-in thermostat at 75 or so?
It is an important load but its priority changes: After the morning hot shower/s are done the temperature of the hot water normally isn’t a priority until the evening.
So by that time if the water isn’t hot then the grid backup system should kick in. This type of control is more accurately called ‘time of day’ control as opposed to a timer.
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As you stated, external temp sensor. The internal one is maxed out to 70 and I just control the power to it.
I also use Home Assistant to control my loads dynamically as well using a few Sonoff switches and IR controllers.
My system will automatically charge the batteries with any available solar while running the usual household loads. Once the batteries are fully charged, only then will the geyser kick in, what ever time of day that may be while there is PV available. If the panels aren’t producing sufficient power and its pulling the power from the batteries then the geyser switches off automatically, waits 10 minutes and tries again. The geyser will then automatically switch off at a preset temperature.
At the same time, when the batteries are charged, the aircons and / or heaters in the house switch on to either cool or heat the house depending on the season.
I also have a overload rule that will switch the geyser and aircons or heaters off should the system exceed a threshold. So no need to worry about accidentally running the dishwasher while the geyser is running, the system will see the overload and automatically turn the geyser off.
I have switches in Home Assistant that allow me to set any variation of these conditions in a million scenarios. I can set the temp of the aircons and the geyser and run the heaters in a round robin to reduce the load on the system if I need to.
This way I can maximize my solar array and make use of the gas geyser in case of bad weather if need be.
Using my system this way, I have managed to use only one 48kg gas bottle in the last 18 months.
I also dynamically charge my EV when the SOC on the batteries are high enough. I use Bluetooth to communicate with the EV which when the SOC of the EV reaches a set point will also switch off the charger using a sonoff.
