frivan

Sounds good. Just note the risk of 300 degree air coming out with natural convection. With galvanized water pipes, you can easily build a radiator (heat exchanger) close to the top of the sand. I would put the elements in the bottom of the sand. Perhaps add a few pipe coils in the box for convection and heat distribution.

Most definitely you can do it. Will you get a CoC (electric and gas) for it, not sure. Will it blow up, probably only if you go from 0 to 75 degrees inlet water quickly. I don't have the manual, but check if there are high inlet temperature trips. Otherwise you must devise an electric cut-out for the gas heater if the electric geyser temperature is too high.

I like it. Was wondering if a couple of 50mm holes through the wall will work for the external box... But screw it, dig up the floor!

...if the black and white wires are the right way around.

On Deye/Sunsynk you program the battery size and maximum charge limits on the inverter. The communication with the batteries can reduce charging further but it doesn't override the inverter settings.

Why not use a closed, slow combustion fireplace in stead of a rocket stove? One could add some vent controls in the house to distribute the heat throughout the house.

I will give you the short version: The more warm water you use, the more energy you use. The warmer the water in the geyser, the more losses you add to your system. Controlling time is a poor way of controlling hot water temperature and quantity in the geyser. Geyserwise and some smart thermostats measure water temperature inside the geyser. In your situation, you should consider what you can hide from the landlord. I suggest installing an Elon thermostat: ELON SMART WATER THERMOSTAT https://leroymerlin.co.za/elon-smart-water-thermostat-81504247?sfdr_ptcid=32806_617_759128507&sfdr_hash=7335bbd6c20f0137a8f17f884afc1515&gad_source=1&gad_campaignid=17335597113&gclid=CjwKCAjw0o3SBhBVEiwAh28-jSaEDa18r5LEgEY0IkANeWI_WTyUOj0ZvL4DGkbWcgE9jZvnfXWOXhoCy1UQAvD_BwE

Add two more panels on the eastern side of the smaller roofs, try vertical panels, drill holes in the trees and pour in diesel... Lots of options.

This is what you will see on the outlet pipe: Geyserwise / a dedicated pocket is better.

Your grid neutral needs to be connected to earth, and your UPS neutral must be connected to earth if you want the EL to work. So, in that sense the neutrals are connected?

Lithium batteries have cells balanced by the BMS. If charge settings are according to the battery requirement, leave equalization.

No. Your solar can only do 110A. Lower charging rates is good for your batteries. Do you have a generator?

I started with the thermometer on the element side but it only shows when the element is on: Going to try the output side of the gryser now.

Unfortunately from an asset price point of view, tech prices come down. I would start with the current price and linearly depreciate over the life of the equipment...10 years.