Hi all. I have been looking for ways to control geyser power. At this point in time I am looking for control while my inverter is off-grid. However, I came across a solid state relay that like it will do the job for those on grid power: SSR-40VA. It seems like phase angle control based on a connected resistor. Does anyone have experience with this relay and can you confirm if this would work for reducing geyser power?

Just don't back up the inverter. No grid - it can't run.

Or am I missing something?

5 minutes ago, Bobster. said:

Just don't back up the inverter. No grid - it can't run.

Or am I missing something?

I want to run my geyser on the inverter but I think this SSR will induce harmonics. My question is if the SSR can be used to make a 4kW element run at less power, say 2kW.

1 hour ago, frivan said:

My question is if the SSR can be used to make a 4kW element run at less power, say 2kW.

Aha! Thanks. My understanding of the term "relay" goes back to my days working at the then Department of Posts and Telecommunications. IE it has two states: closed and open.

Why not get a 2kW geyser element? The stainless steel models last a lifetime

1 hour ago, chrisc said:

Why not get a 2kW geyser element? The stainless steel models last a lifetime

My view is that maximum power is nice when you quickly want to heat up the water just before you need it (early morning). Variable power can have much benefit when you want to match it with solar. A fixed element size won't allow as much customization.

One could even use a little solar panel to manage the power consumption of the geyser.

1 hour ago, frivan said:

My view is that maximum power is nice when you quickly want to heat up the water just before you need it (early morning). Variable power can have much benefit when you want to match it with solar. A fixed element size won't allow as much customization.

How about a simple diode? Only half wave gives you half power. It can be shorted by a switch for full power.

Diode would have to be for 400V and 10A. Probably will require a heath sink.

10 hours ago, frivan said:

Hi all. I have been looking for ways to control geyser power. At this point in time I am looking for control while my inverter is off-grid. However, I came across a solid state relay that like it will do the job for those on grid power: SSR-40VA. It seems like phase angle control based on a connected resistor. Does anyone have experience with this relay and can you confirm if this would work for reducing geyser power?

I used proportional control on my geysers for several years and it worked fine.

At first I used a 40A SSR from Alibaba - when that blew up I found that it had a 20A triac inside.

After that I built my own circuit with a proper 40A triac and heatsink and all worked well. I controlled geyser power in 1% increments using phase control with a microcontroller.

There are some who say that this is not a good idea, especially if the geyser load is a significant portion of the inverter capacity.

Lots of information can be found here: Choosing an Energy Diverter — OpenEnergyMonitor 0.0.1 documentation

Change the 4kw or 3kw element to a 2kw element half hour job then no nead to try and control the power with a SSR or by any other means.

I made my own smart geyser controller with a Geyserwise thermostat (R260) and a Sonoff THR320 (20A relay, R400), having first replaced the element with a 2kW. Has been working perfectly for 2-3 years now. Sonoff is running custom ESPHome firmware, and switches between a target of 45C and 70C based on available solar power/grid availability, etc. I calculate I can sink about 4kWh into the water tank (2kWh ~= 13C difference in a 150l tank)

2 hours ago, RoganDawes said:

I made my own smart geyser controller with a Geyserwise thermostat (R260) and a Sonoff THR320 (20A relay, R400), having first replaced the element with a 2kW. Has been working perfectly for 2-3 years now. Sonoff is running custom ESPHome firmware, and switches between a target of 45C and 70C based on available solar power/grid availability, etc. I calculate I can sink about 4kWh into the water tank (2kWh ~= 13C difference in a 150l tank)

Thank you for this information. If I had WiFi coverage at the geyser, I would have considered it. But I also want to incorporate a change over between grid power and inverter power. I have a 12V digital thermostat (R40) and want to drive a SSR-40DA with it (R120).

At this stage I am thinking of placing the RTD on the flange plate. This should be safe if it only controls grid power and the geyser thermostat remains.

Does anyone know if GeyserWise uses NTC 10k temperature probes? If so, and according to my calculation, soldering in a 1.0 kOhm resistor will make your geyser go to 75 degrees Celsius when the GeyserWise shows 60 degrees. At 40 degrees the GeyserWise will show 36 degrees. The DC temperature on the GeyserWise MWS also allows PV to push the geyser to 75 degrees.