2kw immersion element

[Murdoch]

The whole house... Thats the only thing left i need to sort out now.

So you are running your whole home off solar /batteries? with no mains

 

[Ucatchmydrift]

So you are running your whole home off solar /batteries? with no mains

Yep. The mains are there if i need them, and to charge the batteries overnight in the winter, but thats all. Just want to stop using the power shower as thats the last thing. So will use hot water from the immersion once i replace the element with a 2kw.

 

[Sharpend]

So are you paying a daily standing charge for the electric without using the electric?

 

[Ucatchmydrift]

So are you paying a daily standing charge for the electric without using the electric?

Like ive said above, i use cheap rate over night only to charge the batteries when needed in the winter, and i pay 44p a day standing charge with edf. I am switching to utilita as ive found out that they have no standing charge, and 5p kw/h night rate. So, total of £12 a month based on 8kw usage a day, not including any free solar i get. Anyone beat that?

 

[Ucatchmydrift]

I got my cooking sorted using the 3kw inverter a few days back (thanks santa!) :



No need for 4+ kw of big cooker to do the dinner! Got a 550w multi oven and 1200w air fryer to do it all! . With them both running at the same time, and with the tv on, amplifier on, router, phones, top balancing a new a big battery bank at 5 amps, fridge, freezer etc. All comes to under 2kw:



So, just the shower to replace now like ive said, with a new element! Amazing.

 

[Ucatchmydrift]

They release energy in bursts, so you can power a 3kw resistive load from as little as 50W - clever stuff. It's also why you can't have any electronic controls, the pulses trash them. What I have done in the past is wire the immersion control in parallel with the existing supply/ timers. This allows the immersion to be fed from two sources to ensure sufficient hot water mid winter.

3kw of panels isn't a lot for what you are doing. Are you trying to go completely off grid? Or just set the solar system up that way?

Can i ask, im now having a look into these devices,, do you know if they require a grid tie inverter? If not, do they communicate with the inverter at all? And, if they are supposed to use any spare power from pv, how would it know, for example, that the battery bank is full and i have spare pv energy? Thanks

Also, if it hadnt heated the water tank enough during the day, would it then allow me to press a button to heat the tank with 2kw from the battery? - can i specify a max kw to heat with? Thanks

 

[johnb2713]

Can i ask, im now having a look into these devices,, do you know if they require a grid tie inverter?

They only work with grid tie inverters, theyre the only ones that export.

If not, do they communicate with the inverter at all?

Theres no need to communicate with the inverter.

And, if they are supposed to use any spare power from pv, how would it know, for example, that the battery bank is full and i have spare pv energy?

They see export running, if youre exporting you have excess spare PV and can divert it to the hot water tank via the immersion heater. The clever aspect of the diverters is in they give out the exact same power that you were/would export. Even if theres a 3kW element in there they can sink a spare 600W into it.

Also, if it hadnt heated the water tank enough during the day, would it then allow me to press a button to heat the tank with 2kw from the battery? - can i specify a max kw to heat with? Thanks

You can boost the water for a set time, I havent seen a variable power output option. Technically yes you can, it depends if the software has been implemented to do it.

 

[Ucatchmydrift]

They only work with grid tie inverters, theyre the only ones that export.


Theres no need to communicate with the inverter.


They see export running, if youre exporting you have excess spare PV and can divert it to the hot water tank via the immersion heater. The clever aspect of the diverters is in they give out the exact same power that you were/would export. Even if theres a 3kW element in there they can sink a spare 600W into it.

You can boost the water for a set time, I havent seen a variable power output option. Technically yes you can, it depends if the software has been implemented to do it.

Thank you, yes, ive been watching a few videos on youtube about them now, i see they have a clamp meter style device to detect whats going into the grid and then divert that energy to the water tank etc. So, yes unfortunately no good for me .

Best option for me would be using a raspberry pi or the like to measure the voltage of my battery bank, and when its at say 3.4v per cell, and day time, to then switch the immersion heater on for 15 mins, then off, then repeat if above conditions met still. Definately a good next project to think about to use up that last bit of spare energy on sunny summer days! Hmmm

 

[johnb2713]

Best option for me would be using a raspberry pi or the like to measure the voltage of my battery bank, and when its at say 3.4v per cell, and day time, to then switch the immersion heater on for 15 mins, then off, then repeat if above conditions met still. Definately a good next project to think about to use up that last bit of spare energy on sunny summer days! Hmmm

I assume you have a BMS on your system, could not listen to the BMS data with a Raspberry Pi and trigger the Immersion at a % SOC? I have somewhere some of the comms protocols used.

 

[Ucatchmydrift]

I assume you have a BMS on your system, could not listen to the BMS data with a Raspberry Pi and trigger the Immersion at a % SOC? I have somewhere some of the comms protocols used.

Yes, a jk bms, not sure if they have their own protocol or use another companies. Thats a definate possibility though... I also have a shunt that has relay control based on battery voltage that i could use, and control it via the bluetooth app.
Theres always a way

 

[Flylead]

https://www.elmatic.co.uk/I've had specials made up by these people in the past, mght be worth asking them.

 

[johnb2713]

Yes, a jk bms, not sure if they have their own protocol or use another companies. Thats a definate possibility though... I also have a shunt that has relay control based on battery voltage that i could use, and control it via the bluetooth app.
Theres always a way

Battery voltage is a bit iffy for determining state of charge, adding a load will drag the voltage down which may cause control loop issues. If you can gram SOC from the BMS it would be a better parameter to use.

A shunt to operate a relay based on battery voltage sounds wrong, surely the shunt would operate a relay based on battery current?

 

[Ucatchmydrift]

Battery voltage is a bit iffy for determining state of charge, adding a load will drag the voltage down which may cause control loop issues. If you can gram SOC from the BMS it would be a better parameter to use.

A shunt to operate a relay based on battery voltage sounds wrong, surely the shunt would operate a relay based on battery current?

Yes didnt think about that. It would only operate when at a high state of charge, say 3.4-3.45v - but if the batteries were being charged at the time with a reasonable load, that could cause the voktage to be at 3.45 whilst being charged, but then drop back down etc when relay switched on etc. The shunt will control the relay based on voltage, for over voltage and under voltage, similar to a bms for protecting the cells. It will also operate a relay based on current and temperature readings but no soc!.

 

[Ucatchmydrift]

View attachment 14689
https://www.elmatic.co.uk/I've had specials made up by these people in the past, mght be worth asking them.

Thanks ill check them out..