Tesla “smart” immersion heater

[AliG]

Yes, this is not a practical solution.

 

You would need 3kW spare and to be available to switch it off and on. Leaving it on for just a small amount of extra time could offset any savings.

 

The output of solar panels is extremely variable.

 

I picked a random day in September to display the chart from my Eddi (I only installed it in early September). I agree it is expensive, but it seems work very well. As we have Octopus at 7.5p, we also use it to heat water with the immersion during the night.

 

 

 

 

[martinwinlow]

  On 18/12/2022 at 14:18, dpmiller said:

how often will you actually have a full 3kW going spare?

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...at the moment about 80% of that is going onto the grid (50kW max - any more is burned off in warming the log store, ie wasted)... and the *average* wind speed for the 4 months of last year, here (Nov-Feb) was 8.5m/s... 

[AliG]

If you have that much going spare all you need is a WiFi controlled fused spur.

 

Something like this-

 

https://www.ledbulbs.co.uk/products/timeguard-wi-fi-controlled-fused-spur-tuya-edition-fstwifitu?variant=39550838505530&currency=GBP&utm_source=google&utm_medium=cpc&utm_campaign=google+shopping&gclid=EAIaIQobChMIlKirvLWD_AIVxtLtCh2awwNKEAQYASABEgJ8mvD_BwE

 

I did look into getting one of these and the only issue is that a number of them are prone to burning out. I would try and find one that can take 16amps to give it a bit of headroom.

[Radian]

  On 18/12/2022 at 14:48, martinwinlow said:

 

...at the moment about 80% of that is going onto the grid (50kW max - any more is burned off in warming the log store, ie wasted)... and the *average* wind speed for the 4 months of last year, here (Nov-Feb) was 8.5m/s... 

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Haha, that's shut me up! 🤣

Well, not exactly. The ability to put variable power into an immersion comes from solid-state switching the power far more rapidly than a mechanical relay could. But in your case, as you've already figured out, that's unnecessary. Is there a software API for the generator output that's giving you that display?

[SteamyTea]

  On 18/12/2022 at 15:12, Radian said:

Is there a software API for the generator output that's giving you that display

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The larger SMA inverters used to have a relay that could be programmed to activate at over 5A. 

A simple energy monitor should be able to be hacked to activate a relay.

[Radian]

  On 18/12/2022 at 15:20, SteamyTea said:

The larger SMA inverters used to have a relay that could be programmed to activate at over 5A. 

 

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That's interesting. Maybe a 1000:1 CT could drive a small relay (i.e. 13mA for 3kW generation) with a parallel diode to discriminate between import and export.

[Radian]

Oh, what am I saying. AC would need rectifying then you've no idea re. import export. Scratch that.

[martinwinlow]

  On 18/12/2022 at 15:12, Radian said:

Is there a software API for the generator output that's giving you that display?

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Not that I'm aware of... but it warrants further investigation...

[SteamyTea]

  On 18/12/2022 at 15:54, Radian said:

Scratch that

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If the CT clamp was on the AC lead from the inverter, it could detect what the current was. 

If, as the OP had shown, he has loads of current, then it would work.

Only when dealing with very small amounts it becomes a problem.

[martinwinlow]

  On 18/12/2022 at 14:53, AliG said:

If you have that much going spare all you need is a WiFi controlled fused spur.

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Well, that gets me half-way there... I just need something that can detect export power greater than 3kW at the point where the turbine feeds the grid (1/4 mile away) that can then interweb a switch on command to the Timeguard (or something a bit more robust, as you say - I could always use the Timeguard to activate a much chunkier contactor...)

[martinwinlow]

Just found this on eBay: https://www.ebay.co.uk/itm/394363330368
 

... with the potentially interesting feature: "Automation , It allows to make a Scene for this device working with other tuya devices.  Set Automation for the Measured Device.  For example, If Power or Current Is over the Value, then other tuya device starts to work ."

[Radian]

  On 18/12/2022 at 16:13, SteamyTea said:

If the CT clamp was on the AC lead from the inverter, it could detect what the current was. 

If, as the OP had shown, he has loads of current, then it would work.

Only when dealing with very small amounts it becomes a problem.

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Yes of course. I keep thinking in terms of export in relatively low power situations. If a relay pulled-in above, say, 20A flowing out of the generator then that'd be fine. Just needs a 1000:1 CT and AC coil relay that would operate at 20mA e.g. 1200 Ohms 24VAC coil.

[Radian]

  On 18/12/2022 at 16:27, martinwinlow said:

Just found this on eBay: https://www.ebay.co.uk/itm/394363330368
 

... with the potentially interesting feature: "Automation , It allows to make a Scene for this device working with other tuya devices.  Set Automation for the Measured Device.  For example, If Power or Current Is over the Value, then other tuya device starts to work ."

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Looks perfect!

[SteamyTea]

  On 18/12/2022 at 16:56, Radian said:

Just needs a 1000:1 CT and AC coil relay that would operate at 20mA e.g. 1200 Ohms 24VAC coil.

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Can you easily get them?

[Radian]

  On 18/12/2022 at 17:13, SteamyTea said:

Can you easily get them?

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Close but no cigar:

https://docs.rs-online.com/8122/0900766b80080c05.pdf

The coil for this contactor requires 4.2VA at 110V so 0.038A or switching at around 10kW of generation. The question is, how happy would the windings of a CT be at 110V? 

[SteamyTea]

  On 18/12/2022 at 17:41, Radian said:

Close but no cigar:

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Can't you just wire it into an opamp used as a comparator.

[Radian]

  On 18/12/2022 at 17:43, SteamyTea said:

Can't you just wire it into an opamp used as a comparator.

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Oh yes, I could suggest any number of simple electronic circuits to provide a power switch but I wondered if there was a more direct way that anyone could simply and safely connect up a CT and contactor.

[SteamyTea]

  On 18/12/2022 at 18:04, Radian said:

Oh yes, I could suggest any number of simple electronic circuits to provide a power switch but I wondered if there was a more direct way that anyone could simply and safely connect up a CT and contactor.

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Make some and send them out to people on here.

Soon find out if they work or not.

Edited December 18, 2022 by SteamyTea