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had an R240, got an R90, might get a ZE50
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Discussion Starter #1
I have just had a 250 litre hot water tank installed with twin immersions (Megaflo 250DD), and I have a 3.6kW PV system with deemed 50% export.
I'm aware that the iBoost and Eddi products can manage twin immersions and divert my unused solar to the tank, and also operate as timers. However, they seem to be full of capacitors that are not good for the grid.

I've got a 6mm2 dedicated cable to the tank, so I can power both immersions simultaneously. My perfect immersion controller would monitor prices (assuming time of use tarif) and power one or both immersions when prices were low, switch the top immersion on when my export was over 2.5kW (which would be around peak solar), and would ensure hot water in the morning. It would also tell me quantity and temperature of the hot water.

I know there are some clever folk who do things with Arduinos and Raspberry pi and other home automation, anybody done anything similar to the above ?
 

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But presumably even one immersion takes 3kw doesn't it? Why would you want to put two on at once, and so draw current from the grid?
 

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The point of the "solar diverters" (and the reason they're full of electronics) is that they play with voltage and/or frequency (PWM) to put less power through your immerser, so that you can "follow" the generation and only export a minimal amount to the grid.

I have a fairly standard Myenergi "Eddi" that plays such tricks, but actually monitors all three phases of our supply (and PV generation) rather than just one.

If you have a "normal" domestic single phase install and want a cheap solution to making as much use as possible of your PV in the interim, I could sell you my slightly-used Solar iBoost (with iBoost "Buddy" remote monitor) at a good price (it was replaced by the Eddi back in October and I still haven't gotten around to putting it on eBay). Send me a PM if interested.
 

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had an R240, got an R90, might get a ZE50
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Discussion Starter #4 (Edited)
The reason for using two immersions would be to maximise power consumption in the possibly short periods of time when electricity is effectively going to waste ie the grid has to throttle wind turbines back as there is not enough demand,
or just heat the water up quicker.
 

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The reason for using two immersions would be to maximise power consumption in the possibly short periods of time when electricity is effectively going to waste ie the grid has to throttle wind turbines back as there is not enough demand.
Oh, well I think that's only going to happen in the wee small hours isn't it, (when the sun isn't shining)? I think the sensible thing would be to have the upper immersion connected to something like an 'Ohme' so it warms half a tank on the cheapest electricity available, and then have jmacneil's gadget connected to the lower immersion.

Then even if the day turns out to be dull you have half a tank for morning showers & washing up. Any time the sun shines, that gets stored over the afternoon to reduce the need for subsequent heating overnight.
 

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I think the recommended way to wire up the iBoost is to use the top immerser for "heater 1" and the lower one for "heater 2", so that the lower one is only used when there is excess generation - and if there is no PV, the timed "Boost" at least ensures that the top immerser heats enough hot water to get by with.
 

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The Eddi will only power one immersion heater at a time, it has a max output of 16A. To power both you need 2 of them, which is why I bought another system 5 years ago but the company folded and one of them stopped working so I had to buy something else, and bought the Eddi.

There are people on here who have made their own charge point that works with the solar panels, but openenergymonitor might be somewhere to start looking if you want to work out your own system, no idea if there's an easy way to do it though. I imagine it is more complex than varing the charge rate for a car, which has to be able to vary the charge rate anyway.
 

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had an R240, got an R90, might get a ZE50
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Discussion Starter #8
This might be a good start.
One of these on each heater and then start learning how to create a program or app to switch the heaters on when I want it.
Or just tell Alexis to turn the immersion heater on when electricity is less than 1p per unit or I am generating more than 2.5 kW.
Not that I've got one of those Alexis things, or am on Agile for that matter.
Have been on EdF GoElectric for a few months.
 

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This might be a good start.
One of these on each heater and then start learning how to create a program or app to switch the heaters on when I want it.
Or just tell Alexis to turn the immersion heater on when electricity is less than 1p per unit or I am generating more than 2.5 kW.
Not that I've got one of those Alexis things, or am on Agile for that matter.
Have been on EdF GoElectric for a few months.
An 'Alexis' thing?

When you ask her to do things, does she call the butler to do them? :)
 

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had an R240, got an R90, might get a ZE50
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503 Posts
Discussion Starter #10
She can't make a cup of tea but just about manages to put the wireless on apparently.
 

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had an R240, got an R90, might get a ZE50
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503 Posts
Discussion Starter #11
I am told she's called"Alexa", why can't people have normal names anymore ?

Anyway, it seems the app used to control the timeguard is a bit "rubbish", given that the timers have a MAC number etc would it be possible to use some other app / software to control them ?
 

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"I am told she's called"Alexa", why can't people have normal names anymore ?"

Intentional, just imagine if it was called John or some other common name. Also is 3 syllables... Which is why Serge chose the horrendous impersonal" hey google"
 
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