Okay. Just plugged it in. Literally a five minute job.
So the actual keypad is still dumb and doesn’t sync with the app but as a quick test, I set the block 4 temp to 75 on the app and created a schedule to power on via the app and it took the geyser temp from 59 to 68 and then I turned it off as no point using grid now to test to 75.
It goes past 65 though which the old one couldn’t do.
I don’t know how they can argue that it saves electricity. Something about the current reducing as it approaches 75 deg…
How does this save electricity compared to on/off thermostat control? :
The PTC element can run directly on DC or it can run on AC. That is the elemect Geyserwise use along with the PV Solar panels and MPPT and that is the part that save you money. Only when there is no sun will the AC element be used as the backup and use your Eskom power. With the PTC element you can convert any old geyser into solar geyser without any plumbing changes, which is nice considering how much plumbers cost these days 
Well, technically for the PTC element with the pv and mppt, won’t you need a plumber and an electrician. Now considering how much plumbers and electricians charge coupled with the cost of the ptc element, what’s the ROI on this. 
I actually forgot that a large part of their sales pitch is also much longer life compared to traditional elements. 2200 W PTC AC Element - Geyserwise
Thing is, you can literally buy more than 10 traditional 2 kW elements for the price of 1 PTC.
Ok maybe a different story if you factor in the labour cost to replace the elements, but they make it sound like you have to replace a traditional element once per year.
There must be decent brands out there, Grohe even makes showers with thermostatic valves built in.
I’m a Geyserwise supporter (and I have one of their systems) but they need to stay true to the laws of physics. I reckon that their main reason for opting for a PTC element is the safety aspect. If a PV powered system were to drive a geyser to boil and rupture this would be put down to this technology being unsafe and the end of their innovative company… 
I think my 2kw element is the limiting factor, I cannot get >65.
Have you tried it via the APP?
Don’t think the 2kw element is a problem. I have a 2kw element in a 200l geyser and when I have excess solar I take that up to 80 degrees via a sonoff th16 with a hacked geyserwise thermostat.
I mean theoretically, it should just take longer to get heated and shouldn’t prevent you going passing 65.
I did yes.
App and the display and the previous display, max 65.
Titbit: In trying that today, I saw that altering the display manually, disconnects the Wifi. Had to switch the geyser off/on at the DB to re-connect it.
Minor issue.
I can already switch the geyser on/off using NodeRED, locally, not via the Tuya website.
Next is to try and get the temp/status from the display, but there seems to be a bug with that. Still looking.
Hmm. That’s so weird.
As mentioned my display can only go to 65 but the app can set it to 75.
I’m using the smart life app but the Tuya app should be the same. Will see how to integrate the smart life app with home assistant / nodered and then play with the flows.
Here is the start … let me know what you get right, we can maybe help each other, and provide the final solution back here?
Just to clarify: This is a dual element (one for mains and the other for PV)
I think their saving electricity pitch is to do with the direct connection of PV panels to the element, not the fact that they use a PTC element…
Oh I have seen several people pushing a PTC-element (only) as an energy saver! The sales pitch will usually tell you that your geyser is one of the biggest consumers in your home (that is accurate), that the geyser is very inefficient (that is INACCURATE… usually), and that you can save up to two thirds of your electricity (which is true sometimes, but is more like a best case scenario).
Then they take that number, extrapolate it, and show that the expensive element will pay for itself (it probably won’t).
I’ve engaged such ads on Facebook a few times, explaining that it takes 1.16Wh to heat one liter of water by one degree Celsius, regardless of how you do it, and usually that just gets me blocked.
Sometimes they will tell you one of…
Oh but the traditional element is covered in limescale and that makes it less efficient, while this ceramic one doesn’t do that. Sure… but that wouldn’t really impact efficiency, the element would just heat the layer of limescale which would then heat the water, right? The heat still has only one place to go in the end.
Oh but the ceramic element slows down as the water reaches temp, and can never overheat/burn out. Sure, but that still doesn’t save energy (which is power integrated over time). Slowing down just means using the energy over a longer time period. There is no savings in that in a residential setting.
Aaah no, but it heats only the water you use, or something like that, usually some argument about not heating the entire tank but just the top layer. Sure, that would save a little energy, since it cuts down on the standing loss of the tank, but given that the standing loss is usually a fraction of the total and most of your energy cost is because you actually use… you know… hot water, again, reheating that at 1.16Wh per liter per °C gets you no savings.
In short, these PTC things is a legitimate technology, but the way they sell it is almost always a scam, even if the seller might not realise it.
Uhm … it does work like that, I’m doing that already. Thing is, to make it work properly, to get the “savings”, you need a vertical geyser.
I saw that the geyser temp shows 17deg. C yet the shower water is a “wife happy” temp, one, maybe even 2 quick showers sometimes.
So I figured, hold on, if someone wants a quick shower, get the temp at the top and shower, or heat for a couple of minutes till the temp at the top is where you want it to be. THAT saves money.
But be careful, someone told me. You have to heat the entire geyser if you want multiple showers, don’t use the temp at the top to heat the geyser, for that you need a temp reading at the bottom.
So I figured, you can use a electrical geyser like a gas geyser and heat just what you want to use in a sense. Either get a 50l geyser or heat a vertical geyser for a few minutes.
Also learned, that sitting in a bath when it is filling, you actually use less water than in a shower. “Maar ek sit nie in my eie poep water en was dan my gesig”.
Oh I know, even in a horizontally-mounted setup, the hot water moves to the top. My point is that there are a few kinds of tech out there (the “Turbo element” was another one from a few years ago, went out of business) that specifically aim at using stratification to save energy. I doubt all the PTC ones even do it, but it is one possible way of having a small amount of savings. Heat less water at a time.
Of course, as you say, if you want multiple hot showers, you need to heat more of the tank.
If you want to save on the standing loss, there are ways of doing that, as you discovered. And it is not a completely dead end, if a 150 liter geyser needs 8kWh to heat itself, and 2kWh to stay warm for 24 hours, then the standing loss is a good 20% and the entire system is really only 80% efficient (though changing elements will not change that). To reduce the 20% standing loss, the tank has to be kept at a lower temperature during times when it is not in use. And I can think of no better way to do that than the geyserwise.
Also, people underestimate how quickly a geyser reheats. If you turn it off half the day (while at work), and it loses 1kWh, it takes 20 minutes to put that back. This idea that you’re saving lots of electricity because you only turn it on an hour before people start showering… may well save you nothing 
The only way to save money AND HEAT THE SAME AMOUNT of water is a solar geyser or a heatpump.
Even then you might not recoup the investment. Most savings come from doing more with less. Gas geysers really shine here, until you need to heat the same amount of water,
I used to dismiss them, until I realised one day that the savings on the 2kWh standing loss (on your average 150l tank) adds up to a good R5-R7 per day, and you have to use a LOT of hot water (I think I calculated around 200 liters) before the more expensive LPG-heater catches up to that.
In order, a solar water heater saves the most (on an annual basis), followed by a heat pump, then a gas geyser, properly insulating your electrical geyser (if not already done), fitting some sort of device to lower the standing loss (ideally switch the geyser off BEFORE the morning shower, and leave it off until tonight), and only THEN do we even get to the possibility of saving with some kind of fancy element…
So true that. Our geyser sometimes stays cold for more than a day on bad weather days. Heated 100% by solar on good days … if one can become hard of hearing.
I’m on a mission to fine-tune geysers (plural), giving people manual overrides via App’s whilst I send, unbeknownst to them, all the spare solar to the geysers based on parameters I’m still fine-tuning. Think the trick is when batts are recharged, set the system to Keep Charged, and gooi the geysers. The 100% SOC not working so well as you know.
The joke is, since I went on this geyser mission to get it out of my sphere of tasks, I now see that on most days, that cooking food after 5 pm costs more Eskom than all the geysers. They should not have complained so much about geysers’ methinks, cause now my next lifestyle drive AFTER I have “gone nazi” on 5 out of 7.1 people here, is why the f…k is there >500w draw when everyone is asleep!? 
The wife, who is now paying the Eskom bill (I spent a few rands on solar, I ain’t paying for electricity ever again) and I am going to have some wine chatting whilst sitting in the kitchen close to the DB, switching breakers off. Then whilst sipping wine and chatting, we wait to see who comes running out complaining.
Have some fun they said … ok.
Tried that, Got prices for heat pumps, plural, EV tubes, Geyserwise panels, gas geysers … all of it. The sums do not make sense. Lifestyle adaptations, clever planning, using what you have optimally, make a lot more sense.
