Modulate heating power

[svanscho]

Hi all,

What a great project! Keep up the good work, I was so stoked when I found out about this project.
Exactly what I needed!

After a lot of playing around (I have a background as electronics engineer and work for a Domotica company) I have one more feature I would like to build: modulate the heating power. Where I live (in Belgium, but I know there are many other countries) we get feed-in tarrifs for our solar energy which are much lower than the consumption tariffs. Therefore I have modulated my SPA to mainly heat on solar energy whenever possible. There is only 1 problem: the maximum output of my solar inverter is 1500W. The heating element of the SPA is 2000W. So even in an ideal world where I only heat the SPA when the sun is shining, I still have a 500W base consumption.

I could build some electronics to modulate the heating (e.g. phase cut dimmer) but would like to avoid fiddling with the electronics close to the water as much as possible.

@visualapproach Hence the following question: is there any API/method you know of where we can leverage the CIO to modulate this power? If I can bring it down to around 1000-1500W this would greatly improve my power bill :-)

Thanks in advance for all the help!

[ChadH360]

I noticed today, that on the back of my pump unit, it states that heating consumes 2050W, and heating+bubbles consumes 1850W - seems odd that heating+bubbles is lower power than heating only.
My guess is that the heater is actually made up of 2 x 1kw heaters. When heating only, it runs both heaters (+50W for the filter pump).
And when bubbles come on, it just runs 1 heater and the air pump.

Pure speculation, but it might help with a solution to what you're trying to do.

PS I got my WiFi module in my 2021 Maldives today. Sooooo chuffed! It's absolutely awesome.
Don't forget to send visualapproach a coffee or 10 if this awesome project has benefited you :)

[visualapproach]

Hi @svanscho ! Great question. It depends on what pump you have. Mostly the 6-wire systems is considered better because we can know what the display shows, and take actions. But in this case you're lucky if you have a 4-wire, because then we can control both heater elements individually. The 6-wire versions is just ON or OFF and when we simulate a press on HEATER ON it does it's thing without any means to control it. Some speculation here: There is two heaters as @ChadH360 said. I haven't examined it too much, but there might be some ways to exploit it's behaviour. Like disconnecting the airbubbles pump and always start airbubbles when heating. Possibly the CIO will think it's on and only start one heater element. The other thing would be to confirm that heater 1 starts some fixed amount of time ahead of heater 2, to avoid power surges. In that case maybe one could turn on heat for that amount of time, then turn it off briefly and turn it on again, and so on.

@ChadH360 Thank you for your support!

[visualapproach]

@tunnus-1 to be honest it's not on my actual todo list, but I've had it in the back of my head all the time. Maybe one day it will happen, and since there is now a request for it, that day is somewhat closer. Have a nice day!

[visualapproach]

Now I know why it wasn't on the todo list. It was already done 😁 Although with a bug. See #529

[GSzabados]

@visualapproach, does this work for the 6 wire Maldives as well? If yes, then I have to do on my todo list to update the firmware of the ESP to use it. 😃

[visualapproach]

No only for 4-wires unfortunately.

[GSzabados]

Thanks! I would love to hear a yes, but nothing can be perfect.

[svanscho]

Thanks guys. I'll explore the double heaters.

I can already confirm my Helsinki SPA does not do any power surge protection. The graph below is not that clean as the P1 is my total consumption of the house, but you get the idea:

• The blue line is the solar power production
• The green line is the net production. You can clearly see that from the moment I turn on the heaters, it jumps to around 2kW instantly and stays like that all the time.

What I did:

• I turn on the SPA at 34C around 9AM
• SPA turns off around 1PM
• (intermittent glitch of dishwasher)
• I set the temp to 37C around 4:50PM

[ChadH360]

I'm toying with the idea of disconnecting the airpump from the control panel, and then connecting it up to to an smart module that would allow me to switch it on/off manually or via Alexa (something like this - https://www.amazon.co.uk/gp/product/B089LWGNJ5 - which has low voltage on the switch side). I use these modules on a lot of my lighting circuits at home.
That way, I still have bubbles control, but my 'Bubbles' button on the pump unit then becomes a button to run the heater at half power instead of full power.
Might be an option for you, unless the unit throws an error.
I can't imagine it would though - surely it's just a relay that disconnects one of the heater elements and connects the air blower to the mains.

[admiralroflknife]

You are correct, the relay board is pretty basic and you can clearly see each one and could change the wiring to suit.

[visualapproach]

As I don't want anyone to be hurt while playing with this project, let me just remind you to use proper protection circuits. Water and mains voltage can be dangerous. I know you know that but I felt obligated to mention it.

[admiralroflknife]

Definitely! Safety is paramount with this for sure. The plug does have a GFCI built in luckily, and I have it in a smart plug that also has a GFCI function.... And the outlet it's plugged into has GFI... I might be overkilling it a little but yolo.

I did end up fully disconnecting both wires off the one heater and wrapped the ends to ensure there's no voltage floating around. I encourage anyone else using this to be very careful as well.

[GSzabados]

Let me chime in as well. This is how the consumption of a Maldives looks like when the heater kicks in:

It has a rush current at the beginning going up to 2150W and settles around 1850W. (middle of the graph) The circulation pump itself is around 50W.

I still haven't installed this project into the pump as I am waiting for it to run out of warranty first. But the pump is connected through a measuring plug and gives a good idea how much electricity is used during the summer.

I really like the idea of being able turning on only one of the heaters, as the solar inverter operates as a current generator, and produces equal current all three phases, so to cover the pump it needs to produce 6000W and that is not happening all day long. Direct consumption would be the best for this purpose.