Immersion Heater add Wifi control? can you add simple wifi switch AFTER the existing fused spur.

[Bignose2]

Hi,

Have normal fused immersion heater switch.

I would like to add a smart wifi switch to it so when my Solar is producing over 3k spare, going back to the grid (once the battery is charged) it can heat the water instead, save using the gas for the PM heat up. Will use Home Assistant.

I know the immersion need to be on DP fused spur so ideally keep the existing switch & just add wifi control, Sonoff or Shelly1 (both 16amp)

Can I just add the wifi between the Spur & the immersion, perhaps even between the CU & before the spur but think that is a bad idea as not then separately fused. Will check the fuse in the existing switch, as won't want that higher than the 16amp. I guess protected by the CU MCB but that's not the point. Not sure is has to be 20amp?

I will prob. change the element to 2kw so more likely to be running as I only have the 3.6kw solar licence so does restrict how often it would be running, but the other day, nice & sunny & I manually turned the immersion on & ran for 3 hours without using anything from the grid.

Will have to program so not switching every few seconds as the sun comes in & out but just work some logic in to that.
Seen a 13amp wifi in TLC etc. but not powerful enough & whilst not too expensive the amount does add up & then benefit & ROI would be surprisingly long so £15 just for an additional e.g. sonoff.

Like the proper device, Solar iBoost I think its called, but was over £350+ installed & Roi I think would have been 10 years & they did not seem to last that long anyway. I know the eco point but also does have to make finiancial sense.

Would be nice to regulate depending on available spare watts, not sure how the iBoost etc. worked as sent reduced power if not enough solar. I guess that might be what was paying for.
Would that have been just less volts?
Anyway don't think I can cheaply replicate & 2kw element will be fine.

 

[Avo Mk8]

Can I just add the wifi between the Spur & the immersion,

Yes

perhaps even between the CU & before the spur

Bad idea

Will check the fuse in the existing switch, as won't want that higher than the 16amp.

it will likely be 13A

I guess protected by the CU MCB but that's not the point. Not sure is has to be 20amp?

The MCB is rated to protect the cable, so might typically be 16A or poss. 20A

Seen a 13amp wifi in TLC etc. but not powerful enough

this one Is powerful enough: WiFi Controlled 16A 7 Day Programmable Timeswitch | Timeguard (NTTWIFI) - https://www.tlc-direct.co.uk/Products/SMNTTWIFI.html

Anyway don't think I can cheaply replicate & 2kw element will be fine.

you don't have to change the immersion do you?

 

[Bignose2]

Yes

Bad idea

it will likely be 13A

The MCB is rated to protect the cable, so might typically be 16A or poss. 20A

this one Is powerful enough: WiFi Controlled 16A 7 Day Programmable Timeswitch | Timeguard (NTTWIFI) - https://www.tlc-direct.co.uk/Products/SMNTTWIFI.html

you don't have to change the immersion do you?

Thanks for the advise
As I say, the only problem with the 3kw immersion is with a 3.6kw solar inverter, it does not take much other use in the house before its over the 0.6kw spare and would then be drawing from the grid.

If I have a 2kw immersion I could use approx 1.6kw in the house on other stuff or if not quite sunny enough for near full solar production still some leaway. I do have 4.2pv so does generates quite a lot.

Sort of why I was thinking if there was a way to reduce the current drawn or sent to the immersion.