Smart plugin / inline switches to control load with PV

Forums › Gadgets, robotics, home automation, electronics (including wearables) › Smart plugin / inline switches to control load with PV

deadlyllama

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#303887 17-Mar-2023 16:00

We're looking at getting solar power and I thought "great I can use some of those wifi inline switches to turn loads like the water heater, EV charger, ... on and off."

Was thinking of things like the Bunnings smart in-line switch https://www.bunnings.co.nz/deta-grid-connect-smart-inline-switch_p0098816

But it doesn't seem to have power monitoring, and I would like something if possible that doesn't need the cloud to operate... sounds like Tuya devices do have a local mode, and I can give them their own VLAN/SSID.

What is out there that

* has plug-in AND inline wire-in (like the above) products
* can monitor power consumption of the appliance/circuit it is controlling
* has SDOC/etc available

Jase2985

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#3051254 17-Mar-2023 16:41

Water heater will likely be too much current for one of those as will an EV charger unless your using a standard outlet one

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richms

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#3051262 17-Mar-2023 17:09

The grid connect one is just a relay.

I have not seen any that are able to measure loads and have control that also are internetable from anywhere locally.

Tuya local needs them registered on the cloud and then it pulls the IDs from the cloud account, its problematic when I tried it as it seems to not handle things going off and online again and getting assigned different IP addresses - like much of home assistant it lacks decent discovery etc for things and I was often left with things showing as no go on HA, but working fine from the tuya apps.

Cloud connected also lacks most interesting devices for tuya. May have improved since I had a play with it but it was at the time worse off than IFTTT at what it could do to things.

Richard rich.ms

deadlyllama

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#3051270 17-Mar-2023 17:32

Answering my own question, the Shelly relays look like they could do the trick. Is 16A enough for a hot water heater?

https://smarthomeshop.co.nz/collections/shelly/products/shelly-1pm

Ge0rge

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#3051279 17-Mar-2023 18:04

Depending on your hot water cylinder element size, technically yes.

However when I got one for the same purpose, I chose not to use it in the end - the terminals are only just capable of taking 2.5mm² fixed wiring, and I was not comfortable putting 3500W through such small terminals and tracks. The Shelly devices are fantastic for lights, and I have them all over the house for that, but I wouldn't use them for high current - unless you used a PM to drive a relay, but then you lose the power measuring capability.

davidcole

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#3051343 17-Mar-2023 22:17

There’s a pro range of Shelly as well. Designed to be on distribution boards. Might handle higher loads.

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billgates

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#3051381 17-Mar-2023 22:57

For hot water, you are better off going with something like myPV AC.Thor9, myenergi Eddi, Paladin or Catch Relay or their Green Power as all these will detect excess solar being sent to the grid and instead divert it to your hot water cylinder. These are much smarter because you do not have to worry about relying on a specific time like 10AM to 4PM which is when you expect good solar but it might be raining from 1PM to 4PM for e.g so these smart devices will not use grid power between that time if excess solar is not available where as a timer device like you are looking at will use grid power even when it is raining outside unless you want to manually control that which will get tiring very soon.

Do whatever you want to do man.

eonsim

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#3051389 17-Mar-2023 23:21

You can use a Shelly most of the products are now certified for NZ usage.
If you've got 2kW element you might be able to get away with one of the Shelly plus 1PM. However it works be safer to use a Shelly EM or 3EM with a contractor. Use the contractor to switch the hot water cylinder load and then use the CT clamps from the Shelly to measure the power usage. That setup still be able to handle any size hot water cylinder and be much less likely to die on you.

A EM or 3EM can pretty much handle any load you can realistically throw at it on a domestic supply as long as the contractor is sized correctly. For the actually relays Shelly plus 1pm I wouldn't recommend running them near there Max list for significant amounts of time.

A much more expensive option but far superior is to use a solar diverter to control your hot water cylinder (like a my energy eddi or Paladin or catch power green, fronius ohmpilot) they monitor how much solar your system is generating and only feed the excess solar to the cylinder. In a similar manner the smart car chargers from fronius, my energy and other companies will monitor your solar power and only send the excess to the car. This minimizes the amount of grid power you need to use. These devices can 'power shape' as in if you have a 3kW cylinder but are generating only 2kW of solar they can send just the 2kW to the cylinder and prevent it using grid power. The Shelly's can't do this they can only turn it on or off. Do if your generating 2kW and use the Shelly to turn the hot water on it will use the dollar plus 1kW from the grid. Or if you set it to only turn on when they're is 3kW available then you'll end up exporting power you could have used to the grid.

SomeoneSomewhere

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#3051407 18-Mar-2023 01:55

Resistive loads are very fixed current - they'll either draw pretty much rated current, or nothing if the thermostat has cut it off. Is monitoring necessary at all, other than on the incoming mains to measure import/export?

HWC duty is one of the more brutal loads out there for components. It regularly runs at rated current for hours, and rated current (13A) is quite close to the equipment rating of typically 16A. Any poor connection or bad contact will cause issues.

SpookyAwol

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#3052111 19-Mar-2023 17:30

Im using a shelly 1pm with temp add on for my cylinder for over a year now with no complaints.
Its a 3kw element and the pm suggests its actually pulling about 2.8 at best.

Like you want with solar, I use it to schedule the best times, or when I have free power via Contact using Home Assistant.