Use of Shelly 1PM plus to control water heater

Forums › Gadgets, robotics, home automation, electronics (including wearables) › Use of Shelly 1PM plus to control water heater

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37 posts

Geek

#3277601 31-Aug-2024 23:07

Awww man. Any other options then that work well with Home Assistant, fit in behind the plug, have energy monitoring, and won't catch fire 😅

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neb

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#3277603 31-Aug-2024 23:18

Nothing I know of, you could use the Shelly to drive an appropriately-rated contactor but that won't fit behind the plug any more. A HWC on the one hand is a purely resistive load and so the least awkward one to switch compared to a range of different loads with odd characteristics like high inrush currents, but I really wouldn't use that Shelly for it. There was a thread on here on this very topic last year... ah, here it is.

SomeoneSomewhere

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#3277806 1-Sep-2024 13:38

A PDL 600RM is rated for a 6A inductive or 16A resistive load, and takes up a standard 600-series module slot. You could put one in a 691X socket-with-extra-switch.

Poor clearance between traces doesn't necessarily mean it will burn up from thermal overload, though. It means there's more chance of a flashover due to overvoltage and/or contamination, regardless of loading.

It doesn't look like there's any ELV parts that are supposed to be separated from mains so personal safety isn't likely to be an issue (unlike e.g. phone chargers) but it does mean it's not going to handle surges/spikes well. That MOV looks pretty small, too.

cjkbarnett

37 posts

Geek

#3277925 1-Sep-2024 18:57

These look pretty decent, 20a rating is nice, gives plenty of headroom for a 2.4kw system. Much beefier looking terminals too, and sonoff works well with Home Assistant.

https://sonoff.tech/product/diy-smart-switches/pow-elite/

The legalities of installing something like this though are beyond me... Is there certain paperwork one must present to have a sparky put this in? Has several certifications listed on the product information page, but then again, that side of it is all beyond me.

SomeoneSomewhere

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#3277960 1-Sep-2024 22:51

Must have a Supplier Declaration of Conformity (SDoC), prepared by the NZ manufacturer or importer, with independent test reports as evidence.

neb

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#3277962 1-Sep-2024 23:24

cjkbarnett: These look pretty decent, 20a rating is nice, gives plenty of headroom for a 2.4kw system. Much beefier looking terminals too, and sonoff works well with Home Assistant.

https://sonoff.tech/product/diy-smart-switches/pow-elite/

From the page:

Thicker and heavier terminal wirings made of cold-rolled steel, more stable and reliable for carrying higher currents.

Those are giants riding mammoths down there. Do you think your cold rolled steel's gonna stop them?

SpookyAwol

626 posts

Ultimate Geek

#3301457 25-Oct-2024 13:32

Well, after 2 years of service it decided enough was enough..... Contactor it is!

russelo

328 posts

Ultimate Geek

#3301460 25-Oct-2024 14:14

I've also stopped using Shelly as it keeps tripping off the Shelly thermal protection.

I'm now using Switchbot to flick the original switch on/off.

johno1234

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#3301461 25-Oct-2024 14:17

Was setting that up a fiddly or straightforward job?

SpookyAwol

626 posts

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#3301476 25-Oct-2024 15:19

russelo:

I've also stopped using Shelly as it keeps tripping off the Shelly thermal protection.

Before its sudden and untimely demise, temps were always steady.
Mine was running in eco mode and that was always 10-20 degrees cooler than without eco

russelo

328 posts

Ultimate Geek

#3301478 25-Oct-2024 15:31

johno1234:

Was setting that up a fiddly or straightforward job?

It depends on your physical switch.

In my case, I have to 3d print a custom leg to reliably toggle the switch on/off.

lloydw

21 posts

Geek

#3301523 25-Oct-2024 16:56

russelo:
johno1234:

Was setting that up a fiddly or straightforward job?

It depends on your physical switch.

In my case, I have to 3d print a custom leg to reliably toggle the switch on/off.

Wow, that cool. I have a SwitchBot lying around and would like to try this, would you mind sharing the STL?

neb

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#3301528 25-Oct-2024 17:17

SpookyAwol: Mine was running in eco mode and that was always 10-20 degrees cooler than without eco

Are those internal temps? No wonder it died, typical electrolytic caps are rated -40 to +85, sometimes +105, but it's usually only one or two thousand hours at those temps. So running a +85 rated electrolytic at close to that temp means its warranty is void after that time.

This is why lots of LED bulbs never get close to their 50,000 hour lifetime: Duh, cap rated for 105 degrees, we run at 100 degrees, we all good.

SomeoneSomewhere

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#3301530 25-Oct-2024 17:35

That's not a capacitor failure; that's a high resistance contact. Looks like it could be the terminal rather than the relay contact.

It appears to have mostly been operating at 70C ish while on until the last failure. That is still toasty. Definitely sized at the limit.

A hot water cylinder at 3000kWh/year is only running for 1000h/year so even 85C caps should last 10+ years
under that duty.

russelo

328 posts

Ultimate Geek

#3301657 25-Oct-2024 23:38

lloydw:

Wow, that cool. I have a SwitchBot lying around and would like to try this, would you mind sharing the STL?

I highly doubt this will fit your setup but here you go.

https://www.thingiverse.com/thing:6808709

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