Use of Shelly 1PM plus to control water heater

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25 posts

Geek
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#3305160 4-Nov-2024 12:45

russelo:

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

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

I printed this today and looks like it will work well, thank you!

phoenixmarine

7 posts

Wannabe Geek
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#3308867 14-Nov-2024 10:00

Has anyone tried just using the Shelly EM with 50amp clamp and then wiring that to a contactor.

That way you should get the best of both worlds power monitoring and switching control.

This should even be able to be linked to a main EM or EMPro in the DB monitoring your grid connection so if you were generating enough with your solar array you could turn on the HWC and consume it yourself rather than minimal buy back from the grid.

SpookyAwol

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Ultimate Geek
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#3308878 14-Nov-2024 10:19

The EM would do that just fine, I'm using a combination of both as I still want to measure temperatures at the tank.
So EM to monitor power and PM to switch the relay and take temps
You can't use just an EM in this instance as the EM doesn't have capability for the add on

phoenixmarine

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#3308922 14-Nov-2024 11:24

I guess you could have used a Shelly Uni for doing the temp monitoring instead and left the em to do the switching, but sounds like you've got a decent setup. Do you have any stats on how much savings you get by controlling the hot water cylinder?

SpookyAwol

639 posts

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#3308927 14-Nov-2024 11:40

That was part of the dilemma, if I switched a contactor at the board, you'd loose the power at the switch which is needed (in my case) for powering the uni/pm to monitor temps.
I'm doing that so I can control heat up for when solar is best or free power periods.
With solar, my power is basically free , so my stats = 0 :)

jbm

20 posts

Geek
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#3322075 18-Dec-2024 18:37

I hope this isn't a derailing of this thread, but my questions are kinda on-topic (all but the last at least):

If you're using the dry contacts/relay of a Shelly Pro EM-50 (or similar) to control the contactor, is it easiest to get a 230V coil contactor so you can hook the 230V supplying the EM-50 up to the EM-50 relay contacts and then to the contactor and switch the contactor coil that way? That seems easier than trying to source a separate 12V or 24V supply to control the coil via the EM-50 relay, but I'm not sure I've got a proper understanding of the connections between contactor and EM-50 and control of the contactor by the EM-50.
Does the contactor replace, or augment and sit 'downstream' of, the existing circuit breaker controlling the hot water cylinder? I believe it is the latter, but if the former that would be helpful as our switchboard is pretty chocka.
If the contactor is in addition to the existing circuit breaker, is there anything preventing one from installing a small enclosure/DIN rail setup closer to the hot water cylinder with the contactor and EM-pro, to allow the existing circuit breaker to remain in place but provide the control/switching? I think this is possible given some of the posts earlier in this thread showing external enclosures and switches. I realise a separate setup like this would lose some of the monitoring functions of the EM-pro/clamps, but would still allow monitoring of the HW circuit itself I think, and would probably be easier to run cat6 to, too?
Does anyone have any recommendations for an electrician in Auckland (North Shore, ideally) who has some experience installing both a contactor (probably most?) and hooking the contactor up to a Shelly EM-pro?

Thanks for any help on this.

Cheers,

John

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SomeoneSomewhere

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#3322114 18-Dec-2024 22:05

1) Yup, 230V coil contactor is easier than ELV if you can switch it with something rated to switch 230V.

2) Sits downstream. Contactor provides control (auto off, auto on), breakers provide protection (off in a fault or manually, on manually).

3) Perfectly valid option.

jbm

20 posts

Geek
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#3322146 19-Dec-2024 07:49

@SomeoneSomewhere - thanks very much! Glad I'm not too far off track...

SirHumphreyAppleby

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#3346493 25-Feb-2025 08:05

timmmay:

After all the chat and various problems people have had, has anyone set up the Shelly with a contactor? I'm looking for a recommendation for a DIN mounted contactor. It looks like you can pay anything from $50 to $250 for a contactor, is there anything at the lower end of the price range that's reliable?

Coincidentally, I was planning to post in another (less active) thread and ask about the suitability of these Siemens contactors for controlling hot water. They have a 1000W incandescent lamp load, but I don't think that applies to hot water heating.

I've ordered a Shelly Pro EM-50 to monitor our solar generation, so I figured I might as well use the built-in relay to control the hot water more intelligently than simply using a timer. I specifically want a manual override and these revert from on to automatic when a control signal is applied.

timmmay

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#3346515 25-Feb-2025 09:11

SirHumphreyAppleby:

Coincidentally, I was planning to post in another (less active) thread and ask about the suitability of these Siemens contactors for controlling hot water. They have a 1000W incandescent lamp load, but I don't think that applies to hot water heating.

I've ordered a Shelly Pro EM-50 to monitor our solar generation, so I figured I might as well use the built-in relay to control the hot water more intelligently than simply using a timer. I specifically want a manual override and these revert from on to automatic when a control signal is applied.

I had deleted my post because I realised I had cross posted, but thanks for the reply. That Siemens contactor looks great, it even has the bypass switch. I wonder if you'd want a second, separate bypass switch so that if the contactor fails you can still have hot water. A switch should be fairly cheap.

Perplexity pointed me at Chint contactors, specifically the Chint 25A 2 Pole 2NO Contactor. It's only $22, which is cheap compared with the Siemens and Schneider products, but Perplexity says they're a reputable brand. Does anyone have any thoughts on the suitability of this contactor, or how reliable it's likely to be?

SomeoneSomewhere

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#3346522 25-Feb-2025 09:35

Chint is one of the more well known Chinese brands, but still not highly reputable. If you used them on a commercial project I'd expect to be told to rip them out.

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timmmay

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#3346533 25-Feb-2025 10:06

SomeoneSomewhere:

Chint is one of the more well known Chinese brands, but still not highly reputable. If you used them on a commercial project I'd expect to be told to rip them out.

Ah ok, thanks. Maybe ok for residential, but I'd like something that will last a long time. The Siemens for $75 or so would probably be a better option then.

jbm

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#3346654 25-Feb-2025 14:55

I ended up having a contactor installed, controlled by the relay on the Shelly Pro EM-50, with both downstream of a breaker operating as an auto (i.e, Shelly)/manual override, all of these downstream of another breaker acting as an isolation switch. This replaced the simple isolation switch previously installed, with the sparky coming up with a much more cost effective way of providing the manual isolation than my proposal of a three-way switch. Cost ~$520 incl GST all up (about $260 for the parts excluding the Shelly I think). I see that this is getting pretty close to the cost of a dedicated solar diverter mentioned above, but I hadn't found anything equally inexpensive at the time, and I'm not sure how easy those things are to integrate into something like HomeAssistant. Seems to be working well thus far, though my HA automation could do with some work...

timmmay

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#3346707 25-Feb-2025 15:09

Looks good! I can see why it would be a bit expensive, with its own enclosure, breaker, etc. I'm hoping to put mine in the switchboard, so it's just the cost of the Shelly, the contactor, and maybe a three way switch.

How much did that Voltex contactor cost? I can't find a price online.

SirHumphreyAppleby

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#3346742 25-Feb-2025 18:41

timmmay:

I had deleted my post because I realised I had cross posted, but thanks for the reply. That Siemens contactor looks great, it even has the bypass switch. I wonder if you'd want a second, separate bypass switch so that if the contactor fails you can still have hot water. A switch should be fairly cheap.

I expect a modern contactor is going to very reliable and see me out. Even the cheapest of cheap relays I've purchased from China will take significant amounts of abuse. I've not killed one yet, even with their coils powered up inside a hot greenhouse and cycling on/off several times each day for years in the early morning/evening trying to maintain 27-30C.

The equivalent part without the switch is the 5TT5800-0, $40.51.

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