Submetering 220V devices

Support for Smart Plugs has been a great addition to Sensing & analyzing specific devices within my “noisy” home. Now I’m adding a HPWH and I’d really like to have a smart plug that works for 220v appliances so I can get a good handle on it’s usage within the Sense app. There’s been discussion about this topic in other threads, and I apologize if the answer is elsewhere, but I couldn’t find the latest & greatest recommendation.

In “LG Refrigerator never detected” @oshawapilot described how he’s done it with a regular 110V smart plug, but politely declined to provide a wiring diagram and I’m pretty hesitant to short two 220V legs together.

But I’d be more inclined to try some special wiring through TWO of the smart plugs, one for each leg… has anyone tried this? Or are there any commercial 220V products available yet that could work with Sense? Or any specific suggestions from Sense?


I’ll let others chime in on the TP-Link hacking, but that’s definitely not a recommended solution for safety reasons.

Others have gotten mileage out of repurposing the solar CTs, but that’s not without its issues.

As for commercial options, 240V smart plugs are sorely lacking. I did stumble upon this recently, but I have not tested it. In any case, it won’t be compatible with Sense so you won’t be able to see usage within the Sense app, but you could at least isolate it:

I’ll comment that there are HS-110s that work at 240V - you just need to get your hands on a Europe model.

A few comments (some of which have come up before regarding HPWH & 208/240V monitoring):

e.g. Remote sensors for 240V

  • I took apart a Wemo thinking “How hard could it be to hack this thing?”. <<Don’t do it>>. The key thing about UL listing is non-modification and no matter what you do you’re going to end up with something at least potentially more dangerous. Even unmodified a Smart Plug certainly adds more potential danger to an electrical system as does pushing current through anything “small”.

  • IF (and only if) you were running a HPWH in HP mode only (i.e. not using the 4kW-ish elements) you could theoretically connect it to 120V only and use a regular Smart Plug.

  • Have you chosen/got a tank yet? @andy has recommended Vaughn and it seems they have a hybrid with nice specs that can actually be built single-phase!

  • The beauty of such things as heat pumps is, as we all know, that they use less energy. They also, by their nature, can use less wire and so less copper. This is of course a pretty irrelevant observation in the scheme of things but I think philosophically it helps. Meaning: If you can go with a lower energy feed, do it! I migrated some of my lighting to using a Power over Ethernet switch (ports limited to Class 4, 25W) and strung things using Category 6 cable. Having run quite a lot of conduit and BX in my life there’s nothing like throwing a few skinny cables around knowing they are safer and encouraging lower energy use … and actually getting more convenience. I also, btw, can per-port monitor the consumption at the PoE switch at 10mW resolution.

  • This thread has the potential to go over well-beaten territory on a 240V “Sense Plug”. @kevin1’s advice is currently the best option for low energy devices (<<1800W) but won’t help you on a “standard” HPWH (with resistance element mode). And btw neither will a hack (due to the high energy load). Here’s my very recent reiteration of a reiteration on the topic with my solution:

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As @kevin1 said, you can get the European model. Be careful as the amperage rating is low.

We have one of those Aeotec 240 V switches. It works well for control and power monitoring. But because it uses Z wave, which is slow, won’t be supported by Sense.

@RyanAtSense & @jlj.pers: Thanks for the info on the Aeotec. Too bad Z wave is a problem, and it’s not yet UL listed in the US, which is probably bad from an insurance standpoint.

@kevin1: I still don’t see how a European 2 prong device (right?) could work with our 3-prong 220V system. But even if that were possible it sounds like the resistive backup heater in the HPWH draws too much power for these low power smart sockets anyway. :frowning:

@ixu: The Vaughn does look good but I’m getting a rebate from my local utility so only had a few options. I got a Rheem XE50T10HD50U1 from Home Depot.
Also, you wrote:

A second Sense (Solar) gives you 2 Smart Plugs so works out at $175/plug.

Sorry, but do you mean an additional set of CT clamps or a completely new additional Sense? The HPWH is far from my existing Sense installation (~80’) so I don’t think an extra set of clamps would work. And wouldn’t it be screwy to have one Sense sensing another sub-Sense?

@RyanAtSense: If there’s anything in the works that will solve this problem please let me know (privately or otherwise); I can wait several months and would really prefer something that works with Sense.

@steve, Well that’s the Rheem I wanted to get but couldn’t make it fit!

Regarding a second Sense, yes it can get confusing. I’m tempted to create a whole table for you but basically (perhaps repeating myself here) if you have a Sense without the Solar CTs you can add them and use those CTs for your HPHW circuit.

If you have Sense Solar already but aren’t using the solar CTs (unlikely I guess) you can do the same.

If you are already using a Sense Solar “as directed” then you would need an additional Sense to monitor your HPMW circuit. You would put Sense#2 Mains CTs on your HPHW circuit. That second Sense could be purchased as a Sense Solar with the 2 sets of CTs and then you could use the Solar CTs for another circuit. That’s the scenario I have and the other circuit is my AC.

FYI: @kevin1’s suggestion isn’t precluded by the different plug … but you would need a plug adapter. As long as you are in the voltage range it would work. BUT yes, do not try that on anything like a hot water heater. Even a HPHW will go into a 4kW-ish mode and likely fry things. I would not do any non-UL stuff. Meanwhile insurers seem to like Sense judging by some stories I’ve seen.

[A note here: It is much safer to be monitoring higher current loads via CTs vs inline. There’s a reason an electricians Fluke meter generally maxes out at 10-15A current input when in series … after that you need a CT]

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A few clarifications based on my experiences putting EV chargers into various places:

  • There are two Euro versions of the HS110: One uses a type F Schuko plug and the other a UK style G, both of which have 3 connections - a safety ground (pins at top and bottom in the Schuko), a hot and a neutral.
  • Most US 240V outlets and connections have two active prongs (hot L1 and hot L2) plus a safety ground. Only a couple NEMA outlet configurations include the neutral wire.
  • The safety ground in both are NOT power delivery connection. They merely connect the outlet/device to (usually) an earth ground for safety reasons.
  • And when those types of US outlets are used hot-to-hot, it is essentially the same as hot to neutral outlet, since there isn’t a true neutral reference point.

From what I can tell, the Euro HS110 models have higher power ratings than the US model, but I believe that is driven by the max current rating of the same relay used in all models. Beyond that it’s all software, so you might still need the software for the Euro model to get the power right when the supply is 240V.

  • Schuko version - 16A - 3.68kW
  • UK version - 13A - 2.99kW
  • US version - 15A - 1.8kW

I say that because if you look at a teardown of the US model, you’ll see that the Omron relay that is used to switch the power is rated at 16A, 250V.

So if you can live within 3.68kWh, you should be able to use the Shuko version.

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And regarding the Sensing-a-Sense question: That’s not the case. You could (in theory) have as many Sense’s as you want on multiple circuits. If the CTs and devices could fit in a panel there isn’t really a technical limit. Maybe your internet connection!

[I’m sure @RyanAtSense could post some fun pictures of loaded test panels at Command Central]

As regards to us building specialized smart plugs, it’s unlikely in the near term. Integrating with an existing product is far more likely, but as has been noted, there’s not many of those out there.

I could! But I’m working from home today. Remind me some time.