Another mystery device


So is the neutral side of the plug not required? I’m not familiar with EV plugs and chargers. I’m thinking about 240 wiring for appliances that don’t use or even have a neutral wire.
Notice you said you use 2 of them to monitor. That’s not the same as putting a Hot from each leg into both sides of the Sam HS110


The HS110 does not need a neutral to operate.

To be clear, I am using 2 on 240V. 2 Hot leads, 1 ground. That’s it. They work fine and even measure the higher wattage perfectly. Here’s mine charging my Volt right now as an example.

EV charging hardware does not need a neutral as there are no 120V components in an EVSE.

As for appliances not having a neutral wire, most modern appliances DO require a neutral and it’s been code for many decades for appliance plugs to carry one - without neutral (or using the ground as one, see next comment) you can’t achieve 120V anywhere on the appliance, and since 120V is typically needed to power electronics plus any lighting (IE, the oven light - that’s a 120V bulb remember, not a 240V bulb), many appliances wouldn’t function right.

Very old homes with 3 (vs 4) prong plugs for 240V appliances (typically, stove and dryer) are wired to use the ground as a neutral - this is no longer code (and carries a lot of risks), and the reason why you won’t find 3 prong 240V outlets in any house built in the last 40-50 years or so. The modern 4 prong appliance plugs carry both a ground and a neutral.


In Kentucky the four prong wasn’t adopted until after 2000. That’s when mine was built and water heater, dryer and stove are all the old theee prong. Mobile homes are different and have required four as long as I can remember.
It appears you are correct about the internal workings of the HS110 as the screenshot clearly shows it cannot be a 120 load at that wattage.
No amperage issues?
My HS110 has trouble with 1500 watts which is less than the stated 13 amp rating.


The HS110 is capable of 16A at 240V. It has no issues whatsoever at that amperage nor is there any discernible heat build up whatsoever. They run cool as a cucumber even for the 3.5-4 hours it takes our EV’s to charge.

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That’s good to know for the “projects” I would like to monitor.
I think the first HS110 I got is defective as not only will it not stay on at 12 amps, the WiFi range is terrible. I bought the T P link range extender and it helps with range but it’s size makes the HS110 look miniature.


Something is definitely wrong with it then.


My HS110’s run reliably (and cool) at 14-15 amps and 60’ plus two floors away from the router. I suggest that you get a replacement and return your dud.

I’ve not tried, and don’t plan to try, the 240v hack, which is definitely NOT US code compliant.


I should have returned it to Newegg after hearing how well others performed. I missed the window and have chatted with T P Link support. The refer me to a page on how to set it up and another on how to reset. I’ve done everything several times. I gave up on getting replaced through warranty after getting the run around.
The range extender is working but sure hated having to buy a device so I could use the other. The range extender does work as another router for distant devices unrelated to T P Link. I just had to find a receptacle out of sight so the wife doesn’t throw it away, it’s huge.


I’m no fan of range extenders because many are half duplex, so they cut your effective bandwidth in half when a device is communicating through them.

I am a good fan of high end routers, however. Often just replacing a cheap router or bypassing one of those terrible ISP provided modem/router combos with a good solid high end router will solve a lot of signal strength issues for people.

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Your absolutely correct @oshawapilot, at least about this extender. I tried transferring files between computers and quickly realized that the extender was only going to work for my smart plug problem.
I had several of the same routers and I could have set all of the same settings on the same WiFi, just more access points and that would have been a better solution if I had thought before throwing them away a couple weeks ago.


Agreed. My Comcast provided router was virtually useless, both range and data speeds. I turned off its wireless and added a Netgear Nighthawk, which has made a huge difference in my 2 story 4,000 sq ft home. Everything, including Sense wireless and HS110’s, works great now.

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Okay so after spending almost 3 hours at the DMV with my wife and kid this morning we finally got home and as soon as my wife and daughter left to go to a friends house for a birthday party i was able to get back up in the attic to do some testing. here is what i have found and I can say that I am about 99% confident that motor 2 is actually the blower motor for my HVAC system in the attic. I have an ecobee3 thermostat so I can control everything from my phone which makes testing super easy. I was able to turn on the heat in the house and as soon as the furnace/HVAC system turns on the power ventor fan turns on and runs the entire time the furnace is lit and burning a flame so motor 2 isn’t the power ventor fan BUT while i was up there i could hear a relay click and change the speed of the air handler fan inside the system and as the speed of the fan changed up and down I got the motor 2 on and off notification respectively so I am pretty sure that its the control logic in the HVAC system changing the fan speed making sense think there are multiple motors.


I went ahead and plugged the furnace into a new HS110 since the HS110 is rated for 15A and my furnace says it uses less than 12A and this should also get more accurate reading from the furnace as well as the fan and that has multiple settings. I have one HS110 left that I think i might install in my garage on a power strip that has multiple rechargeable batteries for my power tools and lawn mower but not 100% sure yet.

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Your probably hearing relays for fan speed. There is only one fan motor in the air handler for circulation. That motor can run at different speeds and I think sense has picked up on one of those as motor 2


Yeah thats what i said. The logic board in the system controls the relays that change the speed of the fan. anyways just a minute ago after letting sense detect the new HS110 and run through a complete heating cycle I got a new notification from sense and it says " Sense found a new device and named it ‘Heat 3’. "


I see that now, sorry @mike_gessner for not reading that better


Not a problem but I think its pretty funny that i get that notification immediately after installing the HS110 inline with the furnace about finding another heating device. :rofl:


Oh and I noticed that when the fan or furnace isn’t running that its pulling 8W which i think the HS110 uses 2W so the other 6W might be the ecobee3 that is installed on the system


The Ecobee 3 is spec’ed at less than 3.5VA so that so that 6W is probably spread between the furnace logic board (probably mostly the power supply section) and the Ecobee. BTW - My HS110 measurements for my two furnace at idle come in between 6-7W, both with Ecobee 3’s.

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So motor 2 was 100% the furnace and isn’t a mystery device anymore. Thanks to everyone that responded on this thread and tried to help me out. I am waiting for my next mystery device to show up so i can work on tracking it down. The one great thing about sense and using this thing is I have learned a lot more about my house and the electronics within it and I have a greater understanding of how everything works together. Oh and this morning sense was telling me that the iron was on again but wasn’t and the only thing that was on that uses that much power was the dishwasher so i think I will be plugging the extra HS110 into that today.