Supply power for the monitor itself

Originally I was thinking the Sense ran off 240VAC across the red and black wires, because I don’t remember connecting a neutral wire when I installed it several years ago. But I read in the forum that it’s actually taking power across the neutral and the black wire and that the red wire is just for monitoring the other phase. I also see the specs say the Sense runs off 120VAC so that fits. But then I have read other posts that the Sense is being used in Australia and the Philippines, both of which have single phase 240VAC, AU @ 50 Hz and PH @ 60 Hz. One Australian mentioned that he hooked the white wire to neutral and the red and black both to the hot wire. So his Sense is being supplied with 240 VAC. He also only is using one CT instead of both. He says it’s working fine. So here’s the technical question, is the Sense actually rated to work off 120 VAC or 240 VAC across white and black? Or are people that use it with 240 VAC going to have a problem eventually?

Modern switched-mode power supplies can generally operate on inputs from 90 V AC to 264 V AC, and over a range of supply frequencies. That’s why you can use your computer or phone charger anywhere in the world as long as you have a physical plug adapter. Things with direct AC motors or heating elements are a different story.

Hi kevin1. Yes, I am aware of all that. But does the Sense use such a modern switched-mode power supply so that is is rated from 90 to 264 VAC? The Sense spec which I read somewhere but of course now cannot find, says 120VAC. I’d really like a definitive answer before I buy another Sense for a 240VAC application. Thanks…

1 Like

Yeah, I understand where you are coming from. I’m guessing that Sense wouldn’t officially vouch for specs until they have completed the 240V equivalent of UL (underwriters laboratory) testing for at least one single-phase 240V geography.

1 Like

A tear down of the Sense monitor was posted in 2017 that includes a picture of the inside. The author describes the green board as an almost-generic power supply board. Discerning if this is a switched-mode power supply is above my pay grade, but maybe someone else can tell.

Hi jefflayman, thanks, I found that article and it is a switching power supply. But it’s not an off the shelf model. Another picture in that article shows the power supply is made by Sense and the text says it contains the “additional function to sample the split phase AC in the North American grid”.

Not all switching power supplies are able to handle 120 and 240. Since I spend time with both voltages (and also 50 and 60 Hz), ie in different countries, I’m usually careful to check the input voltage when I buy something. I do have a handful of switching power supplies that are 120 only. I try to keep them all in the US but some are still here in 240 land. One I used with 240 and a step down transformer. When someone accidentally plugged it into 240 directly, it worked for a couple weeks until I got home and noticed and unplugged it. But maybe I was just lucky. I normally wouldn’t risk plugging one of those into 240 even for a second.

This is why I’m hoping someone at Sense can say. Even if it’s not UL or CE tested for 240, if it’s designed for 240 and some users in Australia are running it successfully at 240, I’d probably accept the risk. But if it’s like the PS above, I wouldn’t.