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Shelly EM (US "split phase 240v) Monitoring


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Since the US power grid chose to do everything so differently, is there a way to effectively double the measured input for the phase the "L" and the CT are connected to?

 

I ask this because I have SEVERAL (240v US) loads that are single loads, IE: a (2) well pumps, (4) heat pumps, (2) water heaters one of which has (4) double pole breakers, a double oven, dryer, pressure washer, several pieces of metal fabrication equipment in my home workshop. All of which I am monitoring and adjusting how and when they are used. 

I can effectively double the energy usage number in the app BUT the "unknown usage number" that the app spits out is GROSSLY incorrect due to the number of split phase loads I am only monitoring one leg of, and I honestly didn't want to spent double for the EM3 and don't want to spend double on more EM 50 and 120 what I have already spent to correct the app calculated (Unknown) number. 

 

Several Energy monitoring devices I have used before can do this to account for the US energy grid being split phase. I know this won't work on main utility inputs for the US where a load center will have several high draw 120v loads on one phase and not the other. However for a single 240v split phase load, it would give a more representative number for the "unknown usage" output and to any automation systems someone may be using ( I am using Home Assistant and it doesn't like when you double the number through its own methods) 

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  • 5 weeks later...

I ran a new 15 amp double pole breaker for my EMs, and I use the Neutral to one leg for 120V loads (the EM returns an inverted sign for one leg, however).  For 240V loads, I used both hot legs, like you would see in Europe.  You need to dedicate an EM to either 120 or 240V measurements this way, but it seems to work.

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