Replies: 5 comments 9 replies
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Yes, that would be the most accurate way to do this measurement. However, in many cases, the current only flows phase 1 -> phase 2 (rather than phase 1 -> neutral), in which case you can only put a clamp on one pole and set a multiplier instead. This is also addressed in the official installation guide, Step 9 (continued). |
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Thanks for the reply, that makes sense. |
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I'm going to revive this because there's another way to measure this: use one clamp, but run each of the legs through it, but in opposite directions. This will yield the total current between the legs and take into account appliances that use only one leg for electronics (for example). I assume in this configuration I wouldn't use a multiplier of 2 on the circuit, but leave it at 1. But what happens with the voltages and power calculations? There doesn't seem to be a way to configure the clamp to indicate it's effectively on 2 phases. Does this mess with any of the reported measurements? |
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I'm having difficulty imagining how one would achieve this in a practical sense. Especially when the mains may be hot. |
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Just clip it around the load wires. See article here: |
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A friend of mine has a significant voltage difference reported between the two phases. Using a constant multiplier of 2 will lead to either under or overreporting the power usage. Assuming the same current flows in both phases, the actual power is |
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I looked at the code a little bit, and while I don't know much about ESPHome and conventions there, I think it might be reasonable to model this as a new phase. This might be named RED_BLACK, or e.g. RED_BLACK_SPLIT_PHASE? |
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what is the cause of the difference between voltages? this could be a symptom of a dangerous situation (floating neutral, what's the voltage between neutral & ground?) or equipment damage at the transformer. You should make sure you have a definitive explanation at the very least. once that is figured out, it is unlikely that a code change is the right thing to do. I don't have this fully thought out, but you are able to set different phases on different current clamps, even if you'd like to use them for the same load. I think then you can then create a template sensor and use that for the total power. |
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Yeah, I've told him as much. He's seeing 115/124, which is a little less than 2% each way from the mean. Is it possible that this is simply a calibration error? It's a pretty unusual setup, I think, as this is in a chalet in the hills. To save on copper on the long run from the property boundary to the chalet, there's a step-up transformer (to 660V, I believe) at the entrance of the property, then a split phase step-down transformer at the chalet. All the big loads are 240V, so this is unlikely due to uneven loading.
Ah - I guess the quick and easy poor man's implementation is to simply define two sensors with the same CT and different phases. This at least would allow him to see whether the energy on the circuits tallies up with the energy on the mains. Right now he's seeing more energy leaving the circuits than enters on the mains :). That being said, 240V split phase is the norm here in North America, and perhaps it makes sense to cater to it with something less kludgy than a fixed multiplication factor? |
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So I had this exact scenario and started looking for a solution. I'm in the US with the standard split phase install, but I have a Whirlpool clothes dryer and the load is different for each phase. The electronics and tumble motor are 120v and use phase 1->N, while the heating element is 240v. So monitoring only one phase (and doubling it) would either be too low or too high. tl;dr: use one CT, but loop the second phase through in the opposite direction. |
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That two wires in one CT is essentially x2, but with current, not voltage, no? SW is using only one voltage anyway, phase a or phase b (or c) |
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Current only. Voltage is measured with the Red/Black wires directly out of the breaker. You match the voltage to the CT in the YAML config. |
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That's my point. This is still not a 100% accurate solution. You will get both currents, but power will be off if phases voltage differ. |
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Power will not be off (for me) by any significant amount worth caring about. My voltage readings are within 1 V of each other. If I really wanted to I could probably figure how to average them and use that. |
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If I wanted to monitor the total energy of a double pole circuit (240 V in America), I would have to put a CT clamp on both and add the power together, correct? Looking at monitoring the AC power usage and some other larger appliances.
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