Any options for a panel mount two phase inductive energy meter? (Ideally cheap) - Page 1
Forum section: electronics / general

author: XOIIO
author_rank: Super Contributor
timestamp: August 17, 2021, 05:46:40 pm
content: Hey everyone, figured I'd post here to ask, I've recently started exploring the world of lost pla metal casting, and I picked up an old kiln that I'm going to refurbish and convert to PID controls to use as a burn out oven, and maybe for ceramic casting medium baking as well.This is a 240v unit that hooks up with a stove/dryer connector, I'll be replacing the cable with a longer one as well, but it means that since I'm replacing all the old mechanical controls, it gives me the chance to do some other neat stuff and measuring power use is one that I want to do.There are all sorts of cheap power meters on amazon that use an inductive clamp and would work fine for most things, however since this using both 120v lines as well as neutral, from what I understand, I'll need to measure the current on both of the live connections to get the true power usage, and the neutral is just an imbalanced return that I think can be ignored?So, I'm in search of a hopefully cheap panel mount power monitor that uses inductive sensors, and combines the total power use.This is something that I could do with an arduino fairly easily, however I wouldn't mind having something that looks a little more polished than a 16x2 lcd.I suppose worst case I order two of those ~$20 power meters and just add up the usage, but a single unit solution would be neater.

author: BrokenYugo
author_rank: Super Contributor
timestamp: August 17, 2021, 06:17:50 pm
content: If this is a single home supply it isn't two phase (which implies a polyphase system with rotation), it's "split phase" a single phase split into two 180* apart by grounding the center tap of the pole transformer.Is the neutral used? It may not be, or only run negligible current control equipment, and if you're replacing all that it could be configured to only run on 240. If so, and if I'm thinking correctly (I was just playing a game of "don't overload the backup generator"), all of the load will be balanced and you can just clip a current clamp on either L1 or L2, measure the voltage across the two hots (~240), and get an accurate power reading.

author: XOIIO
author_rank: Super Contributor
timestamp: August 17, 2021, 08:41:13 pm
content: It is a single home supply, neutral is connected, but according to the manual for this thing, the way it controls power levels is by connecting 240v to the heating elements in either parallel or series, not by splitting them off into 120v sections, at least I think, there's no proper wiring diagram.I just finished making up the chonky new power cord and I'm going to test it out with that since the pid controller and 3 phase ssr will take a while to arrive anyhow (I'm going to cut both lives and neutral to everything but the pid controller and power meters when it's not running), so when I pull the old wiring off it should hopefully make more sense. From the picture I took, it looks like neutral might only be used on the top section of the kiln, and the lower section that can be unplugged gets both live connections and an earth, seems a little odd, but maybe it's a fairly normal kiln setup.If I can get away with a single power meter it turns out, that would be nice since it would be cleaner looking. Though two power meters might look cool, hmm.

author: XOIIO
author_rank: Super Contributor
timestamp: August 17, 2021, 09:27:21 pm
content: Alright, new mains cable installed, it does look like each section of the kiln does use one 120v live connection and the neutral, the multi function switch that changes the series/parallel arrangement for the coils is at the top, that outlet on the right side is how the bottom section connects to the top with the control unit. It's actually a pretty neat little mechanism.So, I think if I do simply connect the inductive sensor around the neutral line I should get the power consumption of everything alltogether, right? Or maybe I got turned around in my thinking again and I will need two power meters.The only thing is I'd like the power meter to display the 240v connection voltage since the kiln is operating using both live connections, so for that I'd tap power off of both live connections I suppose instead of one live and one neutral?Too used to watching content from the uk where 240 is just what they have lol, this is definitely a little odd ball, but it is my first time working with it. The plus side is, this means that on the medium or low settings, I could power one section of the kiln from a standard 120v outlet if I really needed to, and since it breaks into sections I could reduce the space inside by half.posting glitches out when attaching this as a, well, attachment so guess I'll embed.