Am I mad?

[John Alexander]

So, before waste my time down another rabbit hole, how feasible is a DIY 3 phase energy logger?

Just a one-off, to avoid the $1000-$10000 cost of a commercial product.

We need to change our connection from 3x300A to 3x150A, to allow us to change tariffs. If the main breaker trips, we need to know why. Otherwise balancing phases is like rolling dice.

Thanks.

[NiHaoMike]

Just get a clamp meter. They are around $50-100 for a decent one and will come in handy for lots of stuff.

[John Alexander]

A clamp meter (I have several) isn't going to log every 60 seconds for a year, so that if the breaker trips, I can see which phase tripped it, and if was unusual or a trend.

I'll put this into the enclosure, wire it up, and forget about it until I need it.

[mtdoc]

So, before waste my time down another rabbit hole, how feasible is a DIY 3 phase energy logger?

Just a one-off, to avoid the $1000-$10000 cost of a commercial product.

We need to change our connection from 3x300A to 3x150A, to allow us to change tariffs. If the main breaker trips, we need to know why. Otherwise balancing phases is like rolling dice.

Thanks.

FWIW, there are commercial products like The Energy Detective that will do this with a few CTs for a few hundred dollars. Lots of other info logged as well.

[Rerouter]

If you want to skip most of the complex isolation stuff, you can use hobby grade current current transformers like this, https://au.rs-online.com/web/p/products/8199779/

[John Alexander]

FWIW, there are commercial products like The Energy Detective that will do this with a few CTs for a few hundred dollars. Lots of other info logged as well.

That's the sort of thing I want, and the price is right, but it'll only record for 48h at 60s intervals.

If you want to skip most of the complex isolation stuff, you can use hobby grade current current transformers like this, https://au.rs-online.com/web/p/products/8199779/

I'll be using 4x Fluke i400E clamps for current measurement.

[amspire]

You can often pick up an old Dranetz 626 Universal Disturbance Analyzer very cheaply on eBay. There is a good chance you will have to replace the batteries that will cost $25 or so.

Whether it is useful or not depends on the actual cards that are plugged in, but many were configured for 3 phase monitoring, and the cards are also available separately. There is a Yahoo group for the 626 with whatever documentation is available.

They don't have memory, but they print out events on to a thermal paper tape so you can see spikes, brownouts, dropouts, etc. So you can leave it doing continuous monitoring.

It will not give a nice graph of voltages and currents - just status of the power at the preset trigger events. If you have got cards measuring current and voltage, all that will be recorded at the point the power drops out.

You can get the current loads printed out at any time too - perhaps even periodic ones. I cannot remember.

[The Soulman]

If a voltage reading is needed as well I'd advice against a diy solution for safety reasons alone, let alone liability.
Using only the fluke current clamps might me borderline from that stand point as well as their intended use is not permanent installation.

That aside you may need to measure voltage and current and their phase relationship (power-factor) to give accurate results.

What type of building is this and what equipment are they running?

I've been in the same situation and rearranged all groups to equally load all three phases under maximum load (everything switched on) that left about 5% margin on every phase, worked flawlessly for years.

[BrianHG]

FWIW, there are commercial products like The Energy Detective that will do this with a few CTs for a few hundred dollars. Lots of other info logged as well.

That's the sort of thing I want, and the price is right, but it'll only record for 48h at 60s intervals.

It's record is limited by it's onboard memory.  You can always plug in an arduino and record at 1 second updates and store it for  years with enough flash...