3 Phase Metering Question

[Shaun-]

Good morning,

So I’m working on an existing 3 phase solar system and the customer wants a way to use the huge mass of exported solar on their pool.

So currently looking at possibly using MyEnergi Eddi’s or something similar to power a 3 phase heater element (probably split into 3 single phases) and the pool pump.

I’m not really up on how 3 phase metering works and if it’s different in a domestic installation either.

If we went the 3 phase route and the phases are unbalanced (e.g. phase 1 is exporting, phase 2 is exporting but phase 3 is importing) and the sum of all phases mean that there is a net export would you still pay for the energy that is imported on phase 3?
Or does the meter just see a net export so doesn’t count up additional units?

Obviously if this isn’t the case it will have to be 3x 1-P elements to make the largest benefit from the solar.

Any help appreciated.
If anyone has done something similar and has any insight into how they did it that would be great too.

Thanks!

 

[Gavin John Hyde]

ALl depends on whether the inverter can handle asymetrical output ie if Ph1 needs more than Ph2 or 3 it will export ACpower accoding to need, some older inverters chuck out the same across all 3 phases.

As far as I am aware Eddi only handles single phase loads - however I have seen an Eddi wired to a contactor to then switch much bigger loads.

I believe the new 3 phase smart meters group the cumulative import / export so it doesnt really matter what phase the use/export is on. it all gets added together

 

[Shaun-]

ALl depends on whether the inverter can handle asymetrical output ie if Ph1 needs more than Ph2 or 3 it will export ACpower accoding to need, some older inverters chuck out the same across all 3 phases.

As far as I am aware Eddi only handles single phase loads - however I have seen an Eddi wired to a contactor to then switch much bigger loads.

I believe the new 3 phase smart meters group the cumulative import / export so it doesnt really matter what phase the use/export is on. it all gets added together

I’m pretty sure the 3 phase inverter is just equally splitting it between phases, or it would seem so from the power analysis.

Yeah they do only handle single phase loads. So it’s rather have 1 Eddi connected to a contactor to bring on the 3 phase heater element and assume equal loaded (exporting) phases (probably causing some import at times but it should even out if the right phase is being monitored by the Eddi).

Or, 3 separate Eddi’s on separate phases sending out variable power (depending on export at that time) to each of the elements of the 3 phase heater (rewired as 3x 1P elements).

Obviously the first option is easier and cheaper but for some reason I was thinking if 1 phase was exporting and 1 phase was importing, with a net import, then the meter would be racking up units from the phase which is importing.

Not sure why I thought that this morning, think I was thinking pF, but again that doesn’t apply to domestic… must be losing it.

Thanks

 

[Shaun-]

For anyone looking into the same thing I’ve just found a guy who did an experiment to see if this is how the 3 Phase meters counted units and it is. (Was done in 2013 so a bit old but should still apply.)

Example:
PHASE 1 = 1kW Export
PHASE 2 = 1kW Export
PHASE 3 = 2kW Import

ENERGY METERED = 0kW

3-phase metering | Archived Forum - https://openenergymonitor.github.io/forum-archive/node/1613.html