Energy Matters Forums

[engineern6719]

Ok your a sparky.You maybe able to advise me on something.I want to install current transformers to monitor energy usage.On the load side of the main switch I have two wires coming out per phase.Would the accuracy of total current on that phase be affected if I put one current transformer over the two wires rather than modifying the wiring down to a single wire?

[davidg]

No will not affect it.

However you need to ensure that the current flow is going the same way in both wires from the switch to wherever if one of them is reversed ie one pulls current and one supplies current through a CT then one will subtracted from the other giving you the difference between one and the other (Of course this is based on AC). This could be useful for certain types of monitoring but then you have to understand what the monitoring is giving you and you would need to ensure that current indication is able to give a negative reading in the output or you never know which direction the flow is at the time. Also without a voltage reference you will only ever be getting an approximate number of Watts, and will not be able to get things like PF (power factor and so on) very handy to have and yes I do have all this at home using an appropriately accurate meter.

[engineern6719]

Moderator - removed 14 lines of quoted text, leaving the single line of reply. Please read the forum guidelines about excessive and unnecesary quoting of previous posts, which can generally be seen just up there ^^^ in the previous post!




The load of both wires feeding through a single CT will always be in the same direction at all times.

[engineern6719]

A short time ago I followed advice of this forum and had a energy monitoring system fitted.I may be interpreting the graph of the consumption and solar production incorrectly but to me the solar should be exporting to the grid.However the export figure has not changed since the beginning of this billing period(18th June).I have uploaded a snapshot of a typical day displaying consumption and solar production.
Could somebody give me their thoughts from looking at the graph whether I should be exporting to the grid for the day displayed.Looking at the meter in the power box it Looks like it’s charging me for all consumption in the house and ignoring solar.

[Privatteer]

Did your electrician confirm if you are 3 phase or single phase?
If you are 3 phase you need another 2 consumption meters.

That said assuming your usage across the phases is fairly even you should be getting some export recorded on days like above.

[Gordon-Loomberah]

What does the downloadable usage report show?

[engineern6719]

That’s a snapshot from a couple of minutes ago

[engineern6719]

There are three CT Transformers.One for each of the three phases.Consumption is summed to give one reading plus another CT Transformer for solar production.Real time readings of consumption and solar plus the graph for progressive consumption and solar are displayed.

[Gordon-Loomberah]

That’s a snapshot from a couple of minutes ago

Actually, I was referring to this:

report-link.gif (3.26 KiB) Viewed 1718 times

which I assume will be a report showing what was happening every 10/15/30/60 mins or whatever interval is set, rather than only at the instant you grabbed the screen.

Also, with such low consumption, why do you need 3phase?

[engineern6719]

Moderator - just look ^^^^ there to read previous post- no need to quote the whole lot again!



Included is a hourly report for the first day of September.
The reason for the three phase would only be for the ducted aircon which we rarely use.