Monitoring import and export to evaluate installation of export meter

[sunandwindy]

Hi Guys, We've all seen/used the simple clip on energy monitors for your incoming power supply. I wish to go a stage further. Let me explain....

I currently have 3.3Kw of solar PV panels and hope to add addition renewable energy sources over time. Due to our very low power consumption our meter runs backwards a lot of the time , however Goodenergy had cottoned on that my meter goes backwards when we export and want to change it for one that only clock power in, rather than unwinds to clock power back out. They've given me costs for having a proper export meter fitted, so before I cough up for having the export meter fitted, and then monthly charges for the meter, I want to accurately evaluate the comings and goings of my power.

Like others I have the energy suppliers meter, and I also have a total generation meter for the PV panels.

I am going to change my wiring so that I can measure the house consumption separately from the PV generation, as at present the PV is wired in to one of the house circuits, so its going to be difficult to tell if I'm using lots or little of my own generated power when the new meter is fitted.

Is there a *cheap* way that I can monitor the total export to the grid, and also monitor the import from the grid as two separate readings? It would be good if I could connect it to a pc to view the results, though I don't wish to leave a pc on all the time to achieve this.

I probably can't see the wood for the trees....

Any thoughts please?

[plectrum]

Hi sunandwindy, I've been looking into similar issues, although I am trying to use excess generation on sunny days to stop my oil fired boiler coming on to heat the water.

If you don't need the pc logging I see no reason why you can't fit a standard electricity meter wired in reverse in series with your existing meter.

Modern meters do not go backwards and simply freeze when current is flowing in reverse, and my own meter displays 'red' which i think stands for 'reverse, something beginning with e. detected' !

They are readily available on e-bay for between £10 and £20, mine is an Ampy 5224E as supplied by Scottish Power.

Quite how the meter knows which way current is flowing i'm not sure, maybe something cunning to do with power factor/phase relationships?

It will be quite a job to wire your consumer unit to monitor energy being used, if you know pv output, grid in and grid out you can calculate it.

Although this would not give you spot values, only over a reasonable time period.

Normal disclaimer applies! (as in I haven't actually wired a meter in reverse, but can see no reason not to)

[skyewright]

Modern meters do not go backwards and simply freeze when current is flowing in reverse, and my own meter displays 'red' which i think stands for 'reverse, something beginning with e. detected' !

I understand that it's "Reverse Energy Detected"

[jerryduk]

I wanted to do something similar.
I had planned on using my currentcosthttp://www.currentcost.com/ monitor to monitor the PV output and the consumer unit input.

The EnviR has the capability to monitor more than one sensor.

This would allow you to see if you were a net generator or net user.
I don't think it's possible to detect negative current without breaking into the wires. I am sure there must be some clever device but not available to us doing things on the cheap.

I further planned to use spare generation to heat hot water or an underfloor heating element.
Sadly it doesn't seem the current cost unit is accurate enough.
When I look at my generation history some days are far higher than I know they were and at other times the unit seems to just stop working. No good if you want to use it for controls.

Now I am planning to monitor the generation straight from the inverter although that wont know my usage.
I'll keep playing with the current cost device to see if I can get it to work reliably.

J

Hi Guys, We've all seen/used the simple clip on energy monitors for your incoming power supply. I wish to go a stage further. Let me explain....

I currently have 3.3Kw of solar PV panels and hope to add addition renewable energy sources over time. Due to our very low power consumption our meter runs backwards a lot of the time , however Goodenergy had cottoned on that my meter goes backwards when we export and want to change it for one that only clock power in, rather than unwinds to clock power back out. They've given me costs for having a proper export meter fitted, so before I cough up for having the export meter fitted, and then monthly charges for the meter, I want to accurately evaluate the comings and goings of my power.

Like others I have the energy suppliers meter, and I also have a total generation meter for the PV panels.

I am going to change my wiring so that I can measure the house consumption separately from the PV generation, as at present the PV is wired in to one of the house circuits, so its going to be difficult to tell if I'm using lots or little of my own generated power when the new meter is fitted.

Is there a *cheap* way that I can monitor the total export to the grid, and also monitor the import from the grid as two separate readings? It would be good if I could connect it to a pc to view the results, though I don't wish to leave a pc on all the time to achieve this.

I probably can't see the wood for the trees....

Any thoughts please?

[AlanIOW]

Hi

I currently have a Current Cost Envi with two clamps, one for PV generation and the other for consumption, the CC display is connected via a USB cable to a 24/7 server which sends data to PVOutput.org. The website calculates and graphs live on the net and gives data for Generation, consumption, Export, Net and also energy saved.
My system is available here; http://pvoutput.org/intraday.jsp?id=2476&sid=1872

Its worth having a look around as there is loads of data and different graph cutomisations on the site.

One other useful point is there is an option to add a correction factor to increase the accuracy of the Current Cost readings, mine is set at x1.026 which seems about 99% accurate compared to the generation meter.

[shambolic]

So is it actually possible with the clip on power readers to get the power usage only. where do you clip it for that? I have an aurora desktop for reading power generated but would love to see it relative to power used. I have an Eon power reader that looks like a current cost but I was told by the fitters that it would total up the in and out together.

[mysterons]

You need to fit the clamp between where the inverter enters the mains and the consumer unit, if your fitters simply used a spare way on your c/u there's no easy answer.
My inverter is attached to a small garage type c/u which then feeds into the mains on the meter side of the house consumer unit. I have a clamp on the feed from the inverter to the garage type c/u to measure the output from the pv and a second clamp between the main switch and the distribution mcb's on the house c/u. This way I can measure what's being produced and what I'm consuming independantly. In this pic the larger E.On unit is showing my usage (1.89kwh) and the Smartpower unit ( Npower 'wallace and grommit' jobby ) shows the pv output at 3040watts so at the time exporting just over a kW.

[EccentricAnomaly]

I don't think it's possible to detect negative current without breaking into the wires.

You can measure the power factor (including "negative" power factors when generating) using a current clamp and direct measurement of the voltage without breaking the wires (though you do need a connection to the wires). Unfortunately, I don't know of a cheap "whole house" meter that does this though the plug-in (single socket) meters seem to manage it quite cheaply and safely.

[shambolic]

Same unit as mine but it looks like my inverter cables are feeding into the fusebox

[Donald]

So, I think you're all saying that no-one has come up with a simple clip on monitor that can tell when we are pulling from the grid or using our own self generated electricity? For someone that knows didly squat about electricity it seems as though it should be easy!

[MN]

You can get them but they are far from 'cheap'

Look At the Brultech

Details In Here

http://www.navitron.org.uk/forum/index.php/topic,14170.0.html

MN

[ericw]

I don't think it's possible to detect negative current without breaking into the wires.

You can get a voltage in phase with the mains by wrapping a wire around the one of the meter tails to give capacitive coupling.
Comparing the phase of this voltage with the phase of the current in the CT should give you the direction of current flow.

[sunandwindy]

Since starting this topic I've been forced to have my meter changed from the dial type which in my case counted down the units when exporting, to an electronic jobbie that only counts up units 

I've put the feelers out to scrounge/buy (cheaply) a dial meter to connect back in to my system, then I'll be able to accurately find out exactly what I am exporting to the grid using my dial meter reading and the suppliers meter reading. But.... that's on hold until I get a suitable meter.

[JohnS]

Sunandwindy
Just get a 'cheapish' electroinc meter like the import or generation meter and wire it backwards.  That way it counts when exporting and does not cound when importing.  Wire it in series.

John

[sunandwindy]

John,

Can you give an example of the type of meter your referring to please? Have you done/tried this?

Thanks