Solar installation: Matt:e PV+ Grid Voltage Monitor

shargrea

Please can someone help me with some information on a "Matt:e PV+" Grid Voltage Monitor?

I have recently bought a house with a solar PV installation, and it has one of these monitors connected.

The switch on the monitor itself is in the off ("0") position.

I would expect this to mean that the solar panels are isolated from the grid (and consumer unit) and so not generating any power (and no Feed In Tariff payment).

But the inverter (and export meter) indicates that it is generating power (albeit not very much in January).

Unfortunately I do not have any documentation on the installation, and I was unable to speak to the previouis owner.

I'm reluctant to switch it on without knowing what it's doing!

TIA.

paul991

Is this not a unit designed to disconnect a car charger or similar load in event of high of a high grid voltage can you do a diagram of the connections. Has a charger been removed?. If  your still exporting  it will have nothing to do with your solar .I always label everything up which I install to avoid confusion. Have you a outside socket not working? 

shargrea

Hi Paul, Thanks for your reply.

I understand the solar installation dates from 2012, so I guess this unit is the same age.

It seems to primarily be intended to protect a load from grid over-voltage, but seems to have also been sold to "optimise" solar power generation.

I see no evidence of there having been a car charger, and the unit is located far away from anywhere a car could have been parked.

The only connections to the unit I can see are 2 short cables (twin and earth?) which go to the solar AC isolator switch.

paul991

is there a twin and earth in and out or just one cable, If just one I think the unit may have never been used . 

shargrea

There are two twin and earth cables between the unit and the solar AC isolator switch (or at least they look like twin and earth cables):

paul991

so hard to say without seeing all the internal connections these units were put in to protect  equipment in areas with high voltage it maybe bypassed inside, one cable should go to inverter and one to your consumer unit but as your still generating I do not think its in use but may still be live inside

QrizB

From reading the datasheet online it's an interesting idea but all certified grid-tied  inverters should already include circuitry that stops generation if/when the grid voltage goes out of range, high or low. So I don't quite understand why this particular box of tricks is needed.

What make and model is your main solar inverter?

Heedtheadvice

^^^ as above. 

Inverters are designed to cope with the mains voltage variations to the extreme ( and beyond a bit) ends of the spec

Mains voltage is usually well controlled. It has to be by definition.

My local was regularly up at the top end 253v so the DNO was asked to (and did) change the supply voltage average down a bit.

No extra protection is required.

I have also seen a video that claims the unit gives up to 20% improvement in generation. I seriously doubt that will be the case for virtually all solar systems. It would need to have a large(ish) transformer to raise the generated voltage much higher than the mains spec ( if it were at or near the the max of the spec) and that high a voltage is not allowable. The inveter normally manages this as part of the design.

So I see no advantage with it. 

Maybe the protection might be useful in an off grid system when loads on a generator can vary and give high outputs.

Would be interesting to hear if any ( other ) users on the forum have one installed!!

shargrea

The inverter is a Solis S6-GR1P3.6K. I presume it has a maximum output voltage, but it doesn't seem to appear in the specifications.

My concern about the Grid Voltage Monitor is that it is currently switched to off. I would have thought that this would isolate and disable the solar installation from generating any power, but I'm still seeing about 2KWh/day on the export meter.

gefnew

Hi this may help.

Heedtheadvice

I thought of posting that but it does not really help !!

If your inverter shows a grid voltage display and it has a mains voltage reading it reinforces the fact that you are getting a reading for export power. That would indicate that "off" is actually an internal bypass.

That is not what the diagram shows though. Are you sure it is switched off?

Edit[ manual shows that the Solis inverter has grid protection ( as expected ) and that the red generating led shows working normally and must be connected to the grid. Also via the on screen menu you can see the grid voltage. That would not be the case if the box in question was switched off I.e. disconnected

Manual at

https://midsummerwholesale.co.uk/pdfs/solis-dual-s6-manual.pdf