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Is it a problem that my solar PV reads 280 volts?

Posted by Chris Rudge on 17 March 2017 at 4:50 pm

Q. I have 12 solar panels, six facing east and six facing west. I have two inverters, one of which is a 'Sunnyboy', but I don't know which model. It was checked today and I was told its voltage is 281 when it should be around 240 volts. Is this a problem? Do I need something to reduce this? Is it dangerous? The other one is 243 volts. I have a battery, central heating management system and a Growatt voltage optimiser. Am I being conned?

A. A higher voltage at this time of year can be due to two factors:

1) The array in question does not have enough light irradiating the panels to start generating a usable current to enable the inverter to function. This occurs first thing in the morning, or later in the evening. As the inverter is not putting a load on the panels, the 'open circuit' voltage will always be much higher than the 'working' voltage when the inverter is generating power.

2) As this time of year can be quite cold, the panel voltage will increase. I would suggest the array voltage would be around 20v higher at the most when the temperature is around freezing, over a normal 15 - 20 degree day. It may have been the voltage you were checking could have been on the shaded side of the house?

Depending on the battery system, these do work well in storing your excess daytime solar PV power for use in the evening. However, battery systems in the UK are far more functional in the Spring through to Autumn. During the Winter months, there is usually not much spare PV power to store, and the battery system can be dormant during that period. A voltage optimiser works if your grid voltage is very high, say over 245v, as it stops the inverter from cutting out on sunny days. If the grid voltage is lower than that, then an optimiser will not offer any benefit at all.

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Image: Chandra Marsono

About the author: Chris Rudge is a qualified electrician who specialises in renewable energy.

If you have a question about anything in the above blog, please ask it in the comments section below.

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2 comments - read them below or add one

Rudge Energy

Rudge EnergyComment left on: 1 April 2017 at 1:10 pm

I agree Marshman. The whole Optimiser sales thing is a con. Either as a power saving solution for the home, or as in this case, to enable your PV inverter to generate more power.

I have to admit I thought the way the question was written, he was referring to the DC voltage from the array as 281v was mentioned, but now looking again he had encountered a dodgy Optimiser sales guy.

Admittedly, if the summer grid voltage goes over 262V, a PV inverter will shut down and this problem can be allviated with an Optimiser. Any electrician can for one for around £250. Send the sales person away and get your local electrician in to check your grid voltage.

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marshmanComment left on: 1 April 2017 at 12:58 pm

Its a con!!  I beleive the original question was about the grid (mains) voltage. (nominally 240V) .  The inverters should conform to G83 and will shutdown if the gridvoltage rises too high - I think this is around 254V.. Now if both inverters are connected to the grid then they MUST both have the same grid voltage. The "salesman" probably saw the display of the DC PV panel volatge and used it as an excuse to tell the owner there was a problem that their box would fix.  If the grid voltage was indeed 281V a quick call to the local DNO (electricity network operator) for the region would get an engineer on your doorstep checking things out as there would be a definite fault.


These sales people play on peoples technical ignorance.



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