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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.

More information 

YouGen guide to solar electricity 

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Image: Chandra Marsono

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

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