Solar PV "Power failure"? Technicians in North East? Help!

NedS

Telegraph_Sam said:

I suppose that there must be some gut-feel logic in the switches being less liable to trip in cool weather than in hot.

Yes, MCBs use a bimetallic strip that heats up, bends and causes the MCB to trip when excessive current is applied. Very hot weather can cause the bimetallic strip to flex more making it more sensitive and more likely to trip. Once it has cooled down, you will probably be able to reset it until it trips again.

Maybe just make sure the MCB is adequately rated - a 16A MCB on a 3.68kW inverter doesn't exactly give you much headroom, does it? We have a 20A breaker on our old 3.0kW inverter and never had any trouble with it tripping. In the first instance I'd get the electrician to replace the MCB with a 20A.

Telegraph_Sam

Yes that is beginning to make sense, looking back, though the MCB seemed to need a night's sleep before coming back into action again after tripping in the afternoon. Going by the label, what I have purchased, both units, are identical to the originals and I don't want to risk variations - unless a 16 A is truly unworkable.

That is the easy part. Next refer to the instructions on how to get hold of an "electronics electrician", an endangered species, during the summer holiday period.

Telegraph_Sam

NedS said:

Telegraph_Sam said:

I suppose that there must be some gut-feel logic in the switches being less liable to trip in cool weather than in hot.

Yes, MCBs use a bimetallic strip that heats up, bends and causes the MCB to trip when excessive current is applied. Very hot weather can cause the bimetallic strip to flex more making it more sensitive and more likely to trip. Once it has cooled down, you will probably be able to reset it until it trips again.

Maybe just make sure the MCB is adequately rated - a 16A MCB on a 3.68kW inverter doesn't exactly give you much headroom, does it? We have a 20A breaker on our old 3.0kW inverter and never had any trouble with it tripping. In the first instance I'd get the electrician to replace the MCB with a 20A.

"V = I ÷ R" ???

Telegraph_Sam

Yesterday was the first trip-free day in memory.

NedS

Looking at your wiring diagram back on page 4 appears to confirm the inverter is a 3.6kW model (not the 3.0kW model)? Replace the MCB with a B20 and see how you go.

NedS

Telegraph_Sam said:

NedS said:

Telegraph_Sam said:

I suppose that there must be some gut-feel logic in the switches being less liable to trip in cool weather than in hot.

Yes, MCBs use a bimetallic strip that heats up, bends and causes the MCB to trip when excessive current is applied. Very hot weather can cause the bimetallic strip to flex more making it more sensitive and more likely to trip. Once it has cooled down, you will probably be able to reset it until it trips again.

Maybe just make sure the MCB is adequately rated - a 16A MCB on a 3.68kW inverter doesn't exactly give you much headroom, does it? We have a 20A breaker on our old 3.0kW inverter and never had any trouble with it tripping. In the first instance I'd get the electrician to replace the MCB with a 20A.

"V = I ÷ R" ???

Power (W) = Volts (v) x Amps (A)

230v x 16A = 3.68kW.

If you replace with a B20 MCB, then 230v x 20A = 4.6kW which should be ample for your 3.6kW inverter.

Telegraph_Sam

That being so it's unfortunate that, playing "safe" I have purchased a replacement 16 A MCB together with an RCD both to the original spec. 

Telegraph_Sam

Does that mean that from your looking at the Aurora  figures there is no obligation to fit a 16 A MCB,  rather that this was a decision taken by the installer 13 years ago? In which case I could try to exchange with a 20 A MCB (new for new). What about the RCD ( which has been less temperamental) ?

paul991

The mcb protects the cable and circuit supplying the inverter. So should only be changed by a electrician who can take into account other things like installation method ect

Heedtheadvice

No no NO!

Do not replace the 16A  breaker ( MCB) with  20Amp version.

The 16 A breaker is rated to protect the wiring  ( and hence the subsequent equipment, but by design the wiring ). A 16A breaker ( as I wrote previously) reacts to the level of current passing through it and the duration of the overload. Typically it will break the circuit at twice the rating after a couple of seconds overload I.e. 32A for  16 A breaker and thus protecting the wiring from over heating 

 20 Amp breaker reacts similarly but at 40A.

The inverter, under normal  generation circumstances will limit it's output to comply with the G98 spec of 16 A nominal.  Even under limit failure case it's output will not significantly increase more than the solar PV max output ( kWp ) so there is no need to increase the mcb rating and it could be positively dangerous to do so if the inverter were to fail and draw high current from the grid.

At the moment your mcb is either doing it job ....or is itself in need of replacement specifically with the correct ratings.