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

Netexporter

If the system does not trip immediately but repeatedly after a period of time when you have lots of  generation

Could indicate over-voltage caused by a high impedance fault in the local supply. You'd need to monitor the voltage (get a power plug or, less conveniently read it off the smart meter), especially on sunny days. If the voltage varies wildly (more than 2 or 3 volts) it is likely to go over 253 volts, at peak production, that will cause the inverter to shut down. If you do see that voltage instability, ring your DNO and ask them to check the voltage, which they can do remotely with a working smart meter. If no smart meter they'll have to come out and connect a monitor, which is more time consuming.

When I had this problem the fault was fixed within one working day, after two days monitoring.

Heedtheadvice

? Can you explain please  Netexporter how that would cause the MCB to trip?

Telegraph_Sam

I can modify our latest corresp with an update: I was checking the label on the MCB to see if this was obtainable on Amazon etc. In so doing I manually tripped the MCB. However in contrast to previous occasions it refuses to be reset, it keeps flicking back down to the tripped position. To me this increases the finger pointing at a faulty MCB. Outside it is approaching darkness [You advised me to contact the DNO for a voltage check. Is that Northern Powergrid? I've got a smart meter].

The way forward seems to be the same as before: Try to get a local electrician competent and willing to replace the suspect MCB if necessary omitting all the expensive investigations. Failing which contact one of the MCS people like susenergy and get them to look for a root and branch solution.

Any advance on that?

QrizB

I think we're all on the same page here.

Good luck with your search for an electrician!

Telegraph_Sam

 .......

Telegraph_Sam

The saga continues: Out of habit I flicked the "suspect" MCB back on (again) at 8 pm this evening and was amazed to see that this time it remained "on" - with the previous result that all lights and indicators on the inverter were back to normal. This presents me with a dilemma as far as next action (contact MCB-friendly local electrician) is concerned. Are MCB's "binary" in operation - either they work or they don't - or is there some half way house?  And given a correct replacement MCB on tap how easy / quick a job is it for an electrician to replace it?

QrizB

It's knackered. Get it replaced.

Telegraph_Sam

Search continues for a MCB-happy local electrician. I'm guessing that it is possible to replace the MCB independently of the RCD/RCB?
You mentioned previously getting a RCBO. Apart from this being something "new" in the chain, are there advantages and disadvantages in installing this (replaces both the RCD/RCB and the MCB?)?

QrizB

An RCBO combines the functions of an RCD an a MCB. Earlier in this thread you said you had two MCBs and hadn't mentioned an RCD.

As it turns out that you already have an RCD, I don't see any need to consider a RCBO.

Telegraph_Sam

What you say is correct. I'm still only half way through learning what the jargon means ..

Latest plan is to purchase what looks like an identical MCB from eBay, and simultaneously establish contingency contact with a suitable electrician with the aim of being able to react quickly in the event of another power failure.