Anyone had a rotary isolator fail?

[Oldgreybeard]

Had a frustrating evening. Decided to get things ready for a consumer unit change, by moving the FIT generation meter and the internal AC rotary isolator by a couple of inches. Only wiring change was a new bit of cable from the rotary isolator to the old CU, as the existing cable was a bit too short. It was around 9pm by the time I'd finished, so I did all the testing indoors, turned the power back on indoors and all seemed fine, the generation meter came on etc.

I then went outside to turn the outdoor inverter rotary isolator on and the inverter seems to be dead. Tried turning the isolator on and off a few times, to no avail. It's too cold and dark out there to start faffing around pulling the cover off the isolator and checking to see if power is actually getting to the inverter. There's power at the indoor end of the cable, that's wired directly to the generation meter, and I've checked and all is well there.

I can only assume that either the inverter has just died (maybe it didn't like being turned off) or that the outdoor rotary isolator has failed. This was probably the first time that isolator has been switched since the system was installed in 2014.

Anyone else had one of these fail open circuit?

I can check tomorrow, but I'm curious if rotary isolator failure is something that happens when these things are outdoors and not operated for years.

[marshman]

My sunny boy is "dead" if there is no pv output. Are you sure its not just because it is dark?

Had issues with loose terminals in various bits of switchgear but not actual failure of the switch.

[Oldgreybeard]

My sunny boy is "dead" if there is no pv output. Are you sure its not just because it is dark?

Had issues with loose terminals in various bits of switchgear but not actual failure of the switch.

Damned good point! Not sure I've ever looked at it in the dark before, so maybe it does just shut down if there is no PV input. Be heartening if that does turn out to be the case.

[Mr Gus]

I'm hoping it's a case of tne obvious staring you in the face (likely you spent time kicking your own backside overlooking that one OGB) with daylight being the most cost effective fix / resolution.

I'm guessing that after this some dissembly & some contact spray or similar will be considered for occasionally moving parts hereafter.

[chris_n]

We used thousands of rotary isolators on production lines, every machine had one. I don't ever recall one being changed due to failure in the 10 years I was in charge of the maintenance team. Some did get damaged when people did stupid things (impacts).

[Joeboy]

We used thousands of rotary isolators on production lines, every machine had one. I don't ever recall one being changed due to failure in the 10 years I was in charge of the maintenance team. Some did get damaged when people did stupid things (impacts).

Same here across all the decades on offshore gear in harsh environments. Not once. Hopefully a simple dry joint or similar.

[Oldgreybeard]

Panic over, OGB is an idiot . . .

Seems the inverter does shut right down with no PV input, as it's alive and seemingly well this morning, and delivering a whole 340W at the moment.

The odd thing is that I have memories of a supply problem some years ago, that kept causing the inverter to trip out and when the SSE chap came around to check and fix it (it was a problem of theirs very local to us) I turned the inverter off (from indoors) and turned it back on in the evening, when SSE had fixed the problem. I was sure it was dark then, and the SSE chap wanted to check the inverter hadn't been damaged by the surges/spikes caused by their fault, so we both watched it start and do it's self-testing routine. Maybe there was just enough light to wake it up, although it seemed dark from what I remember.

[Oliver90owner]

Just a point. Isolators are just that - isolators. They are not designed for switching purposes - that is when they are more likely to become failures.

[Oldgreybeard]

Just a point. Isolators are just that - isolators. They are not designed for switching purposes - that is when they are more likely to become failures.

Indeed, and hence the reason why I was doing this work in the evening, when it was too dark for the inverter to be producing any power. FWIW, the sequence of events was that I pressed the test button on the 32A RCBO that supplies the inverter (might as well give it its six monthly test whilst turning it off), then I turned off the indoor rotary isolator. That was fed from the outdoor isolator though, so to be sure the cable I was moving was dead (in addition to normal dead testing as a part of safe isolation before working) I turned off the outdoor rotary isolator.

I then moved the generation meter and indoor isolator down about 2", to make room for the new consumer unit, added a slightly longer bit of 6mm² cable from the indoor isolator to the 32A RCBO in the existing consumer unit, did the normal dead and live testing indoors, then turned the isolators back on. I didn't bother re-testing out to the inverter, both because it was dark and because the only bit of the circuit I'd interfered with was the cable and connections from the indoor isolator to the consumer unit.

I did issue myself with a minor works chit, and lodge it with the other paperwork, just in case someone comes along and wonders who has done what and what the test results were, given that we seem to be getting increasingly conscious of the need for lots of bits of paper now.

[Oldgreybeard]

Just a point. Isolators are just that - isolators. They are not designed for switching purposes - that is when they are more likely to become failures.

Just putting out the recycling and was about to fold up the box that the Garo rotary isolator came in and I noticed the label on the side:

Garo Load Break Switch.jpg (52.5 KiB) Viewed 1315 times

It seems that Garo, at least, do design their rotary isolators to be used for switching purposes, and to isolate circuits under load. TBH I'd not realised this until reading this label, and had assumed that these isolators were best switched when not under load. There is a noticeable difference when operating this Garo rotary isolator though. It clacks across with an almighty whack as you turn it, so clearly has a powerful spring that moves the contacts apart quickly, perhaps to reduce the risk of an arc sustaining.