A while back we had a highveld special electrical storm in my neck of the woods, and there was a strike close to my property.
Amongst other damages on various properties was my garage door motor. The control electronics were fried, and the motor had tried to close a door that was already closed, which meant that some of the linkage between the motor and the door got bent, and the door was under tension and so jammed until I got a socket set out and disconnected the bent links.
I have surge protection on my PV system - on both sides of the inverter. The garage motor is on a backed up circuit. But the surge protection is in the DB and the cable to the garage goes underground at some point before going up into the garage roof in a conduit to a 3-pin socket. Then there’s a power lead from the socket to the motor (Centurion). So quite a lot of way for the pulse or whatever from the lightning to get into the motor.
Assuming it isn’t just ethereal if the strike is close enough.
So what I’m getting around to asking is if more surge protection, immediately before that 3-pin plug up in the garage roof, is going to help should these circumstances re-occur in the future (we’re in the house for 13 years, and this has happened once, so it’s not an everyday occurence)?
I have a couple of a Dehn Guard arrestors lying around looking for something useful to do. At present the motor has one of those surge-arresting plugs fitted to the AC lead, but I have a feeling in my water that the Dehn will do a better job (plus I can get the necessary siging off from an electrician for insurance purposes).
I had an old ET-blue opener in the past that had a Varistor built into the PSU. A 275V device iirc, with a fuse, so if the voltage spikes too high it clamps it and blows the fuse. Maybe yours already have something like that built in.
A nearby strike always creates a little EMP, which creates spikes in any long cable (if you have one wired to a push-button switch for opening the door, for example). It could be any one of those.
I’ve lost network switches and modems (when those were still a thing) due to nearby strikes, where the spike was on the signal wire and not the power supply. Long story short: This might not be your power supply.
Thanks. You may have solved the problem. The surge arrestors I mentioned didn’t trip and nothing else on the property was affected, so I was puzzled, but there is a long cable run from the DB (and thus the surge arrestors) to the motor. But also the motor is not the only thing on that circuit and nothing else popped.
However there are multiple cables into the motor/control unit including one from a receiver for the remote openers, and one for the push button your describe.
Am I right that the varistor is required because fuses blow on current, not on voltage?
Probably. A Varistor is a voltage-dependent resistor. When the voltage reaches the breakdown voltage it starts conducting. By placing it across the supply, with a fuse in line, it disconnects the device by creating a dead short and blowing the fuse. If the event is particularly severe, it may also blow up the varistor.
It is similar to when people put a reverse-biased diode over the DC supply, with a fuse, so that if you connect it in reverse it blows the fuse.
Trying to protect electrical/electronic equipment from lightening is challenging.
The electrical transients will travel in all cables and anything conductive so not only via the power cable.
Industrial electronics always has opto isolated inputs from wiring to the outside but this costs more so I doubt if garage door/gate operators have these built in.
Screened cable is also used to protect cabling but the same applies.
As you point out it’s a rare occurrence for this to happen so the most important is to ensure all equipment is insured (and this includes your way bigger $$ investment in your solar system!)
Ah yes. I remember this.
Had a huge highveld thunderstorm and decided to unplug the PC, TV etc. to be on the safe side and then BAM lightning strike in the veld not too far away and I could just hear the bzzzzzz of something frying and the modem was gone as it came through the copper telephone wire. If i remember correctly it also ended up taking out the PC’s network port.
Those ADSL modems could not be protected!
They lasted a given amount of time and then they were replaced. It was something to do with the data signal on top of the audio: They could not isolate this signal with an opto-isolator.