Need help figuring out how to fix damage from a lightning strike

[Peyton]

I'm helping a school with some upgrades to their lighting system and a big issue is that recently the school was struck by lightning and it has started causing intermittent issues with the dimming system. It's a dimming rack with conventional fixtures, about 20 years old. Some circuits don't work at all, and some fixtures will keep blowing after being used for a day or two. My guess is some conductors were welded together and bringing stuff up will overamp the circuit. Potentially phase crossover even? It sounds like some nasty stuff is going on.

Obviously they want to fix this but to me it sounds like Electrician (with a capital E, i.e. commercial/certified) territory. However, I don't know if they will want to get involved in a theatrical system.

We might end up replacing the dimmer rack, but I wouldn't want to put in a new processor and everything without assurance that these issues won't keep happening. So it is necessary to ferret out where specifically the damage is.

Can anyone provide some insight about where to start or what to look for? The school staff does not really have the knowledge to help much.

Thank you.

 

[Mac Hosehead]

I would say you need an electrician to at least check out the power feed to rack. The last time I heard of similar symptoms in a lighting system, the rack had lost the neutral conductor.

 

[FMEng]

When you say "some fixtures will keep blowing" are you saying the bulbs go out, or the breaker on the dimmer trips? If it is the bulbs, do the filaments visibly burn out or do they look intact? What brand and model of dimmer rack is it?

 

[Peyton]

When you say "some fixtures will keep blowing" are you saying the bulbs go out, or the breaker on the dimmer trips? If it is the bulbs, do the filaments visibly burn out or do they look intact? What brand and model of dimmer rack is it?

It's the bulbs. The system is an ETC Unison with Sensor 48 rack

 

[FMEng]

If the bulbs are burning out, then I agree with Mac that a loose power neutral to the rack is a possibility. It could cause excessive voltage to the lights, which kills bulbs fast. Get a qualified electrician to inspect the power connections inside the rack and inside the panel feeding it.

The reason I asked about the condition of the bulbs is that bad fixture sockets can burn the bulb pins, causing the light to go out. Putting a new bulb in a bad socket will work for short time, but the pins will burn up again. I've seen it many times in older fixtures. The telltale signs are that the bulb filament looks fine and one or both pins are discolored and pitted. A bad connection causes arcing, and the arcing causes the connection to get worse until there is no connection. I have a bunch of 30 year old ellipsoidals that I had to put new sockets in to make them reliable.

Once the rapid demise of bulbs is solved, then tackle the dead circuits. It could be a bad dimmer module, or bad wiring from the dimmer to the outlet. Trade a tested good dimmer to the slot of a suspected bad dimmer. If the problem moves, it's the dimmer. If the same circuit still doesn't work, it could be the wiring.

A Sensor 48 is modern and widely used, so parts are available and it should be repairable. It's unlikely that anything major is wrong with it.

 

[derekleffew]

Can anyone provide some insight about where to start or what to look for? The school staff does not really have the knowledge to help much.

Make friends with @Van .

 

[Mac Hosehead]

A Sensor 48 is modern and widely used, so parts are available and it should be repairable. It's unlikely that anything major is wrong with it.

The rack I encountered running with the missing neutral also was a Sensor 48. After the power feed was fixed, the rack ran normally. The only damage was to the lamps which didn't survive.

The other complaint at the time was that lights would change that were not part of the fade.

 

[Van]

Make friends with @Van .

Why me? What did I do? I'm not responsible for Lightning, That's Thor, or Odin, Tyr maybe, or Zeus, or someone. I mean, I'd certainly recommend looking for carbonized conductors at connection points and toasted components in assemblies but, end of the day, that thing is going to need an Electrician first and then an ETC tech. I would guess, however that the problem IS in the dimmer rack, and similarly to above suggestion, your neutral is fried somewhere.