Storm scare....I need some thoughts/opinions

[General Lee]

Hey everyone.... Strong thunderstorm just came through with heavy lightening and tornado warnings etc. Took shelter in the basement and during the height of the storm I started hearing some electrical "ticks" or sparks overhead along the steel beam. Shortly after a good lightening strike hit nearby and sparks flew from where my duct work ends and meets the block wall. There is fiberglass insulation on the wall and goes around the duct work. The insulation is backed with aluminum which is in contact with the duct work to some degree.

From what I can tell lightening did not strike the house but it was close. I'm thinking the electrical current came through the ground and the house acted as the ground and the duct work caused the short?? I'm not an expert in this area. What are your thoughts.

I've been monitoring everything and checking the attic for fire. Its been about an hour since all this has happened. Everything still works and no breakers were tripped.

Anything else I should check for and what do you all think happened? I know electricity can do some strange things but this is making me nervous.

 

[Fawken]

Hey everyone.... Strong thunderstorm just came through with heavy lightening and tornado warnings etc. Took shelter in the basement and during the height of the storm I started hearing some electrical "ticks" or sparks overhead along the steel beam. Shortly after a good lightening strike hit nearby and sparks flew from where my duct work ends and meets the block wall. There is fiberglass insulation on the wall and goes around the duct work. The insulation is backed with aluminum which is in contact with the duct work to some degree.

From what I can tell lightening did not strike the house but it was close. I'm thinking the electrical current came through the ground and the house acted as the ground and the duct work caused the short?? I'm not an expert in this area. What are your thoughts.

I've been monitoring everything and checking the attic for fire. Its been about an hour since all this has happened. Everything still works and no breakers were tripped.

Anything else I should check for and what do you all think happened? I know electricity can do some strange things but this is making me nervous.

You are right about most electrical damage comes from lightning hitting the ground or trees- not the house- and then searching for the best ground. Many times it comes in on a buried phone or CATV line because the phone & CATV companies' grounds are often marginal. From there it generally finds it's way into small appliances, cordless phone bases, TV's, etc. Sounds like it jumped onto your ducting. If no damage to small appliances check the grounding on any buried lines coming into the house including stuff you may have run to out buildings. There are many threads here about running electrical to sheds or shops, but little is mentioned about grounding at the service entrance. Here is NEC art. 250 in easily digestible format: http://fyi.uwex.edu/mrec/files/2011/04/W4.-Biesterveld-NEC-grounding-MREC2010.pdf

 

[wmonroe]

I am far from any kind of expert but what about tiring the ductwork and steel beam into a ground rod?

 

[JRobyn]

When I converted from my temp power pole to the permanent meter, I couldn't get the temp ground rod out. So I added a new one near the base of the meter. And my foundation contractors left a long end of the slab rebar about 5ft from where the meter is. So I ran 4/0 solid copper to all THREE and clamped them to the rods with good bronze clamps.

I'm hoping that I have a good, solid ground now!

- Jay

 

[General Lee]

Many times it comes in on a buried phone or CATV line because the phone & CATV companies' grounds are often marginal. From there it generally finds it's way into small appliances, cordless phone bases, TV's, etc.

Well, the direct tv receiver in the living room can't get a signal now. All other receivers are working but not this DVR one. Hmmm wonder if its storm related. The receiver works, and I can watch stuff I recorded but it just won't get a signal. Been on the phone with tech support and had to resort to scheduling a tech to come out out.

 

[Fawken]

When I converted from my temp power pole to the permanent meter, I couldn't get the temp ground rod out. So I added a new one near the base of the meter. And my foundation contractors left a long end of the slab rebar about 5ft from where the meter is. So I ran 4/0 solid copper to all THREE and clamped them to the rods with good bronze clamps.

I'm hoping that I have a good, solid ground now!

- Jay

The rebar doesn't do much for you. Here's an interesting case I worked for the Illinois Teacher's Retirement Fund in 1999: Orlando, Florida. Lightning capital of the world. The Retirement Fund was the majority shareholder in the Wyndham Orlando Resort Hotel & Convention Center. After tracing a transient surge that did $169,000 damage back to a backhoe accident, I was asked to verify all building ground rods with a Megger. This resort is a campus with 28 separate buildings originally constructed in the early 70's as an apartment complex. Turns out virtually all of the original ground rods were bad due to being encased in glass. Lightning had entered the circuit and turned the silicon based sandy soil to glass.

 

[bcp]

Speaking of lightning, you can see where it is here:

Real-Time Lightning Map :: LightningMaps.org

Bruce

 

[3930dave]

The rebar doesn't do much for you. Here's an interesting case I worked for the Illinois Teacher's Retirement Fund in 1999: Orlando, Florida. Lightning capital of the world. The Retirement Fund was the majority shareholder in the Wyndham Orlando Resort Hotel & Convention Center. After tracing a transient surge that did $169,000 damage back to a backhoe accident, I was asked to verify all building ground rods with a Megger. This resort is a campus with 28 separate buildings originally constructed in the early 70's as an apartment complex. Turns out virtually all of the original ground rods were bad due to being encased in glass. Lightning had entered the circuit and turned the silicon based sandy soil to glass.

Hearing it after the fact, that (extreme-heat + sand = glass) story makes sense..... easy to say now, after it was figured out :thumbsup:

Great example of what can go wrong with Gnd rods - thanks for posting that, and the NEC link.

Rgds, D.

 

[Fawken]

Speaking of lightning, you can see where it is here:

Real-Time Lightning Map :: LightningMaps.org

Bruce

That's just too cool! Too bad I retired from that line of work. Looks like I'd be real busy!

 

[Fawken]

Hearing it after the fact, that (extreme-heat + sand = glass) story makes sense..... easy to say now, after it was figured out :thumbsup:

Great example of what can go wrong with Gnd rods - thanks for posting that, and the NEC link.

Rgds, D.

You're welcome. The general contractor wanted so badly for me to declare lightning as the cause- and the insurance company would have bought it since Orlando really gets hammered by it, but I try to be honest. A backhoe operator had hit the main power feed for the complex, but only cut the neutral. Thus 240v was sent to the phone system, computers, TV's, and even the radio clocks in all the rooms.