Residential Damage - Mystery Cause?

[bcm]

Hi Gang!

My brother-in-law had a strange occurrance this week, and I'm dying to get some opinions on what caused it.

As the story goes:

"We heard the computer UPSs beep and heard electrical noises. We get into the home office in time to hear the Mac go "pop" while we madly start disconnecting stuff. Both mine and my wife's computers are on an APC, and other than lots of "complaints", everything else in the office is fine. However, the Mac, the power strip it was plugged into, and the power strip that the monitors on my computer are plugged into are fried. That one was the weird one, because it was plugged into a conditioned outlet on the APC -not on the battery side but on the filtered side. We think something really strange just happened with the Mac, but later, I see that the oven computer is off (it's dead). We start doing a more thorough search and discover the PC in our son's room is hosed, too. We find that the fan on the a/c has been running for hours but the house isn't cooling down - check the external part of the a/c and then find a non-functioning unit with the slightly
melted corner of the disconnect faceplate (CB & a capacitor melted). No circuit breakers in the main panel are tripped. No neighbors have been affected. We are the closest home to the pole-mounted transformer.

Power company checked the house and said all power levels were normal, including going through the fuse box in the house (he checked each switch). So, the problem was likely a ground wire touching something it shouldn't INSIDE the house. The electrician found no house wiring problems, and says it was a surge on one of the two lines from the power company. The power company says it wasn't a spike from them."

Now, given this info from my in-laws, I have to wonder why the spike didn't fry pretty much every electrical device plugged in... why was no other house affected.... why did NO CBs trip?

Anybody have some insight on this? I'm super curious!

Thanks!

 

[augie47]

It will probably remain a mystery. There are a few possibilities the most common being associated with power company problems especially if the damage was mostly to items on the "non-battery" side of your APC..
Power companies NEVER find power quality problems...I've seen "Problems" disappear as they work on the lines, but, when asked, they found 'no problem' .SOP..they are trained to answer correctly.
If damage was done to items on the APC filtered side, you may be covered by their (APC's) warranty.

 

[Mr. Bill]

I'm thinking power company too. Momentary voltage surge? Wonder if they'll tell you if any work was being done on their lines nearby at the time of the problem. Still seems like the neighbors would have noticed something then. I think we're all just going to be guessing blindly.

 

[Sierrasparky]

Have you found out what is wrong with the ac unit.
I wonder if the A/C compressor locked-up. I have seen a one lock up and all the lights go dim and bright and the CB failed to turn off. This caused lots of problems.

 

[bcm]

Residential Damage - Mystery Cause?

I only know that an AC company came and checked the air conditioning. Not only was the CB melted (in-laws words, not mine), but the AC guy replaced a capacitor in the unit. As soon as it powered back up, it tripped the switch. He said the air unit has a short in it now and the unit is dead.

Thanks for responding!

 

[Sierrasparky]

I wonder if the AC was the culprip somehow.

 

[hillbilly1]

Is the service underground or overhead? Underground feeds that are 30-40 years old are very bad at having open neutrals. Your problem may still be there.

 

[hillbilly1]

While I was typing my last post, you had posted that the A/C compressor had fried, an open neutral would not have caused that.

 

[cowboyjwc]

Could have been that when the AC failed, only one leg failed and that could cause an unbalanced load, sending the balance through the neutral. Just taking a stab.

 

[Jraef]

Just to clear things up:

Breakers don't protect against voltage issues, except as they cause excess current draw. So if there was a surge on the line, the fact that no breakers were opened would mean nothing.

If the problem took place on one side of a 230V circuit, such as your AC unit, it would not necessarily travel to or affect loads connected to the other half of the circuit. That would explain why not all of your loads were damaged, only the ones on the same leg saw the spike.

Most likely if that's the case, it was not a problem with the utility supply. Sounds more like a motor capacitor in your AC unit took a dump and took everything on that circuit with it.

It happens...

 

[jmellc]

Don't know about the HVAC part, but have seen stuff burned up by neutral getting lost & 120 v ckt getting 240. Can be hard to find, can be slightly loose neutral lug in panel or meter base, acting up sporadically.

 

[Pierre C Belarge]

It will probably remain a mystery. There are a few possibilities the most common being associated with power company problems especially if the damage was mostly to items on the "non-battery" side of your APC..
Power companies NEVER find power quality problems...I've seen "Problems" disappear as they work on the lines, but, when asked, they found 'no problem' .SOP..they are trained to answer correctly.
If damage was done to items on the APC filtered side, you may be covered by their (APC's) warranty.

I would check to see if the POCO had linemen working in your neighborhood/area. Also, there may have been some load switching by the POCO. Were there any lightning storms somewhat close (miles) to the house?

Also check to see if any of the neighbors had similar issues.

 

[K8MHZ]

I think the best two possiblilities have been covered.

I am glad our power company, Consumer's Energy, is honest to work with. They not only readily admit when surges do damage, but help determine the cause.

I did a job on a new home that was the replacement for one that burnt to the ground due to a power company issue. Old secondary lines had lost their insulation and in a storm touched together, overloaded a transformer, stopped touching, transformer surged primaries, night light caught fire and house burned while no one was home. Cost to insurance company was around $480,000.

Yes, we did install a whole house surge protector on the new panel.

For less than 100 bucks they seem to be good insurance.

I think mitigation is more important than diagnostics at this point. Protect the home first. If the indecent happens again and it is on the line side, you have some protection. I am not sure how they work for internally generated voltage spikes.