I spent five years as a forensic electrical engineer, investigating fires, equipment damage, and personal injury for insurance claims and lawsuits. AMA

What’s the craziest fault you found that helped a client?

I’m reminded of the faulty spring in the ignition that a forensic investigation of a car that caused the electric steering to shut down and caused a girl to swerve into oncoming traffic resulting in her death. She had been assumed as just being a negligent driver but her dad believed otherwise and hired the forensic investigator.

The first one that comes to mind didn't end up helping the insured but it was close. It was a factory that one morning randomly had a fire in a cable tray. They had contractual obligations to maintain production so they had already ripped out all the cable before I got there. I asked them to ship me the cable, so they did. A few days later a semi backed up to my loading dock and dropped off six tons of burnt cable.

Six. Tons.

I spent the next few days going through every last piece of that cable until I found the culprit. Years before, a single run had been installed improperly. It had extra length, instead of cutting it short, the installer had left it coiled up in the cable tray. The extra heat from that was enough to damage the insulation a little bit every time it ran, until after several years the insulation finally failed entirely.

They were going to sue the installer, until they realized the installer was their own subsidiary...

That only took you a few day? That’s impressive.

24 man hours is a long time, really.

What does that even look like? How can you tell that the cable was coiled up and overheated? Did they have every cable labelled and give you a detailed map of the building's wiring diagram? I would expect that they would have chopped up the cables to make it easier to pull out and it would look like an eldritch version of the flying spaghetti monster.

Also, if you've never heard of it, /r/cablefail is a fun sub when you want some schadenfreude (it's geared more towards IT workers, but still).

I would expect that they would have chopped up the cables to make it easier to pull out and it would look like an eldritch version of the flying spaghetti monster.

Well said, that was pretty accurate. It helped that most of the cable wasn't burned. I could eliminate anything with no burns, and then narrow to the part that was most burned. Which turned out to be a coil which conveniently had melted itself into shape and couldn't uncoil any more. There were enough markings on it far enough away from the burning that I could ID the cable type, and nobody uses VFD-rated motor cable for anything but running a motor on a VFD.

What kind of cable was it? Is it okay to leave coils in cables below a certain threshold for example? Like signal cable I'm assuming would probably be fine, maybe low voltage stuff, just not mains voltage, or what? I know to fully unwind an extension reel for that reason.

It was some kind of European VFD-rated motor cable, as I recall.

As for what would be okay, the only answer is "follow the manufacturer's instructions" and "follow the NEC." As a broad statement about what's more or less likely to cause a fire, anything running at close to its current limit is more likely to cause a fire when it can't get airflow. So signal wire would, as a broad general statement, be safer to coil up. But it still might have issues, especially considering things like PoE exists, or it might mess up the signal integrity, or or or.

Follow the standards and the manufactuer's instructions.

How many incidents have you seen that are related to the cheap unbranded or counterfeit phone chargers and power supplies being sold at Amazon etc?

I saw a school burn pretty hard because of one of those, yeah. I was able to identify the exact model, but for some reason the attorney didn't want to pursue against the manufacturer or importer. I still suspect that was a mistake on his part, but I'm not an attorney.

I saw another one in a small restaurant, started in the back office. Couldn't identify the manufacturer of that one, nothing to be done.

how bad is it really to have a power strip plugged into an extension cord, and other types of daisy-chaining?

Follow the manufacturer's instructions, always, 100%.

Now, as ways of abusing extension cords go, there are worse ones than daisy-chaining. Daisy-chaining is more likely to lead to voltage drop rather than overheating, for example, and voltage drop on a motor load (or switching power supply) can result in more current draw and thus fire. But you'd have to chain a whole hell of a lot of cord to achieve that. I think the more likely failure mode is just by having so much exposed cable, you dramatically increase the odds of mechanical damage.

Of course, that's just straight daisy-chaining. Branching multiple high-current loads off one multi-tap could definitely start a fire, as /u/Ziazan points out.

Once I got into this field, I put arc fault breakers everywhere in my house. I don't understand how we're not all on fire, all the time.

What’s an example of a residential fire that arc breakers prevent?

The typical example is if you have a damaged cord. One failure mode is that the conductor breaks, but can still make intermittent contact. That intermittent contact causes an arc, which (given the right circumstances) can ignite the insulation of the wire. Alternately, you can get an arc from hot to neutral or ground through damaged insulation, same deal. The combination arc fault breaker has pretty good chances of detecting those faults and tripping, where a regular or ground-fault breaker won't.

Amusingly, I once had an arc fault breaker in my house trip spuriously, repeatedly. Every time, it was during a specific moment of a specific episode of Samurai Jack. Turned out my power strip was sitting on my subwoofer, and the signal to generate the sound of gunfire was coupling into my power lines and tricking the breaker. Moved the cord, no more problems.

Why did you watch that one episode multiple times?

Because the power kept going out in the middle of it!

I’m in construction industry and it’s well known that arc fault breakers hate Lg washers and dryers for some reason. I live in a brand new house built by me and my LG washer would constantly trip my arc fault breaker. I had multiple electricians come out and do tests and everything was testing as fine. Ended up running a new wire for the washer with same results, warrantied the washer and got a new one, it worked ok for a bit but the issue came back. I ended up replacing to a non-arc fault breaker, and it works fine now. But it’s always a concern in the back of my mind. Am I overthinking it? I don’t really know what else I could possibly do.

Just wanted to hear your thoughts on it

False trips already common problem with arc fault breakers, that's true. I don't know particularly about that specific equipment. I don't know that I would do differently than you did.

How do you know what a good arc fault breaker is?

There's probably only one that fits in your panel. But if that's a question you need to ask, you probably want an electrician to do the job for you.

What were some of the most obvious boneheaded things you've caught?

Technician bypassing an overtemp limit to get equipment running again is a classic...

Wait, isn't that basically the equivalent of hardwiring around a circuit breaker because the breaker kept tripping???

Yes, that's a very good analogy. Stick a penny behind your blown fuse, for another older one.

There's actually a place called Fire Findings in Michigan that puts on a week-long appliance fire course. It's amazing. Their room is full of trophies where students are expected to look at the equipment and figure out what went wrong with it. More than one was that.

Lots of people know how to make things work. Far fewer of them know how to make things work so that they won't kill people in almost any imaginable circumstance.

That's one example yeah. Oh the 5A fuse blew. I'll stick a 13A in there. Oh its on fire.

"Pft, why's there a lockout on this breaker? Lock this out!" breaks out bolt cutters.

"And that, your honor, is when I beat him to death with his own bolt cutters." "Not guilty!"

What do you think about all these cheap uncertified smart outlets and PD outlets being sold everywhere, even Costco?

Is it okay to purchase the $30 ones or should people be buying the $70 Eaton and Leviton?

Buy nothing that isn't certified by UL or ETL or some equivalent agency. I'm appalled that any distributor even sells things that aren't.

I would ask you about the least traceable way of starting an electrical fire, but instead I'll ask: what was one of the most successful ways to get away with starting an electrical fire in the past that you'd never get away with nowadays?

what

was

one of the most successful ways to get away with starting an electrical fire in the

past

that you'd never get away with nowadays?

Oh, that's an interesting question. I think the fact that investigators are vastly more tech-saavy and probably have a digital forensic specialist on speed dial has closed a lot of windows that might have existed for a while there. There being so many cameras everywhere contributes too.

Mechanical engineer here, consumer products, etc. Do you have a couple design defect stories? Or even better, any common product design aspects you feel are unsafe, or any knowledge we design engineers could use to make better products? Thank you, I appreciate your perspective.

Oh, nice question!

One bugaboo of mine is heating pads. Every heating pad on the market is required by UL standards to have a particular label on it, saying "Don't use this if you're diabetic" among other things. Diabetics can have impaired bloodflow and peripheral neuropathy, so the pad can burn them more easily, and they might not feel it. And heating pads, just by the job they are required to do, get quite hot. I got called in on a case where a diabetic ignored the label, put a heating pad on his foot, fell asleep, and when he woke up most of his foot was burned off.

Question for me was this: did the manufacturer do anything wrong?

Well, the pad didn't malfunction, we confirmed that first thing. And the manufacturer followed all the applicable design standards. They could have put a timer on the heating pad, which would have prevented the injury. Why didn't they? Because people don't want heating pads with timers. If you google the subject, the first results are "how do I defeat this stupid heating pad timer so it stays on?" The first company to just say "all our pads have timers now" will get their lunch eaten by the other companies that don't. But timers would objectively prevent serious injuries at minimal cost and inconvenience. Every heating pad on the market should be required to have a timer. The only argument I could possibly make was that the entire industry was wrong.

The lesson here for product design is that the hierarchy of hazard controls applies there too. If you could design the product with a guard to prevent injury, but instead rely on a warning label, your design is wrong. I'm not sure if product designers are generally even aware of the hierarchy of hazard controls. I wasn't when that was my job.

Wow, great example and discussion about Hierarchy of Hazard Controls. Do you employ failure mode effects analysis? I think you do. If done well, DFMEA can add perspective.
Yeah that warning label kept you out of court, but someone got burned? Fail! Now we need the whole team to understand this. Must come from the top.

Formal FMEA didn't come up much, though I did use fault trees on a couple notable occasions. They're particularly helpful in injury cases, because the whole idea of an event having a single root cause is flawed. By the time someone has an electrical injury there are often ten different things that have gone wrong. So I used fault trees to identify all the contributing factors, so I could identify which ones were unreasonable or otherwise erroneous.

Since there are so many asking about untraceable fires I'll sk instead... What was the dumbest, "I can't believe some idiot could actually think this would have worked", insanely stupid, hilariously obvious, blatant attempt to do so (for whatever reason) you ever witnessed?

You know, I didn't see too much in the way of purposeful attempts to start fires. I did get called in to consult on an obvious arson once. (Obvious as in there were witnesses to the guy throwing fuel onto the fire.) They just wanted me to look at the electrical to preempt any attempt by the accused to say, "look, it was electrical!"

Why do we hear of many new housing developments catching on fire and being razed to the ground as they are being built?

Fire suppression in an incomplete structure is problematic. The structure has to exist before fire suppression can be added to it. Some detectors are easily set off by sawdust, so they end up getting overridden or otherwise defeated by the construction crew. Lots of potential ignition activities occur in the structure while it's being constructed.

I just read the news article on the homes I was basing my question on and you were spot on. No fire protection yet. Fire started in one home and spread due to winds to destroy all twenty. Thanks!

Not many completed homes have fire suppression anyways, I don't think I've ever seen a home with a sprinkler system, all you have is small fire extinguishers and smoke alarms (wired smoke alarms if you're fancy).

I think some newer codes require residential sprinklers, but I'm not too informed about that.

How did you get involved in this? Your job is kind of my dream job except I'm a structural engineer. Been trying to find something like this for structures but don't know where to even begin.

I spent ten years in design, got my PE, and then saw an opening. There are relatively few PEs that want to do this sort of thing, so it's not too terribly hard to get into if any of the major firms have an opening near you. The industry seems to constantly be churning, buyouts, companies disintegrating, but once you're in, there's almost always a place for you.

There are plenty of forensic structural guys. Look at some of the larger firms: Exponent, ESi, Envista, Jensen Hughes, Rimkus, there are a ton.

Yup. Other big names lately include JS Held and YA.

My wife is an Insurance Underwriter. She has said that furniture stores and tobaco stores are common for catching fire miraculously in the night. Multiple cases where it seemed obviously fraudulent but couldnt be proved (some that were proved as arson of course).

Have you experienced that sort of thing with certain thpe of businesses?

Well, that wasn't usually my end of things with fires. Typically, the scene is owned by the fire marshall until he releases it. Their guys look for arson potential, and if they find it, I basically never get called in. Only afterward does insurance get to the scene and possibly get involved.

Arson investigator wants to know, "Do I need to put anyone in jail?" Insurance wants to know, "Do I need to write a check?" "How big a check?" "Can I sue anyone after I write the check?" Different goals and priorities.

What is one the best practises people can take to avoid creating fires accidentally that you have seen?

What is the most ridiculous case you have seen?

Best practice, don't abuse extension cords. Don't run them under doors. Don't squeeze them in hinges. Don't drill holes in things and permanently install extension cords. If they're damaged, throw them the hell out right now.

I had to run two extensions through an exterior door recently, thoroughly wedged the door open and explained to them in very clear terms: these must be removed at the end of the night before you close the door. Do not close the door over these cables. Unplug them and remove the cables from the doorway.
Show up the next day to take out all the kit that was there, behold, two high quality long extensions jammed under the locked door. When a guy with a key came to meet us to get access to things inside, he asked us if it was okay if he unlocked a different door instead because they had issues getting that door to lock last night.
The cables were internally severed/shorted/mangled but at least that's the only bad thing that came of it.

I found that my mother in law had run an extension cord under her metal storm door. The jacket and neutral insulation were trashed. If it has been the hot, the door would have been electrified.

How about daisy chaining extensions? Just how dangerous is it?

[See elsewhere in the thread.]

How would you classify "abusing an extension cord"?

The examples I gave were ways I've seen extension cords abused, some of which started fires.

So repairing extension cords or repairing cords on things like fans or electronics a no go?

There might be listed and approved ways of doing that. If there are, follow the instructions, 100%. When in doubt, throw it out.

Most ridiculous case... someone once had a hole appear in the side wall of a well, a hundred feet under ground, and asked me if lightning could have caused it... In fairness, that's definitely a question they should have asked. For all they knew it could have been possible.

Any idea what actually caused it?

I could speculate, but it's outside my realm of engineering expertise, so it wouldn't be appropriate for me to have any sort of engineering opinion on it.

Any good crazy ex stories?

You know, not that I can think of. Very few of the cases hours involved with had a criminal aspect. I did see one or two I was reasonably certain were insurance fraud of some kind but I couldn't prove it. When a fire mysteriously starts under a toaster, burns downward into the countertop (which fires generally do not do) and the burn pattern is the exact size and shape of an 8.5 x 11 sheet of paper, you do start to wonder.

Electrical PE here. Any experience with electrical failures in conjunction with seismic events? I've wondered what kinds of damage from faults might occur during an earthquake, before circuits can be interrupted. (Or other structural failures from tornados, hurricanes, etc.).

No seismic events. I seem to recall hearing about a case where a substation was damaged to a hurricane and the lines falling caused some serious problems for the utility, but that might be the closest I have in my experience.

I'm an electrical PE and sometimes get random linked in people asking me to testify as an expert. Are these people insane or did I miss my calling?

It's possible that some legitimate attorney might reach out to you that way, especially if you have a unique skillset or background. It's also possible it's some sort of clearinghouse trying to make a list of experts they can sell to attorneys.

Do you have any stories involving animals or rodents causing a fire?

Oh yes. I once got called to the scene of an explosion. The switchgear in the basement of an office building had just exploded, apropos of nothing. Blew the opposing block wall out of the room. (Good thing it wasn't load-bearing.) We tracked it to the underground power feed between the pad transformer and the building. An arc had formed half-way down the cable. Given the recent pest infestation of the building, the best explanation was that a mouse had crawled down the conduit and chewed through the insulation, causing an arc. And since there's not required to be overcurrent protection between the transformer and those cables, that's a whole hell of a lot of energy in that arc, which all turned into blast pressure down the conduit and into the building.

We didn't find any mouse remains, but then, we wouldn't, after that.

What is the most common and potentially deadly\expensive mistake you've seen in electrical systems?

Unquestionably, bypassing safety systems to make things work.

How much shit did you make up on the spot?

Lol! I figured out tons of stuff live on site, if not afterward during research. But that's not the same as making shit up, of course. It's important to balance making people confident in your expertise against maintaining the intellectual humility of not knowing what's going on when you walk into a scene. One of the worst things you can do is think you know what's happened before you get there.

What an interesting job, thanks for doing this. My question is do you have any home safety tips or devices you recommend that you discovered through your work or feel should be more widely known?

Arc fault breakers. If you don't have them, get them, especially in any room you use lots of extension cords or Christmas lights.

If your house is old enough to not have ground fault protection in the usual places (kitchen, bathroom, exterior) you can add it easily with a breaker upgrade as well.

And as I've said elsewhere, do not abuse extension cords!

EE student here, how did you get into this line of work? Thanks for the AMA!

I spent about ten years in product design, got my PE, and saw an opening. Having a PE is pretty critical to this line of work, because you could end up testifying in court. And the number of experienced PEs who want to do this is relatively slim, so at that point it's not the hardest market to enter.

Have you ever been asked to cross a moral line on a finding? In that a big business is paying the bill, so they request a slight manipulation of any results to weight it towards them?

Not once. The closest I came was when one insured made a mistake that would have looked bad to their own clients, they asked me to not share the report with their clients. Which I couldn't do anyway, because the report is the property of the insurance company I worked for.

I am glad that /u/swcollings hasn't had a pushy client. I have fired clients before for asking me to change an opinion or leave something germane to the investigation out of a report. For many of those clients, the cost of writing off the work is well worth the knowledge of knowing that I dont want to work for that person or entity again.

Yeah, at worst I've been told, "Don't write a report." I don't have any moral problem with that.

How dangerous are space heaters, really?

An modern electric space heater meeting certification standards, in good condition, and used according to the directions is pretty unlikely to start a fire under most imaginable circumstances.

Would you consider it safe to leave certain appliances running whilst you’re out of the house? Say, washing machines and dehumidifiers?

Anything I'd be concerned about leaving running unattended, I wouldn't have in my house in the first place. (Cooktop and oven excepted, of course.)

Not OP, but similar field. Millions of dehumidifiers have been recalled. Don't use a recalled model in any capacity, don't use it with an extension cord, and don't use the hose attachment so it runs 24/7, and you should be OK.

Oh yes, the dehumidifier cases are legendary. I wasn't in the field for a month before some attorney called asking if I'd work on one. Turns out they'd already stiffed my company for quite a bit of money, and they were desperately calling any new engineer that showed up in the entire forensic field.

Are they still an issue with newer dehumidifiers?

It was one particular brand that had serious problems. I don't think it was a general industry problem.

I assume if it goes to court, you become the expert witness? Any stories on craziest defense and best defense from the defending side expert witnesses?

As a secondary question, how much does “due diligence” actually absolve anyone?

Oddly in five years I never had cause to even give a deposition. Just never happened for me. But I did go to some excellent training for being an expert witness, put on by a couple attorneys, which included mock trial. One guy changed "his" (fictional) expert opinion on the stand, which resulted in summary judgment against him. Another time, the expert was handed some evidence and asked, "Is this the evidence you collected" when it totally did not match the evidence collected.

I did hear of one case where the expert on the stand turned out to not even have an engineering degree or something like that. Summary judgment, client lost some absurd amount of money, it was a thing.

The standard of what a reasonable person would know is pretty important, yeah. There was one case I did that I'm still fascinated by.

Woman rents an apartment, moves in all her stuff. Not long after, a breaker trips the circuit behind her bed, which doesn't have much plugged into it, basically just an old lamp. Electrician comes out while she's gone, finds burns on the outlet matching a high-resistance connection, replaces the outlet, puts everything back, and leaves. Shortly after, fire, behind the bed where he replaced the outlet.

Best explanation I could come up with was that the lamp cord was damaged and arc'd, which both tripped the breaker and later started the fire. The electrician solved the wrong problem, but didn't actually cause anything new to be wrong. Now, as an engineer, I know that a high-resistance connection does not trip a breaker. (Unless you're running some very large non-linear load, I suppose, that draws more current to compensate for the reduced voltage, but that's not this case.) But should an electrician have known that? What would a reasonable electrician have known? I still don't know, but I wonder.

What's the most interesting case you came across?

Oh, this one was good.

Setting: a walk-in freezer in a third-story office space. (I think they kept food samples for a sales department.) Being in an office space, there was a sprinkler in the freezer. If you do it right, that's not a problem. And they didn't have problems, until one night the sprinkler suddenly went off for no apparent reason. No fire, no impact to the head, just lots of water. They caught it pretty fast, not much damage.

Until it happened again, and this time it was hours before anyone stopped it. The law office on the floor below was pissed. (SO. MUCH. PAPER.)

The only thing in that freezer of interest was the evaporator coil. We looked at it and discovered it was not wired according to the drawing. The defrost timer was bypassed, meaning the defrost resistor was on all the time. There were maintenance records of not long before the incident. A tech came out, determined that the defrost timer was shot, and ordered a replacement. Later, another tech came out and installed the replacement. Still later, a third tech determined that there was a refrigerant leak.

Hypothesis: the first tech bypassed the faulty timer, in order to get the freezer back online. But he didn't document that he did that, so the second tech didn't know to put it back the right way. This isn't normally a problem, because the heat pump can easily get rid of all the extra heat that resistor generates.

Unless the refrigerant all leaks out and the heat pump shuts down. At which point we now have a 100W resistor dumping heat into an insulated box 24/7.

We thermocoupled up the room, turned it on, and waited. After eight hours it was over 140 degrees in that space. It would easily have set off a sprinkler head.

Hm. I don't know about most interesting, but this is up there.

One of the first ones I did was a failure in some large (small utility scale) natural gas generators. Parts were corroding well before expected service life. They'd replace the parts, and they'd corrode again. Their big five-figure copper heat exchanger and everything downstream was just getting coated in this green metallic gunk.

Turns out the heat exchanger had a temperature set point, and they'd set it too low. Water was condensing out of the fuel stream, but still in the presence of the other pressurized gasses in the fuel. Those gasses included carbon dioxide. That makes carbonic acid, more commonly called seltzer water. The seltzer was dissolving their copper heatsink, then getting blown downstream to evaporate, depositing copper oxides on every surface they could reach.

Amusingly that problem isn't at all electrical.

Interesting. My (natural gas powered) pool heater actually has a warning in the manual about this--that setting the setpoint too low will cause the heat exchanger to corrode.

Oooh! Neat!

Good day Mr. Collings, thank you for taking the time to do this AMA

As someone with zero knowledge in electricity, I would like to ask, in case there's a fire because of electricity, how can we know the source of fire? I mean, is there a special sign or something?

Ha! That's a pretty involved question, actually.

So we talk about fires having origin and cause. This is all formally defined in NFPA 921, which I haven't lived in lately. But informally, the origin of the fire is the place it starts. We determine that by reading fire patterns, which is a whole science in itself that I only dabbled in. I was a CFEI to help me work on suspected electrical fires, but there were full-time fire investigators who saw more fires in six months than I saw in my whole career. So often, there was a lead fire investigator who determined the origin, then brought me in to consult on cause.

The cause of the fire is the combination of fuel, ignition source, oxidizer, and circumstances that bring them together in a self-sustaining reaction. Generally, once you find the origin, you start looking for ignition sources in that area. That's often when we get into "yes, the cause of this fire was electrical"

I’m super paranoid about electrical fires for some reason. Before I travel, I unplug everything. Is that crazy? I had a toaster oven and threw it away when someone said they cause fires. Also crazy? When my heat broke, I refused to get a space heater since I was convinced it would kill me. Probably also crazy. I used to keep all my kitchen countertop appliances unplugged until I used them, which I’m sure is crazy, but that got to be a pain in the butt. I have an electric blanket and I keep that unplugged unless I’m currently using it.

The one thing I do that I’m sure is risky and you’ll probably tell me is crazy - I have heating pads that I leave plugged in. They’re turned off (and have a timer where they turn off after 2 hours on their own - I’m also not a diabetic). I use them every night and sometimes have left the pad on the bed when it was turned off. That’s crazy, right? Probably will kill me someday.

I’m super paranoid about electrical fires for some reason. Before I travel, I unplug everything. Is that crazy?

The engineer who trained me said he did the same thing. I just asked, "Wait, every time you plug and unplug your appliances, don't you increase the chance of a high-resistance connection which could--" "SHUT UP!!!"

Sometimes in life there's what we call "residual risk." Even after all safety precautions are taken, there's still some chance something bad will happen, but the benefits outweigh the risks, so we do it anyway. The risk reduction of everything you just said is non-zero, but it's very, very small. The harm caused to you by your stress over it is almost certainly greater. The risk you take driving where you're going is definitely greater.

Your use of heating pads sounds fine to me (though I'm not a medical expert). Toasters are generally quite safe, as long as you don't shove paper in them or something silly. Space heaters are generally even safer. Are they 100% safe? Absolutely not. What is? But their risk level is small enough to be acceptable.

This actually made me feel tons better. Thank you!

I'm glad! I often use the risk of driving as a sort of floor. If the risk of a thing is less than the risk I take driving every day, then it's not really rational for me to worry about it too much.

Have you had any "that was the last thing I expected" moments ?

Well, there was one where the proof surprised me.

The case involved a residential backup generator with an automatic transfer switch. There was a planned outage in the neighborhood. Linesman was working on the lines and got shocked, and very nearly died. The generator had backfed into the utility grid, which should not be possible with an ATS. (Why he hadn't grounded the lines before touching them is a question for his employer. Nobody asked me about that one, unfortunately.)

There were two panels in the house garage. One was powered by the ATS, the other was tied directly to the utility. We were shown pictures of a jumper from a load breaker on one panel to a load breaker on the other, which is not kosher in all sorts of ways, and would explain the backfeed phenomenon. I drove through a literal tornado to get to the scheduled inspection so I could see these jumpers, only to find that they'd been thrown in the trash a year before by an engineer whose mandate was to make the utility safe to work on. (So yeah, good call on his part, for sure, even if it screwed up my investigation.)

The electrician who had installed the generator years before swore up and down he had not put those jumpers in. The homeowner said the system had always worked fine, and nobody else had ever worked on it. One of them was lying. How could we tell who?

The homeowner was lying. Because if those jumpers had always been there, the generator would always have been tied to the grid. That means during every outage, it would have tried to support the entire neighborhood, and tripped out immediately. It could never have worked. If it ever worked, the jumpers weren't there, and then got added by someone to make the generator support the whole house rather than one panel.

Of course, if the electrician had followed procedure, pulled a permit, and gotten his work inspected by the city, he would have had them backing him up as well. So that's a lesson too.

I recently bought a home from the 70’s that hasn’t been updated in any way. The breakers fall out of the panel when you try to switch them off. But the house has two original fire extinguishers one dated from 1971 and the other from 1976. I’m wondering if they pose any type of exploding threat and how I should safely dispose of them (already bought new ones)?

Oh fuck, get that panel replaced tomorrow. That's a hazard in a few ways all at once.

Ask the fire department about disposing of the extinguishers, they'd probably know.

How common is insurance fraud as % of claims? Any typical fraudster profile?

Very rare in my experience.

I did hear a story from a colleague. As I recall, some piece of logging equipment caught fire at a worksite in the middle of nowhere. The workers claimed they left the site for lunch, went into town, came back, and the equipment was toast when they returned. Hm, says my colleague. You're an hour from town. You would never, ever take three hours out of your day to eat lunch. You're lying to me.

Now, that may be because they set the equipment on fire in order to file an insurance claim. But he concluded that was probably not what happened. The most likely explanation is that someone screwed up. They set the thing on fire on accident, through bad maintenance or usage, and didn't want to get fired by their boss. In trying to cover up their stupidity, they made it look like they committed a felony.

I did have another case where I was pretty confident the insured lied to me to cover up a mistake they made, for similar reasons. So if I can draw a straight line between two points, that might be it.

Now, I've heard of more outright fraud in the area of roofing claims, from structural engineers.

So do you mostly operate on the old "don't ascribe to malice that which can be explained by stupidity?"

Yes, but conversely, sufficiently advanced stupidity is indistinguishable from malice.

What's the most improbable set of circumstances that led to a reasonably clear conclusion? As in, if any one of these factors had been a little different, it wouldn't have happened, but they just Rube Goldberged into failure and fire.

This is a great question but I'm not coming up with a good answer right now...

How often are rodents the cause of fires in office buildings?

Couldn't put numbers on it, but it's a recognized thing.

How much do forensic electrical engineers make, and how do you get into the field?

Looking into switching careers and this sounds fun

Probably comparable to design engineers, most companies have a pretty heavy productivity bonus structure, but how much work you get is somewhat beyond your control. Typically you need a PE and a decent bit of hands-on experience, it's not the first engineering job most people should have.

I'm about to start a reliability engineering internship where part of it will be investigating machine failures, any advice on the overall approach when looking for issues and causes?

Know the machines and their history of past failures. Most things fail in just a few typical ways.

Very interesting AMA, thank you for doing this. I am a building/electrical inspector, what are the most common code related issues/potentials for fire in both residential and commercial construction?

Well, it's not a fire issue specifically, but I do think there's a problem with freezers in garages, since we're talking. I believe I'm both required and forbidden to put mine on a GFCI. Any thoughts there? :)

When it comes to new construction, the big threat is always that it's going to be done cheaply by inexperienced people. They'll use wire that's too small, staple through the insulation, put too much stuff on one breaker, that kind of thing.

Hi there Stephen, thanks for doing this! I have a light fixture in my bathroom that was recently recalled with a hazard of "The internal wires in the lights can be damaged, posing an electric shock hazard to the consumer."

The cost of labor, buying a new fixture, etc. isn't insignificant, so I'm wondering if this actually poses a risk to us to actually combust or create a fire or anything. I'm sure the advice will be to replace this, but I'm curious - Does this actually pose any active threat or risk to my family or if this is just the manufacturer covering their rears?

Thank you!

Here is a link to the recall

If they're issuing a recall it's because they don't want to get sued because someone got shocked to death.

Do you have a top3 list of things to do/check on a daily/weekly/monthly bases so that my house won’t burn down?

The list can also include a significant “DON’T”

Hm. Regular checks. I can't think of many, honestly. I would say you should definitely have smoke detectors, make sure to replace them every ten years or whatever they specify.

Once and for all, do I need any Tripp-lite surge protectors in my house, or would any Home Depot hdx/belkin branded power strips suffice?

I have no data on this, sorry.

I was told (by a firefighter, no less) that if I ever wanted to burn down my house and make it look like an accident, get out a box of Hamburger Helper, put the beef in the pan, start cooking and then "realize" that you ran out of an ingredient for the recipe. Leave your house and go to a store for the ingredients.

After I typed this, I think he said make sure you have two pounds of hamburger and the family size box. I don't own a house, so I am not looking to do anything like this in the near future. Does this seem like a probable scenario?

Edit: Just realized the fires you investigated were electrical in nature. Ignore this question if you don't have an answer!

I suspect what he meant was that it might be difficult to prove you did anything on purpose rather than on accident. But then, now this conversation is on record, right?

If you ever were a victim of damages due to an electrical fire, would people suspect you staged it for insurance fraud? (I.e. is it something you think you could pull off?)

Lol I don't know what they'd think, really. Could I pull it off without leaving enough evidence to prove to a jury I did it on purpose? Probably. Except they'd find this Reddit post, and use it as evidence that I knew I could do it. And since I know that, me saying it is evidence I wouldn't do it. But since they know that I know that they know that I know, clearly I cannot choose the glass of accelerant in front of you!

I'm not really sure what anyone would gain from that, though. For insurance fraud to make sense you would have to have some pretty perverse financial setup. Desperately need to sell your house and can't, for example. Doesn't apply to me. I might have the means, but I have no motive, and motive is a big part of arson investigations.

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That's really outside my wheelhouse, and it wouldn't be appropriate to speculate on so little data.

How did you get started in this? Do you only have an electrical engineering degree, or one related to criminal justice/forensics as well?

I spent ten years in product design, got my PE, and then saw an opening and applied. My employers trained me in all the forensic stuff I needed to know.

Whats the most effective thing the regs require, and what's the most pointless?

I doubt there's anything truly pointless in the NEC. Everything in there is there because someone somewhere found a problem that made something unsafe.

The most effective thing is probably just basic stuff like "use wire big enough that it won't melt under the load."

What would you say is the most common failures you see in fire alarm/suppression systems that end up causing catastrophic damage or loss of life?

My personal experience in that is limited, but from the data I've heard, a properly-designed and properly-maintained suppression system will save the building. A large fraction of cases where that doesn't happen are cases where either the building usage changed (so the existing system wasn't designed for the fuel load now in the building) or someone had a leak that needed fixing, found that inconvenient, and just turned the system off instead.

Have you had any experiences with knob and tube wiring?

I’ve heard a spectrum of differing opinions from electricians. Some say it’s fine and safe as long as it hasn’t been spliced, and is in generally good condition. Others say it’s dangerous.

I never personally saw any, no. Not much construction that old in my area.

Do you run across a lot of problems caused by bootleg grounds?

Not one. But the problems you'd expect from that are more along the lines of personal injury during a fault condition, when some contact surface that should be grounded becomes energized due to all the neutral current. I'm sure that's happened, but I haven't seen it.

How do some one who have no idea about the job get to where you are ?

What course did you study ? What additional training did you get before you are set of the path of getting here.

And advice for someone who wants to get to where you are now.

Thank you!

I became an electrical engineer, worked for several years, and got my PE. The best field of work to prepare for forensics would be anything that gets your hands dirty on a lot of different kinds of equipment and systems.

Did your employer or any other person employing you or seeking your services ever ask you or imply that you should falsify your reporting?

Not once.

What type of work do you do now?

I'm a power systems consultant, also dabbling in classified hazardous areas (explosive atmospheres).

Are all your opinions within a reasonable degree of scientific probability?

I would not express a formal engineering opinion if it was not supported by evidence to within a reasonable degree of engineering certainty.

I was just messing around but in my experience engineers have been some of the most dubious experts I've encountered. They're not used to being deposed/cross examined by attorneys with STEM backgrounds and they're sloppy. I often wonder how they'd feel presenting their opinions to their academic peers.

My first employer was rigorous about that to an absurd degree. Our reports were not allowed to use any word ending in "-ly" on the grounds that it was ambiguous. They made exceptions for "July." Even "only" was not allowed, even though that's the opposite of ambiguous. They had a long list of no-no words, formed by decades of experience with attorneys picking at things.

Have you ever seen a fire started by plant grow lights?

No, but I've heard stories. One coworker said he got to a scene where the insured had "helpfully" moved all the furniture out of the burned room, annihilating any fire patterns he could have used to identify the origin. When he asked if they had photos of where the furniture used to be, they kindly showed him some, which included their grow operation.

I’ve heard that jamming or spraying certain objects or substances into wall outlets causes untraceable fires. Is there any basis to that?

I categorically decline to comment on any possible ways to create untraceable fires. If I knew of any it would be totally socially reprehensible for me to share that.

Was expecting to hear something along the lines of “no matter what is used there’s always evidence left behind”. Interesting, thanks!

Well, if anyone had started an untraceable fire I by definition wouldn't know about it!

What is the best way to set a building on fire without leaving evidence?

I categorically decline to comment on any possible ways to create untraceable fires. If I knew of any it would be totally socially reprehensible for me to share that.

Just plug in a bunch of dollar store extension cords, I’ve heard those are a disaster waiting to happen

I tend to trust anything with an ETL or UL or equivalent cert to be at least constructed correctly to not cause fires or shock people. But that doesn't mean it's not so cheaply made that trivial abuse could make it become dangerous.