[Read!] Damn Near Burned The House Down - Space Heaters

[GeneT45]

Interestingly enough, I have not had any nuisance trips due to the things you might suspect (like vacuum cleaners and other motor loads). The issues I have seen seem tied to LED lighting. Again - there's no electrical spec provided to tell you exactly what situation / combination of situations is determined to be an (incipient) arc fault. I should have mentioned that my AFCIs are Square D Homeline circa 2019.

According to the US NFPA cooking was the leading cause of housefires. https://www.nfpa.org/Public-Education/Fire-causes-and-risks/Top-fire-causes/Cooking.

Also from NFPA:

• In 2015-2019 electrical distribution or lighting equipment, such as wiring, lighting, cords, and plugs, was involved in an estimated average of roughly 32,620 reported home structure fires per year. These incidents caused an average of 430 civilian deaths, 1,070 civilian injuries, and $1.3 billion in direct property damage annually.
• Electrical distribution or lighting equipment ranked first in direct property damage, and third among the major fire causes in the number of home fires, home fire deaths and home fire injuries.
• Wiring and related equipment accounted for 6 percent of all home fires and 11 percent of all home fire deaths.
• Cords or plugs were involved in only one percent of home fires but seven percent of the deaths. Extension cords dominated the cord or plug category.

Source: NFPA's Applied Research Department


GsT

 

[epanzella]

I never use any of those plug in resistance heaters. You're betting your life on a 25 cent chinese limit switch.

 

[JohnDB]

In my experience most households where "Bubba" has been playing electrician they treat the neutral and ground as one in the same...this is the cause for GFCI failures and Breaker failures.

Now this usually causes higher electric bills as current will backfeed through the panel when the load becomes unbalanced.
AND
I can take a wire coming straight off a breaker and put it to a ground rod 1500 feet away pounded into the dirt and the breaker will never trip....put one tiny ground wire from the panel to the ground rod and it trips instantly.
I've done this to demonstrate to apprentices how important that ground wire really is. And this also needs a clean neutral for GFCI to work properly. GFCI might set with a dirty neutral and ground...but don't expect it to work.

Then with plugs....
Most plugs in houses are through wired....meaning that the juice goes to more plugs (and sometimes lights) down the line.

Most plugs are rated for 15 amps but on a 20 amp circuit...but since they are through wired that plug has 20 amps running through it. NOT GOOD!
Those spring clips like on a wago blocks do not load test for plugs...arcs, burning and etc are common when 20 amps go through them. They are fine for final connection for a light fixture that uses a CFL or LED....but otherwise no.

Arc fault breakers do not work for CFL lights....ever. unless they have the old style ballasts in them that are the size of a brick. Even then it's not likely to be stable. And just because you put in a new fixture that doesn't mean that the worn out wall switches aren't arcing when you turn on the lights...or that all the wire nut joints are made well for the circuit. It only takes a small arc for them to pop. And it can be frustrating to find the issue.

House wiring is usually done by the lowest paid electricians out there...if they were any good they usually do commercial or industrial work. It pays much better.

 

[pontiac428]

I never use any of those plug in resistance heaters. You're betting your life on a 25 cent chinese limit switch.

While I understand the sentiment, how is that different from trusting the throttle position sensor in your drive-by-wire car? I mean, the only potentially catastrophic fault condition for a NO switch on a resistance heater is to get fused shut, but the 24 ga wire at the switch makes a pretty good fuse too.

I live in a neighborhood that was booming not long after San Francisco exploded from the invention of the steam ship. My house is 100 years old and entirely made of wood. In the last year, there were 3 house fires and 2 business fires near me, all cited in the paper as being caused by electrical. Some people are still on knob and tube, if they're stubborn. At least mine was converted to nonmetallic in the 1990's, but I wish I could have done the job myself.

Thank Dog my progressive state doesn't require arc fault yet. I can't control transient inrush to the capacitors on every device I own, and I don't want to run to the breaker every time I plug in my phone to charge.

 

[pdentrem]

I spent half the day trying to figure out why the lights stopped working in the bathroom after the hairdryer was plugged in. The GFI did not trip nor the breaker at the panel. This is an old house, plus 70 old, and the original electrician used short runs and junction boxes every 10 ft or so! Found the power feed line and both sides showed hot! So I was chasing that wire to find the other end and possible short. Thinking possible house fire! I ended up at the hall overhead light which was feeding the bathroom. No issues there! Followed the next wire from that overhead down to hall light switch and the box is stuffed. Moved things around and the problem disappeared. Put everything back together and no issue. I believe the wires were too packed in.
Pierre

 

[JimDawson]

Moved things around and the problem disappeared. Put everything back together and no issue. I believe the wires were too packed in.

Sounds like a loose connection, maybe a wire nut? I would recheck and tighten things. Loose connections can get hot and cause a fire.

 

[epanzella]

While I understand the sentiment, how is that different from trusting the throttle position sensor in your drive-by-wire car? I mean, the only potentially catastrophic fault condition for a NO switch on a resistance heater is to get fused shut, but the 24 ga wire at the switch makes a pretty good fuse too.

You just hit on the reason I don't have a drive by wire car. I don't leave a dryer running when I'm out or sleeping. I instructed my wife to never leave a clothes iron or curling iron on when she's out. All electrical resistance units have a limit switch to prevent them from a meltdown and it's the cheapest piece of crap you can imagine.

 

[Shotgun]

What if you have a fire in your shop and the insurance investigator finds a 20 amp receptacle on a 15 amp circuit? How's that going to effect your claim?

What if they find two 10A loads in a 15A plug? What if they find 10A loads on three different outlets that are in different rooms, but the same circuit?

 

[pontiac428]

You just hit on the reason I don't have a drive by wire car. I don't leave a dryer running when I'm out or sleeping. I instructed my wife to never leave a clothes iron or curling iron on when she's out. All electrical resistance units have a limit switch to prevent them from a meltdown and it's the cheapest piece of crap you can imagine.

I don't want you to take this personally, because I know it's safety assurance with you and not psychology, but this point of view is superstitious in a way. The belief in superstitions is similar to object permanence. Object permanence is part of Piaget's theory of cognitive development, where we learn that things don't disappear when we close our eyes, and when we put something in a box, it remains in that box.

In other words, the idea that a pilot light must be watched is usually outgrown by preschool, mentally. Funny how it gets some of us.

Object permanence is the understanding that objects continue to exist even when they cannot be sensed. This is a fundamental concept studied in the field of developmental psychology, the subfield of psychology that addresses the development of young children's social and mental capacities. There is not yet scientific consensus on when the understanding of object permanence emerges in human development.

Jean Piaget, the Swiss psychologist who first studied object permanence in infants, argued that it is one of an infant's most important accomplishments, as, without this concept, objects would have no separate, permanent existence. In Piaget's theory of cognitive development, infants develop this understanding by the end of the "sensorimotor stage", which lasts from birth to about two years of age.

 

[pdentrem]

Sounds like a loose connection, maybe a wire nut? I would recheck and tighten things. Loose connections can get hot and cause a fire.

I replaced every wire nut and tightened every screw as I was rebuilding the circuit. In the suspect box I used a couple set screw version as the regular twist type does not work as well with many wires.
So I just don’t like having that many wires in such a small box. I going to get a 20 cu in box and swap it out. I did find a couple spots where the plastic had been crushed and I am sure there was some leakage between a hot and neutral.