Electronic workbench fire

[ez24]

Hi

Found an interesting video on this forum at https://www.eevblog.com/forum/reviews/zd-939l-hot-air-station-2-minute-teardown!/msg1070546/#msg1070546

The fire starts at about 50 sec in the upper right, it starts to glow first.  It is a soldering station.



Does anyone have any electronic workbench fire videos they wish to share?

Whats with the toilet seat - electronic one?

[glarsson]

Whats with the toilet seat - electronic one?

A small one with a magnifying lens in the seat? It's something else; something rather common on the workbench.

[BillB]

That's scary.  And that's also why I have a camera pointed at my workbench as well.

[glarsson]

About that "toilet seat": You should close the lid when leaving the bench if your shop has windows. Otherwise you might find a second method to set your workbench on fire.

[bd139]

This is one reason I dumped the T12 iron I had and bought a Metcal. 90% less likely to burn your house down.

[hans]

The reason why I've got all my gear hooked up to a single circuit breaker such that I can turn off my whole bench when I'm out.

Ofcourse the point is to then actually use it..

[bd139]

Actually when I did my amateur radio license stuff recently that was in the exam. Single isolation switch on the bench. Basically so whoever walks past, smells bacon and finds you smouldering away stuck to an anode cap on a 1KW valve PA on a bench can turn it off so they don't end up long pig as well.

[aargee]

It looks like the fan failed in the handle of the hot air gun, the element just did it’s thing.
It should have been off when on its holder, I try and keep my Chinese one manually off when I’m not at the bench.

[metrologist]

bidet repair gone wrong

[NivagSwerdna]

I never leave my combined solder/hot air station plugged in when unattended.... I came back to it once and found it very hot... even when OFF

[Monkeh]

The reason why I've got all my gear hooked up to a single circuit breaker such that I can turn off my whole bench when I'm out.

Ofcourse the point is to then actually use it..

Use the light switch.

[richnormand]

Interesting video.

I have a Sunko (ebay look alike) hot air station with the same hot air wand as in the video.
When I turn it off after use the fan will operate for a while to cool the tip.

But I noticed that when I turn off the main power to the whole workbench, when I leave for an extended time, on return, when I power up the bench back on the cooling off fan on the Sunko does turn on for a while and then turn off, like in normal use.
That is while the main Sunko front switch is off. That means the unit is still live even when the front panel switch is off, all the time.

I guess a simple line transient could get an SCR (for the heater) full on with no fan, depending on the logic used to control the unit...

Thanks for the video indeed. It should get more visibility.

My unit is getting pulled tonight and will get a real on/off switch hooked to front panel right at the mains right now....

[Brumby]

I have one of those cheap dual hot air/soldering workstations and it does have a mechanical "off" switch ... on the back panel.  This makes it inaccessible unless I pull it out of the little shelving unit I made, so it just stays turned on.  However everything in that unit runs off a master switch which only gets turned on when I want to do soldering work, heatshrink or dry something off - or if I want power from a bench supply.

This rear mounted switch actually works in my favour, since that unit will always have something displaying on one or more of its red LED displays and being in a prime position in my peripheral vision, I have a "power on" indication.

I also have a master switch for my computer (and associated peripherals) and another for the photographic lighting.  Yes, it's a very multi-purpose work desk.

[SparkyFX]

Got a similar rework station, they do have a delayed shutdown to cool the heater down, therefore prolonging its lifetime, automatically switch it off while in its bracket... in this case maybe the source kept supplying power to the heating element anyway (no visible air flow in the video).

I try to not keep hot tools next to inflammable material and switch the whole unit off when leaving the bench for some time, because you never know and there is no perfect product (even repair tools break, actually they are more likely to break because of additional abuse).

[amyk]

I guess a simple line transient could get an SCR (for the heather) full on with no fan, depending on the logic used to control the unit...

Yes, these mains-element hot air stations connect the heater directly to the mains using only a triac. If it fails shorted, the heater turns on while the control electronics which power the (low voltage) fan don't... and a meltdown soon happens.

I suppose a simple workaround might be to connect the fan to the element through a simple capacitive dropper or similar, so that whenever the element gets voltage, so does the fan.

Thermal fuses might be an option but they don't seem to go much beyond 240C which is a normal operating temperature for a hot air station.

[Tom45]

Back when I was in college in a dorm room I was sound asleep on my bed and my roommate was studying at his desk. Then his desk lamp erupted with an impressive shower of sparks that would put a roman candle to shame. I jumped up still half asleep and ran around the room in a panic. By the time I became fully awake, the lamp had burned itself out.

I now have separate outlet strips. One is for devices that need to be on all the time such as GPSDO and counter/timers and bench meters that go into standby when you use their power switch. One is dedicated to soldering station and hot air station. I turn that off whenever I leave the room.  Other circuits are for test equipment such as scopes that can be turned off when not in use, and a circuit for powering devices under test.

[Dubbie]

Hrm I have one of these things....

Makes me realise that I should turn it off when I am not using it. Which I don't at the moment...

Good cautionary video!

[stj]

nothing is "safe" to turn your back on.

i have seen the older type of cheap hot air unit with the pump in the base  latch the heater on and glow - destroying the handle,
i have had an old analog weller desoldering unit glow red from a failed triac,
i have had an old steel-cased fan heater shower the floor with sparks when the gromet failed and the case rubbed into the power cord,
and most annoying, i have had a regular lamp bulb explode when i switched it on.
worst part about that was it was on the staircase, so i had to climb a ladder to use long-nose pliers to try to extract the lamp base from the holder afterwards!!

[Red Squirrel]

bidet repair gone wrong

The thermal design of it just didn't account for Taco Bell.   


Actually this reminds me, I was testing water sensors once, just a cheap ebay buy.  I set it on the bench and put a drop of water on it.  Turned around to look at my computer to see if the alarm condition came in.  Turn back around and immediately I have smoke in my face.  The sensor caught on fire.  I guess these sensors are for if your insurance covers fire, but not flood so you stick these around your house. lol.

Still have not done anything with them.  I imagine adding a current limiting resistor in right place would stop the fire from happening.

[Eka]

I never leave my combined solder/hot air station plugged in when unattended.... I came back to it once and found it very hot... even when OFF

That's why I have power strips for powering groups of stuff on my bench. One is solely for the lighting. Another is for the computer. The next is for test instruments like the oscilloscope. Another is for the soldering irons, etc. Lastly there is one for powering projects. I can turn everything off at the line conditioner, and the computer and lights off at the UPS. This allows me to test circuits, and have the heat producers like the soldering iron off and unpowered when not needed. Likewise when I'm soldering up a circuit I can have the test instruments and project power supplies off. When I walk away from the bench I just have to switch off the power strips and everything is off.

Oh, I don't trust my soldering equipment. They sit in a steel pan when not in use. They could burn up in it, and not burn down the place.

I also have a medium sized CO2 fire extinguisher close at hand in case it's needed.

[james_s]

I never leave soldering/desoldering gear turned on and unattended for any longer than it takes me to go take a leak. My bench is all plugged into a power strip which also powers the light above it. I've gotten in the habit of shutting it off whenever I'm done working for the time.

[richnormand]

To follow up on my previous post.

"My unit is getting pulled tonight and will get a real on/off switch hooked to front panel right at the mains right now.... "
First picture shows an "OFF" means "OFF" switch that is now installed on the front panel with a monitor light.

From amyk:
"these mains-element hot air stations connect the heater directly to the mains using only a triac. If it fails shorted, the heater turns on while the control electronics which power the (low voltage) fan don't... and a meltdown soon happens.

The second picture is the triac that controls the heater and a quick look at the circuit looks like indeed it could possibly just come on, with no fan, if shorted by a line transient."

I looked at my Pace solder iron, the Pace desolder station and the Weller WX2 and when they are turned OFF at the main switch they are OFF, only this Sunko was still alive with full AC when officially in the OFF position.

[Dubbie]

Good idea. I am going to add a similar switch to the front panel of mine.

[wraper]

It looks like the fan failed in the handle of the hot air gun, the element just did it’s thing.
It should have been off when on its holder, I try and keep my Chinese one manually off when I’m not at the bench.

Nope, as written in description, station does not have power switch. It just started heating by itself. I guess triac failed short.

[wraper]

I suppose a simple workaround might be to connect the fan to the element through a simple capacitive dropper or similar, so that whenever the element gets voltage, so does the fan.

Thermal fuses might be an option but they don't seem to go much beyond 240C which is a normal operating temperature for a hot air station.

Thermal fuse doesn't need high temperature rating. All you need is placing low temperature thermal fuse just  before the heater. Thus if heater is powered in the absence of airflow, it will trip. I just took apart handle of my Quick 861DS and yep, it has thermal fuse before the heater.

[IanMacdonald]

That looks like a certain popular heat gun.  Although these things are cheap and useful I'd strongly advise against leaving them on standby unattended.

In fact after seeing that I think I'll investigate fitting a thermal fuse to mine.

Though I'm wondering if there should be a recall on them.

[CopperCone]

I leave that piece of shit unplugged. Fucking classic chinese engineering. That yihua is the shadiest thing on my bench.

I love when people argue with me about flame retardant plastics and call me paranoid. Should be built to prevent fire in any short that can occur and not trigger the fuse, otherwise you can reasonably blame the fuse. In any mode of operation. It should be glowing red fucking hot but not catch on fire.

Also if you have a hot air station, I highly recommend experimenting with it at maximum settings to see where you can place it incase the heater and fan turn on, so you don't torch something with the hot air.

[langwadt]

The reason why I've got all my gear hooked up to a single circuit breaker such that I can turn off my whole bench when I'm out.

Ofcourse the point is to then actually use it..

get one of those timers where you push a button and it'll be on for xx minutes

[james_s]

and most annoying, i have had a regular lamp bulb explode when i switched it on.
worst part about that was it was on the staircase, so i had to climb a ladder to use long-nose pliers to try to extract the lamp base from the holder afterwards!!

My grandpa had something similar to that happen, the bulb came unglued from the base and the lead wires crossed. He flipped the switch and something hit him in the back of the head. The wires had vaporized and dropped the bulb which happened to be directly above.

The flash and bang failure mode is one of the things I miss least about incandescent lamps. When it happens when walking into a dark room at night or when turning on the bathroom light in the middle of the night it would almost give me a heart attack.

[aargee]

It looks like the fan failed in the handle of the hot air gun, the element just did it’s thing.
It should have been off when on its holder, I try and keep my Chinese one manually off when I’m not at the bench.

Nope, as written in description, station does not have power switch. It just started heating by itself. I guess triac failed short.

Err, nope, even the Russian translation via Google of the Youtube description doesn't make it clear if there is a power switch, but looking at stock photos of the unit - it does not appear to have one. Either way, no fan = incendiary device if the heater is on.

[IanMacdonald]

Just had a look inside my Atten 858D and the front panel switch is definitely in the mains lead. Also, the barrel of the wand has what looks like a thermal cutout just inside the end of the cover. 

I tried obstructing the fan inlet (Much the same as a failed fan)  and nothing untoward happened. The regulator just cut the heating power back to keep the same temp.

So, this one seems relatively safe. I'd advise switching off when not in use though, once it's gone through its cooling cycle. (The cooling cycle is probably there to ensure it doesn't trip the thermal cutout through residual heat seepage along the handle.)

[wraper]

Lukey 852D+FAN

[wraper]

It looks like the fan failed in the handle of the hot air gun, the element just did it’s thing.
It should have been off when on its holder, I try and keep my Chinese one manually off when I’m not at the bench.

Nope, as written in description, station does not have power switch. It just started heating by itself. I guess triac failed short.

Err, nope, even the Russian translation via Google of the Youtube description doesn't make it clear if there is a power switch, but looking at stock photos of the unit - it does not appear to have one. Either way, no fan = incendiary device if the heater is on.

I rechecked it, it is explicitly written in comments. Description says switches were off. I do speak Russian.

[stj]

then it was the older type with the pump in the base - those use soft switching for the cooldown cycle to function.
that's the type i'v seen the triac latch and melt the handpiece - i still have the base.

[aargee]

It looks like the fan failed in the handle of the hot air gun, the element just did it’s thing.
It should have been off when on its holder, I try and keep my Chinese one manually off when I’m not at the bench.

Nope, as written in description, station does not have power switch. It just started heating by itself. I guess triac failed short.

Err, nope, even the Russian translation via Google of the Youtube description doesn't make it clear if there is a power switch, but looking at stock photos of the unit - it does not appear to have one. Either way, no fan = incendiary device if the heater is on.

I rechecked it, it is explicitly written in comments. Description says switches were off. I do speak Russian.

Advantage Wraper - to use a tennis parlance. :-)

[wraper]

then it was the older type with the pump in the base - those use soft switching for the cooldown cycle to function.
that's the type i'v seen the triac latch and melt the handpiece - i still have the base.

Both Luckey 702 and 852D+FAN have blower fan in the handle.

[richnormand]

Both Luckey 702 and 852D+FAN have blower fan in the handle.
[/quote]

OK it has a fan integrated in the handle.
Are these units adjustable for air speed and heating separately?
If it has a similar control circuit for the fan and a separate similar circuit for the heater and a soft line switch could you not look at a similar failure mode? 

[metrologist]

I think I shall unplug mine, even though it has a hard switch. I don't use it enough to leave such potential connected.

[richnormand]

I think I shall unplug mine, even though it has a hard switch. I don't use it enough to leave such potential connected.

Go inside and see how the on/off switch is wired...
Don't turn it on take it apart....

[metrologist]

did that and the hot is routed through the fuse and switch. Still don't trust it.

[TheNewLab]

hum, more power strips, check my fire extinguisher, etc
on positive side I have a smoke alarm in the room linked inti the building and direckly to the FD, about 6 blocks away.

already set it off just from splices and a lot of heat shrink - detects excessive heat too

A restraruant in a very old building requires all that..but no AFCI circuit...

Thanks for this topic, I have so many of econo-Chinese equip