blue flash, baseboards not working

[JoeNorm]

Hi All,

My Sister called and described seeing a subtle "blue flash" and a pop sound in her living room. She checked the service panel and living room baseboard 240v had tripped. I told her to carefully flip it back on and see what happens. It remains in the ON position but her heater appears to be not working now. I had her turn the breaker back off for the time being.

Unfortunately she does not live close so I told her she'll have to call an electrician at this point.

But...it did make me curious what happened. It's older baseboard with a twist-knob round thermostat. Maybe a loose connection somewhere?

Any ideas? And yes, I am a Electrician even if I don't sound like one in this post.

 

[LarryFine]

I'd start by checking all joints at both ends, regardless of which end the T-stat and/or feed are/is.

Simple testing should show 240v across the T-stat when it's off, and across the element when on.

 

[ptonsparky]

To trip the breaker, it needed a fault of some sort. A flash could be an end that burnt free of the thermostat then contacted the heater frame or fell against the other hot. Or the element faulted close enough to one end of the heater to cause an overload.

 

[James L]

There are crimped splice points in both ends of a baseboard heater. If one of those caps became loose, it could overheat the short piece of wire from there to the element, which could short to the frame.

If there was a noticable flash, probably not inside the ends, per se

There's not very much going on in one of those. Only a small handful of possibilities

 

[jusme123]

Was there an awful smell a fried rodent?

 

[Fred B]

Had a service call very similar. Customer called about having a circuit tripped after seeing a flash of a of light (an arc) and a loud popping sound near the electric baseboard heater and the livingroom light went out, she then shut off the heater at tstat. She also stated there was a slight burning smell that went away. Went to investigate, checked the panel board for the breaker that tripped and evidently husband had reset a breaker but she didn't know which one (apparently the one for the light). Only breaker left in off position was a double 20. Went to check baseboard, visually inspected and metered no power but found no shorts. Turned breaker on, it held, and tested again found no apparent issue with heater. Did find minor accumulation of fir and dust on fins of heater, (HO has a dog and a cat). Removed fir and that did have a slight burnt odor. Multiple pieces of furniture were moved prior to my arrival. One included a floor lamp that was behind a recliner. Reinterviewed HO about the incident she basically restated the same issue and that she was sure it was from the heater she saw the flashes. Went to check on the light that she said was on at the time, the floor lamp, went to plug in and found no outlet near the stated location of lamp. As I was taking the cord from around the lamp where it had been draped my had felt a burr on the cord, checked it and found a burn thru and exposed copper. Again asked HO where this lamp had been plugged in, had it been sitting next to the recliner (I already knew as indents in carpet indicated the location of recliner near the heater). She replied yes, I then asked where she had the lamp plugged in as there was no plug near the recliner. (It became obvious but want her to confirm). It was plugged in on opposite end of baseboard, she admitted that it didn't reach and had used a small extension cord that was laid in front of and on the baseboard. She had been cleaning the day before in that area and set the cord up to clean, and that night was the first the heat had been used that season. Evidently the flashes (arcing) was the lamp cord had fallen into the heater and made contact with one of the element fins, burning thru and arcing and causing the breaker to trip on both the lamp circuit and the heater circuit.
Bottom line home owners lie (or atleast leave out important information) and by doing so cost themselves a lot of extra labor.
So there maybe some additional information the OP hasn't gotten from sister as it relates to the heater when it stopped working.

 

[kwired]

The blueish flash was an arc flash that accompanied some short circuit or ground fault. Whatever happened probably burned itself enough to clear the fault but leave the circuit open and reason it now doesn't work. Heater could have been hot when the fault happened and now is cooled and whatever faulted has thermally contracted which may help open the fault path.

What I have seen most often is either faulted element near an end or pinched wiring in one of the end boxes. Fault in middle of element likely has enough of element in series that there is too much of the element in series to have a high fault current.