Spray Foam and Overheated Wire
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- เผยแพร่เมื่อ 27 ส.ค. 2022
- Another quick test to see what happens in a wall when too much electrical current flows though some typical household wire inside a wall. In this case, we try some hardware store type spray foam insulation around the wire to see how the combination of wire and spray foam reacts when a series of electrical faults might result in significant over-current in the wire. Of course different spray foam, cable, electrical current and how they are combined will produce different results - maybe better, maybe worse!
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Foams cure with reaction to moisture, hence spritz water on the surface first. Also, there are VERY few expanding foam can products that really pass the Fire Blocking properties, a huge fail in the various groups that test and certify building materials. DAP FireBreak Flame Resistant Sealant is one, that self-extinguishes when ignited, while most like Great Stuff are just orange versions of the same combustible foam. This video suggests that the quest for better home insulation could very well result in trapping overheating wires and risk of fire.
Thats interesting! So you are indicating that the Great Stuff Fireblock is not much different from regular Great Stuff, and the DAP FireBreak is much better?
"This video suggests that the quest for better home insulation could very well result in trapping overheating wires and risk of fire." Yes - exactly! No its a worst case for every thing scenario - but I sure would be careful with a cable expected to be used for extended period of time close to its rated amapcity in the middle of modern insulation in an already hot environment - ie running though an attic powering an air-conditioner in the summer. I would certainly increase the wire size a gauge or two from that required by code in that type of situation.
Very interesting.
I was surprised to see such a high temperature, 53C/127F at 15 amps. A bit of an extreme situation with the sun beating down, but not unreasonably so. I'm sure that's safe, but I can see why the rating for copper 14 is only 15 amps.
I'm also glad to see the spray foam doesn't just burst into flame. I'd expect some cheaper whiter styrofoam insulation might just do that.
And NM wire, more specifically NM-B, is rated for 90°C, vs the stuff before the mid 80s, which was good for 60°C. We should appreciate the NEC, and also understand we've come a long ways since the first code in 1897, much of today's code requirements came about at a great price, including loss of life.
Yeah! Take the temperatures with a grain of salt - I dont have 100% confidence in the IR thermometer when reading radiation from from small areas, but from past experience them temp is usually too low. I would be nice sometime to do the same with an expendable thermocouple right next to the foam and no "window" in the foam.
I was fully expecting a flaming bubbly molten mess. Like you said, good that it is relatively resistant to catching fire. Your comment got me wondering about not only plain Styrofoam but the better quality pink or blue rigid foam insulation. They shrink away from heat - might be worth trying one of those since that is such common insulation.
@@ElectromagneticVideos you know, I never thought much about those blue or pink foam insulation boards, and some of those, I cannot recall which, but it says "CAUTION: RISK OF FIRE, DO NOT EXPOSE TO HIGH HEAT OR OPEN FLAMES" or some similar wording. The pink panther brand foam seems to ring a bell, maybe because I loved the cartoon when I was a kid, and the 90s seemed to be a more carefree, innocent time. -)
@@Sparky-ww5re Thats funny - I was thinking of the the pink panther brand when wrote my previous comment. If I test some of that foam hope I dont put our favorite cartoon character out of his retirement job!
@@ElectromagneticVideos XPS (the pink stuff) is definitely more common than the cheaper EPS (the white stuff). It might be interesting to see how they both behave between walls with electric cable in them. In a basement it's fairly common to put in a layer of XPS to prevent water intrusion, then a layer of fiberglass inside a stud wall. So the wire woud be butted up between the two.
IIRC XPS is only allowed in walls if it's covered by a layer of drywall, since it can catch fire.
awesome video I run over 150 meters of extension cord i use a multi box in the paddock that will trip if 2 jugs are put on together i was a little worried about the 125 year old wiring from the cottage that I'm supplied by
Amazed how the foam didn't catch fire. Because you hear the legendary tale as follows. Back in the olden days, a homeowner blows a 15 amp fuse. When he replaces it, it blows again after a short time. Unfortunately this time, the homeowner is out of fuses, half the house is dark, the baby is crying, the refrigerator is getting warmer by the hour, and the hardware stores are closed on a Sunday afternoon. So the homeowner removes the blown fuse, slips a penny into the socket (back when pennies were real copper) and screws the fuse back in. The next morning a fire inspector goes through the remains of the house, and finds a scorched fuse box holding the penny.
Was a sparky for 50 years and did hundreds of service upgrades where I always removed the fuses . Only thing that I found a penny behind a fuse was in a little pig slaughterhouse that I replaced a 8 circuit fuse box with a breaker panel. Often seen old houses with over sized fuses. Scary when you came across all 30 amp time delay fuses. Told the homeowner that every new circuit breaker would be 15 Amps due to having all #14 wire and they will probably have problems with them tripping. Yep within a day they called and said I have to come back and fix tripping problem. Told them sure and it will cost several hundreds to run new 20 amp circuits. Laughed at them when they demanded that I fix their problem for free.
@@JohnThomas-lq5qp you gotta wonder how many homes were torched. Today's NM wire seems to be pretty fire retardant, but you'd wonder about the flammability of the old-style cloth braided NM wire, or the tar coated cloth on knob and tube. circuits. I've seen that stuff disintegrate at the slightest touch, particularly in light fixtures where 100 watt bulbs have baked the wires into place. People have installed 30 amp fuses to allow for the fact many decades ago, homes were wired with 30 to 60 amp services, sometimes with only 120 volts available, and one receptacle per room was normal, as were 2 to 6 circuits for an entire home.
@@Sparky-ww5re I can remember buying the old woven jacket what appeared to have some sort of black tar or pitch like material. If you had to pull hundreds of feet of it on hot days hands would be covered in black material. Can remember paying approximately $0.50 cent more for a 250' box of 14/2 Romex for for the new & improved maybe a thermoplastic cover around 1966. Was a lot easier pulling. Both types had what appeared to be TW insulation that if not severely overloaded lasted forever. Was told at an IAEI continuing education class that UL gathered hundreds if not thousands of samples from across the country of clothe covered insulation from old BX cable and old material covered type NM cable ( Romex ), type NM plastic covered romex that had type TW insulation and not sure if they included the far superior type NM-B Romex cable with appears to be type THHN insulation that started being sold in early 1980'S. All of the cable with modern type TW or THHN passed Megger test and for the most part we're in good condition. All of the cloth covered wires had problems.
I somehow missed you discussion here - just saw it - interesting! I'm a bit surprised the cloth covered cables did so poorly in the UL tests. Maybe the black tar contributed to flammability. I do remember it - got some leftover cable of that type after electricity was installed at our cottage/cabin in the late 60s. Of course ended up with tar on my hands. Oh - and it was aluminum cable!
I owned a hardware home center for 4+ decades. Constantly had to advise customers not to use higher amp fuses than what was blown assuming that the blown fuse was the correct amp. Area had lots of old
homes so we watched for anyone buying anything higher than 15A.
Peak season was electric space heater season.
Did you let the foam cure for 24hrs? It produces an exothermic reaction while setting up. Also flammability might be different.
Why don't you get some cheap thermocouples? A lot cheaper than an IR camera.
What model variac do you have?
It actually cured for a week - so many scattered showers that I wouldn't have been able to do sooner if I had wanted to!
I just got some thermocouples but they came after I sprayed the foam.
Its a cheap Chinese one. But the setup is a bit more than that: 120V -> variac -> 240:120 transformer -> AC output welder -> wire under test.
The variac is limited to about 10A out so I double the current out with the 240:120 transformer. That goes into the vintage welder which acts as giant step down transformer with a crude constant current source characteristic. Of course the welder would normally be plugged into 240V.
I do have vintage 20A variac, but the plastic that insulates the shaft from the knob disintegrated and I need to find something to replace it with. Once its going again I would not need the 240:120 transformer.
Have you considered picking up some bimetal temp probes to go with your meter? You could imbed the probe in the great stuff. I use a fieldpiece temp meter for hvac stuff. Interesting :)
Some arrived a day or two after I sprayed the foam. I'm going to order a bunch more expendable probes because I doubt I will be able to extract them from the gooey mess when I try pink rigid foam. Just look up fieldpiece - they are nice and not expensive!
Have you tested or are you gonna test the Fire Block spray foam versions?
You know, I should - I have used that Fire Block spray foam in my house! I'll do it sometime this summer - have to do it outside because of the fumes and its too cold for that right now!
I'd like to see how ceramic wire nuts compare to the usual I mostly see them in furnace hot surface ignitor and also twisted stranded and solid wire with just electrical tape like something you'd see on a trailer
I'll probably have to do another connector test and will include your suggestions. Thanks to your suggestion I learned something - I had to look up "hot surface ignitor" - had no idea such a device existed - I just assumed all were spark or pilot light based on the tiny sample set of boilers installed in houses have lived in. Interesting!
And I was about to fill a small hole coming thru the floor to prevent mice coming in. Seriously what else can I use to fill the hole. Steel wool? Then I will have anxiety of a splinter poking thru the wire! 😩😩
Actually, I wouldn't hesitate to fill a small hole with it - I have myself. Because only a short length of cable will be encased in foam, a lot of heat will leak out the ends and keep temperatures lower than when a length more than a few inches is covered.
There is an anti rodent version of the spray foam (Great Stuff brand I think) that is intended for that and presumably has some sort of rodent repellent smell or taste. There also is a firebreak version of foam to fill in holes between floors to slow air currents (chimneying) from spreading fires. So filling in small holes in floors or in walls is a good thing!
I would not be too concerned about modern 90C rated wire in longer lengths of foam as long as it is not carrying close to the rated max current for extended periods of time (ie being used for a heavy load like a heater or AC).
Not as dramatic as I was expecting.
I felt the same. I was actually ready with fire extinguishers. And the poor lighting from direct sunlight was because I wanted it far enough away from the house in case it really went up. But for everyone including myself with plenty of that product in their homes, it s good thing that nothing exciting happened. But unfortunately it doesn't make as fun a video to watch compared to some of the others.
@@ElectromagneticVideos would like to see same test with cloth covered cable. My house was built in '62 so I have lots of it. Wondering if I should replace whatever can be easily done at least to 1st flr outlets.
@@jimertzman6628 If I ever get some vintage cable like that I will do the experiment. I also would really like to try vintage aluminum cable even thought the issues with it were related to the connections rather than the cable itself.
Certainly quite a question as to if its worth replacing for safety's sake. Does it look in good condition? One thought might be to consider combination arc-fault breakers. They are not cheap but are supposed to trip if there is any sort of arcing and reduce the chance of fire. Note the "combination" part of the name - they are the newer ones that detect more arcing conditions than the older ones.
@@ElectromagneticVideos if I decide to replace any I will send you some. It seems to be in ok condition except some of the outer threading is loose in spots.
@@jimertzman6628 Sounds like wiring I had in some older houses - main thing I noticed was the plastic insulation getting a bit brittle where it was exposed to air in the junction boxes and as long as it was left alone it was OK. And thanks fro the offer - if you ever get rid of any old stuff sending some would be much appreciated!
Your foam prevents heat dissapation, romex needs air. Also, only an idiot would run 40+ amps through 14/2 🤣