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#1
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Is it possible to find wire insulation faults without a visual exam?
I'm working on a newly framed house with lots of 12-2 romex runs and plenty of 24/4 wire low voltage runs to burglar alarm sensors at all windows and doors. Yesterday I arranged for an insulation company to foam the walls of this house. After the spray process was complete I offered to help the foam installer trim the foam that had extruded inside the face of each stud bay. While performing this task, I found myself cutting into something a good deal harder than foam and realized that I had managed to saw through one of the burglar alarm circuits that had become embedded in the expanding foam and pushed outside of the wall cavity. No problem! I had B-connectors and wire strippers in my toolkit so I reconnected the circuit and immediately advised the insulation mechanic to let me know IMMEDIATELY if he encountered (ie inadvertently damaged) any wiring while trimming the excess foam. He agreed and I was confident that everything would be ok. This morning I decided to check all the burglar alarm circuits just for grins and found a second circuit that had been severed albeit not by me. The insulation installer, knowingly or unknowingly, had managed to damage the second circuit, and then (knowingly or unknowingly) had concealed the damage by spraying additional foam to cover the circuit! I dug the damaged wires out of the foam and repaired the connections quickly but I was left with a lingering fear that some of the romex circuits could have been damaged as well. The insulation installer could have sawed into a run of romex just enough to damage the insulation without bothering to warn me about the damage, stuffed it back into the wall like he did with the burglar alarm wire, and then covered it with additional foam. I wouldn't mind a completely cut romex circuit because I could fairly easily test the entire electrical system before the drywall is taped and floated and then remove sections of drywall and foam insulation to rerun any severed cable. However, it would be damn near impossible to cut completely through 12-2 romex with the type of blade used to trim foam insulation. What this means is that any damaged would be confined to the insulation. Very bad! Why is it so difficult for building tradespeople to simply admit it when they inadvertently cause or contribute to a problem instead of trying to cover it up? Is there a way to identify circuits with bad insulation without visual inspection? |
#2
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Is it possible to find wire insulation faults without a visual exam?
Home Builder wrote:
Is there a way to identify circuits with bad insulation without visual inspection? Yes. The equipment you need is commonly called a Megger. It applies a high voltage (usually under 500v -- NM cable insulation is good for up to 600v) and measures very small leakage currents to ground. It takes some experience to give you the best results, and isn't absolutely accurate. You may be able to rent one, but I recommend having an electrician who knows how to use it and interpret the readings test your wiring for you. -- Best Regards Anthony Straight http://dotznize.com/electric This posting is an opinion only. The reader must use his own judgment and assume any risk for following or ignoring my advice. |
#3
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Is it possible to find wire insulation faults without a visual exam?
Home Builder wrote in message news:uMz2c.44391$Ri6.30603@lakeread04...
I'm working on a newly framed house with lots of 12-2 romex runs and plenty of 24/4 wire low voltage runs to burglar alarm sensors at all windows and doors. Yesterday I arranged for an insulation company to foam the walls of this house. After the spray process was complete I offered to help the foam installer trim the foam that had extruded inside the face of each stud bay. While performing this task, I found myself cutting into something a good deal harder than foam and realized that I had managed to saw through one of the burglar alarm circuits that had become embedded in the expanding foam and pushed outside of the wall cavity. No problem! I had B-connectors and wire strippers in my toolkit so I reconnected the circuit and immediately advised the insulation mechanic to let me know IMMEDIATELY if he encountered (ie inadvertently damaged) any wiring while trimming the excess foam. He agreed and I was confident that everything would be ok. This morning I decided to check all the burglar alarm circuits just for grins and found a second circuit that had been severed albeit not by me. The insulation installer, knowingly or unknowingly, had managed to damage the second circuit, and then (knowingly or unknowingly) had concealed the damage by spraying additional foam to cover the circuit! I dug the damaged wires out of the foam and repaired the connections quickly but I was left with a lingering fear that some of the romex circuits could have been damaged as well. The insulation installer could have sawed into a run of romex just enough to damage the insulation without bothering to warn me about the damage, stuffed it back into the wall like he did with the burglar alarm wire, and then covered it with additional foam. I wouldn't mind a completely cut romex circuit because I could fairly easily test the entire electrical system before the drywall is taped and floated and then remove sections of drywall and foam insulation to rerun any severed cable. However, it would be damn near impossible to cut completely through 12-2 romex with the type of blade used to trim foam insulation. What this means is that any damaged would be confined to the insulation. Very bad! Why is it so difficult for building tradespeople to simply admit it when they inadvertently cause or contribute to a problem instead of trying to cover it up? Is there a way to identify circuits with bad insulation without visual inspection? Well..the insulators dont want to hang around while you repair the damage is the most likely reason they just cover up the mistakes. They might get paid by the job and have another one to get too or they simply dont want to hang around while someone fixes the damage.........who know ??? What I cant understand is why with so many wires going into a house today a person wouldnt use conduit in the walls that are being insulated with the foam. It would make repairs or modifications down the road a whole lot easier.... I know not all the wires...control and fire/burgler alarm probably cant be 100 percent protected by conduit.....but I would still get what I could in conduit if I was filling the wall with foam insulation. Lastly....Why were the wires not secured properly in the first place. I have never seen wires run by professionals in a matter where you could pull it out past the face of the stud bay ??? surely they stapled the romex to the studs and at least used some kind of insulated fastener for the control or alarm wires. |
#4
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Is it possible to find wire insulation faults without a visualexam?
cornytheclown wrote:
Home Builder wrote in message news:uMz2c.44391$Ri6.30603@lakeread04... I'm working on a newly framed house with lots of 12-2 romex runs and plenty of 24/4 wire low voltage runs to burglar alarm sensors at all windows and doors. Yesterday I arranged for an insulation company to foam the walls of this house. After the spray process was complete I offered to help the foam installer trim the foam that had extruded inside the face of each stud bay. While performing this task, I found myself cutting into something a good deal harder than foam and realized that I had managed to saw through one of the burglar alarm circuits that had become embedded in the expanding foam and pushed outside of the wall cavity. No problem! I had B-connectors and wire strippers in my toolkit so I reconnected the circuit and immediately advised the insulation mechanic to let me know IMMEDIATELY if he encountered (ie inadvertently damaged) any wiring while trimming the excess foam. He agreed and I was confident that everything would be ok. This morning I decided to check all the burglar alarm circuits just for grins and found a second circuit that had been severed albeit not by me. The insulation installer, knowingly or unknowingly, had managed to damage the second circuit, and then (knowingly or unknowingly) had concealed the damage by spraying additional foam to cover the circuit! I dug the damaged wires out of the foam and repaired the connections quickly but I was left with a lingering fear that some of the romex circuits could have been damaged as well. The insulation installer could have sawed into a run of romex just enough to damage the insulation without bothering to warn me about the damage, stuffed it back into the wall like he did with the burglar alarm wire, and then covered it with additional foam. I wouldn't mind a completely cut romex circuit because I could fairly easily test the entire electrical system before the drywall is taped and floated and then remove sections of drywall and foam insulation to rerun any severed cable. However, it would be damn near impossible to cut completely through 12-2 romex with the type of blade used to trim foam insulation. What this means is that any damaged would be confined to the insulation. Very bad! Why is it so difficult for building tradespeople to simply admit it when they inadvertently cause or contribute to a problem instead of trying to cover it up? Is there a way to identify circuits with bad insulation without visual inspection? Well..the insulators dont want to hang around while you repair the damage is the most likely reason they just cover up the mistakes. They might get paid by the job and have another one to get too or they simply dont want to hang around while someone fixes the damage.........who know ??? What I cant understand is why with so many wires going into a house today a person wouldnt use conduit in the walls that are being insulated with the foam. It would make repairs or modifications down the road a whole lot easier.... I know not all the wires...control and fire/burgler alarm probably cant be 100 percent protected by conduit.....but I would still get what I could in conduit if I was filling the wall with foam insulation. Conduit isn't appropriate for many situations. The aforementioned house has roughly three runs of 1" conduit to every room for network wiring (RG6 QS, cat 5E, etc) --- and each top plate had to be bolstered with steel straps from stud to stud on each side of each hole... a process that only partially restored the strength lost from the large conduit hole and will eventually cause headaches for the sheetrock hangers. In spite of the drawbacks, conduit is appropriate for network wiring because network wiring changes every few years. NOT SO with romex. It would be just plain dumb to run all romex through conduit in my opinion because of the resulting loss of strength in the frame. Lastly....Why were the wires not secured properly in the first place. The wires were properly secured. As with conduit there is a trade-off between various options when you're securing wire. For example, I like to leave a loop of the 24/4 wire in the wall next to all burglar alarm switches. Why? Because switches could eventually fail and the loop of wire allows future repairs to be completed without re-running the wire. Suppose a switch fails. You pull the bad switch out of the hole, clip the leads, reconnect a new switch, and stuff the new switch down into the same hole. This requires at least six inches of slack IMHO which is more than enough to get pushed outside the stud bay and damaged if the foam installer isn't careful. There were roughly 40 burglar alarm circuits in the aforementioned house, and most of them survived the foam. Two were damaged and were easily repaired. Yet the loops are still in the wall to facilitate future repairs. Now what's better? Spending a couple of minutes to repair two damaged circuits in order to facilitate future repair work? Or stapling down the wire so thoroughly that there is NO SLACK WHATSOEVER... thereby forcing the homeowner to rip out the wall or run new wire if/when a switch fails? If I were facing the prospect of stapling low voltage wire every four or five inches, running conduit for all romex, etc, etc, as you suggest, I would find a better solution: Hire foam installers who will NOTIFY ME if/when they damage a cable or a wire so that I can fix it. It only takes a couple of seconds to flag a damaged wire, and it would only take me a couple of minutes to fix it --- a lot LESS time than it would take to install a single run of conduit, staple low voltage wiring every four or five inches, or staple ALL runs of romex so throughly that it would be totally impossible for an inattentive foam installer to damage any cables. I have never seen wires run by professionals in a matter where you could pull it out past the face of the stud bay ??? That's odd. I've never before encounted a professional who has NOT seen this. :-) It's especially common in situations where the electrician may have run the romex down a partially exposed wall channel where it's difficult to staple adequately. There aren't many tasks in construction that you can throughly idiot proof ANY stage of the construction process and this is no exception. For less money than it would cost to install conduit for romex I could hire off-duty cops with sidearms to watch the foam installers and stop them immediately if they damage a cable and attempt to conceal it. surely they stapled the romex to the studs and at least used some kind of insulated fastener for the control or alarm wires. Surely! Thanks for the criticism, but you didn't answer my question. |
#6
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Is it possible to find wire insulation faults without a visual exam?
"Home Builder" wrote in message newsXa3c.49275$Ri6.19383@lakeread04... cornytheclown wrote: Home Builder wrote in message news:uMz2c.44391$Ri6.30603@lakeread04... This morning I decided to check all the burglar alarm circuits just for grins and found a second circuit that had been severed albeit not by me. The insulation installer, knowingly or unknowingly, had managed to damage the second circuit, and then (knowingly or unknowingly) had concealed the damage by spraying additional foam to cover the circuit! I dug the damaged wires out of the foam and repaired the connections quickly but I was left with a lingering fear that some of the romex circuits could have been damaged as well. The insulation installer could have sawed into a run of romex just enough to damage the insulation without bothering to warn me about the damage, stuffed it back into the wall like he did with the burglar alarm wire, and then covered it with additional foam. Why is it so difficult for building tradespeople to simply admit it when they inadvertently cause or contribute to a problem instead of trying to cover it up? similarly, there are probably technical solutions to many ongoing problems, but people are too stuck in their ways to risk trying solutions. Conduit isn't appropriate for many situations. The aforementioned house has roughly three runs of 1" conduit to every room for network wiring (RG6 QS, cat 5E, etc) --- and each top plate had to be bolstered with steel straps from stud to stud on each side of each hole... a process that only partially restored the strength lost from the large conduit hole and will eventually cause headaches for the sheetrock hangers. In spite of the drawbacks, conduit is appropriate for network wiring because network wiring changes every few years. NOT SO with romex. It would be just plain dumb to run all romex through conduit in my opinion because of the resulting loss of strength in the frame. yeah. all those holes concern me. almost like you need continuous access (as in commercial bldg) for all the utilities. Lastly....Why were the wires not secured properly in the first place. The wires were properly secured. As with conduit there is a trade-off between various options when you're securing wire. For example, I like to leave a loop of the 24/4 wire in the wall next to all burglar alarm switches. Why? Because switches could eventually fail and the loop of wire allows future repairs to be completed without re-running the wire. Suppose a switch fails. You pull the bad switch out of the hole, clip the leads, reconnect a new switch, and stuff the new switch down into the same hole. This requires at least six inches of slack IMHO which is more than enough to get pushed outside the stud bay and damaged if the foam installer isn't careful. There were roughly 40 burglar alarm circuits in the aforementioned house, and most of them survived the foam. Two were damaged and were easily repaired. Yet the loops are still in the wall to facilitate future repairs. Now what's better? Spending a couple of minutes to repair two damaged circuits in order to facilitate future repair work? Or stapling down the wire so thoroughly that there is NO SLACK WHATSOEVER... thereby forcing the homeowner to rip out the wall or run new wire if/when a switch fails? minor idea: tuck the crumple of spare wire into a short tube, perhaps also attach the tube to a stud? or include an electrical box for spare LV ends?? (I can't visualize your situation) |
#7
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Is it possible to find wire insulation faults without a visual exam?
Another good question is how properly installed Romex could be pushed
out of the wall cavity by foam insulation. If it's properly routed and stapled in place, it would be virtually impossible for this to happen. |
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