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High Heat May Cause Damage to Romex #31042 11/07/03 02:19 AM
Joined: Oct 2000
Posts: 2,749
Joe Tedesco Offline OP
Member
San Diego area homeowners whose homes had survived the recent fires are filing insurance claims for damage to romex in their walls.

It has been said that when the house next door burns down, the wire in the exterior walls can get hot enough to damage the cable insulation.

Homeowners are making claims and the
insurance companies are requiring an inspection by an electrician.

Has anyone ever heard of this?


Joe Tedesco, NEC Consultant
Work Gear for Electricians and the Trades
Re: High Heat May Cause Damage to Romex #31043 11/07/03 05:54 AM
Joined: Dec 2000
Posts: 4,286
electure Offline
Member
Although I haven't heard of this before, I'm sure there will be many unprecedented claims due to the fires.
I can imagine there were also many vinyl window frames melted, etc.
The ferocity of the recent fires, and their seemingly random way of skipping over some homes while burning others to the ground must have caused some homes to have a great deal of heat damage....And then there's the smoke...
The entire LA basin was covered in smoke and had ash raining down for days on end. We couldn't see the sun here in Anaheim, 40 or so miles away from the closest fire (San Bernadino)...S

Re: High Heat May Cause Damage to Romex #31044 11/07/03 08:51 PM
Joined: Dec 2002
Posts: 228
J
JCooper Offline
Member
So how would an inspection help them, would damaged insulation show up if you megged it out?

Re: High Heat May Cause Damage to Romex #31045 11/07/03 09:26 PM
Joined: Jul 2002
Posts: 8,346
Trumpy Offline
Member
JCooper,
Meggering the wires would be almost the only way to check the wires without resorting to messier alternatives.
But even then, you'd have to be pretty sure of your Megger readings. [Linked Image]

Re: High Heat May Cause Damage to Romex #31046 11/08/03 12:31 AM
Joined: Dec 2002
Posts: 228
J
JCooper Offline
Member
So in theory if all the insulation was melted off the wire but they were, for the moment, far enough apart then the megger reading would show that everything is ok, what happens when somebody drives a drywall screw at just the right angle, at the right place.....

Re: High Heat May Cause Damage to Romex #31047 11/08/03 01:38 AM
Joined: Jul 2002
Posts: 8,346
Trumpy Offline
Member
JCooper,
Which side of the insulating fibres are the cables installed on.
If Insulating Batts are installed over the top of cables, that is poor installation.
If however, the cables are installed and the builder puts the cables on the Dry-wall side of the Insulation, these should provide enough Insulation to prevent too much damage to the installed wiring. [Linked Image]

Re: High Heat May Cause Damage to Romex #31048 11/08/03 02:28 PM
Joined: Feb 2002
Posts: 375
G
George Offline
Member
I think this is an urban legend.

Current romex insulation is good to 90 degrees C (194 degrees F).

That temperature will melt vinyl siding, and blister paint, but 1/2" plywood will keep the temperature inside the house at ambiant until the plywood burns thru. Brick or stone exterior will also protect the interior.

If you have exposed metal conduit or exterior recepts, I expect there will be damage at those locations.

Re: High Heat May Cause Damage to Romex #31049 11/09/03 07:10 AM
Joined: Dec 2000
Posts: 4,286
electure Offline
Member
George,
There's not much brick or stone in the area. This is Southern California. Homes typically have 1" of stucco, and unless they're fairly new, you won't find plywood (even as shear panel) on a 1 story. Keep in mind that the homes are often no more than 10' apart. Boxes/Rx for exterior lighting and recps. would be especially exposed to heat.
JCooper,
The same thing would happen as if someone drove a drywall screw into a piece of Rx that had no heat damage at all...S

[This message has been edited by electure (edited 11-09-2003).]

Re: High Heat May Cause Damage to Romex #31050 11/10/03 10:29 AM
Joined: Nov 2002
Posts: 169
R
rowdyrudy Offline
Member
Why DIYers get in trouble.
Several years past, while living in Phoenix, one Sunday I was adding a mist system to my patio. I needed about 20’ of romex so I went to a big box rather than drive all the way to the office. I noted that the romex at the big box contained THW conductors. I mentioned to the clerk that it was illegal to use this romex in Phoenix due to the temperature rating. He admitted that it was illegal to install but he said “It’s not illegal to sell”. I then drove the 30 mile round trip to the office and obtained my THHN equipped romex.
Rowdy

Re: High Heat May Cause Damage to Romex #31051 11/11/03 09:38 PM
Joined: Jun 2003
Posts: 1,143
D
DougW Offline
Member
Reminds me of a bid I put in for a buddy looking at a house that had suffered a fire, and never been rehabbed - just a think coat of Kilz primer over the scorch and soot stains.

Asked another mutual friend whether or not I'd have to remove the EMT as part of the work - his reply? "As long as it's not damaged to the point where it fails to offer continuous physical protection, and a solid path-to-ground, I'll sign for it".

(he's one of our county building AHJ's)

Never did get the job - my buddy got outbid [Linked Image]


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