house went on fire ? rewire everything?

[mlnk]

The AHJ will decide what needs to be wired, the insurance company will do what they require.

 

[growler]

would you do a whole house rewiring or just what you think needs to be replaced.The walls are gonna be open next week so Ill be able to see inside the walls and ceilings to inspect wires condition

If the fire was bad enough for the sheetrock to need replacement that's good enough for me.

Even if there is nothing wrong with some of the existing wire the owners will always worry about it. If you rewire it then things get much more simple, the owner is happy, the insurance co is happy and you can sleep nights knowing that you have done the best possible job. Best of all you may make some money.

 

[renosteinke]

Sheetrock will often be replaced because of smoke stains and water damage- the wires behind are in perfect shape.

 

[jmellc]

I would gut and rewire. You will have to give a warranty on the job & something may go wrong where you least expected. You may get calls every month for something that survived the fire but had a shortened life. With a totally new job, you know exactly what is there, where you put it and why. If any problems do arise you know what routes to follow.

Always remember Murphy's Law; if something can go wrong, it will.

 

[MichaelGP3]

As others have said, there are fires, and then there are FIRES.

IMO, any area that's getting stripped to the studs might need to be brought up to your current code. This means you may need to add circuits, distribute the circuits differently, increase the service size, add GFCI's and AFCI's, etc. It all depends on the intensity of the fire; a pretty mild fire can cover everything with greasy black soot, yet leave the drywall and electric otherwise undamaged.

Otherwise, as for the wire itself ... I would not 'automatically' replace any wire unless the outer jacket is actually damaged. A simple smoke stain is not 'damage,' IMO. Devices are another matter; you'll get corrosion within from the smoke, so all devices will want replacing.

The usual drywall and insulation we've been using for the past fifty years provides a pretty good fire barrier. It takes a pretty intense fire to actually damage stuff within the walls. Odds are, you had more damage caused by fire department operations (water, pike poles, etc.) than by the fire itself.

What is the difference between a "simple smoke stain" and a 'conductive carbon path' that may not rear it's ugly head until the circuit in question is drawing more current than normal? Also, in areas of the country where there are significant swings in seasonal humidity your megger tests might read ok when done during the dry season. Will your "smoke stained wire" megger readings be the same during the rainy season?

It's not my wish to antagonise; I agree with everything else in your post. Maybe I'm more cautious around this stuff than I need to be.

 

[renosteinke]

My guess is that we're overthinking this.

A little smoke on the outer jacket? You could copper-plate the outer jacket and not affect the insulation of the wires within one bit. All you have is a place where the hot(er) smoke condensed on the outside of the cool(er) plastic jacket.

Ditto for the concerns about elevated temps reducing the 'life' of the PVC. So what? The 'life' referred to is the flexibility, which is lost as the 'plasticisers' in the mix evaporate over time. With the cables installed, who cares if the outer jacket is no longer flexible, or develops cracks?

I once repaired the electrical in a hotel, after a fire. The fire was confined to one room, and the areas immediately outside the window and the door. Within that one room, it was an inferno. The occupant's bones were found resting on the coil springs of what used to be a mattress. The EMT fittings were reduced to being puddles of zinc on the floor.

Did I rewire the entire hotel? Heck no. I replaced the affected circuits.

I only say we need to apply the same to a house fire: rewire the affected area. If the fire is confined to one area, we need not rewire the unaffected areas.

I also ask that we recognize that not all of the 'fire damage' is damage caused by heat and flame. Heck, my wife likes to place little glass candles on the mantle; after a few years of this, you ought to see the smoke stains on the wall behind them. Those stains might be the very devil for a painter to seal in, but the walls never got hot enough to even melt butter. I'm pretty sure the wires in that wall are fine.

Ditto for water-damaged areas. The area damaged by fire department operations is always a lot larger than the immediate fire area. Yet, the wires in this larger area are likely to be just fine.

 

[G._S._Ohm]

For a fire or a flood or a lightning strike it seems to come down to, "How much has the cable life been shortened?" I doubt it has been helped by either of these.

Then,
How old were the cables beforehand?
Is there any way possible to tell if damage has occurred, with instruments or without?
If it has been shortened, can this be reliably measured?

Before Sandy you might have been able to get some unspun answers to the flood question.

 

[G._S._Ohm]

This article
http://www.newark.com/pdfs/techarticles/megger/salvagingFloodDamagedElectEquip.pdf
is related to floods but calls for less than 90C motor insulation temperature during drying because of shortened life.
Sounds like all wiring in a room that contained a fire should be replaced, regardless of wiring age.