XHHW vs THWN - seawater resistance

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cvirgil467

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Hi there. This is a Sandy related question.

Anyone know if XHHW or THWN had resistance properties to sewater/saltwater? I looked at the UL testing procedures of these cables. UL uses tap water for the water test. If we megger test cables now and find conductors pass, that is no indication of performance over time is salt residue start to corrode the insulation.

As an fyi - NYC DoB has recommedned that all wiring subjected to Sandy's water be replaced.

Thanks .
b
 
Interesting that parts of NJ state that the salt water won't hurt it. The NJ State DCA's office is insisting saltwater flooded romex will just dry out and be fine. They refuse to issue something in writing about this but are telling everyone that they just have to replace devices.
 
NEMA has guidelines for flood damaged equipment and wiring. Water will wick 50 ft up romex. Guidelines say romex should be replaced if submerged, our state electrical rules are same as NEMAs
 
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Dennis Alwon said:
Interesting that parts of NJ state that the salt water won't hurt it. The NJ State DCA's office is insisting saltwater flooded romex will just dry out and be fine. They refuse to issue something in writing about this but are telling everyone that they just have to replace devices.
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The current Electrical experts at DCA are issueing bad policy by telling people it is ok and will dry out when there own instructors have held seminars informing working officials to enforce the NEMA guidlines for how to handle water damaged electrical equipment. NEMA says that wiring exposed to comtaminants should be replaced if conductors were submerged or if it penetrated the inside jacket . Most all of the floodwaters that I have encountered during this storm were contaminated with sewerage but surely seawater and anything else you can think of. Have we not learned that from the fires after hurricane Katrina!!!!!!
 
cvirgil467 said:
Hi there. This is a Sandy related question.

Anyone know if XHHW or THWN had resistance properties to sewater/saltwater? I looked at the UL testing procedures of these cables. UL uses tap water for the water test. If we megger test cables now and find conductors pass, that is no indication of performance over time is salt residue start to corrode the insulation.

As an fyi - NYC DoB has recommedned that all wiring subjected to Sandy's water be replaced.

Thanks .
b
Click to expand...

Thermoplastic and thermosetting polymers - the two materials above - or for that matter any type polymers will not 'corrode'. Metals corrode. In case of salt-water the problem is two-fold. One is the immediate problem of a conductive material that could cause short. Indeed, Megger will tel you about that. Short term submergence of polymers will not substantially change their insulation properties after removed from water, even sea-water. Conductive surface tracking may occur.

The danger would be the long term, corrosive effect of the salt residue that will eventually eat away at termination points and contacts and result in fire hazard down on the road.
 
I haven't done much work in shore areas but I'm told that AHJ's in NJ shore communities will not allow aluminum SE cable (w/XHHW insulation) to be used for services because of salt air corrosion. If there are any of you out there who could verify this please say so. I have a friend that is in the mold remediation business and he is doing extensive work in the NJ shore area. He is cutting and removing sheet-rock 48" AFF and throwing it out along with any insulation that was soaked. Not sure what the AHJ's are requiring for electrical wiring in these spaces.
 
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