Best wire to sit in water "forever"

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grasfulls said:
Most every conduit around here fills with water. We have always pulled in THHN/THWN wire, is that the best for longevity / safety?
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As I noted in another post ANY polymer will absorb water over time and fail. Use CLX but review the 'armor' material for corrosion resistance against the surropunding materials. You may have to privide cathodic protection. When led jacketed cables were available - scarce now because of environmental restriction - that was the choice material. Now aluminum, SS or bronze that remains fro corrugated, continously welded metallic jackets.
 
I could at this point mention SWA (steel wire armoured) which I didn't think you guys have, but iwire metioned that it is available in the USA and used by PoCos.

This stuff is suitable for direct burial and wet conditions, and I'd have no hesitation throwing it into a lake; it'll survive better than any other cable I can bring to mind.
 
dbuckley said:
I could at this point mention SWA (steel wire armoured) which I didn't think you guys have, but iwire metioned that it is available in the USA and used by PoCos.

This stuff is suitable for direct burial and wet conditions, and I'd have no hesitation throwing it into a lake; it'll survive better than any other cable I can bring to mind.
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SWA is permable like any other polymer jackets. It is no different than our TC cable with the additional mechanical protection provided by the SWA which does NOTHING, NADA, ZILCH, ZERO against water.

The SWA will last longer than TC because of the additional jacket under rthe SWA, so the water need to permeate three layers; insulation, under(SWA)jacket and overall jacket, which can take a long time, but certainly less than with a CLX cable where the armor is a continuous matallic sheet and IMPERMEABLE.

Si order of 'goodness' is:
  1. CLX
  2. SWA
  3. TC
I do not believe though that SWA is what utilities use. Perhaps cables with concentric neutral that can be mistaken in appearence for SWA.
 
weressl,

That is good info. There are some insulations that I have encountered that are not covered by code, and ones that are that we most commonly use are isolated to a select few. It's good to know what else is out there.

While there are few frost issues and nil on ground water here, we have freaky 32 degree mornings and then 75 afternoons frequently in spring and fall and so condensation within conduits is normal. We find many older buildings with horizontal runs that are full of water within ceiling spaces that are dry areas. The temp changes are such that they have an adverse effect on conductors in conduit over prolonged time.
 
marti smith said:
weressl,

That is good info. There are some insulations that I have encountered that are not covered by code, and ones that are that we most commonly use are isolated to a select few. It's good to know what else is out there.

While there are few frost issues and nil on ground water here, we have freaky 32 degree mornings and then 75 afternoons frequently in spring and fall and so condensation within conduits is normal. We find many older buildings with horizontal runs that are full of water within ceiling spaces that are dry areas. The temp changes are such that they have an adverse effect on conductors in conduit over prolonged time.
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If the insulation is not listed in the NEC then your installing them does not comply with NEC, although still could be OK with your AHJ.

The comment was made that SWA is utilized by Utilities, and they are not governed by the NEC.

Electrical systems breath and suck in moisture laden air that condenses. The greater the temperature difference is the more moisture will one accumulate inside of the enclosures, raceways. The condensed water gets trapped unless there are conduit/enclosure breather/drains installed at low points and the conduits are installed to drain toward one end of the run.
 
On old cable engineer once told me that the only waterproof cable jacket is lead, and even that will leak if it is damaged. Not sure if you can even buy lead jacked cable any more.
 
Back when the big multipair underground phone cables were lead sheathed, they had the cables pressurised with air to keep the water out, and had pressure alarms for when they started leaking.
 
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