Where to obtain submerged Insulation resistance data for XHHM vs. THW ?

[exoticmagneto]

Such as Insulation resistance of wire in submerged water applications after months and / or years in Mohm per specified feet for XHHM vs. THW ?

What I'm seeing in the field is standard water well pump cable often megging out at anywhere from 70's to 125 Mohm @ 500 VDC in new installs - - then in many cases dropping to around 2 Mohm after about 2 years submerged in water (with no damage to cable).

I'm assuming the PVC insulation absorbs some moisture.

 

[mopowr steve]

I too would like to know how TWN, THWN can get listing to be ran in conduit which many times is submerged in water. Most sections of these types of wires often have the copper turn black under the insulation, so what gives? Seems to me moisture IS penetrating the insulation. Which then really makes one wonder about aluminum conductors:huh:

 

[exoticmagneto]

I too would like to know how TWN, THWN can get listing to be ran in conduit which many times is submerged in water. Most sections of these types of wires often have the copper turn black under the insulation, so what gives? Seems to me moisture IS penetrating the insulation. Which then really makes one wonder about aluminum conductors:huh:

Yes Steve, I have pulled dozens and dozens of my relatively newer pump cables out of the lake - - and in as little as 2 to 3 yrs. the copper strands inside the PVC insulation are all black, oxidized ( I have to scrap them to get bare copper before I butt splice and heat shrink them again).

Of course the older cables are really, really bad.

I'm started to wonder if this is a goldmine for the wire sellers - - appears you have "planned obsolescence" or rapid turnover going on here.

That's one reason I'm looking into this XHHM insulation.

 

[Julius Right]

See:
UL 1581/2003 ch.920 Insulation-Resistance Test in Water
and :
LONG-TIME INSULATION RESISTANCE IN WATER UL-83/2001 ch.31 Table 31.1 Minimum insulation resistance at elevated temperature in water

 

[Smart $]

...
That's one reason I'm looking into this XHHM insulation.

Just for clarification, don't you mean XHHW?

 

[Smart $]

FWIW, most thermoplastics are not impervious to water moisture. It is only a question of degree as to whether a particular thermoplastic, or thermoset for that matter, is suitable as an insulation for submerged conductors.

 

[don_resqcapt19]

FWIW, most thermoplastics are not impervious to water moisture. It is only a question of degree as to whether a particular thermoplastic, or thermoset for that matter, is suitable as an insulation for submerged conductors.

Old time cable engineers will tell you that the only waterproof cable jacket is properly installed and undamaged lead jacketed cables...everything else is only water resistant.

 

[exoticmagneto]

yes, I meant XHHW.

yes, I meant XHHW.

Just for clarification, don't you mean XHHW?

Oops, yes, I meant XHHW.

 

[exoticmagneto]

LONG-TIME INSULATION RESISTANCE IN WATER UL-83/2001 ch.31 Table 31.1 ??

LONG-TIME INSULATION RESISTANCE IN WATER UL-83/2001 ch.31 Table 31.1 ??

See:
UL 1581/2003 ch.920 Insulation-Resistance Test in Water
and :
LONG-TIME INSULATION RESISTANCE IN WATER UL-83/2001 ch.31 Table 31.1 Minimum insulation resistance at elevated temperature in water

Well, did a google search, nothing came up.

Went directly to the UL site, found UL-83, all they give you is table of contents, they want you to spend serious moola to take a look at the charts.

Any idea how I can get access ? Go to a university library ?

 

[Smart $]

Old time cable engineers will tell you that the only waterproof cable jacket is properly installed and undamaged lead jacketed cables...everything else is only water resistant.

Not limited to lead-sheathed cables... just that lead-sheathed was more common in earlier times.

One non-lead-sheathed cable example is MI cable... and it is available with a thermoplastic jacket to help protect the copper sheath.

 

[Julius Right]

Megohm/1000 ft
size TW THHW THHN
1/0 75 310 415
2/0 70 280 370
3/0 60 250 330
4/0 55 225 300
250 60 245 330
300 55 225 300
350 50 210 285
400 50 200 255
450 45 190 255
500 45 180 240

 

[Tony S]

I’ve been reading this thread with interest. I’ve installed a number of borehole and lagoon pumps. I’ve always used rubber H07 RN-F Cable to BS7919, you will have to look for the equivalent US standard.

The cable doesn’t fail, the pumps do.

 

[iwire]

I’ve been reading this thread with interest. I’ve installed a number of borehole and lagoon pumps. I’ve always used rubber H07 RN-F Cable to BS7919, you will have to look for the equivalent US standard.

The cable doesn’t fail, the pumps do.

The OPs cable has not failed.

 

[Tony S]

The IR readings aren’t very good. It has already been asked why the cable type has been used. I’m suggesting an alternative and proven cable type.

 

[iwire]

The IR readings aren’t very good. It has already been asked why the cable type has been used. I’m suggesting an alternative and proven cable type.

That's cool but I would be surprised if it will fit in the OPs conduit.



I am assuming your cable is actually that, an assembly of single conductors with an overall outer jacket. What the OP has now is single conducts in a conduit without an overall jacket.

Unless the conduit is oversized the cable will not fit

Also the XHHW currently being used is commonly used for this purpose, regardless of the readings they work fine for decades.

 

[Julius Right]

For XHHW see UL 44/2002 Table 37.1:
UL 44/2002 Table 37.1
cond.ohm/kft
size XHHW
1/0 1105
2/0 1000
3/0 895
4/0 825
250 895
300 825
350 755
400 715
450 680
500 645