Missing phenolic insulator: How much of a problem?

[HomeInspectorKenton]

I'm writing courses for pre-purchase home inspectors. My question is:
Phenolic insulators are the plastic things that separate conductors as they enter the masthead. My understanding is that if conductors of different voltage are close to one another, or have contact with each other, some voltage transfer can take place just like it does in a transformer.
My question is, does enough voltage transfer take place that pre-purchase home inspectors should recommend correction or is it not really a big deal. Talking about 120V residential voltages here.
I guess they also help keep water out of the mast.
My job is to tell inspectors what they should say about missing insulators in their reports.

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[GoldDigger]

I'm writing courses for pre-purchase home inspectors. My question is:
Phenolic insulators are the plastic things that separate conductors as they enter the masthead. My understanding is that if conductors of different voltage are close to one another, or have contact with each other, some voltage transfer can take place just like it does in a transformer.
My question is, does enough voltage transfer take place that pre-purchase home inspectors should recommend correction or is it not really a big deal. Talking about 120V residential voltages here.
I guess they also help keep water out of the mast.
My job is to tell inspectors what they should say about missing insulators in their reports.

​

IMHO the purpose of the insulator is to prevent damage to the wire insulation from rubbing against the other wires or the metal of the weatherhead.
I cannot think of any mechanism where having the wires close or touching would be an electrical rather than mechanical problem
Anybody else have additional ideas?

BTW, once the wires are inside the pipe, they will still be close together.

 

[JDBrown]

IMHO the purpose of the insulator is to prevent damage to the wire insulation from rubbing against the other wires or the metal of the weatherhead.
I cannot think of any mechanism where having the wires close or touching would be an electrical rather than mechanical problem
Anybody else have additional ideas?

BTW, once the wires are inside the pipe, they will still be close together.

I think you've got it pretty well covered -- it's a protection from physical damage, and if it's missing the cables could rub against the mast enough to wear through the insulation and cause a short. At high voltages it's possible to get insulation breakdown if the cables are touching/too close together, depending on what type of insulation you've got, but 120V conductors can touch each other all day long and the insulation will be fine no matter what type it is (recognized insulation types anyway). Just think of how many power cords have the conductors right next to each other with just a thin layer of insulation separating them.

Now, I suppose the phenolic insulator might help keep water out of the mast, but I think that's what weather heads and caulk are for. Maybe a Sparky can chime in on that, though -- I'm just a dumb engineer; I don't actually do this stuff for a living.

 

[iwire]

once the wires are inside the pipe, they will still be close together.

:thumbsup: