Burying arial cable instead of hanging - ramifications?

I just had a strange argument with a local electrician. We were discussing some aspects of hooking up an electrical box and then discussed using some old arial line for the connection between the pole and building. I said I was going to bury the line in the ground and put it in some PVC conduit and he said I couldn't do that, that the arial lines are made to be in the air and putting it into the ground will cause it to deteriorate faster than normal. I tried to explain to them that even if it were put into the dirt directly it STILL would last longer than in the air due to reduced element exposure AND UV exposure. He said I was full of crap and wouldn't listen to me at all, tried to site regulations. I then explained that I was going to emulate the same environment that they'd have in the air essentially since I'm going to put it into a sealed PVC conduit that would only allow the cabling to be exposed to air and the PVC itself. He laughed at me heartily and told me that I was breaking the law and that I'd be replacing my cable within a couple years. Really a sour experience.

I just cannot for one moment believe that this plastic coating will degrade even within the ground as quickly as it would being exposed to various elements within the air when hanging. Furthermore, when in a conduit under the ground it seems that this cabling should be ensured to last LONG past normal life expectancy.

Anyone able to elaborate or clarify what the electrician might be trying to argue and/or if they have any reason to make such an argument and be so rude about it?

Hi Greg,
I am not an electrician, but I think it has more to do with the cable itself, rather than the coating. Arial cables are surrounded by air and can have far more electricity flowing through it because it is exposed to the air and can release heat quickly. If you put it in the ground with the same amount of electricity, and without the ability to release the heat, then the heat would build up, and would degrade the cable and cause problems. You would need to reduce the amount of electricity or increase the size of the cable.

Other than that, I don't know of a reason.

So, I'm assuming were talking about the building supply not a connection cable for a TV antenna? Sorry, just checking, nations divided by a common language and all that.

First off, in the UK, the electrician is right, it's against is against the regs. There are 2 things going on.

Cables underground should be swa (Steel Wire Armour) for mechanical protection (spades and rats...), PVC isn't counted as "protection" in British regs.
Also burying a cable derates it's current capacity. The resistance of the cable causes a slight heat build up in the cable, in free air that heat dissipates. When buried, the heat cannot dissipate and so a larger cable is required for the same current.

Secondly, you're right about the UV resistance bit but possibly wrong about the cable lasting longer for a couple of reasons. Corrosion is far more likely underground, direct burial rated RG6 (TV dish cable) is full of gel to keep water out if the cable gets nicked or snagged. Chemical resistance, being in the soil exposes the outer sheath to nastier stuff than in the air.
While the PVC will initially protect the cable, if it does fail at any point, it will fill with water which will consistently attack the cable. I think that there is a difference in cable sheathing for underground with higher chemical resistance.

Honestly in practice, the difference is probably negligible. There are many underground runs of normal twin and earth that have been there as long as exposed twin and earth and both "should" (that's a Wheaton should) have been replaced years ago and both are working safely.

There is no excuse for rudeness but generally there have been some clever people trying to keep people safe with these regs. They don't always get it right and they aren't good at flexibility due to circumstance but outright ignoring them isn't wise.

Thanks for the additional details @James Alun! Very helpful! Insomuch that I live in the US and I don't know of any such regs and really no one will ever check it since it's out in the boonies and there are no building regulations, I'll move forward with my plan. Seems like I'll get at least a good couple decades out of it if'n society lasts that long anyway. 🙃

Greg, whether or not you go ahead with this is up to you but I will say this.

In this circumstance, if this is the main supply for any significant load that needs high reliability (house, business, workshop) or is only protected by a fuse then I would do the calculations and buy the SWA.
If this is a single cable running a light in an outbuilding, with a gfci on the supply side of the cable and you have absolutely no money, then fair enough but I wouldn't bother with the conduit unless it's at least 2mm thick and even then it's more likely to cause problems than solve them. Covering the cable with smaooth lardge flat rocks or concrete slabs and burying it in sand is far more effective. I would also want that cable at least 18" down.

This is not permission or legal advice. I am not licenced for this level of work.

If this sounds like I'm trying to scare you, honestly I am a little. From what you've said, I personally don't think you've got the knowledge or experience to disregard the local regs even if the sparky was an arse but I'm not your mother.

Greg Payton wrote:Anyone able to elaborate or clarify what the electrician might be trying to argue and/or if they have any reason to make such an argument and be so rude about it?

Code is a PITA, but it's not always wrong, or optional. Code, while inflexible and sometimes dumb, keeps energy flowing and generally prevents harm. Materials engineered to code are quite specific, designed to be reliable in specified conditions. These are not random notions pulled out of a hat.

You, of course don't have to like it, or follow it. You have the luxury of doing whatever you want to do, and the consequences are all on your shoulders. But I get the impression you were asking your electrician to okay an improvised solution with improvised materials. Meaning: putting his license and livelihood on the line. What response did you expect? I know that many tradesmen are not exactly polished in their communication skills, but c'mon man, it's not okay to diss him for telling you how it is.

😆 Thanks @James Alun. Yeah, should be fine. The pipe is 4mm and running into a circuit breaker box in a hobby workshop. Going to bury it for about 50 feet from the pole and then it will be suspended in the conduit for another 40 or 50 feet and run on up into the box. Not going to buy any new cable. This will work fine. Got some electrical background and really I'm just asking the question about this degradation situation - otherwise I'm good. Thanks again!

@Douglas Alpenstock, yep, I'm fine. I was only asking the electrician about some thickness issues on the breaker box and converting the non-covered strand to a smaller connector for the ground bar. I wasn't really talking about anything with them regarding capacity or safety, it just came up. Likewise I'm not really asking any "electrical" questions here either, just simply asking about this degradation situation. We just don't have any licensing issues to worry about in our neck of the woods so code is a nonstarter for discussion for me. Lol, not sure where you're getting the "dissing" stuff from. Certainly not reading anything I said here about it and I didn't ask them for the free advice. 😆 Thanks!

You seemed to have been unaware of the heat dissipation factor - and the water intrusion factor - both of which cause degradation. You should ask yourself what else you might be unaware of.

Edit: For instance, did you know that rodents can be attracted to the electrical field of buried line and will chew through PVC conduit small enough in diameter to fit their teeth around (gophers can chew through 1.5 inches)? I just remembered my step-brother telling me this. He's a journeyman electrician.

You seem to be looking for validation from the group that the electrician was wrong, and a jerk. Becoming an electrician is hard. When homeowners think they know better, it pisses them off. I'm not trying to be a jerk here, but electricity is dangerous. It's wise to heed the advice of a pro. Usually. Even if they are a jerk. Burying cable is perfectly fine if done properly. Please just be careful. Be smart. And good luck.