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  #1  
Old 06-08-2003, 08:49 PM
nineiron nineiron is offline
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tree trimming around electric wires

If one is going to trim a tree which has a few branches that touch electrical wiring, what is the danger in trimming branches that are nowhere near these wires? Is it only a risk if I were to touch the branch that itself touches the wire, or is there danger in touching any of the other nearby branches? I haven't gone anywhere near the thing thusfar, but I wonder if I'm being overly cautious. Part of me thinks it must be OK, since it's not like the entire tree is unsafe, is it? But like I said, I've been going by the "better safe than sorry" route. Obviously I don't want to go too near to the ones that do touch the wire, since touching the wire itself would be a big problem.

I know I can (in theory) call the electric company and have them take care of it through their contractors, but if possible I'd like to take care of it myself. I also know that most people's advice is to steer clear of any trimming job that's near electric wires.

(I've never been good at the whole "grounded" vs. "not grounded" concept. I guess I missed that day in science class in fifth grade.)

Well, thanks for any advice for a clueless guy like myself.
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  #2  
Old 06-08-2003, 09:21 PM
Q.E.D. Q.E.D. is offline
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I would let a professional handle it. There's a risk a branch could catch a wire and pull it loose. Even though there's no direct risk of electrocution from the branch, there would be from a falling electrical line, not to mention the risk of it starting a fire.
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  #3  
Old 06-08-2003, 09:32 PM
Blake Blake is offline
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Don't touch it is the best advice. It's doubtful that the whole tree is live, but it could be. It's also possible that as soon as you put a ladder against the tree you'll enable the current to move to earth where it couldn' through the tree trunk.

And heed what QED says. Unless you are a very experienced tree surgeon you have no idea what is going to happen to branches you cut. The can go down or sideways. Occasionally they can even kick up.
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  #4  
Old 06-09-2003, 05:06 AM
nineiron nineiron is offline
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Actually, I'm talking about trimming branches that are literally nowhere near the wire-touching ones, using not a ladder but a pair of loppers (some of these are quite close to the ground, which is why they need trimming), or a pole saw. So there's not really any way they'd catch a branch which would catch a wire.

Hmm. Maybe I should not touch it anyway?
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  #5  
Old 06-09-2003, 05:10 AM
Desmostylus Desmostylus is offline
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If you can touch the tree and not feel anything, then trimming low branches that aren't near the wires should be OK.
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  #6  
Old 06-09-2003, 05:33 AM
Mangetout Mangetout is offline
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The danger, I believe, is that after detaching the branch, it will no longer be attached to the tree, which is grounded, so if you find yourself in the situation where you are on the tree (or a ladder), holding a detached branch which touches the wire, you are part of the path to earth. This could be a bad thing.
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  #7  
Old 06-09-2003, 07:20 AM
Uncommon Sense Uncommon Sense is offline
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Quote:
Originally posted by Mangetout
The danger, I believe, is that after detaching the branch, it will no longer be attached to the tree, which is grounded, so if you find yourself in the situation where you are on the tree (or a ladder), holding a detached branch which touches the wire, you are part of the path to earth. This could be a bad thing.
Even so, you should be ok. The branches are made out of wood on most trees (wood is a good insulator) and the lines themselves should always be insulated.
I would leave it up to a pro if you have the least bit of doubt.
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  #8  
Old 06-09-2003, 07:28 AM
Annie-Xmas Annie-Xmas is offline
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If the branch does hit the wire, it could also short out the entire area's electricity. Your neighbors will be really, really pissed.

That happened with our phone lines once. Took the company 16 hours to get out and fix the damn thing.
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  #9  
Old 06-09-2003, 07:37 AM
Q.E.D. Q.E.D. is offline
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Quote:
Originally posted by whuckfistle
Even so, you should be ok. The branches are made out of wood on most trees (wood is a good insulator) and the lines themselves should always be insulated.
I would leave it up to a pro if you have the least bit of doubt.
Most trees?
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  #10  
Old 06-09-2003, 07:39 AM
Mangetout Mangetout is offline
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Quote:
Originally posted by whuckfistle
Even so, you should be ok. The branches are made out of wood on most trees (wood is a good insulator) and the lines themselves should always be insulated.
I would leave it up to a pro if you have the least bit of doubt.
Dry timber may be a good insulator, living tree limbs with a reasonable amount of sap (consisting of mostly water, sugars and salts) might actually be quite good conductors.
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  #11  
Old 06-09-2003, 07:44 AM
Mangetout Mangetout is offline
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Quote:
Originally posted by Q.E.D.
Most trees?
Well, a banana 'tree' is not made of wood, but then it isn't truly a tree, it is a herb.
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  #12  
Old 06-09-2003, 07:44 AM
Q.E.D. Q.E.D. is offline
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Quote:
Originally posted by Mangetout
Dry timber may be a good insulator, living tree limbs with a reasonable amount of sap (consisting of mostly water, sugars and salts) might actually be quite good conductors.
Well, yes, sort of. But not at 220 V, which is what most Americans have running into their homes (220 V, center-tapped, resulting in two 110 V circuits). The risk of shock from the branches themselves is fairly low. It's the potential damage to the wires that's the greatest risk.
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  #13  
Old 06-09-2003, 08:04 AM
nineiron nineiron is offline
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OK, very helpful so far. I think I will go ahead and trim only the ones that are literally on the other side of the tree from the ones that abut the wires. Thanks.
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  #14  
Old 06-09-2003, 09:31 AM
stevephillips stevephillips is offline
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Quote:
Originally posted by Mangetout
Dry timber may be a good insulator, living tree limbs with a reasonable amount of sap (consisting of mostly water, sugars and salts) might actually be quite good conductors.
Are we talking about the 220 line from the transformer to the house or the distribution lines before the transformer?

I've seen a green tree short out against power lines. I don't mean the insulated 220 line from the transformer to a house, but the distribution lines that transformers connect to.

It was a elm tree and it had been raining. There was a big flash and an enormous explosion, then the power in the whole area went out. The electric company (a small rural electric company) kept turning the power back on, and there would be a another big flash and explosion. I finally called them and explained that I could see the tree shorting the power line and maybe they should stop turning the power back on. They came out and cut the tree down.

My point is, I'd never cut anything on a tree anywhere near higher voltage lines. The insulated 220 lines running from a transformer to the house, maybe, depending on the branch. But the high power lines scare the hell out of me after seeing that tree short out.
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  #15  
Old 06-09-2003, 12:16 PM
Uncommon Sense Uncommon Sense is offline
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Quote:
Originally posted by Q.E.D.
Most trees?
Ahhhh, you caught me. I was trying to slip one in on you guys. Kind of like my "light photons" pun in a different thread that I`m not sure anyone got.
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  #16  
Old 06-09-2003, 12:23 PM
gazpacho gazpacho is online now
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When I had to trim tree near power lines I called the power company. They came out and trimmed the trees for free and hauled the trimmings away. Really call the power company and see if they will trim near the power lines.
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  #17  
Old 06-09-2003, 12:46 PM
nineiron nineiron is offline
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In regard to the power company thing...

I had some other trees (on the other side of the house) that were dangerously close to the wires. I wasn't going to touch those at all, so I called the power company and was told they'd take care of it. They did, but several months later.

The ones now are more manageable, I think. I'm really not talking about a huge job, and again, the branches I want to cut are not near the wires at all. I've been reassured by many in this thread that it's OK to deal with those. I will probably call the power company to do the branches that are actually on the side of the tree that does touch the wires, though.
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  #18  
Old 06-09-2003, 02:59 PM
Uncommon Sense Uncommon Sense is offline
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As far as being grounded or ungrounded:

The power grid needs a ground reference for the system to work efficiently and safely. In a car the ground is the chasis, in an airplane it is the hull, in the electrical grid it is the earth - hence the word "ground".
If you are "grounded" it means that you have become a low resistance path between the power grid and the earth. For safety sake you are considered grounded unless you take precaution to NOT be grounded.
The legal definition of grounded according to the NEC is - connected to earth or to some conducting body that serves in place of the earth.

A situation where you may not be grounded would be if you are wearing dry, crack free, rubber boots, where your body has no unprotected contact with the earth or any conductive material that has contact with the earth.

As an electrician, I have found that common sense prevails.
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  #19  
Old 06-09-2003, 04:32 PM
Crafter_Man Crafter_Man is offline
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If you want to be 100% safe, then don’t trim the tree. But I wouldn’t have a problem with it if the lines we’re talking about are the 120/240 service lines. This is for two reasons:

1. The conductors are insulated. (This, of course, assumes the insulation is in good shape.)

2. If we assume the risk is between “hot” and earth ground (which is true for 99% of electrocutions), then we’re really only talking about a maximum instantaneous voltage of 170 V. In other words, it’s no more dangerous than what you already have at your living room outlet. While this is certainly lethal under the right (wrong?) circumstances, I would have no problem trimming the tree.

Now high voltage lines are a completely different story. Stay away from them. And stay away from trees that are touching them.
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  #20  
Old 06-09-2003, 04:38 PM
Crafter_Man Crafter_Man is offline
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Put another way, it would be no different than trimming a tree with an extension cord draping from it branches. As long as the extension cord's insulation is in good shape, there's little to worry about...
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  #21  
Old 06-09-2003, 06:15 PM
trabi trabi is offline
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I'm not familiar with your local by-laws, but it's a pretty safe bet that you're obliged to report the branches touching the wires so that the electricity co. can come and remove them.
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  #22  
Old 06-09-2003, 06:19 PM
Q.E.D. Q.E.D. is offline
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Quote:
Originally posted by Crafter_Man
Put another way, it would be no different than trimming a tree with an extension cord draping from it branches. As long as the extension cord's insulation is in good shape, there's little to worry about...
True, except that your average extension cord hasn't been exposed to the elements for decades at a time, and doesn't have a 100 or 200 ampere capacity.
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  #23  
Old 06-09-2003, 06:50 PM
Crafter_Man Crafter_Man is offline
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Quote:
Originally posted by Q.E.D.
True, except that your average extension cord hasn't been exposed to the elements for decades at a time, and doesn't have a 100 or 200 ampere capacity.
Current capability does not matter when it comes to electrocution risk1,2. A regular ‘ol 120 VAC receptacle on your front porch is just as lethal as the secondary of the transformer sitting up on the pole; no more, no less. (The voltage is the same. The load impedance is the same. Thus the current is the same. And it only takes less than 100 mA to fry you.)

You also mentioned the condition of the insulation, and I agree with you on this point. I also mentioned this in my posts.


1 This assumes a single "hot" to "earth ground" electrocution scenario, which is responsible for 99% of electrocutions.
2 Well, it does need to be able to source at least 50 mA or so.
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  #24  
Old 06-09-2003, 07:06 PM
Q.E.D. Q.E.D. is offline
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Well, yes, I realize that. Hence the
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