A unique installation of PVC conduit

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  #1  
Old 11-24-04, 06:30 PM
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A unique installation of PVC conduit

I just completed the installation of a 100 amp subpanel in the basement. For the project I bought 3 20-ft pieces of #2, a bare #6 ground, and 1-1/4" PVC conduit. While the two panels are only 10 feet apart on the same wall, obstructions near the wall forced me to use 1 horizontal and one vertical 90 elbow at each end. I assembled the empty conduit and cut it to size, then put the conductors into the conduit on the floor. I thought it would be possible to take this assembly and, with the help of another person, get the conductors through the knockouts of each panel and drop the assembly into place. How wrong I was. We could only get one end in but not the other.

So the next idea was duct tape the conductors together, slip the two elbows onto one end, stick that one end into the knockout of one of the panels, then assemble the rest of the conduit in the air. This turned out to be an even worse idea for many reasons I'm sure you can imagine.

This leads to the drastic solution which finally worked. We inserted two elbows on one end and inserted the conductors into the knockout and secured it. We then did the same thing at the other end, leaving the middle (straight) section exposed. We took the straight section of conduit and cut it into 8 pieces approximately 1 ft each. Each piece was then sliced down the middle with the bandsaw and cleaned. Each piece was then assembled over the exposed conductors and held together with duct tape. In the end, it was effectively one straight, cohesive piece of conduit.

Now, I assume that this is against code. But is it really? The assembly protects the wire and is secured to the ceiling every 2 feet with 17gage wire, so it is structurally sound, so I don't feel there is anything unsafe about it. The conductors are protected, and its indoors so it doesn't have to be weather tight. Just curious what you guys think of this. Then again, maybe I really don't want to know. LOL...
 
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  #2  
Old 11-24-04, 06:38 PM
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Definitely against code. The conduit must be assembled first then the wire inserted. Duct tape is also not a UL certified electrical device.
 
  #3  
Old 11-24-04, 06:47 PM
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Wow, that was quick. So it is against code, but why is it unsafe in a practical sense?
 
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Old 11-25-04, 09:17 AM
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This is sorta like debating if it would be OK to do the same to plumbing pipe and wrap it with electrical tape. Might it serve the purpose? Sure. Is it 'safe' or secure? No. There are very specific design considerations tha go into the manufacture of PVC as well as the code rules around its use. Those rules are for YOUR safety.

The first problem you'll have is that duct tape won't last forever. I've seen duct tape after a number of years, and it doesn't hold anything. It's a handyman tape, and it is not rated for use in electrical installations. The fact you posted here tells me you doubt the integrity of this installation, and so you should. It's not safe and represents a hazzard.

So how to you run wire in a case like this? There are plenty of people here who could have helped you in that regard.

The first problem is that you probably tried to push the conductors through the pipe. While fine for short runs, any run with a bend will be far too difficult when using large conductors. As noted, you are supposed to assemble your pipe FIRST, then run your conductors. So how do you do it? First thing first, turn off power if either panel is live. (never pull wire in a live panel)

Once the pipe is installed and secured in place to the walls, get a fish tape and push the tape back through the pipe. (fish tape is a small coil of steel wire on a retractable roll) The fish tape is small and flexible, which makes getting through easy. With the fish tape through, use it to pull a rope back through the pipe. The rope should be strong enough to pull the wire without breaking. Now that you have a rope running in the pipe, you connect the rope to the wires and use lots of elecrical tape to make the 'head' of the wires neat and tight. Now you get a bottle of what we call 'yellow', or wire pulling lubricant, and generously coat the end of the wire and the entrance to the pipe.

With one person pulling from one end, have another person FEED the wire into the pipe, trying to keep it so there is a straight run into the pipe. If it's a tough pull, perhaps have two people pulling. In time you'll have your wire through, so long as you properly attached the rope to the wire. (if not it will come off and you'll have to try again) If you have smaller conductors you can use the fish tape to pull, but these conductors are far to big for a fish tape pull through bends. (although I'm sure some people might try it)

The key is feeling the wire and applying lubricant as the wire is being fed into the pipe. A dry pull is hard in the best of times, a dry push through 2 bends would be impossible with that wire.

Why not start over and do it right, and that way you won't have to worry about getting a good night's sleep.

Regards,

Savant
 
  #5  
Old 11-25-04, 11:03 AM
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Thanks for the reply savant. I cannot imagine pushing/pulling all those conductors through four opposing elbows with any amount of lubrication without breaking the conduit or the panels, or ripping the panel off the masonary wall.

I don't see the analogy to water pipe. The conductors are insulated and aren't going to leak electricity if the conduit isn't tightly bonded. The way it seems, the proper analogy to water pipe is if the plumbing code forced you to put a pvc pipe around all properly soldered copper water supply pipes.

What I still don't understand, is that even if all the tape were to unravel right now and all the insulated conductors were suddently exposed, what would be the danger? Everything is secured tightly every 2 feet with 17 gage wire. The conductors are rated for underground use. Short of cutting it with a saw or accidentally driving a nail or other blunt object through it, I don't understand the real world hazard. The hazard can't be heat, since the PVC is combustable.

Here's something else to ponder. A few years ago the power company installed a new underground cable to our house when we (professionally) upgraded from 100 to 200 amps. Since our soil is so rocky, they had to dig a trench. I watched as one of the workers laboriously wrapped a thin flexible PVC around all 300+ feet of the 2/0 or 3/0 cable assembly and secured it with, guess what, duct tape. I asked him why he was going through the trouble, and he said it was to prevent rocks from penetrating the cable during the backfill. I asked how in the world this flimsy tubing was going to provide any meaningful protection, and all he could do was shrug his shoulders and say he had to do it by code.

So on one hand, we have conductors that are buried under about 3 or 4 feet of rocky soil, with only 1/4 to a 1/2 inch of extra insulating material surrounding it. This is supposedly code compliant. But having an "exposed" insulated conductor indoors and out of harms way is against the code. Please help me understand this logic.
 
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Old 11-25-04, 01:16 PM
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Angry

I never try to convince anyone WHY a code requirement is what it is.


Now, have YOU tried to convince your inspector that this installation is OK? ( You DID get it permitted and inspected, didn't you?)
 
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Old 11-25-04, 05:21 PM
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You need to use pulling Ls to get the wires though.
 
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Old 11-25-04, 10:41 PM
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I know it doesn't make much sense, but direct burial is a different beast that mounting in a dwelling.

As noted, there are other options to doing pulls. A 'pull elbow' (like an LB) can allow you to take what would have been a pull through a 90 to be be two straight pulls. Keep in mind that all pull elbows must be kept 'accessible' after the pull. (they can't be covered in a finished wall) Another option is to slightly oversize your pipe, instead of 1 1/4, perhaps 1 1/2 or 2". (depending on your situation.) Then you would have an easier time pulling through the 90's.

There is also the option to use 'teck' cable (armour clad cable covered in flexible PVC) but it would depend on your local code. We use teck cable regularly in Canada when doing runs in 'hazzardous' locations. This cable just mounts straight on the wall, but it's not good at doing outside corners. (for obvious reasons) You can do other bends with it though.

In any case, there are always options, but it's best to ask before you do what you know you shouldn't have done. (I'm sure you knew that ripping the pipe like that wasn't acceptable)

Anyway, perhaps you should decide whether you want to live with the risk. Anyone here will say that you should correct the job, but no one can force you. In the end the decision is yours.

Regards,

Savant
 
  #9  
Old 11-26-04, 04:17 PM
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Hi Savant,

Thanks for the reply and your patience. I actually had bought some LB elbows but they didn't work out because of insufficent clearance from the panel to the ceiling.

I figured it was against code before I did it. I decided to post this topic because I wanted to know what the actual risk of this installation was, because as I did it there certainly didn't seem to be any. So far the responses have confirmed what my gut told me. Nobody's specified an actual, realistic safety risk associated with this installation.
 
  #10  
Old 11-28-04, 01:05 PM
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I don't want to be insulting, but your assessment of the situation is the worst kind of clueless-ness.

The fact is that your installation _may_ be perfectly safe. Or it may have some subtle failure mode that neither you nor anyone else here can predict. Perhaps the tie wire that you've used to hold this mess together will fail due to magnetic stresses during a short circuit. Or perhaps the normal movement of wires in the conduit, caused by heating and cooling as the electrical load changes, will cause the insulation to abrade on the sharp edges of all the many cuts that you introduced into the conduit. I don't know, you don't know, and no-one else here knows. It might be perfectly safe, or it might not be safe, and you don't know; you are simply guessing.

The fact that no one on a random DIY BBS can come up with 'your install will fail in this way because of this physics' is simply not sufficient reason to declare the installation safe.

You should immediately replace this installation with a properly installed _listed_ raceway system.

With conduit, you always assemble the conduit and then you pull the cable through. You will be able to pull the cable as long as you follow the rules for conduit fill and maximum number of bends, and if you use cable lube. You _never_ pull the wire through 'elbows'. An elbow is a sharp bend with a cover; you use an elbow as a pull point. When you need to have a bend between pull points, then you use a 'sweep', a very large radius bend that is easy to pull past. You can buy these pre-made, or you can use a conduit bender. Properly installed, you should have no problem pulling these wires through this conduit.

If your situation can only be solved by assembling the raceway around the wires, then use an approved system for this sort of installation. For example, you can buy _split conduit_ systems that work similarly to what you did with a saw and duct tape, but which have been tested for use. These have carefully designed joining techniques and fasteners that will properly hold the conduit together during short circuits, won't cut the insulation on the conductors, are suitable for use as grounding, etc. Or you could use a system such as wiremold or wire duct.

-Jon
 
  #11  
Old 11-28-04, 08:37 PM
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Thank you for the reply winnie.

In response to the possibility of the sharp edges cutting the insulation, after I cut the PVC I made sure to sand off the sharp edges. The insulation was extremely difficult to penetrate with a razor blade, it's hard to envision blunt plastic making it through.

As for the wire supports, I will replace these ASAP with something more sturdy and non conductive.

I do realize that nothing I say or do will make this installation code compliant or perfectly safe, nor change anyones opinion about my attitude towards the situation.
 
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Old 11-28-04, 10:47 PM
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It is important to follow code if you understand why the code exists. But it is far more important to follow code if you do not understand why the code exists.
 
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Old 11-29-04, 03:54 AM
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No, don't replace the tie wires with non-conductive ties; I was giving examples of _possible_ failure modes because _I don't know_ if this installation is safe or not. It could equally well be that strong metal ties are really what you should be using. _I don't know._

Replace this with a properly listed wireway, otherwise you are wasting my time and yours.

-Jon
 
  #14  
Old 11-29-04, 08:48 AM
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I have to agree with John and Winnie, there is no point trying to rationalize this. With no disrespect to the original poster, you seem to be looking for some form of 'validation' to ease your conscience. Let's face it, if you were 100% comfortable with the way you had done this install, then you wouldn't be here asking for opinions. So the fact you are here tells me you have reservations and you were hoping we could put your fears to rest.

We can't.

Electrical codes are created with a purpose. That being to provide guidelines and rules which will assure a given electrical installation will provide the least amount of risk when completed properly.

Look at it from a historical point of view. A long time ago they used to use 'knob and tube' wiring in homes, and it was completely acceptable. However, that kind of wiring is no longer used and no longer allowed to be installed. Have they forced people to remove properly installed knob and tube wiring? No. However, that doesn't mean that just because the old stuff is considered 'OK' to have in your home, doesn't mean that it is safe by today's standards.

Safety is relative, not absolute. There is no such thing as a 100% safe installation since there is no way to take into consideration every possible situation that might develop. However, given past history and experience, the electrical codes have been developed to optimize safety in electrical installations.

Could a 'sub-par' (not up to code) installation be 'safe'? Again, that's relative. For example, properly installed knob and tube installations are considered safe but they are no longer allowed to be used in new installations. This would rightfully suggest that while a properly installed knob and tube installation is considered safe, a properly installed romex (residential) installation is considered to be safer.

Is it not unreasonable to suggest that we should all strive to have the highest level of safety in our homes? Are our loved ones lives not worth the extra time or effort?

To use another analogy, you could forgo putting a lock on your front door, instead just using the little 'latch' on the screen door to prevent entry. Is that 'safe'? That depends. A prospective burglar may try the screen door, see it is secure, and move on. A more emboldened burglar may instead know that a simple hard tug will breach the latch. Would a deadbolt be safer? You bet. What about cars? You could drive a car that only has seat-belts. However, would not a car that also had air-bags be safer for adult passengers? Which would you rather have if you had the choice? (when driving alone or with other adult passengers) Another example is smoke detectors, which never used to be required in homes. That was considered 'safe' years ago, but it is not considered safe now, even though not having smoke detectors doesn't make a home any more likely to catch fire. I could go on and on...

In the end, safety is relative.

This installation, as you have completed it, you may consider relatively 'safe'. However, since it is not to code, it is not safe as defined by today's standards and codes. Those standards are there for your protection, to help keep you and your family alive. Just because nobody has "specified an actual, realistic safety risk associated with this installation", doesn't mean that it is safe.

In then end you have to decide what is more important to you. The time and cost of doing a job right, (and up to code) or taking the shortcut and possibly endangering the lives of you and your family.

I know what my choice would be.

Regards,

Savant
 
  #15  
Old 11-29-04, 09:14 AM
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Well said Savant.

Electrical codes are created as a result of the post mortem analysis of injuries and fires. Almost anything is relatively safe when all systems are functioning perfectly. The purpose of most electrical codes only is evident when something goes wrong, when a fault occurs.

You could probably put on a blindfold and walk back and forth across the street in front of your house a hundred times and not get run down. That doesn't mean it's safe. Most codes guard against hazards that happen very rarely. But they do happen.

Having said all that, not all code violations are the same. Some are worse than others. The code violation we are discussing here certainly isn't the worst thing I've heard. And I must admit that the code probably does prohibit things that are not unsafe, but just haven't yet been proven to be safe. The code also prohibits some things just to keep the rules from being overly complex.

Follow the code 100% of the time and you're relatively safe. Violate the code and you're on your own. We all do what we have to to be able to sleep at night.
 
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