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Member's Forum Steel Conduit - How to Install ?
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  • galvanised_conduit
  • 25mm conduit
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  • conduit
Related

Steel Conduit - How to Install ?

14rhb
14rhb over 4 years ago

Looking around the internet I've found very little to help me understand how electrical steel conduit is installed.....but I'm sure someone on Element14 knows the answers image

 

The question relates to the 20/25mm galvanised steel conduit often used in the UK - this comes as 3m lengths with a external make thread on one end and a female coupler on the other. Unless the fittings are 3m apart the conduit requires cutting and a new thread to be formed, which I already have tools for. The outlets/fixings also come with pre-cut threads; and example of the 90 degree box is shown below:

image

Whilst I can envisage fixing one of the box outlets to the required position and screwing in a piece of cut/pre-threaded conduit I wonder how the next fitting is added. Assuming that is a cut end which I have added a thread to this second fixing would need rotating onto the conduit. Because the first fixing is on the wall there would be no clearance to rotate the second fixing without putting strain on the existing system, this is especially true when the next fitting has additional bosses on it or as the system design grows.

 

Maybe the entire system is designed and then mounted to the wall ? I would imagine that could result in a very heavy setup plus inaccuracies in getting the fittings where required.

 

Any pointers would be gratefully read, thank you image

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  • genebren
    genebren over 4 years ago +8 suggested
    This seems like a tricky installation. In the US, none of the conduit is threaded. Here we use slip on compression fittings (with simple spin on nuts inside the fixture) to attach the conduit to fixtures…
  • beacon_dave
    beacon_dave over 4 years ago +6 suggested
    When it gets tricky you can use 'running couplers' to join two sections together. Overcut the thread long enough so you can screw the entire coupler (plus lock nut) onto it then offer it up and wind the…
  • shabaz
    shabaz over 4 years ago +5 suggested
    Hi Rod, According to sibling, there should be saddles holding it off the wall, and apparently, that provides sufficient clearance to screw on those fittings. I may have got it wrong in my explanation to…
  • genebren
    0 genebren over 4 years ago

    This seems like a tricky installation.  In the US, none of the conduit is threaded.  Here we use slip on compression fittings (with simple spin on nuts inside the fixture) to attach the conduit to fixtures.

     

    What you outlined sounds doable, but this video shows some techniques that might make this a little easier

     

    https://www.youtube.com/watch?v=I-sIJ7Gznbk

     

    Best of luck!

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  • beacon_dave
    0 beacon_dave over 4 years ago

    When it gets tricky you can use 'running couplers' to join two sections together. Overcut the thread long enough so you can screw the entire coupler (plus lock nut) onto it then offer it up and wind the coupler back half-way onto the thread you want to join to and finally tighten the locknuts. 

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  • shabaz
    0 shabaz over 4 years ago

    Hi Rod,

     

    According to sibling, there should be saddles holding it off the wall, and apparently, that provides sufficient clearance to screw on those fittings. I may have got it wrong in my explanation to him though!

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  • three-phase
    0 three-phase over 4 years ago

    It is generally installed on a case by case basis working your way along the conduit.

     

    In some instances, where the access is tight, it is installed as you say, with the conduit cut to size, bent, threaded and accessories screwed in place. The saddles for the conduit are installed on the wall and then the 'preformed section' screwed in place. Yes some times it takes a couple of people to install a larger section. We would frequently make the conduit in sections, mount up the first section and then make the next section, taking all the measurements from the end of the first section. We would then loosen off or remove the first section to allow the section section to be coupled onto it, then re-secure the first section along with the second. A lot of going backwards and forwards, securing, removing and refitting to get the job done.

     

    However, longer runs of conduit have a certain level of flexibility, so you can fix the box at one end, with one conduit saddle and there will be enough movement in the other end to allow the box to still be screwed onto the conduit at the other end. the box can then be fixed in place and you go back along the conduit securing the remaining saddles.

     

    When using conduit in industry, we will also bend the conduit instead of using boxes to change direction. It looks nicer and the cables are easier to pull through.

     

    Instead of using the threaded conduit boxes, you can also utilise adaptable steel boxes with a clearance hole to put the conduit through with a lock ring either side to secure it to the box. This isn't as water tight as the threaded boxes. We also use brass bushings over the end of the thread on the inside of the conduit box to protect the cables.

     

    As a last resort, you can use the combination of a coupler, nipple and a lock ring. You can screw the nipple into the coupler on the end of the conduit as far as it will go in, put the lock ring onto the nipple, then offer up the conduit box and unscrew the nipple from the coupler into the conduit box, once in far enough it is locked in place with the lock ring. Looks awful after it is done mind you. You can make longer nipples up than standard by threading offcuts of conduit.

     

    It is a real art form on big installations and quite time consuming unless you are constantly using it. Probably why flexible conduit was developed to ease some of the installation into tight areas and ultimately why plastic conduit was developed, that tends to be easier with the glue together concept.

     

    Kind regards

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  • chunkasmaximus
    0 chunkasmaximus over 4 years ago

    As with everything in life Rod H, practice makes perfect!

     

    Donald Lane's answer pretty much sums it up.

     

    You just have to work methodically and in one direction - don't try starting at two different points and meeting in the middle!

     

    I've not looked at what advice or videos are available, but as an electrician who has used the stuff on and off since college, the best advice I can sum up is the following (in no particular order):

     

    1. Practice and experiment joining different sections of conduit, boxes, accessories etc in small sections (using off cuts etc), then dismantle and reassemble. This will enable you to get used to doing things in the most efficient order. There's nothing worse than getting to a point, only to realise you have to undo it all. This will also help you with the planning of slightly larger scale installs, so you'll be less reliant on others for help.

     

    2. Use all the available fittings for your conduit system to make your life easier. Like already suggested in other comments, use fittings like running couplers, nipples, lock rings, bushes and the like. This will give you more flexibility and make assembly a little easier.

     

    3. Make the conduit bender your best buddy. A floor standing one is ideal, with a built-in vice if you can. It will be painful and it will take time but, the more you use it the less joints you'll have, the easier it will be to pull cables, and the neater it will look. It really is an art form, and if you plan to work with steel conduit long term, this is definitely a worthwhile investment.

     

    4. Use the right saddles to give you clearance from the wall. There will be enough space to get your grips, spanners etc around your workpiece and get it fitted. As long as the piece you're attaching to is securely fixed, you would be hard pushed to do any damage - it's steel!

     

    5. Lots of accessories, boxes, equipment etc can be connected to conduit systems, but don't worry if it's not obvious or straightforward at first. You can almost always adapt most things to suit, so don't be shy to make new holes or add conduit adaptors or the like.

     

    6. Experiment with it. There is no hard and fast rule to how you should install or use it. As long as the system is correctly supported throughout its length, and cable entries are protected with bushes/glands, design it how you see fit.

     

    And finally, wear gloves. Burrs and metal splinters in soft skin are no laughing matter! Use cutting compound for threads (if you don't already), and a good round or half round file is essential too.

     

    Hope this helps.

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  • 14rhb
    0 14rhb over 4 years ago in reply to three-phase

    Hi Donald,

     

    A great explanation, thank you, with plenty of tips to try out.

    A lot of going backwards and forwards, securing, removing and refitting to get the job done.

    It's really helpful to know that rather than push onwards regardless, thinking I must keep adding and not taking a step or two back. Maybe I should opt for the PVC, its much cheaper, but I liked the idea of trying my hand at this....definitely an art form though, just like plumbing copper pipework together image

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  • 14rhb
    0 14rhb over 4 years ago in reply to chunkasmaximus

    Great advice, thank you chunkasmaximus ....and definitely the last point about gloves. When I get the bits I'll add in a few of these extra bushes, couplers, lock-nuts etc even if I'm nut sure where I intend to use them and them just experiment as you recommend.

     

    It also looks like you just joined Element14, so a warm welcome to you, and thanks again for jumping in with such helpful advice. Hopefully you'll enjoy the E14 community and take part in the projects, discussions, learning modules and roadtests image.

     

    Did you ever add a drain hole in the lower parts of an external installation incase water gets in ? What I find with anything sealed is that if it isn't perfect moist air gets drawn in and condenses but can never fully escape, instead it just builds up.

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  • chunkasmaximus
    0 chunkasmaximus over 4 years ago in reply to 14rhb

    Thanks! I'm still very new so looking around and finding my way, lots of interesting stuff on here! It seems I may have finally found a place where I can 'talk shop' to my hearts content!

     

    I know what you mean about the drain hole, and no matter how well things are sealed, at some point and more often than not, you will find some degree of condensation.

     

    I put it down to two choices:

     

    1. Add a drain hole, and hope insects and spiders don't find it and stay away, or...

     

    2. Let it potentially build up with moisture and water...

     

    I'll take the dry stuff every time!

     

    Having said that, I suppose it depends on what is inside the enclosure that needs a drain hole. If it's just a right angled terminal box (like your picture in your post) or similar, I wouldn't bother. If it's an enclosure for some control gear etc, then I would be very careful about environmental factors - like sealing the screw holes, perhaps silicone along the top edge and sides, drain hole etc etc.

     

    Whether there is a drain hole or not, it ultimately comes down to this: maintenance.

     

    All electrical systems should be maintained and accessible where appropriate. So if there's a chance something could be damaged by possible water vapour or other external influences, check it every so often! You can't beat a good old nose around every once in a while to make sure it's in good working order image

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  • three-phase
    0 three-phase over 4 years ago in reply to 14rhb

    The PVC is cheaper and does not require the same amount of tooling as steel conduit but it isn't as robust mechanically. It is generally easier to assemble as it has quite a bit more flexibility, and is all push fit instead of threading everything together.

     

    It is important to glue joints together that could be pulled apart. i.e. if you have a straight section of PVC conduit between two boxes that are screwed to the wall, then the joints cannot separate. If the conduit has a right angle in it, then the joints can be pulled apart, even when secured with the saddles. In this case it must be glued, which isn't a problem, it is just that if it ever needed alterations, then it gets cut off and discarded, whereas the steel conduit can be unscrewed and reused.

     

    One thing to be aware of with PVC conduit, it that if installed outside in sunlight, it will expand and contract and if extra saddles aren't used, it can end up twisting or warping between the saddles, horizontal sections can sag under these conditions.

     

    If you have a lot to do, then working with steel conduit is well worth learning and there is a lot of satisfaction in the end result, even if there is a bit of frustration in getting there. If it is a one off job, then PVC would be more cost effective.

     

    The only other deciding factor is the mechanical robustness required. If the installation is in areas where there is risk of mechanical damage, then steel is the way to go. Do remember though that steel conduit is extraneous metal work and therefore must be earthed.

     

    Kind regards

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  • 14rhb
    0 14rhb over 4 years ago in reply to three-phase

    Great tips and words of wisdom, thank you three-phase  ....I haven't actually picked up the sections of conduit yet, but I really like the solid approach of steel.

     

    Do you have any advice on how to feed a cable that comes out of the wall into such a setup. I've a Twin and Earth (T+E) cable exiting the brickwork for my external lights but I cannot see if any of the circular boxes available allow cable entry in the back, I don't think they have knock-outs. I could use a gland in the box but it would look messy and a very small bit of that T+E would be vulnerable.

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