Anyone willing to give a quick tutorial on Cadweld?

[Wowbagger]

I have a repeater site that I'm trying to bring up to best practices. The electrician and I both agree we need more grounds, and to bond them together. However, the electrician is thinking like an electrician - grounds are for safety, they carry at most amps of current if there is a system fault. I think like a radio guy - grounds are for lightning, they carry tens of thousands of amps. He is using your standard Home Despot ground clamps on the rods, I'd like to Cadweld them. However, I've never worked with Cadweld, so I'd like some quick pointers - what do I need to buy to fuse grounding wire onto grounding rods; what molds, what clamps, what extras (e.g. ignitors).

[Jim202]

There are a number of places to obtain some good information. I believe that Cadweld has some information on their site on what and how to do.

The big thing is to make sure you get the ignitor to go with the welding compound tubes. Make sure you don't stand in front of the opening, as it will flash out in that direction when it's ignited. You will need the flat, con-caved weld discs to hold the material in the mold before you fire it off.

Make sure the molds that you get are for the ground rod size and wire size you intend to use. They are not exactly cheap. You will also need the handle that goes with the molds to hold them together and in place.

Do not beat on the molds. They are made from graphite and will break easily. They do need to be cleaned after every use, but be careful as to how you clean them. You don't want to scratch the surface, especially at the openings. This will let out the liquid material before it cools and solidifies.

There are several companies that make the exothermic welding supplies. Cadweld is just one of the brand names out on the market.

If you know a tower crew or an industrial electrician, it may be cheaper to hire them than buying all the materials yourself.

I think Hutton and Tessco carry the supplies.

Jim

[Bill_G]

There are a bunch of YouTube videos on Cadweld and other exothermic products. Super fast and easy ... if you have all the correct stuff. Contact a local electrical supplier for product. Hutton can get you the molds, and wire, but not the charge. It's not something that UPS can deliver to you.

https://www.youtube.com/watch?v=Ru4XvPxl9Ao

[Wiregeek]

I'm gonna chime in and back Jim202 - this may be a scenario where it's better to hire out the work. A tower company will have training and supplies on-the-shelf for this job. You may end up saving money as well, since you don't have to buy all the hardware neccesary.

[Wowbagger]

It's as much a chance to learn something new as anything else. Granted, it's unlikely to help my day job; but it is fun when I run into somebody who thinks that I cannot possibly understand all the intricacies of radio because I do SDR.

[Bill_G]

Are you making a buried ground halo, or just driving stakes into the earth? If you're making a buried halo, then yes - go through the expense of doing Cadweld. But, if you're driving four corner rods tied to an interior halo, then just use good brass ground nuts with No-Ox. They last forever, and can be easily inspected. Much cheaper.

[Wowbagger]

The site has a ground network, and our rods are connected to that ground network. We are bonding the building electrical, antenna entries, and equipment both internally and to the rods.

[Jim202]

The site has a ground network, and our rods are connected to that ground network. We are bonding the building electrical, antenna entries, and equipment both internally and to the rods.

You don't want to use the exothermic welding inside the shelter. The fumes will cause you health problems and set off any smoke detectors you might have in the shelter.

You would be much better off using the 2 hole crimp lugs to do your grounding inside the shelter. Hopefully the master ground bar your using and the ground bar under the coax cable hatch plate both are set up for the 2 hole lugs. Reason being is the migration away from the single hole lugs as they come loose with cable movement. The double hole lugs will not come loose, no matter how much movement the cable might have put on it. But you will need a good heavy duty crimper to use the correct lugs.

Another point to keep in mind is to use some sort of anti oxidant compound under all the ground lugs at their connection point. This is both at the grounding bars and at equipment rack ends. Any paint at the equipment and door frame ends should be removed before making a connection. There is at least one shelter company that tends not to do this most of the time. Make sure you de-burr any drilled holes you may make for the ground lugs. Use stainless steel hardware to secure the ground lugs to the ground bars and equipment racks.

If you don't have a copy of the Motorola R56 standards, you might want to do a search on the Internet for it. It has been available for download from a couple of sources over time. There is a wealth of information in there on grounding. The original A version contains all sorts of other site information beyond just grounding. The B version is more limited to grounding. The A version is over 24 megs in size and the B version is over 10 megs in size.

Jim

[Wowbagger]

No, I'm not looking to use Cadweld in the building - the rods are outside, with ground wires exiting the building to the rods.