Archive for the ‘Lightning’ Category

An Minor Diversion into DNSSEC….

March 21, 2012

I realised recently an interesting milestone has been reached, that will thrill the people who have slaved on DNSSEC for over a decade: DNSSEC running end-to-end, into the house the way “it should really work” without requiring any configuration or intervention has happened.  After all the SOPA/PIPA anguish, seeing DNSSEC come to life is really, really nice. This post may also interest router hackers who’d like a real home router they can afford, particularly one that will do mesh routing.


New ground system

August 31, 2010

For a number of years, I’ve had reason to suspect my house’s ground isn’t what it should be.  Then, again, recent events may have just made me paranoid.  But I think I’m right….

I went on a energy conservation binge several years ago, and bought a TED 1002 to help understand where my power was going.  But I had quite a bit of trouble with it, and it is clear from reading its support forums that its Achilles heel is susceptibility to electrical noise.  In particular, if my well pump went on, its display would stop hearing the MTU’s; as we have geothermal heat pump, this is most of the time I’m using most of my power.  Adding a filter on the well pump circuit reduced, but did not eliminate the problem.  I was able to get it to work just well enough to debug a number of problems in the house’s energy consumption, but never well enough to really reply on it overall.  I’ll try to see if it works properly sometime soon (but I think one of it’s MTU’s was damaged by lightning as well). The one working MTU now seems to signal fine even when the heat pump and well pumps are running, so I’m hopeful I’ve also cured my electrical noise problems.

The existing ground for the entire house had been solely a thumb sized piece of stranded copper cable, that runs entirely across the house to the well located on the far side of the house from the power panels, in parallel to other circuits in the house.  This is far from desirable for a lightning ground, though clearly meeting code requirements, even if well bonded to the well casing well; and I have no good way to inspect that bond regularly.  Some of the reading I had done indicated you may have noise in your house wiring if your grounds are not well bonded to ground.

We have a iron fence (with normally closed gate) that runs a long way from the house under several more oak trees; I was concerned about ground bounce if one of the trees were hit, and you should always bond any metal objects within 4 feet of a ground system (for safety in a storm).

I decided to install a much better ground for the house, and for it to be located on the side of the house nearest the power/cable/telephone entrance.  Additionally, the pool pump had failed this time, which was probably caused by a poor neutral bond in the pool shed (which has its own ground, as it should; but I’ll probably add a fresh ground rod to it sometime soon).

As part of relocating my Comcast cable, they had to trench along the side of the house; I asked the Comcast  contractors who did the work not to fill this trench, just to save effort.

If you read the ARRL documents, you may have learned that copper strap is much better than wire or cable per pound of copper. This is due to the skin effect of conductors, and the fact that lightning occurs so fast it behaves as RF energy, rather than DC current. Big copper cables like the existing house ground are also a PITA to deal with, being very hard to bend.  So I decided to do this right, and use 2″ copper strap rather than wire or cable to connect my single point ground system to the new ground rods I had installed.

While doing my homework, I learned that exothermic welding of the strap to the ground rods is much better than the typical mechanical bonds generally used. Exothermic welding is exactly like thermite: it is a chemical reaction that rather than resulting in molten iron, results in molten copper. This is sometimes called “cadwelding” after the name of one of the companies that supplies the molds and “shots”.  I don’t want the ground rods sticking out above ground just to be able to inspect the bonds; if exothermically welded, there is no possibility of corrosion at that joint, since it is an actual weld, and I could then bury the ground rods and forget about them forever more.

Additionally, the copper ground rod clamps to properly mechanically bond copper strap to the ground rod turn out to be expensive (something like $31 a piece; versus $16 for a “shot” when exothermically welding), and the clamps take time to clean and assemble.  So there is a break-even point where connecting the straps “right” via welding is cheaper than doing it with mechanical bonds.

And I’ve always liked fireworks :-).

So I decided to exothermically weld the strap to the ground rods despite the marginally higher cost for five ground rods.  Ding so was much simpler said than done: finding the right mold to order and where to order it was very time consuming, but in the end I succeeded.  And it worked like an amazing champ!  The 2″ copper strap was solidly welded to each ground rod really quickly and easily.  No possibility of any problems, and it was much faster than assembling mechanical clamps.

Erico CADWELD® is the well known guys on the block.  But I couldn’t figure out for the life of me if Erico sold molds for strap to ground rod.  The other guys who sell exothermic weld molds are Harger: the Harger Ultraweld, and they indeed do make molds for copper strap. The handles for the molds are usually interchangeable between vendors, I gather. You have to buy both a mold and a clamp handle.  So I went with the Harger mold.  I probably should have video’ed the process, but it would have been completely redundant to the existing videos, such as this YouTube video, one of many.

Feeling too poor after this event to immediately install a perimeter ground system all the way around the house, I decided to put in five ground rods on two straps.  Each segment of the iron fence is also bonded to the straps, using special stainless steel pipe clamps (the clams have an extra piece of stainless steel tack welded to them, so that the copper does not bond directly to the steel; you’d have electrolytic corrosion if you don’t take that precaution).

You need to space the ground rods at about twice their length apart to dissipate the energy (about 16 feet, given these were 8 foot ground rods.  With only modest additional digging beyond what Comcast had done for me, we were able to get the strap from the house to the five ground rods using a bit under 100′ of copper strap.  Thankfully, we were able to get all five ground rods almost completely driven without excessive effort; I had worried about hitting ledge or a big rock (this is New England, after all). The tradesman I used was a local guy; your conventional electrician will almost certainly  charge much more and be just as clueless, so you might as well work with someone who can take direction and do what you ask.  Even with a snafu about having the right tool for pounding in the ground rods, we finished up all five including reburial and cleanup in one day, so I got away with only about $400 for labor.  It was probably 10 hours actual work to do all this (but my bad back would not have dealt with driving the ground rod, so I had to hire the hard pounding and digging).

I’ve updated the picture on the previous blog post with the finished work (though I just added the last bolt after I took that picture today).

After properly cleaning the straps, applying the copper joint compound and bonding them to the fence, and doing likewise on the single point ground system, and all the cleanup, I’m done!  This time, I used a little copper plate over the ends of the straps and bolted that to the SPG panel; I’m much happier with that solution than the bolts I used directly when bonding the strap from the SPG panel to the existing house ground cable.

Someday I might like to install a perimeter ground; who knows if I’ll ever do so.  I definitely want to redo the ground rod at the pool shed, as it is old enough to possibly need replacement.

And, of course, I’ll never know if I’ve done all this effort right, statistics being what they are.  But mother nature will tell me if I’ve overlooked anything sometime, I expect. Such is life…..

To save others who want to exothermically weld strap to their ground rods, I include here exactly what I ordered via my local electrical supply company (Harger will happily tell you who acts as distributors for them in your area).  I found it really hard to track this information down, and was unable to find anyone stocking molds for strap online; Harger’s part numbering system for molds is pretty inscrutable and I finally confirmed the numbers with a call to Harger. I suspect a lot of ham operators give up and order ground rod clamps and/or use ground wire/cable in disgust, despite it being better and possibly cheaper to exothermically weld strap. It took less than a week for the order from Harger to be fulfilled, even via my local distributor. The part number below is for 2″ x .022″ copper strap (Harger says the molds aren’t very sensitive to the thickness of the copper strap).

1 HGR GVSO582016K 166.86 166.86
10 HGR UWM200 WELD METAL 16.08 E 160.80
1 HGR MH1 MOLD HNDL CLMP 77.84 E 77.84

As noted before, I could have lived without the clamp with some metal clamps of the right size, though the mold handle is certainly very convenient; and the mold cleaning brush can be almost any small stiff bristle brush (though probably not a wire brush; the molds are made out of graphite).  Keep the mold bone dry.

Single Point Ground System

August 29, 2010

The principles of a single point ground system are well covered in ARRL’s lightning protection page.

First is to identify everything coming into/leaving the house.

In my case, that includes the POTS telephone line, the cable from Comcast, the irrigation system wiring, the house ground itself (more about this in a separate post), power to the pool shed and power from the power company. Since I’m not a ham, I don’t have the additional complication of an antenna and its controls.

In a small house or apartment, a conventional UPS with protection for cable, telephone, and power may very well be all you need in a simple environment of co-located equipment . I’m not very happy with the single UPS idea, since if any single component fails, you get to replace all of them, and it’s not clear you can easily detect if a component fails (nor what the quality of them are).

My house makes life hard; there is a big chimney mass so that I have to run multiple 802.11 access points to get coverage, and I therefore had to run quite a bit of cat6 cable to solve this problem. The length of time to do backups given current disk sizes also argues against complete reliance on wireless.

I’ve had the most failures in my cable modem due to lightning. For me, therefore, a prerequisite was getting Comcast to move the cable, which had been mis-installed on the front of the house, causing a 60′ or so separation from the wire entrances. This was a major adventure that I may blog about later.  After a couple months of effort, I succeeded in getting them to move the cable entrance to near my power and telephone entrance but not until after the most recent and most expensive lighting event, despite having started trying to get them to do so well before the event.

The ham radio industry is the usual hobbyist racket on prices. You can often do better on prices if you shop around: other companies specialize in serving the larger radio station and mobile radio markets. I found a company Georgia Copper was useful for some of what I needed rather than paying the inflated prices for companies catering directly to the retail ham market, particularly for what I needed for my grounding project. This is not to say that the companies catering to the ham market are bad; and Polyphaser in particular is well known and from all accounts sells good stuff that you’ll find in all the reputable RF industry suppliers, just that you can spend a lot more than necessary if you don’t shop around, particularly for joint compound, copper strap and ground rods.

I had space between several power panels to mount the single point ground system, which is based on a 12″x12″ copper plate. Feeling poor (due to having to replace so much gear), I ordered a copper plate of the right thickness (.065″) via Amazon for $30, rather than getting the fancier premade ones you can get for the ham market. Note that the Polyphaser equivalent is about $200, but does include a lot of the ancillary stuff you’ll need, including the anti-corrosion joint compound goop, a some copper strap, and clamp to attach the strap to your main house ground, so my actual savings was probably only a bit over $100. Thinner copper would probably have made it impossible to tap the screw holes. Hams like spending on their hobby, and will often spend much more than they need to; this is common behavior among enthusiasts.

I mounted everything on the copper plate. In this case, this included:

  • A protector for the POTS telephone line
  • A protector for the cable
  • The cable splitter splitting my TV and cable modem
  • A protector for the ethernet output from the cable modem to the rest of my network empire

There are various flavors of these devices: having been burned so much, I got better than usual versions, along the lines of what a ham or radio station might invest in. Even so, they aren’t all that expensive. Note that you want “fail dead” devices, that self-sacrifice, and that they come in a number of flavors, that have different characteristics around how fast they react and how much energy they can absorb. Some of these kinds of protectors may have replaceable neon bulbs that die upon a strike.

The copper plate for mounting the protection devices is thick enough that I tapped holes for machine screws. Others may find it easier to use sheet metal screws. All the protection devices and the copper plate they mounted on were carefully cleaned, and were mounted using special anti-corrosion joint compound “goop” that also has conductive particles of copper in it. You want to use stainless steel or bronze in any fasteners, rather than the usual galvanized steel (bronze is best, but hard to get particularly in small sizes). You don’t want to have to come back years later and find electrolytic corrosion has done in your careful work. Amazon turns out to be a good source for stainless machine screws and hardware; they apparently do a good business for industrial, research and development shops.

Here’s a picture of the resulting single point ground system after initial installation, but before completion with the new house ground and telephone line hooked up.

Finished single point ground system

Finished single point ground system

The upper left hand corner is a Cat6 Ethernet protector, wired on the outside port of my cable modem and connecting to my internal network. The slightly smaller protector beneath the Ethernet protector, not yet wired in this picture, is for the incoming Verizon telephone line. The incoming cable from Comcast is the black cable in the center, and it is protected by a smaller black device with replaceable bulbs; its output goes up to the cable splitter to connect to the existing TV cable wiring in the house and the cable modem (the upper black box with all of the LED’s lit). 2″ wide .022″ thick copper strap is bolted on the upper right corner, and goes over to the house ground, which, until augmented a few days ago, consisted solely of a large thumb size copper cable that runs across the entire width of the house and is bonded to the house’s well casing.

Things I’d do differently if doing it again: I mounted the telephone and cable protectors a bit low on the copper plate. This caused some problems mounting the strap to the new house ground I installed last Friday and ideally, I should have mounted both a inch higher. I also don’t like the bolts and washers holding the ground strap down, so I used a piece of copper plate for the new ground system. The strap to the old house ground cable goes off at the upper right due to mechanical constraints of where I could mount the ground plate; ideally, you’d prefer to keep all the ground straps nearer the bottom.

Why copper straps? I’ll discuss that in my next blog entry about the new grounding system I installed.

Another en-lightning experience…

August 27, 2010

For the third time in two years, we suffered significant damage from a nearby lightning strike.

Remember the old adage “lightning never strikes in the same place twice” is in fact correct: lightning strikes in the same place many, many times. If you’ve had damage once, expect damage again and again.

We live near the top of a hill, the highest for several miles; and it is covered by tall oak trees. A way to think of our house is as though we are surrounded by antennae. As the amount of electronic gear in our house has continued to climb, repairs have become increasingly bothersome and expensive, despite increasing measures to try to prevent loss.

After the first serious event two years ago, I started to do the usual things of simple surge protectors and UPS’s for the computers. The event of summer 2009 and thousands of dollars more damage made it more urgent, and I started reading about what to do more seriously: e.g. putting in more explicit surge protection on my Ethernet cables, etc.

A good general online reference on how to protect yourself about lightning is “How to Protect Your House and Its Contents from Lighting“,  by the IEEE. After some research (e.g. section of the IEEE document), I realised that the cable entering our house had been installed incorrectly; it entered on the front of the house, and should have been located on the side to enter near the electric service. This is bad… Also note that the phone or cable company put in grounds and various protection for their equipment: but those grounds and protectors are to protect their equipment, not yours.

But I was busy with a new job, and very ill most of the winter and spring, so it was only in early May that I started to really take action. Not soon enough, it turned out…. So I called up Comcast, who had bought the mom-and-pop cable outfit for my town some years back, and asked them to move the cable. I’ll spare you all the gory details of several no-shows followed by other problems; but the net result is that the cable had not been moved by the latest lightning strike that occurred the first week of June.

This time, the strike took out the cable modem (third in two years), several ethernet switches, the pool pump, the washing machine, my router and an access point, the irrigation system, a UPS and a surge protector and maybe the ice maker in the freezer (it has a big bucket of ice, and we didn’t notice for a week that it wasn’t making ice, so it’s probably also a casualty). Our computers themselves seem to have been protected by the UPS/surge protectors. (In past events I’ve lost several ethernet interfaces.)


Now the fire drill started, by urgency of different things to get fixed.

Off to the computer store for a new cable modem (it was Friday night, so I couldn’t get Comcast to swap my cable modem), and ethernet switches. In our house, people get really grumpy if they don’t have their Internet fix. Having had way too much experience debugging my network, I knew exactly what was likely busted and what to buy this time….

BTW, if you have Comcast, and they’ve upgraded your service area to DOCSIS 3, it’s worth getting a DOCSIS 3 modem even if you don’t buy faster service. Their “Turboboost” feature lets you get lots of bandwidth for a short period, and its noticeably faster. But this leads to another set of blogging I plan to do soon on discovering what’s been going on in my Internet service, which I’ll save for a later date, for reasons you’ll understand when you read it.

Next on the urgency scale was the washer… At least the lightning had the kindness to kill our hated washing machine and clothes shredder this time, though of course, it is infuriating that you can’t economically fix things anymore. Figuring out it didn’t pay to get it repaired took days of time, of course, by the time we decoded the washer’s error message, and the repair person said it could be either of two expensive components (the microcontroller and the motor controller), which didn’t want to talk to each other any more.

I also had the electricians in to look over to see if any of my wiring was bad: they did find a loose neutral in the pool shed, which may have accounted for the pool pump, and did other checking. I then arranged for them to put in whole house surge protectors, on my electrical panels. Note that unless you do some homework, you might not realize that such surge protectors have a limited life, so you really want idiot lights on them to tell you, the idiot, when they need replacement.

I also had to figure out what to do about the pool pump, which had its electronic brain fried and the pool was turning green. I had been very happy with the new one I bought a year or two back; the Pentair Intelliflow is amazingly low power consumption and extremely quiet, immensely better than older pool pumps. By running the water very slowly, you reduce the turbulent flow in the pipes and it is much more efficient than conventional pumps. I had figured it would pay for itself within a couple years. But the pump gets this by electronic smarts, and they fried. Again, the pricing is such that it doesn’t pay to replace just the pump controller; for only a hundred or two dollars, I could buy an entire new one from Amazon. Grrrrr…. Another example of “you can’t repair things anymore”…

Next on the list is the yard; it was wilting in a dry June summer. This time, the controller was “blown up”; you could see blackness around the electronics controller, and its door blown open, and its surge protector fried. Something slightly less dramatic occurred a year ago, and you can’t really get old fashioned mechanical controllers any more (that had run the irrigation system for so many years). I call up the contractor who had installed it, and ask them to come fix. He installed a new controller, but was completely incapable of figuring out why 1/4 of the zones wouldn’t work. The guy they sent had no idea how to use a multimeter to debug the problem. I got to teach him how to use a meter, to figure out the common on that cable was open causing all zones on that cable to not work. (that cable went near the tree that came down in the storm when the lighting struck; the two may be related). And then I taught him to do a binary search to determine which segment of cable was damaged… Of course, this defeats why you call repair people in the first place; one might hope you don’t have to teach them how to do their job. He should have been paying me for the lesson in repair; rather than me, paying his employer… After much hassle and a day of wandering around the yard, water was flowing again (though I still have a few zones to fix).

It is clear ham operators know lots about lightning, and they are a garrulous sort by nature and like talking about technology. I gave my friend Bdale Garbee (KB0G) a call. While living on a dry mountain side in Colorado (where it is hard to get a good ground and lightning is frequent), and his wife Karen observing 2 direct strikes on his antenna, he’d had about $100 total damage in 25 years. That was more like it. The ARRL has some very useful lighting information on their web site.

My reading last fall and this spring helped me decide to to emulate what the radio industry and ham’s do, and install what is called a “single point ground system” in my house. Any wire entering the house may be the source of your surge; you have to protect them all. In short, you bring every ground to a common ground plate; the house electric ground; the surge protectors for the cable, the surge protector on the telephone line. The idea is you want to keep everything at the same potential; it is voltage differences that cause destruction of equipment. You really want to tie together all the grounds at a single point, else a surge from one wire entering the house travels across the house doing its thing until it reaches ground. This is why having my Comcast cable come in the front of the house was such a problem; a surge from that direction might first enter the house, and then find things like my computer network or the house wiring the easiest path to ground. A year ago, the wall wart for my cable modem was blown across the basement…

I’d already not been happy about my electrical ground: it is a big cable that runs all the way back across the house to be bonded to the well casing; it’s a long run, and I’ve observed electrical noise problems in the house (which I now take to be a sign of a bad ground, having educated myself). If you ever build a house, learn about what is called an “Ufer” ground.

So I decided to take two further steps beyond simple repair, moving the cable, and surge protectors in my panels:

  1. install a single point ground system.
  2. improve the ground for my house.

I’ll talk about both of these steps in future installments on this blog, now that I’ve installed both of these. I had loads of fun with exothermic welding today.

There is a moral here: as we get more electronics in our houses, more and more people will have experiences like mine. If you ever have damage from surges, take the first event, however small, seriously…. It probably won’t be your last.