Lightning protection issues on the Ranch

Summary: For line-shared DSL, it is good to have extra lightning protection and it needs to have a protection threshold of 235 volts or so. For dedicated-line DSL (e.g. SDSL) it is good to have lightning protection with a much lower threshold, such as 16 or 30 volts.

Every year we have lightning season, typically July and the beginning of August. This reminds us that our electronic equipment can be damaged by lighting.

The Coop uses "protectors", electronic devices which are intended to minimize the possibility that lightning might damage the DSLAM in the barn by following the wiring into the barn. The protectors we use may be seen in a photograph.

In August 2002, one of our Coop members lost the use of his DSL modem, probably due to lightning damage. He had to buy another one. This prompted me to look into the availability of protectors which subscribers might purchase and use to protect their own DSL modems.

The protectors which the Coop uses are made by a company called ITW, and it has a web page describing its protectors. ITW makes protectors for use with wiring blocks such as "66" blocks and "110" blocks, and that's the kind that the Coop uses. A few homes in the Ranch are set up with "66" blocks and in such homes, the 66-type protector (called UP2H-16) is ideal (for SDSL lines).

Most of the homes in the Ranch, however, don't have wiring blocks. For such homes it may be easier to use modular-type protectors. With a modular protector, you plug the DSL modem into the protector, and then you connect the protector to the DSL wall jack. ITW makes one of these which has a voltage cutoff of 30 volts, which is well suited for SDSL modems. It is called MODF-30. Unfortunately when I phoned Graybar, they said they don't stock the MODF-30 but only have the MODF-75. This has a higher voltage cutoff and so does not protect quite as well.

You might also want to install additional protectors for your regular telephone lines, as well as for your line-shared (ADSL) lines. The 66-type protector for telephone lines that corresponds to the type that the Coop uses for DSL lines is called UP2S-235. The corresponding modular type (plug the phone into the protector, plug the protector into the jack) is MODF-235.

This table gives the prices that were quoted to me by the Denver office of Graybar.

66-type modular
DSL UP2H-16 ($13.42) MODF-30 (unknown) MODF-75 ($33.24)
phone UP2S-235 ($11.79) MODF-235 ($19.46)

NOTE: It is important to keep in mind that these protectors are of little or no use unless they are securely grounded to a high-quality ground. Don't even bother to spend the money to buy protectors unless you are prepared to make sure they are securely grounded.

Here are some frequently asked questions about protectors and DSL modems.