On Thu, Jun 6, 2013 at 9:58 PM, Daniel Drake <d...@laptop.org> wrote: > Hi, > > Those of us familiar with setting up school networks (server + switch > + APs) in some of our deployments will be familiar with the > occasional loss of hardware, due to surges in the low quality > electrical supply or whatever, even when the system is protected by a > cheap UPS which supposedly offers some protection. > > This has often been the case in Nicaragua, so the group is now buying > more expensive UPSes, PoE switches, and PoE access points for new > schools. This means that the server and switch are connected to mains > power via a UPS which hopefully protects them, and none of the APs are > connected directly to the mains (instead they get Power over Ethernet) > which hopefully offers some isolation from bad electrical conditions. > > This equipment is expensive, especially in places like Nicaragua where > lots of import taxes are applied. But the hope is that the investment > pays off in that the equipment doesn't get zapped. > > However, one week after deploying this equipment in the first school, > we are left with a server that doesn't boot, 3 out of 4 access points > broken with a nice burning electronics smell, and a broken switch with > a lot of visible damage to the electronics. > > And the most surprising thing - we had not even turned on the network > yet, pending some electrical work. Everything was connected up except > one crucial link - the UPS was not plugged into mains power. So all of > this damage happened without any of the devices having a connection to > the mains. > > Connectivity-wise, the setup was: > WAN: Phone line - ADSL modem - XS > LAN: XS - Switch - 4 APs > > And power connections: the XS, ADSL modem and switch were connected to > the UPS. The APs were connected to the switch over ethernet for both > power and data. Again, since the battery was not connected to mains > power, none of the devices had a power source. > > The connectivity engineer's best bet is that a lightening bolt landed > at the school or nearby, and that this caused a power surge on the > phone line. This surge passed through the ADSL modem, server, switch, > and 4 APs, destroying everything in its path (except 1 AP that was > connected over a longer cable than the rest). > > I figured this is a story worth sharing, for any other projects > considering splashing out on more expensive equipment... > > Also, I'm wondering if anyone has any advice/experience here. Would > others expect this more expensive setup to be more resilient to bad > electrical conditions than a cheaper setup - will the investment pay > off? > > I figure that the case of a lightening bolt might be a bit extreme, > but electrical storms are a nightly occurance here almost daily during > the 6 month rainy season. > > I have seen that some UPSs (unfortunately not these ones) allow a > phone line to be passed through them, supposedly offering some > protection. Would such a system protect against a lightening bolt, > assuming thats what happened here?
What is the grounding of the electrical setup there? You may want to invest in having a separate grounding rod installed specifically for the circuit the network equipment is on and possibly a lighting rod. When we built out a small data center in Alewife we actually had the building install a lightning rod on the roof with a dedicated ground circuit to help protect our circuits in the building. In general I have found that more expensive network equipment handles dirty power a bit better than the cheap stuff. As for lightning and other larger power surges, all of it fries about the same. For POE WAP's I would suggest looking at the Ubiquiti lineup. I have a couple of Picostation2's and a Nanostation M2 and have very impressed with their coverage and stability for the price. They are also indoor/outdoor certified. -Jon _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel