ELK - multiple problems after storm/lightening

[apostolakisl]

Unless i'm missing something, i did it to code which is summarized here:
http://forums.mikeholt.com/archive/index.php/t-57182.html

The key is the low voltage i have running between the buildings. Network between them is over fiber, but the elk bus, coax, and phone would be considered paths.

-brad

Code doesn't care about protecting you from lightening transients. The concern with code is fire and electrocution, not your delicate electronic gizmos.

If you have a grounded LV device in one building that is connected to a grounded LV device in the other building, and each building has its own ground, then an induced current can travel through your LV stuff, even if the two grounds are tied together. Basically you have two wires running in parallel (the wire tieing the grounds together and the wire for the LV device), and some current will go through both depending on the relative resistances.

If you have to have a LV device in the second building that is connected to a LV device in the first building, consider powering device in buidling 2 from building 1's power (like poe).

Or, consider isolating the two systems as neurorad suggested or by using rf com.

 

[Del91574]

The best way, if only a data wire/common is being run, would be to install a surge on each side of the conductors where they enter the building and then connect each end to an appropriate surge bonded to ground. Commonly done with fire alarm circuits where they leave/enter buildings, and is a code requirement.

That said, nothing will stop a large enough hit or inductance if it's close enough. Best you can do is to isolate as much as you can from hardware, but in the case of a panel like the M1, you can isolate the main board from expanders pretty easily using a simple 2 or 3 pair surge on each side of the 485 run and then install the expanders/supplies as needed and in each building rather than pulling circuits back to the main panel.

 

[Neurorad]

DEL - What do you mean by '2 or 3 pair surge' for the RS485 bus? Specific product/brand?

 

[Del91574]

Specifically, I've used Ditek LVLP's on Elk M1's multiple times. Only thing I carried through them was the data and a common negative.

You can also use Elk 950, 951, 952, and 955's as well for the data lines. Edco also makes similar units to Ditek.

 

[Neurorad]

Looking at the DTK-LVLP, I see a big ground wire coming off of it.

How does it shunt to ground, if the potential difference is causing a surge?

Ever use any optical isolators, DEL (or anyone else)?

 

[shenandoah75]

I three central panels in the house and one in the outbuilding. Seems like you're recommending protecting only those that run outside the building/underground?

So in terms of the 485 Bus, i could get away with:
Data A / Data B / NEG only (no need for +VKP?)

What about:
1) the other power buses from the M1(SAUX/VAUX) (guessing no if you're not protecting +VKP)?
2) phone lines (both wires in a pair)?
3) broadband (in my case: Uverse over twisted pair)?

thx
-brad

 

[apostolakisl]

The best way, if only a data wire/common is being run, would be to install a surge on each side of the conductors where they enter the building and then connect each end to an appropriate surge bonded to ground. Commonly done with fire alarm circuits where they leave/enter buildings, and is a code requirement.

That said, nothing will stop a large enough hit or inductance if it's close enough. Best you can do is to isolate as much as you can from hardware, but in the case of a panel like the M1, you can isolate the main board from expanders pretty easily using a simple 2 or 3 pair surge on each side of the 485 run and then install the expanders/supplies as needed and in each building rather than pulling circuits back to the main panel.

Elk expansion boards are mostly powered off of the main bus. Some things like the xep have their own power supply but zone expansion boards, relay boards, xsp board, and others are powered off of the Elk panel. There is no concern about separate grounds in different buildings causing a problem because these things have no connection to the other ground.

The risk in these devices is the potential that develops in the wires that attach to these devices, or in other words, the EM field around your house acting on long runs of LV wire. This is very hard to guard against. Elliminate the long runs of wire when possible, use shielded wire and ground it to the same ground as the Elk main panel when possible. Consider RF relays.

Using opto-isolators will protect your Elk from the long runs in relay situations, but it won't protect the opto-isolator itself. So you have to decide if the added cost of putting something like that in is worth it, considered it becomes the sacrificial lamb when a transient strikes.

You sort of need to consider that no matter what, you have risk of getting fried. Every time you buy a new toy, put 10% of the price of the new toy in your "insurance" fund. Figure that you will use that money to replace the stuff if it gets fried. If your lucky, you never need it.

 

[shenandoah75]

Well - i swapped jumper settings and the firmware programming on the M1XSPs (vivia and hai) and looks like it's the M1XSP that's bad (the lighting didn't work at all when. However, the thermostats appear to respond to commands sent by the elk, but they do not seem to report current temp. And they may not be sending commands from the units (as thought they were damaged and reverted to one-way comm?). Anyway, i'm going to buy another serial expander and hope for the best ( i guess even if they've been reduced to one-way, its better than forking out several hundred for new ones).

Also, I found an old thread where Elk repaired the seized lines from surge for someone else:

http://www.cocoontech.com/forums/index.php?showtopic=4478

That response is impressive. I think i'll be calling Elk this morning

-brad