unt going offline intermittently

[Jason22]

I'm having a problem with one of my unt's on my N2 bus going offline intermittently. It's running off of a dx9100 and they're all going back to an N-30 with a workstation. The unt is showing offline on the workstation but does not actually shutdown my MUA. I have other MUA running off of the dx and they are showing online as they should. nothing is wrong with any of the connections I'm just wondering if anyone else has had this problem.

[drivewizard]

Nope, never had that problem.

[klrogers]

Check the routing of all your communication cabling, make sure that it is all well away from any power wiring. A rouge signal in one part of the network wiring will often cause problems in another area.

[joey791]

Jason, everytime I have ran into this it was never a com problem, it was either a controller going out or another controller having a problem that caused the issue

[davem]

I've seen intermittent communication under a couple other circumstances:
Low input voltage to the UNT (16V is enough to get the UNT to power up, but then it will drop out within 30 seconds) - this is not likely, as you say the MUA doesn't shut down.
Identically addressed controllers. The UNT will function perfectly, but depending on which controller answers the poll first, the second one with the same address will show up as incommunicado.
And, like joey hints, hardware failure - we've got an AHU controller we're dealing with right now that will go offline after a month or three - we check its address, reload its program, and all is well for another month or three. Then it goes offline. Given the age of the controller, the owner is OK about replacing it, and given the original installing contractor wasn't careful about maintaining the seals on a NEMA4 enclosure, we can argue about moisture intrusion (especially when the unsealed control conduits enter the airhandler on the suction side of the fan, and pull all the moist Pacific Ocean air into the enclosure).
But I digress... try a quick hardware swap for starters...

[chrisc]

Sounds like a bad UNT to me, how many devices on your N2. If you have a spare UNT handy, try swapping it out. If not remove the UNT and place it on the N2 right close to the known good DX to rule out any N2 wiring issues between the DX and UNT. Also change it's address to 128 and redefine it on your N30, see if that works. I had the same problem today, a UNT1144 was pulling down my trunk causing boards to go off line intermintently, what a pain in the a@#$. I had to troubleshoot 30 devices, finally got it.
Good Luck!

[roper]

How long is your N2 bus? Need a repeater after 5000 feet. Will do weird stuff like this.

[floating point]

Too bad there isn't a protocol analyzer for N2. Sure would make it alot easier to see what is going on with the network.

If it has worked well before then I would also agree with it being a bad controller.

[cmakowk]

I would first try to change the address on UNT and in Metasys to an available address and see if it bounces after that.
If not then it could be bad dip switches. Leave at that address.
If it was addressed the same as another controller then it would see it in the logs that both are bouncing.