Leviton 17A00 expansion enclosure

[kaohao]

Hi cocooners, I am installing an omnipro II with 5 expansion enclosures. I have gotten all of them to communicate effectively with the omnipro II when hooked up individually, but when I have all of them hooked up simultaneously I get intermittent indication of communication failure on the D35 status LED. some of them blink properly at once per second, some blink once per second for a while and then switch to 5 times per second and so forth. Does it harm the omnipro II or the expansion enclosures to leave them powered up when the status LED indicates that something is wrong? Help! -_-
 

 

[RAL]

Do you have all the expansion enclosures mounted near the OP2 panel, or are they scattered around in different locations?  If scattered, how long are the cables?
 
How did you wire the data bus to the 5 enclosures?  Are they all home runs back to the OP2, or daisy chained from one to the next?
 
Do you have a common ground wire connected from the OP2 to each expansion board (not just Data A and B ).
 
Have you set the DIP switches to a unique address on each expansion enclosure?
 
The fact that you are getting status errors shouldn't cause any damage.

 

[kaohao]

Thanks for replying, RAL. I really appreciate that. The expansions are all home runs, except one pair, with about 800 feet total length from OPII. The dip switches are all set properly but there is no common ground. Where would this be connected? To the ground terminal of each board? Thanks!

 

[RAL]

I'm not sure I follow what you are saying.  Is the sum of all the home runs (including consoles) about 800', and one of them has multiple enclosures on it?  Or is there a single run to one of the expansion enclosures 800' all by itself?
 
The documentation on the OP2 is very unclear about the maximum data bus wire length.  In the section of the manual for LCD Console Hookup, it says:
 
"Use 4-conductor 22-gage wire, 1000 feet maximum length. Consoles can be homerun or daisy chained. This length shall be divided by the total number of consoles at the end of the run. For example, for 8 consoles, the maximum length reduces to 125 feet."
 
If you have a single home run with 8 consoles on it, I read that to mean that the wire can be no longer than 125 feet.  But if you have 8 home runs, does the total of all 8 runs have to be less than 125 feet?   Or can each of the 8 be 125 feet?  Or could each be 1000 feet? They certainly don't make it clear.
 
The manual makes no mention of other devices on the data bus, like an expansion unit, entering into the calculation, but from an electrical point of view, they should count, too. 
 
The installation manual makes no mention of having to connect a common ground between the expansion enclosure and the OP2.  But this Quick Start Guide does (see picture 12). 
 
I believe the OP2 uses a differential signal on the data A/B terminals.  In many situations, those two wires are all that is needed.  But on long runs, even a differential signal can have problems without a ground reference.
 
One thing to try would be to add the expansion units one by one and see at what point you run into trouble.  Then, disconnect the last one added and add a different one instead to see if that makes a difference.
 
How are you connecting all the home run wires together?  Using a wirenut to connect all the wires together along with a pigtail that connects to the OP2 terminal?  Or trying to cram all those wires under the screw terminal?

 

[kaohao]

I have 4 home runs one of witch connects 2 expansions to the OP2 for a total of 5 expansion enclosures. The total length of all the home runs is approximately 800 ft. I am using terminal strips to connect them all together to the A and B terminals near near the OP2. 3 consoles are also terminated in these A and B terminal strips which probably puts the total over 1000 ft. I'll try your recommended steps which were along the lines of what I was thinking. I bet adding the common ground will help. Thanks again!

 

[RAL]

One other thing I forgot to point out about the Quick Start Guide.  Picture 12 doesn't show the Data A & B wires connecting to the correct terminals on the OP2 side.   Sloppy drawing by someone.

 

[kaohao]

So....I wired it up like your diagram said, Ral, and everything appeared to be fine with regards to the status LED. Then,the other day, an electrician and I were doing some stuff in the security closet where the OP2 was located and the status led was blinking rapidly at the endvof the day. I figured something was knocked loose so I rewired my ground terminal strip that connects the OP2 and expansion enclosure ground terminals. As I was doing this I disconnected the ground from the OP2 and everything started blinking normally at once per second so I left it ungrounded. Any idea what might be happening? Is it ok to leave the expansion enclosures ungrounded in this manner? They are all individually grounded but now lack the ground back to the OP2 board.

 

[RAL]

The Data A and B wires are a differential pair that are used to send data between the units.  If the ground reference between the two ends differ enough, it can prevent the differential pair from working properly.  When the cable between the two ends is relatively short, say tens of feet, a differential pair often works without a common ground reference. 
 
When you connect a ground wire between the two ends, it forces them to a common reference point, and that should (in theory) make the differential pair more reliable.
 
But its also possible for a ground connection to inject noise from one part of a system to another.  Grounds are supposed to be "quiet" and not be a source of noise, but for many reasons, they sometimes do carry noise.   Usually, it will be due to a less than perfect connection somewhere.
 
It sounds like something changed while the electrical work was being done, and that had an effect on the grounds.  It might not be a problem with the wire you connected between the OP2 and the expansion unit, but could be somewhere else and somehow affecting the grounds in your house. Unfortunately, these sorts of problems are often difficult to track down and isolate.  If things work without the ground connection, you could just leave it to run that way.  But somewhere down the road, new problems might pop up.

 

[akpowerHAI]

I have similar problem.  Have a system OmniPro II with 3 expansion board in the Main House. Had everything working perfectly for 2 weeks. Now just installed 4th expansion board in the Guest House (350 ft away) and the 4th board crashed the first expansion board. Made it say its not ready and then all the WB on the 1st board triggered an alarm.  Once i remove 4th board everything works great again. Tried to change the address on the 4th board to be 5th and than 7th. Nothing helped, still kept on crashing 1st expansion board.   I did not have a common Ground  Will try to hook up a ground and see if that fixes the problem.
If anyone had similar problem please give your input how you solved it.
                                                                              Thank You