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M1DBHR Data Bus Hub

Stainless

Member
I have a rather large system, and part of the system is in a remote part of the building.  That part of the building consists of 4 keypads, a couple of zone input modules, relay modules, and power supply.   But because of the way that building was initially wired, the keypads only have 4 conductor cable going to them.  So I figured the M1DBHR database hub is the perfect solution here without needing to rewire.  I installed the hub in the remote building a couple of weeks ago, wired all the keypads to it (along with the modules), and have not noticed any issues.  However, after I installed it, I noticed in the instruction sheet Elk specifically says not to locate the hub remote from the M1 and it should be mounted in the same enclosure.  So I reached out to Elk through their support forum as to "why" and the response I received really didn't answer my question of "What is the issue with remotely mounting the Hub from the main control board?"  They did say they "recommend" it being mounted as close to the M1 as possible but didn't indicate what potential problems I would have.  I was wondering if anyone here could explain to me any issues that would arise from the M1DBHR being remote from the main board or if others have the same situation.  
 
Some specifics on this installation:
- Wire run from M1 Main Control to M1DBHR is about 150'+/- (Cat5e)
- The M1DBHR, all keypads, along with the input & relay modules in that section are being powered off their own PS212S power supply - no 12V+ power from the main panel, only the NEG, Data A, & Data B are connected
- Everything was installed three weeks ago and no data bus issues or weird panel operation that I am aware of
- Because of the route the Cat5e takes (runs along the top peak of a small attic) I will be installing surge suppression at both the M1 Main Control and the M1DBHR as a precaution (lightning is frequent in this area)
 
 

RAL

Senior Member
Here's my theory on why Elk recommends mounting the M1DBHR close to the M1. 
 
The M1DBHR repeats (or repowers) the databus signals  onto 4 separate databus "copies" or what Elk calls branches.   Each of these copies is able to be up to 4000 feet long.   In order to be able to support that length, the incoming signal to the M1DBHR needs to be as high quality as possible.  The more cable there is between the M1 and the M1DBHR, the more that incoming signal will be degraded.
 
In your case, the M1DBHR isn't terribly far away from the M1, and it doesn't sound like you are trying to drive another 4000 feet on the output branches.  If it is working, I'd say leave it as is.  But if you ever run into databus problems, then that becomes a suspect.
 

Stainless

Member
RAL said:
Here's my theory on why Elk recommends mounting the M1DBHR close to the M1. 
 
The M1DBHR repeats (or repowers) the databus signals  onto 4 separate databus "copies" or what Elk calls branches.   Each of these copies is able to be up to 4000 feet long.   In order to be able to support that length, the incoming signal to the M1DBHR needs to be as high quality as possible.  The more cable there is between the M1 and the M1DBHR, the more that incoming signal will be degraded.
 
In your case, the M1DBHR isn't terribly far away from the M1, and it doesn't sound like you are trying to drive another 4000 feet on the output branches.  If it is working, I'd say leave it as is.  But if you ever run into databus problems, then that becomes a suspect.
 
I figured it has something to do with possibility of the data between the M1 and DBHR becoming degraded - so why not word it as "close to possible" instead of "within the same enclosure".  Then I was thinking maybe there's an issue with the UL listing with it not being in the same enclosure.  But I'll keep an eye on it, so far, no known issues.
 
I like the M1 but I feel the way they designed the databus to operate is it's biggest weakness.  Daisy-chaining keypads and modules puts a weak link in the chain - one wire break and everything after that is inoperative.   
 
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