Bacnet Network

[joey791]

Done a search and found some good info on previous threads, but I'm looking for info(diagrams and explanations for a MS/TP network). Trying to find out how many masters you can have, the difference between masters and slaves, etc. All previous integration experience is with Modbus but from what I'm seeing you can have more than one master unlike Modbus.

I have checked bacnet.org and wasnt too impressed, if anyone could point me in the right direction I would appreciate it.


BTW yes this is my first Bacnet integration.

[exwtk]

There can only be 1 master on the MS/TP bus
I believe max number of slaves is 127

[digo]

Joey, you've got mail

[amigo]

read this, it is short but should explain some things:
http://www.chipkin.com/articles/how-does-bacnet-mstp-discover-new-devices-on-a-network

It is my understanding that most mstp devices are masters. so you can have multiple masters on an mstp network.

Also, concept of master in Modbus is some what different than a master in mstp. They are just different protocols so different conventions and rules are applied.

I thought ASI BACport only did BACnet/IP?
Has ASI released the rumored to be rebranded tridium jace yet?

[ntech64]

There can only be 1 master on the MS/TP bus
I believe max number of slaves is 127

^ This information is not correct.


Chipkin's website does have a lot of good info (see previous post).

[kontrolphreak]

A couple of good books are:

Building Automation System Integration with Open Protocols by a bunch of dudes (I think one is a regular on the forum).

and

Building Automation Communications Systems with EIB/KNX, LON, and BACnet by Merz/Hansemann/Hubner

both can be found on Amazon and have great information not only on BACnet but both LON and the European fieldbus.

Most vendor's controllers are all masters, this means they can initiate communications on the buss, slaves can only respond to requests and can't initiate a request. As to the quantity, this is more manufacturer driven then BACnet driven. The Alerton BSM/BTI can only have 65 controllers per MSTP buss. I am not sure what the limit on the JACE-545 buss is, but they have 4 so you can get quite a few on there. ALC LGR controllers support 99 controllers, but this can be extended with AAR modules at the expense of slowing the network downstream of the AAR down. Delta can have theoretically 99 net1 controllers with 99 controllers under each one for a total of 9801. Reliable is about the same with the MACH-Pro line. Andover's bCX1 can support 127 controllers on it's buss.

kontrol out

[joey791]

Digo,

Thanks alot for the information, exactly what I was looking for in giving me some insight.

amigo,

you are correct on the Bacport, but there is a possibility that they will convert some controllers to Bacnet. First I heard about the Jace today, man I'm busy as all get out right now without throwing in learning Tridium in the mix LOL

phreak,

thanks for the info will check the books out


What I have is 2 Trane chillers with BCI-C interfaces(both masters). I was going to use a Loytec Linx and got Bacnet ms/tp to OPC. I wanted to keep any reset logic native to my controls and looked on a better way of doing that. One option was to go with a Babel Buster and go Bacnet ms/tp to Modbus RTU then pull it into an Asic/2. Another possible option that I'm looking into is going to an Asic/2 with a Bacnet board, only problem is it is slave only. With that option my question would be on an ms/tp trunk is there something I can use to pull the info out of the masters and set in the slave controller for the front end. Like I said this is my first time doing this and trying to figure it out.

It would be different if I had more time but I am slammed right now with work(not complaining).

[amigo]

If I were you, I would ask Paul and see if he can make BACport grab some data out of the BACnet/IP network, if it can then get one of of these:
http://www.ccontrols.com/basautomation/basrouter.htm
for cheap, and then BACport can hit it on the IP side and get the mstp data. may end up being cleaner.

my 2cents.

[joey791]

Amigo, have you used their products before?

[amigo]

Yes, i have used it a couple times with no issues.
But with mstp bus it sometimes is a crap shoot either way, so do some testing first before you jump in.

[BACnet]

Joey,

The Trane chillers may be masters, but they are the very definition of "application specific" controllers. They are set up to be able to physically run the chiller and also to offer points up to the network to be read or written as needed/desired.

While the chillers themselves may be masters on the MS/TP network, they generally wouldn't have the logic coded into them to be able to run custom applications or network management operations. That's not specific to BACnet or Lon, but something that is common for an application specific controller.

While I've no personal experience with the L-INX you mentioned, looking at the data sheet I am led to believe that it is a more of a data server/router than a configurable controller. If you want to set up any complex reset logic to your network you would either have to do that at the front end or add a configurable or general purpose controller to the network to accomplish this.

I see references to a JACE above. The JACE can exist on the MS/TP network directly and it would have the ability to run costom programming that could read and write data points from your chillers very easily.

[cal-cu]

QUOTE Joey, you've got mail

Would you mind sending that info to me also. TIA

[joey791]

Would you mind sending that info to me also. TIA

sent

[crab master]

:ditto: on the info please. TIA.

[digo]

sent

[joey791]

Well more questions

If I have 3 masters on a bus and the are all application specific controllers what do I need to get the points out of 2 of them and put that info in the third? This is MS/TP

[BACnet]

ASC’s are by definition, stripped down controllers that are meant to do one job really well and not a heck of a lot else.

Any MS/TP master has the "right" to read and write data on any other controllers, be they masters or even slaves. That said, it is not a requirement for a simple ASC controller to be able to do such a thing.

Many manufacturers do provide a simple means for ASC controllers to share information. Generally it's a zone temp, a setpoint or the outside air temperature. If you choose a mfg or product that doesn't give you this ability what you need to do is put a smarter piece of equipment on the network.

You can add a general purpose controller to the network to accomplish this. These are generally a bit more costly than a stripped down ASC (perhaps another $100 or so) but they give you the ability to run custom applications, one of which will be the ability to move data around the network as you see fit.

Of course it’s wasteful to add a whole new controller to a network for such a simple task. I would suggest that you replace one of the ASC’s with the general purpose controller and program it to do all that the ASC did and also do the network management operations you were asking about. This way you still have only three controllers to purchase and the cost difference is minor.

[jchapline]

Digo, could you send me that info as well?

Thanks in advance

[digo]

Digo, could you send me that info as well?

Thanks in advance

you got it.