Are Bacnet VAV controllers interchangeable between manufacturers on the same trunk ?
We have a building in our organization to be retrofitted with new chiller, boilers, AHUs, VAVs with reheats added to new multizone AHUs which currently are single zone hot/cold deck AHUs. Zones are created from the single zone AHUs by have duct dampers pass or restrict airflow, acting in reverse or direct mode depending on the temp of the AHU's discharge air.
I sat in on a meeting about the DDC controls aspect of the project. They'll be starting from scratch on the controls in this building, completely replacing a legacy DDC system. Other buildings in our organization have Niagara/legacy or Tracer Summit controls. I'm not involved with most of the Trane controls.
A mechanical engineer has been directed to provide an open, non-proprietary control system specification for the DDC. He is recieving spec writing assistance from a DDC vendor branch rep that has no Niagara, and has LON equipment available, but installs very little LON (all bacnet. except to accomadate Trane Com 5 equipment.) His truck was blue.
When it comes to the VAV controller spec, I asked what was planned. "Bacnet VAVs" were the answer. Having only read the LON/Bacnet controversy threads, I've no actual experience having Bacnet certified products on our systems.
I asked them to look ahead 8 to 10 years from now, to a time when one of the VAV Bacnet controllers has failed, and assume that the original Bacnet VAV controller for some reason can't provide a new Bacnet VAV controller, can we go to another manufacturer and have one other their Bacnet VAV controllers installed on the Bacnet serial com link, have the new VAV controller programmed to take the place of the old failed VAV controller?
I was told by the DDC vendor "I don't know, I'll look in to that". The engineer's response was basically that to keep the VAV's within one network, we'd need to have any replacement VAV controllers be installed by the original supplier of the DDC system.
I said I thought LON VAV controllers of different manufacturer origin could be interchanged on the same network, though possibly some controllers may need proprietary software to get them setup onto the LON network. The engineer was fairly certain that no manufacturer or network type could provide this ability.
Allowing for some miscommunication between myself and the engineer and the DDC vendor, how locked in to the original manufacturer of Bacnet VAV controllers will we be? Can it really be possible that to intermingle different manufacturer's VAV controllers in a building we have to provide separate comm trunk, supervisory controller, head-end software, or even a protocol gateway between the comm trunks?
Secondarily, can we 8-10 years from now replace the supervisory controller and software from different manufacturer without replacing all the field controllers ?
Obviously its tough to suggest what will happen ten years from now. Speaking in todays terms it is possible to install a second manufacturer's VAV controller on a BACnet trunk. You will need access to Company A's network configuration software and Company B's controller configuration software. All BACnet systems are currently sold through dealers with contractual agreements. If you are prepared to pay two contractors to do this intergration there will be no problem. Also, keep in mind that you will be married to the original installation contractor for the next eight to ten years or longer. Dealer's territories are well protected.
The engineer either lied to you or he just doesn't know what he is talking about. I install LON networks all the time with Trane equipment, Distech ASC and programmable controllers and Echelon Web Server of Loytec L-VIS. All different manufacturers, one network, one network management software, the same used for configuring all devices through 'FREE' software plug-ins from each manufacturer. I can just as easily remove any controller and replace it with another manufacturer's and configure it with all the same software if there is a plug-in available. Here is a sampling of some manufacturers that provide plug-ins. http://www.echelon.com/products/networktools/plugin/
Many devices do not require plug-ins to configure. I used Trane equipment for a few years before they provided plug-ins last fall. We also do not have a dealer contract with any manufacturer. LON controls are available through wholesale suppliers.
ps. There is no 'supervisory' controller in a LON system.
Last edited by dapper; 02-25-2008 at 07:47 PM.
Smells like a Dorothy Dixer to me! Looking into the future of this thread I see 40 - 50 plus replies, vented spleens, hyperbole plus plus. If you are really looking for solid information good luck wading through the murky seas of this threads future.
My only advice is don't let the torrent of technical talk that will soon follow distract you too much from things such as can the contractor demonstrate a track record of performance. Are they prepared to give you more then 1 or 2 references of similar installations (using the same systems) and can you talk to the reference directly.
At the end of the day the success of the installation will be far more dependant on the quality of the management and employees of the contractor then the technology they use.
If you are concerned about replacing a couple controllers, have the engineer require the installing contractor to supply X-amount of replacement controllers, zone sensors and VAV actuators as part of the base bid. The bidders will probably not mark up the parts very much to get the project, so it should not add a lot of cost to the project.
And "adrianfromoz" 's comment about hiring the controls contractor based on reputation is good advice. I see a lot of customers hire strictly based on the low bidder and then complain about the installation. If they hired the company with the best reputation, they would have wound up with a much better system and better service when something breaks. And the company with the better reputation probably had a bid that was only 10% more.
Here is the techno mumbo jumbo. My bias is Bacnet. (after years of lon!)
Make sure the network is Bacnet MS/TP 76.8. If this is true then the long and short answer is yes. You can replace on bacnet with another.
Also spec that all bacnet point are network visable. No third party binding software or network tools will be required.
Keep in mind no matter lon, bacnet or modbus you will need the programming software to make any software changes. That should come with the package.
Look on the BTL website and see what they guarantee. They will not guarantee interoperability the way Lonworks will. That's the nature of the bacnet product as each manufacturer implements their own communication hardware.
In Lonworks, the communication and packet handling is consistent for everyone and only the applications are different. Further, if the controllers are Lonmark compliant, even the variable names/types are identical between vendors.
There is no telling how much configuring you will have to do to an AHU controller if the VAV's are working with it in bacnet. You may be juggling a couple software packages and still have issues with bacnet. Contrast that with Lonworks VAV's that are compliant and the terminal load, temps, etc, variables are all there and it's more an interchangeable swap which would probably require no mods with the AHU controller. And, you can use the software package that you started with to commission the new device. No new software required.
Here's a couple links....
Last edited by sysint; 02-26-2008 at 12:48 PM.
Better yet, get a price confirmation for X-years on their product hardware. In my area I see alot of OEM's bid really low to get into the building and a few years later they get to do the redo because they aren't as open as they advertise. A big box furniture store warehouse nearby had that happen....
Originally Posted by jeffk91467