VAV Controllers

[hard-knock learner]

I am using a DMS/Micro Smart building management system, Titus VAV Boxes, and Siebe MN-FLO Controls within the VAV. There are times when one or two VAV's are shown in "TROUBLE" when looking at the points in the DMS. This only seams to effect either the Cold Deck or Hot Deck, not both. The controls use 4-20ma with 24V power.

Can anyone explain what TROUBLE means in DMS and why it could be an intermitten problem? I am not sure how to diagnose.

[powerhead]

I don't know the answer but my wild a## guess would be that the VAV box is not making flow.

Check the VAV box damper and. If it is at 100% open then you have a flow problem.

Check the damper actuator. If the program says the box is 100% open and the flow is low the set shaft screw could have come loose and the box is actually closed.

Either way you have to get off your a## and get a ladder to check. :D

[brnaul]

I'm gonna dig way into my past. Since this is memory, results (and correctness) may vary.

You will likely have to upload the microsmart databases from the affected controllers and view them to see if one of the points affecting the VAV point is in trouble. Trouble high and trouble low were typically values that were set way out of logical range, and were used to trap conditions such as broken sensors, shorted wiring, etc. If you are browsing this from the front panel display of the DMS, I do not think you can not view microsmart from there. I think viewing microsmart required a proper level password through the operator interface and either a laptop interface connection at the controller, or connection at the DMS itself.

[laniban]

Trouble is the points condition or Real-time status.
An analog input (AI) point and the analog output (AO) point displays "TRBHI" or "TRBLO" when the input variable exceeds the trouble high or low parameter setting within that point. Adjust that parameter and see if that helps.
A point created in microsmart and linked to the DMS may also display trouble with "MSTBL". Upload that points microsmart database to see the state of all of the points, especially the AI and AO points.
A start/ stop (SS) type point, status (ST)and alarm (AL) point displays a real-time status of "TRBLE" when there is problems with the contact input (feedback address). This is commonly the case when feedback status is tied to a controller's analog input sometimes requiring a resistor. The resister or wires can be loose under the terminals.
The application (AP) Loop point (LP) Mode control (MC) points get a little spooky. If the INH flag is indicated then the condition stays in it's last state. Always check the input variable point. Tell me the point type and maybe I can get more specific.

[hvactalker]

Another thing to check when trouble intermittantly flashes on either the DMS level or MicroSmart/MicroNet VAV controller Integrator level... either level will report this event..

The MicroNet S-link tstat/sensors board sometimes need reseating and its termination screws retightened into the tstat base on the wall. This hasn't always worked for me in clearing "Trouble" on a MicroNet VAV, but definitely has worked sometimes, when the only other path seemed to be replacing the S-link sensor with a new one.

I've never yet verified that a TROUBLE on a MicroNet FLO VAV was a result of actual air flow readings not meeting minimum flow setpoints, but it sounds possible.

I have had erratic VAV operation and CFM values corrected by replacing cracked vinyl tubing from the VAV FLO controller to the flow measurement ring in the VAV box. In that instance I don't recall any Trouble messages from the erratic controller.

[stopher9]

what exactly does DMS stand for im pretty new to the controls industries and only know siemens software

[brnaul]

It stands for Digital Management System. It was a name born way back in Robertshaw's history for their automation system. The term sort of morphed into the acronym used for the central panels such as the DMS-35, DMS-350, and DMS-3500, some of which have keypads and displays on them.

[hvactalker]

I'd like to fill out the history a bit by saying the term "Microsmart" came about in the late 1980s as the name for a series of smarter controllers replacing the old field slave boards, giving the Robertshaw system distributed processing, allowing one field controller to stand on it's own away from the network should the network go down, or with a real time clock option, become a standalone control system. Before Microsmart, all processing was done at the area controller. The Microsmart level was added, offering more reliability in control.

The "DMS" tends to refer to physical head end or software configurations located in the head end DMS 35, 350, 350A, or 3500. The Microsmart term refers to the physical field controller or software configurations located in the controller.

The VAV controller listed earlier in the thread "Siebe MN-FLO" refers to a Barber Coleman VAV controller in the Micronet2000 family that was later integrated into the Microsmart comm trunk by a translator module, that looks to the DMS like a Microsmart controller; mapping VAV controller values into the Robertshaw system.

This gets into the Seibe history later to become Invensys, later to become orphaned thank you very much..

We found when adding Tridium Jaces or Invensys UNCs to DMS/Microsmart system, better to first remove the DMS3500 and use a Niagara Microsmart driver instead of leaving the 3500 in place using a Niagara DMS driver. Much better throughput on a big Niagara system without the DMS3500. Hook the Microsmart bus to the Jace/UNC without first going through the DMS3500. That's the explaination Invensys gave for 7-8 minute delays in value updates on the system that had the DMS3500 hooked to the Jace/UNC. In the building with Jace/UNC and without a 3500, screen update is less than one minute. All Microsmart controllers in the system monitored by the Jace/UNC must be Rev 11.x firmware.

Hopefully the Jaces will allow us (I'm with the owner) a migration path away from DMS/Microsmart.
thanks for listening if you made it this far...

[rspeir]

I am using a DMS/Micro Smart building management system, Titus VAV Boxes, and Siebe MN-FLO Controls within the VAV. There are times when one or two VAV's are shown in "TROUBLE" when looking at the points in the DMS. This only seams to effect either the Cold Deck or Hot Deck, not both. The controls use 4-20ma with 24V power.

Can anyone explain what TROUBLE means in DMS and why it could be an intermitten problem? I am not sure how to diagnose.

Sounds to me that you may have a bad control or a wiring problem. Does the micro smart reflect the same information?

[ddctech]

hvactalker -

Do you have a sample database or the VAV point types with an Ax integration with Micronet VAVs through an MN-MSI? During the learn command, cool, heat, flow and space temp are the only points returned for each VAV. How do you add the points for temp & flow stpts?

Thanks,
Brian