Priority Shutdown causes in Varitrac CCP III

Issue:

Priority Shutdown causes in Varitrac CCP III

Resolution:
From VAV-SVU01A-EN page 17:

Priority Shutdown

Priority shutdown forces the following control actions:

 

Turns off the main supply air fan (minimum-on time not enforced)
Disables all stages of heating and cooling (minimum-on time not enforced)
Disables all VAV local heat, if present
Disables all VAV parallel fans, if present
Drives all VAV dampers to the maximum open position
Drives the bypass damper(s) to 50-percent

 

 

A CCP III (changeover bypass) system priority shutdown is caused by:

 

- A CCP priority shutdown detected at inputs TB2-6 and TB2-7 on the CCP termination board. Verify that there is 12VDC across TB2-6 and TB2-7 across the open set of contacts. 0VDC tells the CCP that it is in a priority shutdown.

- Invalid supply air temperature value. Bad sensor, non communicating bypass controller, no power to the bypass controller
(changeover-bypass configured Varitracs only).

- No Address 33 UCM - Failure to detect a communicating sensorbypass control assembly (changeover bypass mode only).

- No communicating zone UCMs (at least one zone controller must be communicating for CCP system to run).

- If RTU is in Emergency Shutdown, will trigger Priority Shutdown of the VariTrac CCP III panel (does RTU run in test mode)

- If Tracker front end - A global priority shutdown command received from Tracker front-end.

- High temperature input from the Voyager high temperature input connected to the TCI 3/4 board or Reliatel options
module. This causes Voyager to go into priority shutdown.

A CCP III (deliverd vav )system priority shutdown can also caused by :

The CCP has auto-configured as a Delivered VAV system (communicating with a Voyager Commercial 27 to 50-ton VAV RTU) and there is no operator display on the CCP. An operator display on the CCP is required for delivered VAV.

*Voyager unit lost communication to the RTAM board this would cause the same diagnostic.

Table from Varitrac operator guide VAV-SVU01A-EN)

Note: A Rover service tool connected to Lontalk link can cause priority shutdown because CCP detects a second master on the link. For example, if Rover overrides vav controllers to max flow, the CCP is no longer in control and goes into a priority shutdown.

The VariTrac CCP returns to normal operation when the priority shutdown condition is corrected.

 

Needs to do VAV UCM box balancing using CCP software, not Rover service tool

 

 

 

If the Priority shutdown lists Local Emergency Shutdown, this is the emergency shutdown circuit in the Precedent or Voyager rooftop unit. One option on these units is a phase monitor. These are wired in series with the emergency shutdown circuit.

On Precedent units the termination is on a spade terminal behind LTB terminal 6 and the phase monitor is behind the LTB so hard to see. Check for 24 VAC to ground on J1 Pin 12.  It should have 24VAC in a normal condition.

 

Notes:

 

Changes:

 

Other Question/Problem/Cause Statements:

• What happens when CCP is in priority shutdown
• What causes priority shutdown in CCP
• what can cause a change over bypass priority shutdown
• Bypass comm fail
• CCP is in a priority Shutdown. WHY?
• Tracker displays "3 Complete VAV UCM Comm Fail" in its alarm log

Facts:

• VariTrac III Central Control Panel (CCP)

Original wave: wave2822