Trane VAV-UCM 4.2 User Manual

48 VAV-SVX01C-EN
Sequence of Operations
Chapter Overview
This chapter contains information about the following:
• Single Duct Units
• Override Conditions (Single Duct)
• Fan-Powered Units
• Parallel Fan-Powered Units
• Override Conditions (Parallel Fans)
• Series Fan-Powered Units
• Override Conditions (Series Fan)
• Zone Sensor Functions
•Flow Sensor
• Failure Modes
Single Duct Units
When the UCM control action is COOL, the UCM controls the modulation of the air valve as a
cooling source to maintain the “active cooling set point”. Airflow is varied between the minimum
and maximum flow set points to maintain temperature set points. A PI control algorithm is utilized
to minimize the measured difference between the active zone set point and the actual zone
temperature.
It is possible for units to utilize electric or hot water heating coils to maintain temperature set points.
After the temperature loop calls for minimum cooling flow and the zone temperature is at or below
the heating set point, these units shall control to their respective “Minimum Heating Flow”. Once
this “Minimum Heating Flow” is established, heat is allowed to operate according to the “Heat
Control Type” specified for the controller. For electric heat units, this heating minimum flow set
point must be at or above 20% of the unit cataloged airflow. Electric heat may be pulse width
modulation or staged electric heat. Staging has the following ON and OFF switch points. UCM 3.3
and later allow hot water to turn on regardless of flow/position
Hot water heat control may be either ON/OFF or proportional. ON/OFF hot water is activated on the
same schedule as staged of electric heat.
Utilization of the “Heating Minimum Flow” set point allows separate minimum flows to be active
depending on whether or not the unit heat is active.
Override Conditions (Single Duct)
The UCM occupied controls can be overridden by the following override commands:
Unoccupied
If the control mode is unoccupied (either as edited by software or as determined by the binary
input), the unoccupied cooling and heating temperature set points are used for temperature
control. Heat outputs remain active.
Table 9. Set points
Stage ON Switch point Off Switch point
1 At the heating set point 0.5°F above the heating set point
2 1°F below the heating set point 0.5°F below the heating set point
3 2°F below the heating set point 1.5°F below the heating set point

Trane VAV-UCM 4.2 Specifications

General

Series	VAV-UCM
Version	4.2
Input Voltage	24 VAC
Communication Protocol	BACnet MS/TP
Product Type	VAV Controller

Summary

General Information

Unit Control Module 4.2 (UCM 4.2)

Describes the UCM 4.2, its function as a DDC controller for VAV units, and its capabilities.

VAV Start Up/Check Out Procedure

UCM 4.2 Pre-Power Check-Out

Details essential pre-power checks to ensure safe and correct installation of the UCM 4.2.

UCM 4.2 Installation and Wiring

UCM 4.2 Power Wiring

Provides instructions and safety precautions for connecting power to the UCM 4.2 unit.

Zone Sensor Wiring

Communication Wiring

Wireless Zone Sensor

Setting the Address, Mounting, Wiring, and Associating the Receiver and Sensor

Provides a step-by-step procedure for installing and associating wireless sensors with receivers.

UCM Programming and Operation

Accessing Rover/Comm4

Setpoints Tab

Sequence of Operations

Single Duct Units

Describes the operational logic and control sequences for single duct VAV units.

Fan-Powered Units

Failure Modes

Explains various failure conditions that the UCM can detect and the corresponding operating sequences.

Air and Water Balancing

Air Balancing

Covers procedures for balancing the air distribution system of VAV units using VariTrane units.

VAV Single Duct Unit Air Balancing

Water Balancing

Troubleshooting

Diagnostic Log and Table

Explains diagnostic logs, tables, and failure parameters for system troubleshooting.

UCM and Communication Failures

Addresses UCM operational failures and communication loss procedures between UCM and Tracer Summit.

Zone Sensor and Setpoint Failures

Details troubleshooting for wired and wireless zone sensor and setpoint reading errors.

Airflow and Damper Failures

Guides on diagnosing and resolving issues with airflow readings and VAV damper operation.

Fan and Heat Failures

Covers troubleshooting for VAV fan and electric/hot water heat output failures.