6
VAV-SVX01B-EN
Chapter Overview
This chapter contains information
pertaining to the following:
Pre-power up check-out for the UCM
4.0
UCM operational LEDs
Zone Sensor check-out
UCM 4.0 Pre-Power
Check-out
[ ]Check the supply voltage at TB1. Proper
polarity must be maintained. TB1-1 is
the hot side (+) and TB1-2 is the ground
side (-) of the 24 VAC input. The UCM
cannot be powered from a common 24
VAC transformer that is supplying
power to a device containing a full-
wave rectifier bridge in its power
supply. The acceptable voltage is 20 to
28 VAC (24 VAC cataloged). However,
voltages at either extreme may result in
increased system instability.
[ ]Verify that communications wiring has
properly been terminated atTB2-1 (+)
and TB2-2 (-). Polarity is very important
on the communications link.
[ ]Verify that the zone sensor connections
are correct as detailed in the UCM
wiring chapter.
[ ]Verify that the proper unit DIP switch
settings have been set on each UCM.
[ ]Verify that the tubing is properly
connected to the transducer.
Light Emitting Diode (LED)
Operations
The UCM has one green LED located
near TB3 and one yellow LED located
near TB2 on the UCM circuit board. These
LED’s are used to help diagnose commu-
nication (yellow) or circuit board prob-
lems (green).
The green LED (red on older boards) is a
power indicator. It is steady on when the
power is on and the software is
functioning correctly. If it blinks with a 1
second on 1 second off cycle when
power is applied, then the board is not
functioning and must be replaced.
Table 1 - Green LED Power Function Indication
LED State
Indication
“On”
Board functioning correctly
Blinking
Board malfunction (Replace Board)
“Off”
Board does not have power
The yellow LED functions as the
communication indicator. The indication
from the yellow LED is as follows:
Table 2 – Yellow LED Communication Indicator
Function
LED State
Indication
“On”
Incorrect (reversed)
communication polarity, no
connection, or shorted lines.
Blinking slowly
Communication is occurring on the
approx. 1
link but not for that particular UCM.
blink/sec.
Blinking quickly
Communication is occurring on the
(multiple blinks
link, specifically with that UCM.
blinks/sec.
“Off”
Polarity is correct and no
communication is occurring on the
link
VAV Start-Up/
Check-Out Procedure
Zone Sensor Check-out
If an erroneous temperature is being
reported to the UCM, use the Zone
Sensor Temperature-Resistance Table to
verify the integrity of the adjustable set
point potentiometer or sensor. The
resistance should be measured across
the terminals to which the device is
connected.
Note: Disconnect the zone sensor from
the UCM when making the checks listed
in the table below.
Table 3 – Zone Sensor Temperature-Resistance
Table
Thermostat
Thumbwheel
Sensor
Temp.
Resistance
Resistance
(°F)
(Ohms)
(k Ohms)
55
792
17.0
56
772
16.5
57
753
16.1
58
733
15.7
59
714
15.4
60
694
15.0
61
675
14.6
62
656
14.3
63
636
14.0
64
617
13.6
65
597
13.3
66
578
13.0
67
558
12.6
68
539
12.3
69
519
12.1
70
500
11.8
71
481
11.5
72
461
11.2
73
442
11.0
74
422
10.7
75
403
10.4
76
383
10.2
77
364
10.0
78
344
9.7
79
325
9.5
80
306
9.3
81
286
9.0
82
267
8.8
83
247
8.6
84
228
8.4
85
208
8.2
Note: Thumbwheel resistance checks
are made at terminal 2 and 3 on the zone
sensor. Temperature sensor resistance is
measured at terminal 1 and 2 of the zone
sensor.
CHAPTER 2: VAV START-UP/CHECK-OUT PROCEDURE