Cooling Sequence; Heating Sequence; Lead/Lag Sequence - Bard W3RV2-R Literature Assembly

COOLING SEQUENCE

Compressor Operation
The cooling capacity of the WV series is controlled
by loading or unloading the compressor. On a call
for cooling, the unloader solenoid is energized for
one second to ensure pressure equalization in the
compressor. The compressor contactor, RLY 2, is
then energized and the compressor will start. A
PI control loop then calculates the compressor
capacity needed to reach set point and modulates the
compressor. Modulation range is from 20% to 100%
capacity. Modulation is accomplished by a pulse width
modulated signal from OUT 8 which energizes the solid
state relay (SSR) and energizes or de-energizes the
unloader solenoid. The required compressor capacity
is calculated every 15 seconds.
20% load means 0 VDC for 3.0 seconds and 5 VDC for
12.0 seconds from OUT 8.
30% load means 0 VDC for 4.5 seconds and 5 VDC for
10.5 seconds from OUT 8.
40% load means 0 VDC for 6.0 seconds and 5 VDC for
9.0 seconds from OUT 8.
50% load means 0 VDC for 7.5 seconds and 5 VDC for
7.5 seconds from OUT 8.
60% load means 0 VDC for 9.0 seconds and 5 VDC for
6.0 seconds from OUT 8.
70% load means 0 VDC for 10.5 seconds and 5 VDC
for 4.5 seconds from OUT 8.
80% load means 0 VDC for 12.0 seconds and 5 VDC
for 3.0 seconds from OUT 8.
90% load means 0 VDC for 13.5 seconds and 5 VDC
for 1.5 seconds from OUT 8.
100% load means 0 VDC for 15 seconds and 5 VDC for
0.0 seconds from OUT 8.
Outdoor Temperature Sensor
A sensor probe projects out the bottom of the ECU
control box into the outdoor section, and this provides
input for the outdoor fan sequences below 55°F and
above 115°F described under Outdoor Fan Motor
Operation.
Discharge Temperature Sensor
This sensor is mounted on the compressor discharge
line and protects the compressor against overheating.
It opens at 250°F and closes at 200°F.
Manual 2100-615A
Page 18 of 24

HEATING SEQUENCE

On a call for heating, if the space temperature falls 1°F
below setpoint, the first stage of heating, RLY 4, will
cycle ON. If the space temperature falls 3°F below
setpoint, the second stage of heating, RLY 5, will cycle
ON. Indoor Blower airflow is maintained at the Rated
unit airflow at all times during heating.

LEAD/LAG SEQUENCE

The digital controllers can be used for dual units used
in a redundant application by using the scheduling
function as follows:
1. The controllers should be mounted side by side so
they are in the same temperature zone.
2. The time setting on both controllers need to be
synchronized to the same time of day. NOTE: there
is a 72-hour time retention if power is removed. If
power off-time exceeds 72 hours, the time clock
in each device must be reset to match. The exact
time is not important as long as both controllers are
set the same unless it is critical to control the time
of day when the units swap operating positions.
3. Set one controller #1 to be Occupied for a 12-
hour period and Unoccupied for the other 12-hour
period. Set controller #2 so that it is exactly the
opposite. Unoccupied for the 12-hour period
when #1 is Occupied and Occupied when #1 is
Unoccupied.
4. Set Occupied cooling setpoint the same for each
controller, and Unoccupied the same for each. 4°F
difference is suggested.
5. Set controllers to "Auto" mode of operation.
Example:
1. Both Unit #1 and #2 have Occupied setpoint
of 74°F and Unoccupied setpoint of 78°F
2. Unit #1 set for Occupied from 1:00 a.m. to
1:00 p.m. & Unoccupied from 1:00 p.m. to
1:00 a.m.
3. Unit #2 set for Unoccupied from 1:00 a.m. to
1:00 p.m. & Occupied from 1:00 p.m. to 1:00
a.m.
4. Every 12 hours the units will swap position
as being the lead unit, and the lag unit is
available for back up operation at the higher
temperature should the situation ever arise.
Control
Normal
Device
5VDC Red LED lit when 24VAC
Power present. 5VDC present at
Supply solid Red and solid Black
wires. Both jumpers on Half.
3A 250V fuse.
Abnormal
Red LED not lit. 5VDC not
present at solid Red and
solid Black wires.
Both jumpers on Half.
Check 3A fuse.