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Table 11. Merit
Operating Sequence
System
Step
Y1
Condition
NO CALL FOR DEHUMIDIFICATION
Normal Operation
1
On
- Y1
Normal Operation
2
On
- Y2
BASIC MODE (only active on a Y1 thermostat demand)
Normal Operation
1
On
Dehumidification
2
On
Call
PRECISION MODE (operates independent of a Y1 thermostat demand)
Normal Operation
1
On
Dehumidification
2
On
Call
Dehumidification
1
On
Call ONLY
BASIC MODE (only active on a Y1 thermostat demand)
Normal Operation
1
On
Dehumidification
2
On
Call
PRECISION MODE (operates independent of a Y1 thermostat demand)
Normal Operation
1
On
Dehumidification
2
On
Call
Dehumidification
1
On
Call ONLY
Jumpers at indoor unit with a two-stage outdoor unit
With Condensing unit - Y2 and R to O
With Heat Pump - none
* During dehumidification, cooling air handler speed is as follows: 70% of COOL cfm for 018, 024, 030; 65% for 036; 60% for 042, 048 and 060 units.
** Thermostat will maintain the room temperature up to 2°F (1.2°C) cooler than the room thermostat setting in precision mode.
HEAT JUMPER
The HEAT jumper is used to determine CFM during
electric heat operation only. These jumper selections are
activated only when W1 is energized.
DELAY JUMPER
The DELAY jumper is used to set the specific motor fan
operation during cooling mode. Depending on the
application, one of four options may be chosen by moving
the jumper to the appropriate set of pins.
#1 Pins Jumpered
A- Motor runs at 100% until demand is satisfied.
B- Once demand is met, motor ramps down to stop.
A
100% CFM
OFF
COOLING
DEMAND
#2 Pins Jumpered
A- Motor runs at 100% until demand is satisfied.
®
CBX25UHV, Thermostat and Two‐Stage Outdoor Unit Operating Sequence
System Demand
Thermostat Demand
Y2
O
G
W1
W2
On
On
Acceptable
On
On
On
Acceptable
Room Thermostat Calls for First-Stage Cooling
On
On
Acceptable
On
On
On
On
On
Acceptable
On
On
On
On
On
On
Room Thermostat Calls for First- and Second-Stage Cooling
On
On
On
Acceptable
On
On
On
On
On
On
Acceptable
On
On
On
On
On
On
B
OFF
Relative Humidity
Com
Status
D
pressor
24 VAC
Low
24 VAC
High
24 VAC
Low
Demand
24 VAC
High
24 VAC
Low
Demand
0 VAC
High
Demand
0 VAC
High
24 VAC
High
Demand
0 VAC
High
24 VAC
High
Demand
0 VAC
High
Demand
0 VAC
High
B- Once demand is met, motor runs at 100% for 60
seconds.
C- Motor ramps down to stop.
A
OFF
#3 Pins Jumpered
A- Motor runs at 82% for approximately 7-1/2 minutes. If
demand has not been satisfied after 7-1/2 minutes -
B- Motor runs at 100% until demand is satisfied.
C- Once demand is met, motor ramps down to stop.
A
OFF
Page 21
System Response
Air
Handler
CFM
(COOL)
Comments
70%
Compressor and indoor air handler follow
thermostat demand
100%
70%
Thermostat energizes Y2 and de-ener
60%/65%
gizes D on a call for dehumidification
70%*
70%
Dehumidification mode begins when hu
60%/65%
midity is greater than set point
70%*
Thermostat will try to maintain room hu
60%/65%
midity setpoint by allowing the room
70%*
space to maintain a cooler room thermo
stat setpoint**
100%
Thermostat energizes Y2 and de-ener
60%/65%
gizes D on a call for dehumidification
70%*
100%
Dehumidification mode begins when hu
60%/65%
midity is greater than set point
70%*
60%/65%
Thermostat will try to maintain room hu
70%*
midity setpoint by allowing the room
space to maintain a cooler room thermo
stat setpoint**
B
100% CFM
100% CFM
(60 seconds)
COOLING DEMAND
B
7 1/2 MIN
100% CFM
82%CFM
COOLING DEMAND
MERIT
C
OFF
C
OFF
®
CBX25UHV SERIES
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