Operation And Checkout - Honeywell C7046C Product Data

SOLID STATE ECONOMIZER SYSTEM

OPERATION AND CHECKOUT

Operation
Controller Dial Setting
Control setpoint scale is located on the W7459 Solid State
Economizer Logic Module. Control points A, B, C, and D are
field selectable; A, B, C, D control points are used for single
enthalpy or temperature sensing. One enthalpy or temperature
sensor is connected to the solid state economizer control for
single enthalpy or temperature. Turn D (fully clockwise
when the differential enthalpy or temperature control is desired.
Two enthalpy or temperature sensors are connected to the
solid state economizer control for differential enthalpy control.
See Fig. 10 and 13.
IMPORTANT
Do not use C7650A Solid State Temperature
Sensors with W7459D high enthalpy limit devices.
C7046C and C7150B Mixed/Discharge Air Sensors
The C7046C and C7150B Mixed Air Sensors consist of a
thermistor sensing element mounted in a tubular probe. The
sensors are applied at various locations throughout single
zone and multizone duct systems. The negative temperature
coefficient (NTC) characteristic of the thermistor element
causes its resistance to decrease as the sampled air
temperature increases. See Fig 14. To stabilize system
control, the resistance shift is balanced with other system
sensor signals by appropriate system logic panels.
4500
4000
3500
3000
2500
2000
1500
1000
55 60 65 70 75
15 20
TEMPERATURE (DEGREES)
Fig. 14. C7046C and C7150B Air Temperature Sensors
resistance versus temperature.
63-2484—1
3,000 OHMS AT
77°F (25°C)
80 85 90 95 100
F
25 30 35 C
M9099
C7400A Solid State Enthalpy Sensor
The C7400A Solid State Enthalpy Sensor is used with a solid
state economizer control and damper actuator to proportion
an outdoor air damper in a ventilation system.
Figure 15 is a partial psychometric chart with single C7400A
Sensor and W7459A Economizer Logic Module performance
curves. The curves illustrate the reset in the temperature
control point due to changes in relative humidity.
The enthalpy control setpoint A,B,C, or D combines
)
temperature and humidity conditions, resulting in the control
curve shown in Fig. 15. When the enthalpy or outdoor air is
below (left of) the appropriate curve, the outdoor air damper
can proportion open on a call for cooling. If outdoor air
enthalpy rises above (to the right of) the control curve, the
outdoor air damper closes to the minimum position.
For differential enthalpy, turn the control setpoint to D (fully
clockwise). If outdoor air enthalpy is lower than return air
enthalpy, the outdoor air damper proportions open on a call
for cooling.
If outdoor air enthalpy is higher than return air enthalpy, the
outdoor air damper closes to minimum position. Differential
enthalpy control provides energy savings and increased
comfort by using the air with the lowest enthalpy.
If outdoor air enthalpy and return air enthalpy are equal, the
outdoor air damper proportions open on a call for cooling.
The relationship between the C7400A Sensor output current
and relative humidity is shown in Fig. 16.
C7650A Solid State Temperature Sensor
The C7650A Solid State Temperature Sensor is used with a
solid state economizer control and damper actuator to
proportion an outdoor air damper in a ventilation system.
When outdoor air temperature is higher than return air
temperature, the outdoor air damper closes to the minimum
position. When the outdoor air temperature and the return air
temperature are equal, the outdoor air damper proportions
open on a call for cooling.
The relationship between the C7650A Sensor output current
and the air temperature is shown in Fig. 17.
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