Bryant 580F installation instructions R. CO2 Sensor Configuration, Demand Ventilation Control

minimum position (configuration item number 15), unless the remote potentiometer is used to override it.

For the demand ventilation control logic, the user configures the lower and upper actuator position to establish the base ventilation rate (IAQMIN_SP) and the design ventilation rate (ECONOMIN_SP) for full occupancy. When the EconoMi$er+ damper is being modulated for demand venti- lation control, the damper position will be between IAQMIN_SP and ECONOMIN_SP. The upper IAQ differen- tial set point is DAQHI. The lower IAQ differential set point is DAQLO.

The differential set points represent the differential CO2 level (in ppm) above the outdoor reference IAQ levels. Normally, the outdoor reference IAQ levels are around 400 ppm, but the value should be configured based on the reference levels taken at the job site.

The following equation is used to determine EconoMi$er+ damper position (ECONOMIN_POS):

(ECONOMIN_SP – IAQMIN_SP) * (IAQ – OAQ – DAQLO)

IAQMIN_SP + =

(DAQHI – DAQLO)

R. CO2 Sensor Configuration

The CO2 sensor has preset standard voltage settings that can be selected anytime after the sensor is powered up. See Table 7.

1.Press Clear and Mode buttons. Hold at least 5 sec- onds until the sensor enters the Edit mode.

2.Press Mode 2 times. The STDSET Menu will appear.

3.Use the Up/Down button to select the preset number. See Table 7.

4.Press Enter to lock in the selection.

Press Mode to exit and resume normal operation. The cus- tom settings of the CO2 sensor can be changed any time after the sensor is energized. Follow the steps below to change the non-standard settings:

1.Press Clear and Mode buttons. Hold at least 5 sec- onds until the sensor enters the Edit mode.

2.Press Mode 2 times. The STDSET Menu will appear.

3.Use the Up/Down button to toggle to the NONSTD menu and press Enter.

4.Use the Up/Down button to toggle through each of the nine variables, starting with Altitude, until the desired setting is reached.

5.Press Mode to move through the variables.

6.Press Enter to lock in the selection, then press Mode to continue to the next variable.

S.Dehumidification of Fresh Air with Demand Control Ven- tilation (DCV)

Information from ASHRAE (American Society of Heating, Refrigeration and Air Conditioning Engineers) indicates that the largest humidity load on any zone is the fresh air intro- duced. For some applications, a device such as a energy recovery unit is added to reduce the moisture content of the fresh air being brought into the building when the enthalpy is high. In most cases, the normal heating and cooling pro- cesses are more than adequate to remove the humidity loads for most commercial applications.

This makes the control of the dehumidification device simple when using the enthalpy or differential enthalpy sensor. The enthalpy sensor or differential enthalpy sensor is installed on the equipment to determine economizer operation. The high enthalpy signal from the temperature and humidity sensors or differential temperature and humidity sensors can be used to turn on the outdoor air moisture removal device any time fresh air is required for the space.

The energy recovery device should be sized for maximum latent and sensible conditioning at maximum ventilation on a design day.

A calculation for leaving-air temperature on a low ambient, low ventilation day should also be done to determine the supply-air temperature of the return and pre-conditioned outside air. The design should produce air temperature somewhat near room conditions to prevent reheat of the air mixture. The energy recovery device should be interlocked with the heat to turn off the device when in the heat mode.

DAMPER
POSTION
		FULL OCCUPANCY
ECONOMIZER		VENTILATION RATE
MINIMUM
OCCUPIED
DAMPER
POSITION
(ECONOMIN_SP)
	VENTILATION FOR PEOPLE
IAQ
MINIMUM
ECONOMIZER
POSITION
SET POINT	VENTILATION FOR SOURCES
(IAQMIN_SP)
			CO2 LEVEL
OUTDOOR REFERENCE	100	700	INSIDE/OUTSIDE CO2 DIFFERENTIAL
LEVEL (OAQ)= 400	500	1100	INSIDE CO2 CONCENTRATION

AQ	AQ
DIFFERENTIAL	DIFFERENTIAL
LOW (DAQLO)	HIGH (DAQHI)

Fig. 32 — Demand Ventilation Control

Table 7 — CO2 Sensor* Standard Settings

			VENTILATION	ANALOG	CO2 CONTROL	OPTIONAL	RELAY
SETTING	EQUIPMENT	OUTPUT	RATE			RELAY SETPOINT	HYSTERESIS
			(cfm/Person)	OUTPUT	RANGE (ppm)	(ppm)	(ppm)
1	Interface with Standard	Proportional	Any	4-20 mA	0-2000	1000	50
2		Proportional	Any	7-20 mA	0-2000	1000	50
	Building Control System
3		Exponential	Any	4-20 mA	0-2000	1100	50
4		Proportional	15	4-20 mA	0-1100	1100	50
5	Economizer	Proportional	20	4-20 mA	0- 900	900	50
6		Exponential	15	4-20 mA	0-1100	1100	50
7		Exponential	20	4-20 mA	0- 900	900	50
8	Health & Safety	Proportional	—	4-20 mA	0-9999	5000	500
9	Parking/Air Intakes/ Loading Docks	Proportional	—	4-20 mA	0-2000	700	50

LEGEND

ppm — Parts Per Million

*Available sensor part numbers are listed in Table 4.

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