Carrier 50EJ Ð Attaching Seal Strip to Filter Cover, Ð Differential Enthalpy Control, and Sensor

Minimum Damper Position Setting Ð Setting of the out- door air damper position is performed in conjunction with a shortened version of the ®eld-run test. This is performed by ®rst opening DIP (Dual In-Line Package) switch no. 6 then no. 4. See Fig. 17 and Table 7.

The outdoor-air damper closes. The control allows 90 sec- onds for the damper to close in case it is in the full open position. Next, the indoor-fan contactor will energize. The outdoor-air damper will remain at 0% for 30 seconds. It will then move to the 10% position for another 30 seconds. This will be repeated at every 10% increment for 30 seconds until the damper reaches 100% open. Close DIP switch no. 6 dur- ing the 30 seconds immediately after the desired outdoor air minimum damper position. The 30-second time period is to allow time where DIP switch no. 6 can be closed. The de- fault value of the minimum outdoor air damper position is 20%. If the desired minimum position is 30%, allow the damper

BLACK SEAL STRIP (CENTERED)

FILTER COVER

Fig. 27 Ð Attaching Seal Strip

to Filter Cover

HH57AC077

ENTHALPY CONTROL

C7400A1004	HH57AC078
	ENTHALPY SENSOR

+	(USED WITH ENTHALPY
	CONTROL FOR DIFFERENTIAL
	ENTHALPY OPERATION)

Fig. 28 Ð Differential Enthalpy Control

and Sensor

position to go to 10% for 30 seconds, then 20% for 30 sec- onds, and when it reaches 30% close DIP switch no. 6 dur- ing the 30-second period following the 30% position.

The minimum outdoor air damper position is now set.

ECONOMIZER SETTINGS

Accessory Enthalpy Control (Fig. 28) Ð The control (HH57AC077) is mounted in the economizer hood. See Fig. 19. The enthalpy setting adjustment is on the enthalpy control. For maximum bene®t of outdoor air, set enthalpy control to A. See Fig. 29 and 30.

Accessory Differential Enthalpy Control Ð The control (HH57AC077), in conjunction with the accessory enthalpy sensor (HH57AC078), controls economizer operation ac- cording to the differential enthalpy. The control is mounted in the economizer hood. The sensor is mounted in the return duct (50EJ/EK) or return air plenum (50EW/EY).

NOTE: Switches shown in high enthalpy state. Terminals 2 and 3 close on en- thalpy decrease.

Fig. 29 Ð Wire Connections for Solid State

Enthalpy Control (HH57AC077)

CONTROL	CONTROL POINT
CURVE	(APPROX. DEG.)
	AT 50% RH

A73 (23)

B70 (21)

C67 (19)

D63 (17)

RH Ð Relative Humidity

Fig. 30 Ð Psychrometric Chart for

Enthalpy Control

28