Carrier 48EK, 48EW, 48EY024-068, 48AW, 48AY020-060, 48AK Differential Enthalpy Control and Sensor

7.Route the wires from the enthalpy sensor to the return air enthalpy control through the holes on the inside of the hinged filter access panel. The holes are blocked by plug buttons which should be removed.

8.Use field-supplied wire ties to attach the violet wire to the + terminal and the blue wire to the SR terminal.

9.Replace economizer filters.

10.Return power to unit.

Disable Economizer — For applications where the economiz- er will not be used (areas of high humidity), the economizer should be disabled. To disable the economizer, perform the following:

1.Turn of power. Ensure disconnect is locked out.

2.Locate the OAT (Outdoor Air Thermostat) in the right hand outdoor air damper area.

3.Locate the splice connecting the violet wire coming from T24 on the base control board to the red wire coming from T29 on the base control board. Remove the wire nut and break the red to violet wire splice.

HH57AC077

ENTHALPY

CONTROL

HH57AC078	C7400A1004
ENTHALPY SENSOR
(USED WITH ENTHALPY	+
CONTROL FOR DIFFERENTIAL
ENTHALPY OPERATION)

Fig. 46 — Differential Enthalpy Control and Sensor

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

Fig. 47 — Wiring Connections for Solid-State

Enthalpy Control (HH57AC077)

4.Cap off both wires. When the connection is broken the base control board is fooled into thinking that the enthalpy is not acceptable and economizer operation is disabled.

5.Return power to unit.

NOTE: When the economizer is disabled, the damper will function as a 2-position damper.

Step 11 — Position Power Exhaust/Barometric Relief Damper Hood — All electrical connections have been made and adjusted at the factory. The power exhaust blowers and barometric relief dampers are shipped assembled and tilted back into the unit for shipping. Brackets and extra screws are shipped in shrink wrap around the dampers. If ordered, each unit will have 4 (48AJ,AK,AW,AY020-050 and 48EJ,EK,EW,EY024-048 units) or 6 (48AJ,AK,AW,AY060 and 48EJ,EK,EW,EY054-068 units) power exhaust blowers and motors or 4 (48AJ,AK,AW,AY020-050 and 48EJ,EK,EW, EY024-048 units) or 6 (48AJ,AK,AW,AY060 and 48EJ,EK, EW,EY054-068 units) barometric relief dampers.

1.Remove 9 screws holding each damper assembly in place. See Fig. 50. Each damper assembly is secured with 3 screws on each side and 3 screws along the bottom.

Save screws.

Be careful when tilting blower assembly. Hoods and blow- ers are heavy and can cause injury if dropped.

2.Pivot each damper assembly outward until edges of damper assembly rest against inside wall of unit.

3.Secure each damper assembly to unit with 6 screws across top (3 screws provided) and bottom (3 screws from Step 1) of damper.

4.With screws saved from Step 1, install brackets on each side of damper assembly.

5.Remove tape from damper blades.

VAV DUCT PRESSURE TRANSDUCER — The VAV duct pressure transducer (VAV inverter pressure transducer) is locat- ed behind the filter access door on the lower inner panel. See Fig. 51. A section of field-supplied 1/4-in. plastic tubing must be run from the high pressure tap on the differential pressure switch and connected to a field-supplied tap in the supply-air duct. The tap is usually located 2/3 of the way out on the main supply duct. Remove plug button in panel to route tubing.

VAV BUILDING PRESSURE TRANSDUCER — The VAV building pressure transducer (modulating power exhaust pres- sure transducer) is located behind the filter access door on the lower inner panel. See Fig. 51. A section of field-supplied 1/4-in. plastic tubing must be run from the high pressure tap on the differential pressure switch to the conditioned space. The pressure tube must be terminated in the conditioned space where a constant pressure is required. This location is usually in an entrance lobby so that the building exterior doors will open and close properly. Remove plug button in panel to route tubing.

The low pressure tap is factory-routed to the atmosphere. For a positive-pressure building, route the high tap to building air and low tap to atmosphere. For a negative-pressure build- ing, route the high tap to atmosphere and the low tap to build- ing air.

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