Carrier 42NH Installation, Operation And Maintenance Instructions

Also see for 42NH series: Installation, operation and maintenance instructions Original instructions

Contents

16English4.4.1 - Actuator replacement procedureThe actuators on both the chilled water and the hot watervalves may be replaced if either develops a fault.• Disconnect the power supply to the unit before carryingout any work on a unit.• Disconnect the actuator power supply cable.- 230 V type actuator used with the Carriernumeric controller: Disconnect the actuatorpower supply cable fitted with a quick connector.- 230 V actuator used with an electronicthermostat: Remove the plastic protection coverheld in place with two screws. Disconnect theactuator power supply cable connected to thequick connector. This can be done by pressingdown the spring tongue using a screwdriver andpulling out the wire from the appropriate terminal.• Uncouple the faulty actuator. Refitting is by the reversalof the procedure described above.WARNING: Ensure that the actuator is firmly screwed tothe valve body (maximum torque 15 N·m).4.4.2 - Valve body replacement procedure• Disconnect the power supply before carrying out anywork on a unit.• Close the isolating valves on the manifolds.• Unscrew the union nuts to disconnect the flexible waterpipes.• Remove the valve actuators taking care to identify thecooling and heating valves.• Disconnect the flexible condensate drain pipe which isheld in place by a collar (the collar is not supplied byCarrier).• Remove the two-way or four-way water flow controlvalve bodies. Depending how the unit is configured,the four-way valve coupling may be fitted with aheating/cooling changeover switch, if so do notremove it.• Fit the new valve body to the coil (fit new gaskets).• Reconnect the flexible condensate drain pipe which isheld in place by a collar (the collar is not supplied byCarrier).• Refit the valve actuators taking care to ensure thatthey are correctly fixed to the valve body.• Reconnect the flexible water pipes by tightening theunion nuts. Retighten all the water connections andensure that all gaskets have been changed and correctlyfitted (maximum torque 15 N·m).• Open the isolating valves on the manifolds and purgeall air from the system.• Check that there are no leaks and reconnect the powerto the unit.WARNING: When replacing a valve always ensure thatthe direction of flow through the valve is as shown by thearrow on the valve body. If the direction of flow is wrong,the valve body will deteriorate rapidly and the flowcontrol will be distorted.4.5 - Optional electric heaterWARNING: Disconnect the power supply before carryingout any work on the unit.If the electric heater develops a fault, it must be replaced;this requires the removal of the fan motor assembly: Fig. 12.CAUTION: Do not touch the live metal heater elementswhen the electric heater is connected to the power supply.electric heater replacement procedure:• Remove the filter.• Remove the fan motor assembly access panel.• Identify and note the fan speeds wired to the auto-transformer terminal block. Disconnect the powersupply cable.• Remove the fan motor assembly.NOTE: Be careful not to touch the fan blades duringthe removal process to avoid unbalancing the fans.• Disconnect the electric heater power supply cablesand remove them through the cable conduit.• Unscrew the defective heater(s) and replace it (them).• Replacement of the fan motor assembly is by thereversal of the above procedure.Carrier Electronic thermostat type B is embedded withElectric heater relay 8 Amps. Accordingly, Carrier requiresan additional protection relay for electric heater withabove 1400 W capacity.Moreover, all units delivered with an electrical box or aCarrier controller are always equipped with a relay if thecapacity of the electrical heater is above 1400W.WARNING : In case of customer supplied controller, it isthe responsability of the installer to set up an additionalprotection relay corresponding to the electrical heatercapacity.4.6 - Optional sensorA water temperature sensor can be provided. It has to beinstalled on the water circuit as described below :• For 2-pipe coil : the sensor shall be installed on acooling water pipe (for change-over function).• For 4-pipe coil : the sensor shall be installed on aheating water pipe (for cold-draft function thatprevents the operation of the unit when the heatingnetwork is off).NOTE: In case of 2-pipe coil, the sensor is installed on apart where the water flow is continuous.