Optional Electric Heater; Optional Sensor - Carrier 42NH Installation, Operation And Maintenance Instructions

4.4.1 - Actuator replacement procedure
The actuators on both the chilled water and the hot water
valves may be replaced if either develops a fault.
• Disconnect the power supply to the unit before carrying
out any work on a unit.
• Disconnect the actuator power supply cable.
- 230 V type actuator used with the Carrier
numeric controller: Disconnect the actuator
power supply cable fitted with a quick connector.
- 230 V actuator used with an electronic
thermostat: Remove the plastic protection cover
held in place with two screws. Disconnect the
actuator power supply cable connected to the
quick connector. This can be done by pressing
down the spring tongue using a screwdriver and
pulling out the wire from the appropriate terminal.
• Uncouple the faulty actuator. Refitting is by the reversal
of the procedure described above.
WARNING: Ensure that the actuator is firmly screwed to
the valve body (maximum torque 15 N·m).
4.4.2 - Valve body replacement procedure
• D isconnect the power supply before carrying out any
work on a unit.
• Close the isolating valves on the manifolds.
• U nscrew the union nuts to disconnect the flexible water
pipes.
• R emove the valve actuators taking care to identify the
cooling and heating valves.
• D isconnect the flexible condensate drain pipe which is
held in place by a collar (the collar is not supplied by
Carrier).
• R emove the two-way or four-way water flow control
valve bodies. Depending how the unit is configured,
the four-way valve coupling may be fitted with a
heating/cooling changeover switch, if so do not
remove it.
• F it the new valve body to the coil (fit new gaskets).
• R econnect the flexible condensate drain pipe which is
held in place by a collar (the collar is not supplied by
Carrier).
• R efit the valve actuators taking care to ensure that
they are correctly fixed to the valve body.
• R econnect the flexible water pipes by tightening the
union nuts. Retighten all the water connections and
ensure that all gaskets have been changed and correctly
fitted (maximum torque 15 N·m).
• O pen the isolating valves on the manifolds and purge
all air from the system.
• Check that there are no leaks and reconnect the power
to the unit.
WARNING: When replacing a valve always ensure that
the direction of flow through the valve is as shown by the
arrow on the valve body. If the direction of flow is wrong,
the valve body will deteriorate rapidly and the flow
control will be distorted.
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4.5 - Optional electric heater

WARNING: Disconnect the power supply before carrying
out 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 elements
when the electric heater is connected to the power supply.
electric heater replacement procedure:
• Remove the filter.
• R emove the fan motor assembly access panel.
• I dentify and note the fan speeds wired to the auto-
transformer terminal block. Disconnect the power
supply cable.
• R emove the fan motor assembly.
NOTE: Be careful not to touch the fan blades during
the removal process to avoid unbalancing the fans.
• Disconnect the electric heater power supply cables
and remove them through the cable conduit.
• Unscrew the defective heater(s) and replace it (them).
• R eplacement of the fan motor assembly is by the
reversal of the above procedure.
Carrier Electronic thermostat type B is embedded with
Electric heater relay 8 Amps. Accordingly, Carrier requires
an additional protection relay for electric heater with
above 1400 W capacity.
Moreover, all units delivered with an electrical box or a
Carrier controller are always equipped with a relay if the
capacity of the electrical heater is above 1400W.
WARNING : In case of customer supplied controller, it is
the responsability of the installer to set up an additional
protection relay corresponding to the electrical heater
capacity.

4.6 - Optional sensor

A water temperature sensor can be provided. It has to be
installed on the water circuit as described below :
• For 2-pipe coil : the sensor shall be installed on a
cooling water pipe (for change-over function).
• For 4-pipe coil : the sensor shall be installed on a
heating water pipe (for cold-draft function that
prevents the operation of the unit when the heating
network is off).
NOTE: In case of 2-pipe coil, the sensor is installed on a
part where the water flow is continuous.