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4 - INSTALLATION AND CONNECTIONS
To prevent injury or damage to the unit or room, work must only be carried out by qualified
personnel.
4.1 - Mechanical connections
Prior to installation, check that there will be sufficient space to allow maintenance and servicing work to
be performed.
The 42NH must be secured to the ceiling or floor using 4 threaded rods either 6 mm or 8 mm in diameter (not
supplied), which are fixed to the unit's 4 mounting systems using anti-vibration resilient mounts (fig. 3, a) or a nut/
washer assembly positioned on either side of the mounting bracket (fig. 3, b).
Note: CARRIER strongly recommends the use of anti-vibration resilient mounts when securing the unit, in
order to reduce the transmission of vibrations through the building structure during operation.
Warning:
■ The unit must be perfectly level in relation to the suspended ceiling to prevent condensate draining
problems (see procedure for removing the condensate pan)
■ If a room thermostat is fitted, place it on an inside wall (not behind a door) and at a height of 1.50 m from
the floor. Keep it away from sunlight and all sources of heat.
4.2 - Air connections
■ Air quality
Comfort units are not designed to control the humidity of outside air. Fresh air handling must be provided by an
independent system in accordance with accepted engineering practice (see air handling unit ranges).
Warning: all collars must be connected, whatever the model. None must be capped, either for the supply
or return air.
■ Fresh air knockout
If the fresh air return leads directly outside, the duct must not exceed 5 metres in length. The fresh air temperature
must not be below -10 °C. A rain guard grille and a filter must be fitted (at the installer's expense) to prevent water
or other material entering the duct from outside. If an auxiliary fan is being used (supplied by the installer), the flow
of fresh air must be limited to 10% of the unit's nominal flow rate to prevent noise, coil frosting or air filter bypass
problems.
■ Adjusting the fresh air collars (Fig. 4):
Either remove or leave on the shims needed to obtain the desired flow rate. The flow rate ranges are given on the
label on the casing. 2 shims for minimum flow, 1 shim for medium flow, no shims for maximum flow.
The pressure difference must be between 50 and 100 Pa in order to obtain the desired flow rate.
Maintain the controller in the "BAS" (down) position.
4.3 - Hydraulic connections
Water always flows into the bottom of the coil and exits at the top.For 4-tube coils, please respect the instructions
given on the labels affixed to the coil.
The pipe system is positioned according to fig. 5.
The coils are equipped (fig. 6) with flat face swivel nuts with a female thread, diameter G ½˝ or G ¾˝ depending on
the size of the unit, and an O-ring (supplied by CARRIER).
The manifold is equipped with an air bleed valve (fig. 6, a), at the high point with partial draining at the low points
(fig. 6, b) that can be manoeuvred using a 7 mm Allen key or a flat-blade screwdriver.
IMPORTANT: The coil can be partially drained, however precautions must be taken during winter if the
installation is shut down. To drain completely, air must be blown through the circuit.
Once the hydraulic connections are completed, it is not necessary to insulate the valves to prevent
condensation (unless specifically required for the particular valves). A naturally inclined pan extension
may be supplied with the unit as an option. This recovers condensate from the valves and drains it via
gravity or using a condensate drain pump (supplied as an option).
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