Carrier 42EM Series Installation, Operation And Maintenance Instructions

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Contents

13English4.4 - Optional filter and filter access4.4.1 - DescriptionThe Carrier unit is fitted with G3 filter as standard (85%gravimetrie filter) or G4 filter as option, according tostandard EN 779. Medium fire rating M1, metal wireframe.Different filter access are available:• Unit with non-ducted return air: Access is from therear of the unit.• Unit with ducted return air: Access is from below.4.4.2 - Air filter replacementAir filters should be changed regularly. Filter life depends onthe rate at which the filter becomes clogged, which dependsupon the cleanliness of the working environment.If clogged filters are not changed they can increase the airpressure drop, trapped dust particles may be given off andentrained in the air supply, and the general performance ofthe unit may be degraded (as the air flow reduces).NOTE: When installing a unit in a ceiling void, checkthat no T-bars will obstruct filter access and removal.4.5 - Fresh air controller4.5.1 - Fresh air controller with constant air volumeThe 42EM unit can be fitted with a constant fresh air flowcontroller, fixed at 8.5 l/s (30 m3/h) or adjustable from 17 l/s(60 m3/h) to 44 l/s (160 m3/h) to allow contol of theintroduction of fresh air and of the air change rate.Controllers with adjustable fresh air flow:The diameter of the spigot housing the fresh air flowcontroller is 125 mm.The fresh air controller may be modified on site by relocatingor removing two plastic restrictors in order to change themaximum constant fresh air flow of 17 1/s (60 m3/h) to 44 1/s(160 m3/h). A label on the 42EM shows how to adjust thetwo plastic restrictors (Fig. 11).Modification procedure• Disconnect the fresh air duct from the spigot on theunit.• Remove or reposition the two plastic restrictors,following the fresh air flow controller.• Reconnect the fresh air duct to the spigot.IMPORTANT: If the unit is fitted with a return airtemperature sensor, the constant fresh air flow rate mustnot exceed 50% of the supply air flow delivered by theunit at minimum speed.NOTE: To operate correctly, the 8.5 l/s (30 m3/h) theconstant fresh air flow controller requires a differentialpressure in the range of 50 Pa to 200 Pa. The controller withadjustable fresh air flow from 17 l/s (60 m3/h) to 44 l/s(160 m3/h) requires a differential pressure in the range of70 to 200 Pa.4.5.2 - Fresh air controller with variable air volumeThe 42EM unit can be equipped with an optional variablefresh air flow controller from 0 to 55 l/s (0 to 200 m3/h).This is connected to the numeric Carrier controller and canregulate the fresh air intake in two ways:• Either using a fixed rate set by the installer that can bereconfigured as required• Or based on the CO2 level; in this case it is connectedto a CO2 sensor via the Carrier numeric controller (theCO2 sensor is located opposite the fresh air inlet).NOTE: With the variable fresh air flow controller theupstream pressure in the fresh air duct must be 180 Pa.4.6 - Optional water flow control valvesThese valves are either two-way or four-way type (three-way with integral bypass). The body of the valve is designedto withstand a 16 bar operating pressure.With this option, the couple (valve + actuator) is usuallynormally closed (NC).Thus, the water flow is null in case ofpower cut. To fill the installation, to equalise the watercircuits and to purge the units, the actuators must beconnected to the power supply and the valves must beopened via the controller (thermostats or BMS).For the replacement of these components refer to thechapter ‘‘4.6.3. - Actuator replacement procedure’’.4.6.1 - 230 V - ActuatorsTwo types of valve actuators are provided : electrothermalactuator (on/off control) or modulating actuator (3-point).The actuator supply is 230 V a.c.4.6.2. 24 V - ActuatorsThree types of valve actuators are provided : oneelectrothermal actuator (on/off control) or two modulatingactuators (3-point or 0-10V).Both modulating actuators can be operated manually with ahexagonal key. The 0-10V command voltage range of themodulating actuator can also be adjusted.The actuator supply is 24 V a.c.NOTE: 24V actuators are not compatible with Carriercontrollers (Thermostats A/B/C/D, HDB & NTC).4.6.3 - Actuator replacement procedureThe actuators on both the chilled water and the hot watervalves may be replaced if either develops a fault.WARNING : Do not connect on the same neutral wire thevalve actuator 24 Vac and the controller.

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