Carrier 30GX Installation, Operation And Maintenance Instructions

Also see for 30GX Series: Installation, operation and maintenance instructions Installation, operation and maintenance instructions

305.12 - Motor cooling valve controlThe temperature of the motor windings is controlled to asetpoint of 85°C. This is achieved by cycling of the motorcooling valves to allow the refrigerant to flow across the motorwindings, if necessary. For units with economizer, instanta-neous vapour leaves the high side of the economizer andcontinuously flows across the motor windings. All refrigerantused for motor cooling returns to the rotors through an orificesituated mid-way along the compression cycle and iscompressed to the discharge pressure.5.13 - Head pressure control on air-cooled units• The saturated condensing temperature is controlled byreference to a fixed setpoint (user-definable in the Setpointsmenu). This temperature is maintained by cycling fans onand off, as well as by varying the speed of a fan.NOTE: Certain units can have up to 4 fan stages and a vari-able speed fan per circuit, depending on their configurationand wiring.5.14 - Head pressure control on water-cooled units• The saturated condensing temperature is controlled byreference to a user-definable fixed setpoint. This temperatureis maintained by using the valve to control the flow of waterin each condenser circuit.5.15 - Head pressure setpoint selectionThere are two head pressure setpoints available: the first iscalled “head pressure setpoint” and the second “reclaimsetpoint”. These setpoints only have an effect when the controlsystem is controlling head pressure: air or water-cooled unitsoperating in cooling mode (only when they are fitted withcondenser water valves).The active setpoint can be selected in one of the followingways:• With the operating type selector button: selections L-C1 andL-C2 activate the head pressure setpoint. Selections LC1rand LC2r activate the reclaim setpoint (see section 4.2.2,description of the operating modes).• With a volt-free selection contact connected to the customerterminal block when the unit is in Remote operating type(rEM). See section 3.4.4, description of the control contacts.• With a network command when the unit is in CCN operatingtype (CCn).5.16 - High pressure load shedding functionThis function does not require an additional board. It preventshigh pressure breaks on a circuit by the following means:• Preventing any capacity increase on the circuit once the highpressure value has reached an initial threshold.• Shedding one or more capacity stages once a second protect-ion threshold has been reached.In the event of capacity stages being shed, no capacity increasewill be authorised on the circuit concerned for a period of 5minutes.NOTE: The last capacity stage cannot be shed by this protect-ion function. An alarm is activated, if the high pressure is stilltoo high.5.17 - Start-up procedure - prelubricationThis procedure describes the necessary procedures to ensure thelubrication of the compressor before start-up.The control follows the sequence below:For the lead compressor (the first compressor in the circuit tostart):1. Start the oil pump and measure the initial oil pressure.2. Wait approximately 30 seconds.3. Verify the oil solenoid valve tightness, i.e.: if oil pressureincreases and the solenoid valve is not open, the oilsolenoid valve failure alarm is activated and prelubri-cation is stopped. The procedure is aborted.4. If not, the oil solenoid valve is activated.5. Wait approximately 15 seconds.6. If oil pressure increases, prelubrication is assured and thecompressor can start.7. If not, a further prelubrication cycle is started. Return topoint 1.NOTE: After three cycles, the low oil pressure alarm at prestart-up is acctivated, and prelubrication is also stopped.For the lag compressor (one compressor in the circuit is alreadyin operation).1. Activate the oil solenoid valve.2. Wait approximately 15 seconds.3. If oil pressure increases, prelubrication is assured and thecompressor can now start.4. If not, the low oil pressure at start-up alarm is activatedand the prelubrication is also stopped.5.18 - Master/slave assembly5.18.1 - GeneralTwo PRO-DIALOG Plus units can be linked to produce amaster/slave assembly. This feature is only authorised incooling mode. The two machines are interconnected over theCCN bus. To operate as master/slave, both units must havetheir chilled water temperature probes located on the commonevaporator entering and leaving line. In addition interlockcontrol of the cooler water flow and a freeze protection switchis imperative on each unit.The master/slave link only operates when both units are inCCN operating mode. The master/slave assembly will beinactive in the following cases:• If either of the chillers is in Local or Remote mode, or inheating mode.• A demand limit command is sent to the slave unit.• One of the following CCN variables is forced on the slaveunit: start unit, demand limit or control point.