Carrier 50PG20-28 Controls, Start-up, Operation, Service And Troubleshooting Instructions

Also see for 48PG20---28: User's information manual User's information manual Installation and service instructions

Carrier 50PG20-28 Controls, Start-up, Operation, Service And Troubleshooting Instructions Manual pdf 80 page image

Scrolling Marquee Display i This device is the key-pad interface used to access rooftop information, read sensorvalues, and test the unit. See Fig. 26. The Scrolling Marqueedisplay is a &key, 4-charactm; 16-segment LED (light-emittingdiode) display. Eleven mode LEDs are located on the displayas well as an Alarm Status LED. See Scrolling Marqueesection on page 2 for further details.Accessory Navigator TM Display i The accessoryhand-held Navigator display can be used with the 48/50PGseries units. See Fig. 27. The Navigator display operates thestone way as the Scrolling Marquee device. The Navigatordisplay plugs into the LEN port on either TB2 or the ECBboard.Carrier Comfort Network® (CCN) Interface iThe 48/50PG units can be connected to the CCN it"desired.The communication bus wiring is a shielded, 3-conductorcable with drain wire and is field supplied and installed. Thesystem elements are connected to the co_rnnunication bus in adaisy chain arrangement. See Fig. 28. The positive pin of eachsystem element communication connector must be wired to thepositive pins of the system elements on either side of it. This isalso required for the negative and siNmt ground pins of eachsystem element. Wiring connections for CCN should be madeat TB2. See Fig. 14-17. Consult the CCN Contractor's Manualfor further information.NOTE: Conductors and drain wire must be 20 AWG (Ameri-can Wire Gage) minimum stranded, tinned copper, hldividuatconductors must be insulated with PVC, PVC/nyton, vinyl,Teflon, or polyethylene. An aluminmn/polyester 100% Ibilshield and an outer jacket of PVC, PVC/nylon, chrome vinyl, orTeflon with a minimum operating temperature range of _0 Cto 60 C is required. See the table below for acceptable wiring.MANUFACTURER PART NO.Alpha 2413 or 5463Belden 6772Carol C2528West Penn 302It is important when connecting to a CCN colrnnunicationbus that a color-coding scheme be used for the entire networkto simplit) the installation. It is recolrnnended that red be usedfor the siNml positive, black for the signal negative and whitefor the sisal ground. Use a similar scheme for cables contain-ing different colored wires.At each system element, the shields of its colrnnunicationbus cables must be tied together. The shield screw on TB2 canbe used to tie the cables together. If the communication bus isentirely within one building, the resulting continuous shieldmust be connected to a ground at one point only. The shieldscrew on TB2 is not acceptable for grounding. If the colrnnuni-cation bus cable exits fiom one building and enters another,the shields must be connected to grounds at the lighming sup-pressor in each building where the cable enters or exits thebuilding (one point per building only). To connect the unit tothe network:1. Turn offpower to the control box.2. Cut the CCN wire and strip the eMs of the red (_), white(ground), and black () conductors. (Substitute appropri-ate colors for different colored cables.)3. Connect the red wire to (+) terminal on TB2, the whitewire to COM terminal, and the black wire to the @)terminal.4. The RJ14 CCN connector on TB2 can also be used, but isonly inteMed tbr temporary connection (for example, alaptop computer running Carrier net_xx_rksot_vare).Fig. 26 1 Scrolling MarqueeFig. 27 1 Accessory Navigator TM Display5. Restore power to unit.IMPORTANT: A shorted CCN bus cable will preventsome routines fiom running and may prevent the unit fiomstarting. If abnormal conditions occur, unplug the connec-tor. If conditions remm to normal, check the CCN connec-tor and cable. Run new cable if necessary. A short in onesection of the bus can cause problems with all system ele-ments on the bus.Subcooler Heat Exchanger (SHX) i The purposeof the subcooler heat exchanger (SHX) and the subcooler TXVis to increase the capacity of the evaporator by sending sub-cooled liquid refi-igerant into the evaporator. Normally, thecondenser subcools the liquid refi-igerant by approximately10 F. The SHX adds another 10 F to 15 F degrees of subcoolingbefore the refi-igerant reaches the evaporator. This allows therefi-igerant to absorb more heat fiom the mixed air, thereby pro-viding more cooling capacity.The subcooler functions by taking a small percentage of thehigh pressure, medium temperature liquid refiigerant whichexits the condenser and converting it into a low pressure, lowtemperature gas. This is accomplished by using the subcoolerTXM The gas is then routed thiough a reverse-flow heatex&anger (SHX), which transI_rs heat from the remainingliquid refiigerant in the liquid line to the reverse flow gasrefrigerant. The moderate temperature gas is then sent to thecompressor to complete the loop and the cooler liquid refiiger-ant continues its normal path to the main TXV and theevaporator. See Fig. 29.80