Carrier 48HC 04-28 Controls, Start-up, Operation And Troubleshooting

Also see for /50HC 04-28: Manual

Contents

Carrier 48HC 04-28 Controls, Start-up, Operation And Troubleshooting Manual pdf 68 page image

68Communication FailuresCommunication is critical for ERV operation. It can fail on twodifferent paths; between the UPC and the rooftop (LEN), or be-tween the UPC and the EXCB. This makes the UPC critical toERV operation. Make sure the UPC DIP switches and rotaryswitches are set correctly. Make sure the board hardware jumpersare set on EIA 485 and 2W. During normal operation the 4 com-munication LEDs will flash interchangeably. If all 4 LEDs are notflashing then there is a communication problem. Check connec-tions between Port 1a and rooftop’s LEN connection and Port 2and the EXCB J23 (verify with the proper unit schematic).The ERVs, LCD screen will show specific communication fail-ures when they occur. Use the LCD screen to help troubleshootcommunications failures. If communication is established, theLED shows “communication connected”.COMM FAILURE1 – UPC TO LEN FAILThis will be displayed if the EXCB can communicate with theUPC, but the UPC does not receive information from the Com-fortLink controller. This will occur if the cable is pinched ordisconnected, wired wrong or loose, or if the UPC is config-ured wrong.COMM FAILURE2 – UPC TO EXCB FAILThis will be displayed if the EXCB cannot communicate withthe UPC. This will occur if the connection between them is dis-connected or pinched. This will also occur if the UPC does nothave power or software, or if it has an error or configuredwrong.On-Board Pressure TransducersThe EXCB uses on-board pressure transducers to measure theair pressure of the incoming outside air and the building ex-haust air. The CFM values are then calculated based on thesereadings and the fan speed. There is a pressure transducer forthe outside air and one for the exhaust air. These are screwedinto the EXCB board to J24 and J25 respectively. They havethree pins: IN, GND, and OUT. The IN pin is 5vdc input powerand GND is the common or ground pin. The OUT pin will be0.26 to 4.5vdc based on the pressure reading. There are twodifferent transducers used, two inch of water column (in.wg)and 5 in.wg. Table 28 shows the voltage/pressure characteris-tics of each.MAJOR SYSTEM COMPONENTSGeneralThe 48/50HC single package rooftop units contain the Com-fortLink electronic control system that monitors all operations ofthe rooftop. The control system is composed of several main con-trol components and available factory-installed options or field-in-stalled accessories as listed in sections below. See Figs. 24-31 fortypical control and power schematics for 48HC and 50HC. Referto the base unit installation instructions or actual unit control boxfor specific unit wiring diagrams.Table 28 — Transducer/Voltage vs. PressureVoltage (vDC) Pressure (in.wg)2 in. transducer 5 in. transducer<= –0.26 0.00 0.000.5 0.12 0.281.0 0.34 0.871.5 0.53 1.462.0 0.82 2.052.5 1.06 2.643.0 1.30 3.233.5 1.52 3.824.0 1.76 4.414.5 2.00 5.00