Carrier WeatherMaster 48HC04 Service And Maintenance Instructions

Also see for WeatherMaster 48HC04 Series: Installation instructions

42MINIMUM HEATING ENTERING AIR TEMPERATUREWhen operating on first stage heating, the minimum temperatureof air entering the dimpled heat exchanger is 50°F continuous and45°F intermittent for standard heat exchangers and 40°F continu-ous and 35°F intermittent for stainless steel heat exchangers. Tooperate at lower mixed-air temperatures, a field-supplied outdoor-air thermostat must be used to initiate both stages of heat when thetemperature is below the minimum required temperature to ensurefull fire operation. Wire the outdoor-air thermostat OALT (part no.HH22AG106) in series with the second stage gas valve. SeeFig. 61. Set the outdoor-air thermostat at 35°F for stainless steelheat exchangers or 45°F for standard heat exchangers. This tem-perature setting will bring on the second stage of heat wheneverthe ambient temperature is below the thermostat set point. Indoorcomfort may be compromised when heating is initiated using lowentering air temperatures with insufficient heating temperaturerise.Fig. 61 — OATL ConnectionsTroubleshooting Heating SystemRefer to Tables 19 and 20 for additional troubleshooting topics.CTBW2ThermostatTH1TH2W1W1W2OALTTable 19 — Heating Service TroubleshootingPROBLEM CAUSE REMEDYBurners Will Not Ignite.Misaligned spark electrodes. Check flame ignition and sensor electrode positioning. Adjust as needed.No gas at main burners.Check gas line for air, purge as necessary. After purging gas line of air,allow gas to dissipate for at least 5 minutes before attempting to relightunit.Check gas valve.Water in gas line. Drain water and install drip leg to trap water.No power to furnace. Check power supply, fuses, wiring, and circuit breaker.No 24-v power supply to control circuit. Check transformer. Transformers with internal overcurrent protectionrequire a cool down period before resetting.Miswired or loose connections. Check all wiring and wire nut connections.Burned-out heat anticipator in thermostat. Replace thermostat.Broken thermostat wires. Run continuity check. Replace wires, if necessary.Inadequate Heating.Dirty air filter. Clean or replace filter as necessary.Gas input to unit too low. Check gas pressure at manifold. Clock gas meter for input. If too low,increase manifold pressure, or replace with correct orifices.Unit undersized for application. Replace with proper unit or add additional unit.Restricted airflow. Clean filter, replace filter, or remove any restrictions.Blower speed too low. Use high speed tap, increase fan speed, or install optional blower, assuitable for individual units.Limit switch cycles main burners. Check rotation of blower, thermostat heat anticipator settings, andtemperature rise of unit. Adjust as needed.Too much outdoor air. Adjust minimum position.Check economizer operation.Poor FlameCharacteristics.Incomplete combustion (lack of combustionair) results in: Aldehyde odors, CO, sootingflame, or floating flame.Check all screws around flue outlets and burner compartment. Tighten asnecessary.Cracked heat exchanger.Overfired unit — reduce input, change orifices, or adjust gas line ormanifold pressure.Check vent for restriction. Clean as necessary.Check orifice to burner alignment.Burners Will Not Turn Off. Unit is locked into Heating mode for a oneminute minimum.Wait until mandatory one-minute time period has elapsed or reset powerto unit.