Carrier WeatherMaster Puron 48HC D17 Service And Maintenance Instructions page 43

MINIMUM HEATING ENTERING AIR TEMPERATURE
When operating on first stage heating, the minimum temperature
of air entering the dimpled heat exchanger is 50°F (10°C) con-
tinuous and 45°F (7°C) intermittent for standard heat exchangers
and 40°F (4°C) continuous and 35°F (2°C) intermittent for stain-
less steel heat exchangers. To operate at lower return or mixed
air temperatures, a field-supplied outdoor-air thermostat must be
used to initiate both stages of heat when the temperature is below
the minimum required temperature to ensure full fire operation.
Wire the outdoor-air thermostat (OALT) (part no. HH22AG106)
in series with the second stage gas valve. See Fig. 53. Set the
outdoor-air thermostat at 35°F (2°C) for stainless steel heat ex-
changers or 45°F (7°C) for standard heat exchangers. This tem-
perature setting will bring on the second stage of heat whenever
the ambient temperature is below the thermostat setpoint. Indoor
comfort can be compromised when heating is initiated using low
entering air temperatures with insufficient heating temperature
rise.
PROBLEM
Misaligned spark electrodes.
No gas at main burners.
Water in gas line.
Burners will
No power to furnace.
not ignite
No 24 v power supply to control circuit.
Miswired or loose connections.
Burned-out heat anticipator in thermostat. Replace thermostat.
Broken thermostat wires.
Dirty air filter.
Gas input to unit too low.
Unit undersized for application.
Restricted airflow.
Inadequate heating
Blower speed too low.
Limit switch cycles main burners.
Too much outdoor air.
Incomplete combustion (lack of
Poor Flame
combustion air) results in: Aldehyde odors,
Characteristics.
CO, sooting flame, or floating flame.
Burners Will Not Unit is locked into Heating mode for a one
Turn Off. minute minimum.
Table 18 — Heating Service Troubleshooting
CAUSE
Check flame ignition and sensor electrode positioning. Adjust as needed.
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 relight unit.
Check gas valve.
Drain water and install drip leg to trap water.
Check power supply, fuses, wiring, and circuit breaker.
Check transformer. Transformers with internal overcurrent protection require a
cool down period before resetting.
Check all wiring and wire nut connections.
Run continuity check. Replace wires, if necessary.
Clean or replace filter as necessary.
Check gas pressure at manifold. Clock gas meter for input. If too low, increase
manifold pressure, or replace with correct orifices.
Replace with proper unit or add additional unit.
Clean filter, replace filter, or remove any restrictions.
Use high speed tap, increase fan speed, or install optional blower, as suitable
for individual units.
Check rotation of blower, thermostat heat anticipator settings, and temperature
rise of unit. Adjust as needed.
Adjust minimum position.
Check economizer operation.
Check all screws around flue outlets and burner compartment. Tighten as
necessary.
Cracked heat exchanger.
Overfired unit — reduce input, change orifices, or adjust gas line or manifold
pressure.
Check vent for restriction. Clean as necessary.
Check orifice to burner alignment.
Wait until mandatory one-minute time period has elapsed or reset power to
unit.
43
Thermostat
TH1
W1
TH2
Fig. 53 — OATL Connections
TROUBLESHOOTING HEATING SYSTEM
Refer to Tables 18 and 19 for additional troubleshooting topics.
REMEDY
CTB
W1
OALT