Carrier 48HG016 Controls Operation And Troubleshooting Download

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The burners will ignite within 5 seconds. If the burners do

not light, there is a 22-second delay before another 5-second
attempt. If the burners still do not light, this sequence is repeat-
ed for 15 minutes. After the 15 minutes have elapsed, if the
burners still have not ignited, heating is locked out. The control
will reset when the request for heat is temporarily removed.

When ignition occurs, the IGC board will continue to moni-

tor the condition of the rollout switch, limit switches, Hall
Effect sensor, and the flame sensor. If the unit is controlled
through a room thermostat set for fan auto, 45 seconds after
ignition occurs the indoor-fan motor will be energized (and the
outdoor-air dampers will open to their minimum position). If
for some reason the overtemperature limit opens prior to the
start of the indoor fan blower, on the next attempt, the
45-second delay will be shortened to 5 seconds less than the
time from initiation of heat to when the limit tripped. Gas will
not be interrupted to the burners and heating will continue.
Once modified, the fan on delay will not change back to
45 seconds unless power is reset to the control.

When additional heat is required and the MBB senses that

W2 is On, the MBB closes the HTR.2 relay and sends power to
the second stage of the main gas valve. If the thermostat
removes the call for W2, the unit will turn off HTR.2 (mini-
mum on-time 2 minutes [MRT.H], minimum off-time 2 min-
utes [MOT.H]). If W1 is satisfied, the main base board will
open HTR.1 (minimum on-time 2 minutes and minimum
off-time 2 minutes), interrupting the flow of gas to the main
burners. The IGC also has a minimum on-time of 1 minute.
Therefore, in modes such as Service Test where the long mini-
mum on-time and off-times are not enforced, the one minute
minimum on-time for the IGC will still be followed. If the unit
is controlled through a room thermostat set for fan auto, the
indoor-fan motor will continue to operate for an additional
45 seconds then stop. If the overtemperature limit opens after
the indoor motor is stopped within 10 minutes of W becoming
inactive, on the next cycle the time will be extended by 15 sec-
onds. The maximum delay is 3 minutes. Once modified, the
fan off delay will not change back to 45 seconds unless power
is reset to the control.

An LED indicator is provided on the IGC to monitor opera-

tion. The IGC is located by removing the heat section side
panel. See Fig. 4. During normal operation, the LED is contin-
uously on. See Table 26 for error codes.

If the user has selected Adaptive (see Cooling section) for

its thermostat mode, the algorithm will follow the configurable
delays for adding and removing stages. When adding addition-
al heat stages, the delay is measured from when the last stage
was added (H.INC). When removing stages, the delay is mea-
sured from when the last stage was removed (H.DEC). There-
fore, if W1 and W2 turn on simultaneously, the second stage
will turn on after a H.INC delay.
NOTE: If the mode is not Adaptive, then there are no delays
for adding and removing stages.
SPACE SENSOR CONTROL — During Space Sensor con-
trol, the electronic control uses information from the space sen-
sor to determine the number of heat stages. Once the number of
stages needed for heating is determined, this information is
passed to the IGC by turning on either HTR.1 or HTR.1 and
HTR.2. See Thermostat Control section for description of IGC
operation.
NOTE: The jumper wire in the installer’s packer must be con-
nected between R and W1 when using a T55, T56, or T58
device. See Fig. 1 and 2.

During Space Sensor control, two methods are used to add

stages of heat and two methods are used to subtract stages of
heat. The first method of adding and subtracting stages causes
the unit to operate around its configured steady state number of
stages. For example, if the correct number of stages is between
0 and 1, this method will cause the first stage to cycle. If the

correct number of stages is between 1 and 2, this method will
cause the second stage to cycle.

The second method of adding and subtracting stages causes

the unit to find the steady state number of stages. The first
method will not add or remove a stage of heating unless the
current Heat Demand (set point – SPT), corrected by the rate of
change in the Heat Demand, is greater than Heat Demand
Positive Level (HT.PD) or less than Heat Demand Negative
Level (HT.ND). The correction term is the Heat Thermal Lag
(H.LAG) multiplied by the change in the Heat Demand. There-
fore, if the corrected current demand is in between –1.0 and
1.0, the number of stages will not change no matter how long
there has been a positive error. Because the corrected heat
demand incorporates the rate of change in heat demand, it will
have a tendency to add or remove stages earlier when the
temperature in the space is moving very rapidly, thereby
reducing overshoot.

Because the first method of adding or removing a stage of

heat is used to operate around the steady number of stages, this
method can not be used to add an additional stage until a stage
has been subtracted. Likewise, if this method has subtracted a
stage, it can not be used again to subtract another stage until a
stage has been added.

The second method will add additional stages of heat when-

ever Heat Demand is greater than HT.PD + 0.5 and the heat de-
mand is increasing at rate greater than 0.3 F per min. Addition-
al stages of heat will be removed whenever the Heat Demand is
less than HT.ND – 0.5 and the heat demand is decreasing at
rate less than 0.3 F per min.

Table 26 — IGC LED Indications

LEGEND

NOTES:
1. There is a 3-second pause between error code displays.
2. If more than one error code exists, all applicable error codes will

be displayed in numerical sequence.

3. Error codes on the IGC will be lost if power to the unit is

interrupted.

Heating (50HG Units)

NOTE: THE 50HG units have 2 stages of heat.

For 50HG units, the heat type will automatically be set to 2

for electric heat units if the electric heat was installed in the fac-
tory (HT.TY). If electric heat is being installed in the field, the
user must change HT.TY from 0 to 2. If a 15 kW heater is in-
stalled, N.HTR must be changed from 2 to 1.

Heat will not operate if the outdoor temperature is greater

than the heat lockout temperature (HT.LO).
THERMOSTAT CONTROL — The first stage of electric
heat (HTR.1) will follow the W1 input and the second stage
(HTR.2) of heat will follow the W2 input. During auto fan, the
indoor fan will follow the HTR.1 output. During continuous
fan, the indoor fan will follow the G input.

ERROR CODE

LED INDICATION

Normal Operation

Hardware Failure

Off

Fan On/Off Delay Modified

1 Flash

Limit Switch Fault

2 Flashes

Flame Sense Fault

3 Flashes

Five Consecutive Limit Switch Faults