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The Control Will Not Energize Second Stage
Heating
1. The thermostat is not displaying the second stage indi-
cator. A decimal point on the thermostat display screen is
the indication that the thermostat is asking for second stage.
a. Check to see if the space demand is equal to or greater
than 2° F. The control must see a 2° F demand before
it will call for second stage.
b. Check the Temperature Trend Staging option. If this
option is on and space conditions are improving, the
control will hold off second stage.
c. Check the space demand. If the control entered a mode
and had a demand equal to or greater than 8° F, it will
hold off second stage for 21 minutes.
2. The thermostat is displaying the decimal point.
a. Check to see if the H2 LED is lit on the Apollo con-
trol. If it is not lit, replace the Apollo control.
b. The LED is lit but second stage is not energized. Check
the voltage across the H2 relay contact. If it reads
24 VAC, replace the relay board. If it reads
0 to 2 VAC, check the H2 contactor and the unit trans-
former.
The Control Will Not Energize Cooling
1. The thermostat is not displaying the cool annunciator.
a. Check the cooling lockout temperature set point and
options to make sure the outside-air temperature is not
locking out cooling mode.
b. Ensure that a sensor in the system is not reading be-
low the cooling low limit temperature. If a supply
air sensor or a DX coil sensor is not connected to the
relay pack, turn off High Low Limits at the
thermostat.
c. Check the Cool switch and make sure it is in the AUTO
position.
2. The thermostat is displaying the cool annunciator.
a. Check to see if the C1 LED is lit on the Apollo con-
trol. If it is not, replace the Apollo control. If the
C1 LED is lit on the Apollo control, check the voltage
across the C1 relay contact. If it reads 24 VAC, re-
place the Apollo control. If it reads 0 to 2 VAC, check
the C1 contactor and the unit transformer.
The Control Will Not Energize Second Stage
Cooling
1. The thermostat is not displaying the second stage indi-
cator. A decimal point on the thermostat display screen is
the indication that the thermostat is asking for second stage.
a. Check to see if the space demand is equal to or greater
than 2° F. The control must see a 2° F demand before
it will call for second stage.
b. Check the Temperature Trend Staging option. If this
option is on and space conditions are improving, the
control will hold off second stage.
c. Check the space demand. If the control entered a mode
and had a demand equal to or greater than 8° F, it will
hold off second stage for 21 minutes.
2. The thermostat is displaying the decimal point.
a. Check to see if the C2 LED is lit on the Apollo con-
trol. If it is not lit, replace the Apollo control.
b. The LED is lit but second stage is not energized. Check
the voltage across the C2 relay contact. If it reads
24 VAC, replace the Apollo control. If it reads
0 to 2 VAC, check the C2 contactor and the unit
transformer.
The Control Will Not Energize The Fan
1. The fan annunciator is not lit on the thermostat.
a. The Fan switch is in the AUTO position and the con-
trol is not in a mode (HEAT or COOL).
b. The Fan switch is in the ON position but the thermo-
stat is in setback and has no mode.
c. The thermostat has just received power or has just re-
set and is going through its initialization process.
2. The fan annunciator is lit on the thermostat.
a. Check the fan LED on the Apollo control. If it is not
lit, replace the Apollo control.
b. If the Fan LED is lit, check the voltage across the fan
relay contact. If it reads 24 VAC, replace the relay board.
If it reads 0 to 2 VAC, check the fan contactor and the
unit transformer.
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