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Table 3 – Status Code Descriptions for ISC Board LEDs
ERROR# ERROR NAME
LED INDICATION
LED01 LED02 LED03 LED04 LED05
1 Check Smoke Detector/PMR/AUX RED
Blinking
Green
LED
(Note 1)
2 Check HPS/LPS/COFS RED RED
3 C all f or Y3 with no call for Y1. Check Y1 wiring. RED
4 Call for Y3 with no call for Y1/Y2. Check Y1 wiring. RED RED
5 C all f or Y2 with no call for Y1. Check Y1 wiring. RED RED
6 Call for W2 with no call for W1. Check W1 wiring. RED RED
7 Call for heat (W1/W2) and cooling (Y1/Y2/Y3). Check thermostat wiring. RED RED RED RED
8 Call for heat (W1/W2) with no G. Check G wiring. RED RED RED
9 Call for cooling (Y1/Y2/Y3) with no G. Check G wiring RED RED RED
10
Call for heat (W1/W2) and cooling (Y1/Y2/Y3) with no G.
Check thermostat and G wiring.
RED RED RED
11 Check ISC Board and the thermostat wiring RED RED RED
12 Check ISC Board and the thermostat wiring RED
13 Check ISC Board and the thermostat wiring RED RED
14 Check ISC Board and the thermostat wiring RED
15 Check ISC Board and the thermostat wiring RED RED
NOTES: 1. Green LED Blinking at 1HZ indicates n ormal operation.
2. Solid red LED indicates an error exists, see above LED configuration.
Cooling —
In the Cooling Mode, the sma ll and large compressors will
be sequenced to maintain the thermostat temperature
setpoint. The chart below shows the cooling operation
based on the following conditions.
INPUT OUTPUT
Thermostat
Comp re sso r
C1
Comp re sso r
C2
Indoor
Fan
Speed
Outdoor
Fan
Speed
First Stage Cooling
(Y1)
On Off Low
Low
(700 rpm)
Second Stage Cooling
(Y2)
Off On Medium
Medium
(800 rpm)
Third Stage Cooling
(Y3)
On On High
High
(1000 rpm)
The outdoor fan a nd VFD controlled indoor--fan will
operat e at low, medium and high speed. The RPM is
factory set by the CFM and static pressure requireme nts
for the unit installed.
Humidi--MiZer
R
System (Optional) —
In the Dehumidification Mode, both compressors will run
and Indoor airflow will be rise to High Speed.
At subcooler re heating mode (reheat--1), during part load
conditions when the room temperature and humidity are
above the set point, the unit initiates the sub--cooling
mode of operation; a call for cooling and
dehumidification. RDV (Reheat Discharge Valve) and
TWV (Three Way Valve) close; Indoor and Outdoor
airflow will rise until reaching 100% of Speed.
At hot--gas--bypass reheating mode (reheat--2), when there
is a call for dehumidificati on without a call for cooling, a
portion of the hot gas from the compressor bypasses the
condenser c oil when RDV opens and hot gas is fed into
the liquid line, TWV closes in this mode and the system
provides mai nly latent cooling. Indoor airflow will rise
until reaching 100% of Speed, Outdoor airflow will run at
High speed as long as outdoor temperature is above 80_F
(26.7_C); when operating in this mode below 80_F
(26.7_C) OAT, the system outdoor fan will operate as
shown in the table below based on Size:
LC Size RPM Number of Fans On Number of Fans Off
07 250 2 0
Economizer (Optional) —
When the economizer is in Free Cooling Mode and a
dema nd for cooling exi sts (Y1 on the thermostat), the
econom izer will modulate the outdoor--air damper to
provide a 50_F(10_C) to 55_F(13_C) mixed--air
temperature into the zone and run the indoor--fan at high
speed. As mixed--air temperature fl uctuates above 55_F
(13_C) or below 50_F(10_C) da mpers will be modulated
(open or close) to bring the mixed--air temperature back
within control. Upon more call for cooling (Y2 on the
thermostat), the outdoor --air damper will maintain its
current position, compre ssor C1 will run and the
outdoor--fan will run at low speed. If there is further
dema nd for cooling, the outdoor--air damper will maintain
its current position, compressor C2 will run and the
outdoor--fan will run at medium speed. The VFD
controlled indoor--fan will operate at high speed
regardless of the cooling demand.
If the increase in cooling capacity causes the mixed--air
temperature to drop below 45_F(7_C), the outdoor--air
damper will return to the minimum position. If the
mixed--air temperature continues to fall, the outdoor--air
dampe r will close. Control returns to normal once t he
mixed--air temperature rises above 48_F(9_C). The
power exhaust fans will be energized and de--energized, if
installed, as the out door--air damper opens and closes.
In field--installed accesso ry CO
2
sensors are connected to the
economizer, a demand contro lled ventilation strategy will
begin to operate. As the CO
2
level in the zone increases
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