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Table 17 — Wet Coil Pressure Drop
UNIT SIZE
AIRFLOW
(cfm)
PRESSURE DROP
(in. wg)
018*
600 0.069
700 0.082
800 0.102
900 0.116
024
600 0.039
700 0.058
800 0.075
900 0.088
030
900 0.088
1000 0.095
1200 0.123
036
1000 0.068
1200 0.088
1400 0.108
1600 0.123
042
1000 0.048
1200 0.069
1400 0.088
1600 0.102
048
1400 0.068
1600 0.075
1800 0.088
060
1700 0.082
1900 0.095
2100 0.108
2300 0.123
*Unit 588A only.
D. Cooling Sequence of Operation
With the room thermostat SYSTEM switch in the COOL po-
sition and the FAN switch in theAUTO. position, the cooling
sequence of operation is as follows:
When the room temperature rises to a point that is slightly
above the cooling control setting of the thermostat, the ther-
mostat completes the circuit between thermostat terminal R
to terminals Y and G. These completed circuits through the
thermostat connect contactor coil (C) (through unit wire Y)
and blower relay coil (BR) (through unit wire G) across the
24-v secondary of transformer (TRAN).
NOTE: The blower relay coil (BR) is used on standard non-
ICM units, ICM units use evaporator (indoor) fan on (IFO)
connection.
The normally-open contacts of energized contactor (C) close
and complete the circuit through compressor motor (COMP)
to condenser (outdoor) fan motor (OFM). Both motors start
instantly.
On standard non-ICM units, the set of normally-open con-
tacts of energized relay BR close and complete the circuit
through evaporator blower (indoor) fan motor (IFM). On ICM
units, the IFO completes the circuit through evaporator blower
IFM. The blower motor starts instantly.
NOTE: Once the compressor has startedand then has stopped,
it should not be started again until 5 minutes have elapsed.
The cooling cycle remains ‘‘on’’ until the room temperature
drops to point that is slightly below the cooling control set-
ting of the room thermostat. At this point, the thermostat
‘‘breaks’’ the circuit between thermostat terminal R to termi-
nals Y and G. These open circuits deenergize contactor coil C
and relay coil BR. The condenser and compressor motors stop.
After a 30-second delay, the blower motor stops. The unit is
in a ‘‘standby’’ condition, waiting for the next ‘‘call for cool-
ing’’ from the room thermostat.
MAINTENANCE
To ensure continuing high performance, and to minimize the
possibility of premature equipment failure, periodic mainte-
nance must be performed on this equipment. This combina-
tion heating/cooling unit should be inspected at least once each
year by a qualified service person. To troubleshoot heating or
cooling of units, refer to tables at the back of the book.
NOTE TO EQUIPMENT OWNER: Consult your local dealer
about the availability of a maintenance contract.
WARNING:
The ability to properly perform mainte-
nance on this equipment requires certain expertise, me-
chanical skills, tools, and equipment. If you do not pos-
sess these, do not attempt to perform any maintenance
on this equipment other than those procedures recom-
mended in the User’s Manual. FAILURE TO HEED THIS
WARNING COULD RESULT IN SERIOUS PERSONAL
INJURY AND POSSIBLE DAMAGE TO THIS
EQUIPMENT.
WARNING:
Failure to follow these warnings could re-
sult in serious personal injury:
1. Turn off gas supply, then turn off electrical power to
the unit before performing any maintenance or serv-
ice on the unit.
2. Use extreme caution when removing panels and parts.
As with any mechanical equipment, personal injury
can result from sharp edges, etc.
3. Never place anything combustible either on, or in con-
tact with, the unit.
4. Should overheating occur, or the gas supply fail to
shut off, shut off the external main manual gas valve
to the unit, then shut off the electrical supply.
CAUTION:
Errors made when reconnectingwires may
cause improper and dangerous operation. Label all wires
prior to disconnection when servicing.
The minimum maintenance requirements for this equipment
are as follows:
1. Inspect air filter(s) each month. Clean or replace when
necessary.
2. Inspect indoorcoil, drain pan,and condensate draineach
cooling season for cleanliness. Clean when necessary.
3. Inspect blower motor and wheel for cleanliness and check
lubrication each heating and cooling season. Clean and
lubricate (if required) when necessary. For first heating
season, inspect blower wheel bimonthly to determine
proper cleaning frequency.
4. Check electrical connections for tightness and controls
for proper operation each heating and cooling season.
Service when necessary.
5. Check and inspect heating section before each heating
season. Clean and adjust when necessary.
6. Check flue hood screen and remove any obstructions if
necessary.
7. Check vent screen and clean if necessary.
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