Page 24
System Operation
IMPORTANT
Some scroll compressors have an internal vacuum
protector that will unload scrolls when suction pressure
goes below 20 psig. A hissing sound will be heard when
the compressor is running unloaded. Protector will
reset when low pressure in system rises above 40 psig.
DO NOT REPLACE COMPRESSOR.
The outdoor unit and indoor blower will cycle on and off
as dictated by demands from the room thermostat. When
the thermostat's blower switch is in the
ON
position, the
indoor blower will operate continuously.
HIGH PRESSURE SWITCH (S4)
ML14XC1 units are equipped with a high-pressure switch
that is factory-wired and located in the liquid line.
The switch is a Single Pole, Single Throw (SPST), au-
to-reset switch which is normally closed and removes
power from the compressor when discharge pressure ris-
es above factory setting at 590 ± 10 psig; resets at 418 ±
5 psig.
CRANKCASE HEATER (HR1) AND THERMOSTAT
(S40)
Compressors in some models are equipped with a 40 watt
or 70 watt, belly band type crankcase heater. HR1 pre-
vents liquid from accumulating in the compressor. HR1
is controlled by a single pole, single through thermostat
switch (S40) located on the liquid line (see figure 1 for
location).
When liquid line temperature drops below 50° F the ther-
mostat closes energizing HR1. The thermostat will open,
de-energizing HR1 once liquid line temperature reaches
70° F.
THERMAL PROTECTION SWITCH (S173) - COMPRES-
SOR MOUNTED
Some units are equipped with a compressor mounted
normally closed temperature switch that prevents com-
pressor damage due to overheating caused by internal
friction. The switch is located on top of the compressor
casing. This switch senses the compressor casing tem-
perature and opens at 239-257°F (115°C-125°C) to shut
off compressor operation. The auto-reset switch closes
when the compressor casing temperature falls to 151-
187°F (66°C-86°C), and the compressor is re-energized.
This single-pole, single-throw (SPST) bi-metallic switch is
wired in series with the 24V Y input signal to control com-
pressor operation.
Maintenance
Your heating and air conditioning system should be in-
spected and maintained yearly (before the start of the
cooling and heating seasons) by a licensed professional
HVAC technician. You can expect the technician to check
the following items.
These checks may only be con-
ducted by a licensed professional HVAC technician.
Outdoor Unit
1. Inspect component wiring for loose, worn or damaged
connections. Also check for any rubbing or pinching of
wires. Confirm proper voltage plus amperage of out
-
door unit.
2. Check the cleanliness of outdoor fan and blade assem-
blies. Check condition of fan blades (cracks). Clean or
replace them, if necessary.
3. Inspect base pan drains for debris and clean as nec-
essary.
4. Inspect the condition of refrigerant piping and con-
firm that pipes are not rubbing copper-to-copper. Also,
check the condition of the insulation on the refrigerant
lines. Repair, correct, or replace as necessary.
5. Test capacitor. Replace as necessary.
6. Inspect contactor contacts for pitting or burn marks. Re-
place as necessary.
7. Check outdoor fan motor for worn bearings/bushings.
Replace as necessary.
8. Inspect and clean outdoor coils, if necessary and note
any damage to coils or signs of leakage.
NOTICE !
Failure to follow instructions will cause damage to
the unit.
This unit is equipped with an aluminum coil.
Aluminum coils may be damaged by exposure to
solutions with a pH below 5 or above 9. The alumi-
num coil should be cleaned using potable water
at a moderate pressure (less than 50psi). If the
coil cannot be cleaned using water alone, Lennox
recommends use of a coil cleaner with a pH in the
range of 5 to 9. The coil must be rinsed thoroughly
after cleaning.
In coastal areas, the coil should be cleaned with
potable water several times per year to avoid corro-
sive buildup (salt).
Indoor Unit (Air Handler or Furnace)
1. Inspect component wiring for loose, worn or damaged
connections. Confirm proper voltage plus amperage in
-
door unit.
2. Inspect and clean or replace air filters in indoor unit.
3. Check the cleanliness of indoor blower and clean blow-
er, if necessary.
4. Inspect the evaporator coil (Indoor) drain pans and con-
densate drains for rust, debris, obstructions, leaks or
cracks. Pour water in pans to confirm proper drainage
from the pan through to the outlet of the pipe. Clean or
replace as necessary.
5. Inspect and clean evaporator (indoor) coil, if necessary.
6. Inspect the condition of the refrigerant lines and con-
firm that pipes are not rubbing copper-to-copper.
Also, ensure that refrigerant pipes are not being affect
-
ed by indoor air contamination. Check condition of insu-
lation on the refrigerant lines. Repair, correct, or replace
as necessary.
