JOHNSON CONTROLS
16
FORM 145.26-IOM1 (908)
21. MAINTAININg UNIT IN gOOD WORKINg
ORDER
WARNINg: Follow these procedures
before inspecting furnace.
• Turn room thermostat to its lowest or off
setting.
• Wait at least five minutes for furnace to cool if
it was recently operating.
• Turn off furnace electrical power; failure to do
so could result in injury or death.
Use only recommended replacements
parts. Failure to do so could cause im-
proper furnace operation, resulting in
damage, injury or death.
Perform periodic preventive maintenance once before
heating season begins and once before cooling sea-
son. Inspect, clean and repair as needed the following
items:
1. all electrical wiring and connections, including
electrical ground.
2. all supply air and return air ducts for obstructions,
air leaks and loose insulation.
3. Blower housings, motors and wheels, and air filters.
Blower motors do not require oiling.
4. Inspect evaporator and condenser coils for accu-
mulations of dirt and debris, and clean as required.
If the coils appear dirty, clean them using mild
detergent or a commercial coil cleaning agent.
Dirty or clogged evaporator coils cause low suction
pressures and lost cooling capacity.
With a clean condenser coil, the air temperature leaving
the condenser fan discharge should be approximately
33ºF above the outdoor air temperature. The saturated
condensing temperature should be approximately 38ºF
above the outdoor air temperature.
Outdoor Temp ºF
Condensing Pressure (psig)
70
220
75
235
80
255
85
270
90
290
95
310
If the condensing pressure is higher than shown in the
table above, dirt in the condenser must be suspected.
To clean the condenser coil, remove the wall grille from
the outside and remove the accumulated dirt from the
air intake face of the coil using a brush and/or vacuum
cleaner. after cleaning, always remove all dislodged
dirt from inside the wall sleeve so that it will not be
sucked back into the condenser coil when the unit is
restarted.
