Commercial Air Conditioner
Model: heat pump, 10SEER UNITS
11
Distributor assy
Fig.4-4
REFRIGERANT CIRCUIT
There are two types of outdoor coil circuiting: single and multi-circuited.
The 10 series are all multi –circuits.
Fig.4-5
SERVICE VALVES
There are two types of service valve used on the air conditioning .They are the service port valve or
“Schrader valve” and the refrigerant line valve. The Schrader valve is like a tire valve in an automobile.
The stem or core is removable with a flexible seal at its base held closed with a spring. Schrader valves
allow a technician to connect gages to the system with a minimum loss of charge. Use a cap with an
inner seal to prevent leakage and keep dirt and moisture out..
The refrigerant control valve lets the system be isolated into two separate sections. In split system,
These valves hold the charge in the outdoor section from the time of manufacture until the unit is
connected to the indoor section by the installer.
5.ELECTRICAL CONTROL DEVICES
THERMOSTATS
Thermostats are the most obvious control in the air conditioning ,since these controls are accessible by
the consumer. Contact the local distributor for information on part numbers of various manual
changeover, auto changeover and set-back thermostats or see the thermostat and subbase selection
information found in the wiring diagram booklet.
In the cooling mode, the thermostat calls for cooling by energizing the compressor contactor and the
indoor blower control. The indoor blower can operate continuously by setting the thermostat subbase fan
switch to the “ON” position.
PROTECTION DEVICES
Protection for the unit begins with the installation of appropriate fuses or circuit breakers by the installing
contractor. Breaker or fuse size is governed by local codes and the National Electrical Code. Current
requirements for each unit are found in the unit specifications.
OVERLOADS AND LIMITS
Overloads protect against over-current or over-temperature conditions. Those located in the outdoor unit
include the automatic reset internal overload in the fan motor and the compressor automatic reset
internal overload. Such controls are not serviceable but their operation may influence service
troubleshooting .For example ,the compressor internal overload may stay open for several hours .A
technician may incorrectly diagnose an open compressor winding.
There are similar overloads in the indoor air handling portion with the electric resistance heaters. The
indoor blower motor has an internal overload. The electric elements use two types of protectors ,both
replaceable. Some electric heat section use fusible links. They are a one time over-temperature
protector and must be replaced upon opening. Limit controls are thermal discs that automatically
reset .Normally, limit open and stop a heat rise before the fusible links open.
NOTE: Never disconnect or wire around a safety device .First determine why it opened, then replace it
with a properly rated part.
HIGH PRESSURE CUT OUT SWITCH (optional)
The high pressure cut-out is a pressure activated switch. It opens an electrical circuit when the
refrigerant pressure exceeds a pre-determined limit of 440 to 460 p.s.i.g. This
switch can restore
