SERVICING
29
WARNING
DISCONNECT POWER SUPPLY BEFORE SERVICING.
Turn power off.
Testing relay holding coil
1. Remove the leads from the holding coil.
2. Using an ohmmeter, test across the coil terminals 1 and 3.
If the coil does not test continuous, replace the relay.
Testing relay contacts
WARNING
DISCONNECT POWER SUPPLY BEFORE SERVICING.
Turn power off.
1. Using a VOM, test resistance across relay terminals 2 and
4. Should read open.
2. Turn power on.
WARNING
LINE VOLTAGE NOW PRESENT.
3. Apply 24 volts to coil terminals 1 and 3.
4. Using a VOM, check for 24 volts from terminals 3 and 2 of
relay. Should read 24 volts. If no voltage, check low voltage
wiring from transformer to relay. If voltage present, proceed
to step 5.
5. Using a VOM, check for 24 volts from terminals 3 and 4 of
relay. Should read 24 volts.
If not as above, replace relay.
S-11 CHECKING LOSS OF CHARGE
PROTECTOR
(Heat Pump Models)
The loss of charge protector senses the pressure in the liquid
line and will open its contacts on a drop in pressure. The low
pressure control will automatically reset itself with a rise in
pressure.
The low pressure control is designed to cut-out (open) at ap-
proximately 7 PSIG. It will automatically cut-in (close) at ap-
proximately 25 PSIG.
Test for continuity using a VOM and if not as above, replace
the control.
S-15 CHECKING CAPACITOR
CAPACITOR, RUN
A run capacitor is wired across the auxiliary and main wind-
ings of a single phase permanent split capacitor motor. The
capacitors primary function is to reduce the line current while
greatly improving the torque characteristics of a motor. This is
accomplished by using the 90° phase relationship between
the capacitor current and voltage in conjunction with the motor
windings so that the motor will give two phase operation when
connected to a single phase circuit. The capacitor also re-
duces the line current to the motor by improving the power
factor.
CAPACITOR, START
SCROLL COMPRESSOR MODELS
Hard start components are not required on Scroll compressor
equipped units due to a non-replaceable check valve located in
the discharge line of the compressor. However hard start kits
are available and may improve low voltage starting characteris-
tics.
This check valve closes off high side pressure to the compres-
sor after shut down allowing equalization through the scroll
flanks. Equalization requires only about one or two seconds
during which time the compressor may turn backwards.
Your unit comes with a 180-second anti-short cycle to prevent
the compressor from starting and running backwards.
MODELS EQUIPPED WITH A HARD START DEVICE
A start capacitor is wired in parallel with the run capacitor to
increase the starting torque. The start capacitor is of the elec-
trolytic type, rather than metallized polypropylene as used in
the run capacitor.
A switching device must be wired in series with the capacitor
to remove it from the electrical circuit after the compressor
starts to run. Not removing the start capacitor will overheat the
capacitor and burn out the compressor windings.
These capacitors have a 15,000 ohm, 2 watt resistor wired
across its terminals. The object of the resistor is to discharge
the capacitor under certain operating conditions, rather than
having it discharge across the closing of the contacts within
the switching device such as the Start Relay, and to reduce
the chance of shock to the servicer. See the Servicing Section
for specific information concerning capacitors.
RELAY, START
A potential or voltage type relay is used to take the start ca-
pacitor out of the circuit once the motor comes up to speed.
This type of relay is position sensitive. The normally closed
contacts are wired in series with the start capacitor and the
relay holding coil is wired parallel with the start winding. As
the motor starts and comes up to speed, the increase in volt-
age across the start winding will energize the start relay hold-
ing coil and open the contacts to the start capacitor.
Two quick ways to test a capacitor are a resistance and a
capacitance check.
To Next Page
Loading...
