Service manual

SERVICING
28
S-2 CHECKING WIRING
WARNING
Disconnect Electrical Power Supply:
1. Check wiring visually for signs of overheating, damaged
insulation and loose connections.
2. Use an ohmmeter to check continuity of any suspected
open wires.
3. If any wires must be replaced, replace with comparable
gauge and insulation thickness.
S-3 CHECKING THERMOSTAT, WIRING, AND
ANTICIPATOR
S-3A Thermostat and Wiring
WARNING
LINE VOLTAGE NOW PRESENT
With power ON and thermostat calling for cooling.
1. Use a voltmeter to check for 24 volts at thermostat wires
C and Y in the condensing unit control panel.
2. No voltage indicates trouble in the thermostat, wiring or
external transformer source.
3. Check the continuity of the thermostat and wiring. Re-
pair or replace as necessary.
Indoor Blower Motor
With power ON:
WARNING
LINE VOLTAGE NOW PRESENT
1. Set fan selector switch at thermostat to "ON" position.
2. With voltmeter, check for 24 volts at wires C and G.
3. No voltage, indicates the trouble is in the thermostat or
wiring.
4. Check the continuity of the thermostat and wiring. Re-
pair or replace as necessary.
Resistance Heaters
1. Set room thermostat to a higher setting than room temp
so both stages call for heat.
2. With voltmeter, check for 24 volts at each heater relay.
3. No voltage, indicates the trouble is in the thermostat or
wiring.
4. Check the continuity of the thermostat and wiring. Re-
pair or replace as necessary.
NOTE: Consideration must be given as to how the heaters
are wired (O.D.T. and etc.). Also safety devices must be
checked for continuity.
S-3B Cooling Anticipator
The cooling anticipator is a small heater (resistor) in the
thermostat. During the "off" cycle it heats the bimetal ele-
ment helping the thermostat call for the next cooling cycle.
This prevents the room temperature from rising too high
before the system is restarted. A properly sized anticipator
should maintain room temperature within 1 1/2 to 2 degree
range.
The anticipator is supplied in the thermostat and is not to
be replaced. If the anticipator should fail for any reason,
the thermostat must be changed.
S-3C Heating Anticipator
The heating anticipator is a wire-wound adjustable heater,
which is energized during the "ON" cycle to help prevent
overheating of the conditioned space.
The anticipator is a part of the thermostat and if it should
fail for any reason, the thermostat must be replaced. See
the following for recommended heater anticipator setting.
The first stage heat anticipator setting for heat pump mod-
els is .40. The heat anticipator setting for the package gas
models is .80.
S-4 CHECKING TRANSFORMER AND CONTROL
CIRCUIT
A step-down transformer (208/240 volt primary to 24 volt
secondary) is provided with each package unit. This al-
lows ample capacity for use with resistance heaters.
WARNING
Disconnect Electrical Power Supply:
1. Remove control panel cover or etc. to gain access to
transformer.
With power ON:
WARNING
LINE VOLTAGE NOW PRESENT
2. Using a voltmeter, check voltage across secondary volt-
age side of transformer (R to C).
3. No voltage indicates faulty transformer, bad wiring, or
bad splices.
4. Check transformer primary voltage at incoming line volt-
age connections and/or splices.
5 If line voltage available at primary voltage side of trans-
former and wiring and splices good, transformer is in-
operative. Replace.
S-6 CHECKING TIME DELAY RELAY
Time delay relays are used in Amana Package Units to
improve efficiency by delaying the blower off time. This fea-
ture is incorporated into the electronic controls. See S-23
to check control board.