Friedrich YL24J35A, Service & Parts Manual

Page: 21 / 62

TTJ-0198 (10/97) (Page 21 of 64)
HEATING ELEMENT - See Figure 12
All heat pumps and electric heat models are equipped
with a heating element with the exception of the YS09J10.
The "YS", "ES" and "EK12" models are equipped with a
3.3 KW element. The "YM", "EM" and "EK18" models
are equipped with a 4.0 KW element. The "YL" and "EL"
models are equipped with a 5.2 KW element.
The heating element contains a fuse link and a heater
limit switch. The fuse link is in series with the power
supply and will open and interrupt the power when the
temperature reaches 161.6°F, or a short circuit occurs
in the heating element. Once the fuse link separates, a
new fuse link must be installed. NOTE: Always replace
with the exact replacement.
The heater element has a high limit control. This control
is a bimetal thermostat mounted in the top of the heat-
ing element.
Figure 12: HEATING ELEMENT
Should the fan motor fail or filter become clogged, the
high limit control will open and interrupt power to the
heater before reaching an unsafe temperature condi-
tion.
The control is designed to open at 110°F ±6°F. Test con-
tinuity below 110°F and for open above 110°F.
The heating element for the "Y" model is energized by
an outdoor thermostat. The outdoor thermostat is ad-
justed at a predetermined temperature to bring on the
heating element and turn off the compressor. The room
thermostat will then control the cycling of the element
when the selected indoor temperature is reached.
Testing of the elements can be made with an ohmmeter
across the terminals after the connecting wires have
been removed. A cold resistance reading of approxi-
mately 14.5 ohms for the 3.3 KW heater, 11.9 ohms for
the 4.0 KW heater and 9.15 ohms for the 5.2 KW heater
should be registered.
DEFROST THERMOSTAT
(Heat Pump Models Only)
This thermostat (Figure 13) is single pole - double throw
with contacts between terminals "2" and "3" closing on
temperature rise and contacts between terminals "2"
and "1" closing on temperature fall. When the contacts
between terminals "2" and "1" make, power is supplied
to the heater element.
This control is dual purpose control that acts as an out-
door thermostat and defrost control.
When the sensing bulb, attached to the condenser coil,
senses enough icing on the outdoor coil, it will interrupt
power to the compressor and supply power to the heat-
ing element until the coil temperature reaches above
43°, then the heater will shut off and the unit will resume
operating in the reverse cycle mode.
When the outdoor coil temperature drops below 20°,
the unit will operate in electric heat mode continuously
until the outdoor coil temperature rises above 43°.
The fan motor will not turn off when defrost occurs, and
the 4-way valve will not reverse.
Figure 13: DEFROST THERMOSTAT
(Heat Pump Models)