Lennox LCH092H Unit Information page 48

D-Electric Heat Components
See ELECTRICAL / ELECTRIC HEAT DATA and ELEC­
TRIC HEAT CAPACITIES (table of contents) for electric
heat match-ups and electrical ratings.
Electric heat is shown in figure 20. All electric heat sections
consist of electric heating elements exposed directly to the
air stream.
1-Heating Elements HE1, HE2
Heating elements are composed of helix wound bare
nichrome wire exposed directly to the air stream. Three
elements are connected in a three‐phase arrange­
ment. The elements in 208/230V units are connected in
a "Delta" arrangement. Elements in 460 and 575V units
are connected in "Wye" arrangement. Each stage is
energized independently by the corresponding contac­
tors located on the electric heat vestibule panel. Once
energized, heat transfer is instantaneous. High tem­
perature protection is provided by primary and redun­
dant high temperature limits and overcurrent protec­
tion is provided by fuses.
2-Contactors K15, K16
Contactors K15 and K16 are three‐pole double‐break
contactors located on the electric heat vestibule. All
contactors are equipped with a 24VAC coil and are en­
ergized by the A55 Unit Controller. Contactors ener­
gize the first and only stage of heating elements. On M-
volt units, contactors
manufacturer (Siemens). See figure 6.
3-Primary Limit Switch S15
S15 is a SPST N.C. auto‐reset switch located on the
back panel of the electric heat section below the heat­
ing elements. The switch is wired in series with the first
stage contactor coil. When S15 opens, indicating a
problem in the system, contactor K15 is de‐energized.
When K15 is de‐energized, first stage and all subse­
quent stages of heat are de‐energized. The switch is
factory-set to open at 200_F + 5_F (93.3_C + 2.8_C) on
a temperature rise and automatically reset at 160_F +
6_F (71.1_C + 3.3_C) on a temperature fall. The switch
is not adjustable.
4-High Temperature Thermostat S19
S19 is a SPST N.C. auto‐reset thermostat located on
are CE approved by
Page 48
the back panel of the electric heat section below the
heating elements. The thermostat is wired in series
with the first stage contactor coil. When either S15 or
S19 opens, indicating a problem in the system, contac­
tor K15 is de‐energized. When K15 is de‐energized,
first stage and all subsequent stages of heat are de‐en­
ergized. The thermostat is factory-set to open at 170_F
+ 5_F (76.7_C + 2.8_C) on a temperature rise and auto­
matically reset at 130_F + 6_F (54.4_C + 3.3_C) on a
temperature fall. The thermostat is not adjustable.
5-High Temperature Limits S20, S158
Limits are SPST N.C. manual-reset thermostats. Like
the primary temperature limit, S20 is wired in series
with the first-stage contactor coil (K15). When S20
opens, heating elements (HE1, HE2) are de-ener­
gized. S158 is wired in series with the second-stage
contactor coil (K16). When S158 opens, heating ele­
ments (HE1, HE2) are de-energized. When the contac­
tors are de-energized, first-stage and all subsequent
stages of heat are de-energized. The thermostat is fac­
tory-set to open at 220_F + 6_F (104_C + 3.3_C) on a
temperature rise and can be manually reset when tem­
perature falls below 160_F (71.0_C).
6-Terminal Strip TB2
Terminal strip TB2 is used for single point power instal­
lations only. TB2 distributes L1, L2 and L3 power to
TB3. Units with multi-point power connection do not
use TB2.
7-Terminal Strip TB3
Electric heat line voltage connections are made to ter­
minal strip TB3, located in the upper left corner of the
electric heat vestibule. TB3 distributes power to the
electric heat components.
8-Fuse F3 and F42
Fuses are housed in a fuse block which holds three fus­
es. Each fuse is connected in series with each leg of
electric heat. Figure 20 and table 3 show the fuses
used with each electric heat section. For simplicity, the
service manual labels the fuses F3 - 1, 2 and F42 - 1, 2.
9-Unit Fuse Block F4
Three line voltage fuses provide short circuit and
ground fault protection to all cooling components in
units equipped with electric heat. The fuses are rated
in accordance with the amperage of the cooling com­
ponents. On M-volt CE units, fuses are equipped with
fuse covers..