Lennox LDT Series Owner's manual
Page 1
LDT
Service Literature 6.5 / 7.5 / 8.5 /10 / 12.5
100086
LDT DUAL FUEL SERIES
WARNING
To prevent serious injury or death:
1- Lock-out/tag-out before performing maintenance.
2- If system power is required (e.g., smoke detector main
tenance), disable power to blower, remove fan belt
where applicable, and ensure all controllers and ther
mostats are set to the “OFF” position before
performing maintenance.
3- Always keep hands, hair, clothing, jewelry, tools, etc.,
away from moving parts.
The LDT commercial combination heat pump and gas heat
unit is available in 6.5 / 7.5 / 8.5 / 10 / 12.5 ton cooling ca
pacities. The LDT078, 092, 102, 122 and 150 refrigerant
systems utilize two compressors, two reversing valves, two
accumulators (122, 150 only), and other parts common to a
heat pump. Units are available in 130,000, 180,000 or
240,000Btuh (38.1, 52.7 or 70.3 kW) heating inputs. Gas
heat sections are designed with stainless steel tube heat
exchangers.
LDT078-150 units are equipped with variable-volume, di
rect drive blowers. These units will provide supply air at
lower speeds when cooling demand is low and increase to
higher speeds when cooling demand is high. Refer to Sup
ply Air Start-Up sections.
LDT units are designed to accept any of several different
energy management thermostat control systems with mini
mum field wiring.
Information contained in this manual is intended for use by
qualified service technicians only. All specifications are
subject to change. Procedures outlined in this manual are
presented as a recommendation only and do not super
sede or replace local or state codes.
If the unit must be lifted for service, rig unit by attaching four
cables to the holes located in the unit base rail (two holes at
each corner). Refer to the installation instructions for the
proper rigging technique.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person
al injury or loss of life. Installation and service must
be performed by a licensed professional HVAC in
staller or equivalent, service agency, or the gas sup
plier
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal in
jury. Take care while handling this equipment and
wear gloves and protective clothing.
WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon
nect switch(es). Unit may have multiple
power supplies.
Table of Contents
Options / Accessories 2..........................
Specifications 5.................................
High Altitude 7..................................
Blower Data 8..................................
Electrical Data 11................................
I Unit Components 14............................
II Placement and Installation 28....................
III Start Up 28...................................
IV System Service Checks 31.....................
V Maintenance 34................................
VI Accessories 35................................
VII Wiring Diagrams 40...........................
Page 2
OPTIONS / ACCESSORIES
Item Description Catalog
Number
Unit Model No
078 092 102 122 150
COOLING SYSTEM
Condensate Drain Trap PVC 22H54 XXXXX
Copper 76W27 XXXXX
21Z07 OX OX OX OX OX
GAS HEATING SYSTEM
Bottom Gas Piping Kit 54W95 XXXXX
Combustion Air Intake Extensions 19W51 XXXXX
Gas Heat Input OOOOO
OOOOO
OOOO
22A51 XXXXX
460V 22A55 XXXXX
575V 13X65 XXXXX
LPG/Propane Conversion Kits 14N22 XXXXX
Medium Heat 14N23 XXXXX
14N25 XXXXX
42W16 XXXXX
BLOWER - SUPPLY AIR
® OOOOO
CABINET
24C86 OX OX OX
24C87 OX OX
OOOOO
51W25 XXXXX
54W96 OX OX OX OX OX
CONTROLS
21Z10 OX OX OX OX OX
CPC Einstein Integration OOOOO
® 54W27 OX OX OX OX OX
Novar® OOOOO
53W67 OX OX OX OX OX
21Z08 OX OX OX OX OX
11K76 OX OX OX OX OX
11K80 OX OX OX OX OX
Page 3
OPTIONS / ACCESSORIES
Item Description Catalog
Number
Unit Model No
078 092 102 122 150
INDOOR AIR QUALITY
Air Filters
®
MERV 8 50W61 OX OX OX OX OX
MERV 13 52W41 OX OX OX OX OX
MERV 16 21U41 XXXXX
Y3063 XXXXX
Indoor Air Quality (CO) Sensors
77N39 XXXXX
23V86 XXXXX
87N52 XXXXX
87N54 XXXXX
CO 85L43 XXXXX
77N3990N43 XXXXX
Needlepoint Bipolar Ionization (NPBI)
22U15 XXXXX
UVC Germicidal Lamps
1® 21A93 XXXXX
10H20 XXXXX
10H21 XXXXX
ELECTRICAL
OOOOO
OOOOO
OOOOO
80 amp 54W56 OX OX OX OX OX
150 amp 54W57 OX OX OX OX OX
OOOOO
74M70 OX OX OX OX OX
OOOOO
67E01 XXXXX
³ OOOOO
10C89 XXXXX
1
2
3
Page 4
OPTIONS / ACCESSORIES
Item Description Catalog
Number
Unit Model No
078 092 102 122 150
ECONOMIZER
20U80 OX OX OX OX OX
Horizontal Barometric Relief Dampers
53K04 XXXXX
Economizer Controls
Order 2 21Z09 OX OX OX OX OX
OOOOO
21Z09 OX OX OX OX OX
13J77 XXXXX
13J76 XXXXX
OOOOO
OUTDOOR AIR
Outdoor Air Dampers With Outdoor Air Hood
Motorized 14G28 OX OX OX OX OX
14G29 XXXXX
POWER EXHAUST
53W44 OX OX OX OX OX
53W45 OX OX OX OX OX
53W46 OX OX OX OX OX
ROOF CURBS
11F54 XXXXX
11F55 XXXXX
11F56 XXXXX
11F57 XXXXX
Adjustable Pitch Curb
54W50 XXXXX
CEILING DIFFUSERS
13K61 X X
13K62 XXX
13K56 X X
13K57 XXX
C1DIFF30B-1 12X65 X X
C1DIFF31B-1 12X66 XXX
Page 5
SPECIFICATIONS 6.5 TON | 7.5 TON | 8.5 TON
General Data Nominal Tonnage 6.5 Ton 7.5 Ton 8.5 Ton
High High High
Model Number LDT078H4E LDT092H4E LDT102H4E
Blower Type DirectPlus™
ECM Direct Drive
with MSAV®
DirectPlus™
ECM Direct Drive
with MSAV®
DirectPlus™
ECM Direct Drive
with MSAV®
Cooling
Performance
79,000 92,000 100,000
1 78,000 90,000 98,000
2400 2800 2800
1
1
R410A R410A R410A
Heating
Performance
1 73,000 84,000 94,000
2600 3000 3400
1
1 40,000 46,000 53,000
1
Gas Heating Options Available
Compressor Type (number)
Outdoor Coil
3/8 3/8 3/8
333
20 20 20
Outdoor
Coil Fans
Motor rpm 530-950 530-950 650-1010
140-620 140-620 220-700
333
3600-7000 3600-7000 4600-7500
Indoor
Coil
3/8 3/8 3/8
444
14 14 14
Indoor
Blower
Filters
Electrical characteristics
1
Cooling Ratings
High Temperature Heating Ratings
Low Temperature Heating Ratings
Page 6
SPECIFICATIONS 10 TON | 12.5 TON
General Data Nominal Tonnage 10 Ton 12.5 Ton
High High
Model Number LDT122H4E LDT150H4E
Blower Type DirectPlus™
ECM Direct Drive
with MSAV®
DirectPlus™
ECM Direct Drive
with MSAV®
Cooling
Performance
121,000 141,000
1 118,000 136,000
3400 4200
1
1
R410A R410A
Heating
Performance
1 114,000 128,000
3600 4200
11
1
1 65,000 73,000
1
Gas Heating Options Available
Compressor Type (number)
Outdoor Coil
3/8 3/8
3 3
20 20
Outdoor
Coil Fans
Motor rpm 530-950 530-950
180-800 180-800
3 3
5500-10,600 5500-10,600
Indoor
Coil
3/8 3/8
4 4
14 14
Indoor
Blower
Filters
Electrical characteristics
1
Cooling Ratings
High Temperature Heating Ratings
Low Temperature Heating Ratings
Page 7
SPECIFICATIONS GAS HEAT
Heat Input Type Standard Medium High
Number of Gas Heat Stages 2 2 2
Gas Heating
84,500 117,000 156,000
130,000 180,000 240,000
104,000 144,000 194,000
Temperature Rise Range - °F 15 - 45 30 - 60 40 - 70
2150 2250 2600
80% 80% 81%
HIGH ALTITUDE DERATE
NOTE - Units may be installed at altitudes up to 2000 feet above sea level without any modications.
At altitudes above 2000 feet units must be derated to match gas manifold pressures shown in table below.
At altitudes above 4500 feet unit must be derated 2% (130K through 180K) and 4% (240K) for each 1000 feet
above sea level.
NOTE - This is the only permissible derate for these units.
Refer to the Installation Instructions for more detailed information.
Heat Input Type Altitude Feet
Gas Manifold Pressure
in. w.g. Input Rate (Btuh)
Natural Gas LPG/ Propane
2001 - 4500 84,500 / 125,000
2001 - 4500 117,000 / 173,000
2001 - 4500 156,000 / 221,000
Page 8
BLOWER DATA
BLOWER TABLE INCLUDES RESISTANCE FOR BASE UNIT ONLY (NO HEAT SECTION) WITH DRY INDOOR COIL AND AIR
FILTERS IN PLACE.
Maximum Static Pressure With Gas Heat - 2.0 in. w.g.
Total
Air Volume
cfm
Total Static Pressure - in. w.g.
0.2 0.4 0.6 0.8 1.0 1.2 1.4
RPM Watts RPM Watts RPM Watts RPM Watts RPM Watts RPM Watts RPM Watts
1750 759 223 864 298 961 359 1049 420 1128 508 1199 607 1260 704
2000 846 271 943 345 1035 410 1117 488 1189 598 1255 704 1313 804
2250 945 303 1030 391 1111 476 1184 577 1247 697 1310 806 1367 905
2500 1035 366 1109 476 1180 583 1245 688 1306 797 1368 903 1426 1008
2750 1113 476 1182 601 1248 715 1310 809 1371 902 1432 1011 1491 1129
3000 1195 596 1261 718 1324 827 1385 922 1444 1024 1503 1146 1559 1279
3250 1282 711 1346 827 1406 935 1464 1044 1521 1167 1576 1306 1629 1460
3500 1372 821 1432 940 1489 1060 1544 1192 1598 1337 1650 1494 1700 1663
3750 1461 949 1517 1081 1571 1221 1624 1373 1675 1532 1725 1700 1773 1875
4000 1549 1109 1602 1256 1653 1413 1703 1576 1753 1743 1801 1916 1847 2091
4250 1637 1298 1687 1458 1735 1625 1784 1795 1831 1966 1877 2139 1923 2310
4500 1724 1510 1772 1678 1818 1851 1864 2023 1910 2195 1955 2365 2000 2530
4750 1811 1738 1856 1910 1901 2083 1946 2254 1990 2423 2034 2587 2079 2746
5000 1897 1973 1941 2144 1985 2314 2028 2480 2071 2644 2114 2805 2158 2959
5250 1983 2205 2026 2373 2069 2538 2111 2699 2153 2860 2195 3017 - - - - - -
5500 2070 2428 2112 2595 2153 2756 2194 2912 - - - - - - - - - - - - - - - - - -
5750 2156 2643 2197 2809 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Total
Air Volume
cfm
Total Static Pressure - in. w.g.
1.6 1.8 2.0 2.2 2.4 2.6
RPM Watts RPM Watts RPM Watts RPM Watts RPM Watts RPM Watts
1750 1316 793 1373 875 1432 963 1491 1064 1548 1175 1604 1300
2000 1368 894 1425 982 1483 1081 1540 1196 1596 1322 1650 1458
2250 1423 1001 1480 1101 1537 1216 1593 1344 1647 1483 1700 1629
2500 1483 1117 1539 1236 1594 1368 1648 1509 1700 1657 1752 1810
2750 1547 1256 1601 1394 1654 1539 1705 1690 1756 1846 1806 2004
3000 1612 1425 1664 1577 1715 1734 1765 1893 1815 2053 1864 2213
3250 1680 1623 1729 1787 1778 1949 1828 2110 1876 2269 1925 2426
3500 1748 1835 1796 2003 1844 2165 1893 2324 1942 2479 1991 2633
3750 1819 2048 1866 2214 1914 2374 1963 2530 2012 2684 2061 2837
4000 1893 2260 1940 2423 1988 2581 2036 2737 2084 2891 2134 3044
4250 1969 2475 2016 2634 2063 2790 2111 2945 2159 3098 - - - - - -
4500 2046 2689 2093 2844 2140 2998 2187 3153 - - - - - - - - - - - -
4750 2124 2900 2170 3053 - - - - - - - - - - - - - - - - - - - - - - - -
5000 2203 3111 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
5250 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
5500 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Page 9
BLOWER DATA
POWER EXHAUST FAN PERFORMANCE
Return Air System Static Pressure Air Volume Exhausted
in. w.g. cfm
0 3175
2955
2685
2410
2165
1920
1420
1200
FACTORY INSTALLED OPTIONS/FIELD INSTALLED ACCESSORY AIR RESISTANCE - in. w.g.
Air
Volume
cfm
Wet Indoor Coil Gas Heat Exchanger
Economizer
Filters Return
Air
Adaptor
Plate
092, 102 122 Standard
Heat
Medium
Heat
High
Heat MERV 8 MERV 13 MERV 16
1750
2000
2250
2500
2750
3000
3250
3500
3750
4000
4250
4500
4750
5000
5250
5500
5750
6000
Page 10
BLOWER DATA
CEILING DIFFUSERS AIR RESISTANCE - in. w.g.
FD11 Flush
Unit Size Air Volume
cfm 2 Ends Open 1 Side, 2 Ends
Open
All Ends & Sides
Open
2400
2600
2800
3000
3200
3400
3600
3800
3600
3800
4000
4200
4400
4600
4800
5000
5200
4200
4400
4600
4800
5000
5200
5400
5600
5800
CEILING DIFFUSER AIR THROW DATA
Model No. Air Volume
1
RTD11 Step-Down FD11 Flush
cfm ft. ft.
078, 092
2600 24 - 29 19 - 24
2800 25 - 30 20 - 28
3000 27 - 33 21 - 29
3200 28 - 35 22 - 29
3400 30 - 37 22 - 30
102, 122
3600 25 - 33 22 - 29
3800 27 - 35 22 - 30
4000 29- 37 24 - 33
4200 32 - 40 26 - 35
4400 34 - 42 28 - 37
150
5600 39 - 49 28 - 37
5800 42 - 51 29 - 38
6000 44 - 54 40 - 50
6200 45 - 55 42 - 51
6400 46 - 55 43 - 52
6600 47 - 56 45 - 56
1
Page 11
ELECTRICAL DATA 6.5 TON
Model No. LDT078H4E
1Voltage - 60Hz 208/230V-3ph 460V-3ph 575V-3ph
Compressor 1
Rated Load Amps
105 62 39
Compressor 2
Rated Load Amps
70 31 27
Outdoor Fan
1
15 15 20
Motor
2Maximum
50 25 20
50 25 20
3Minimum
39 21 16
42 22 17
1
2
3
ELECTRICAL DATA 7.5 TON
Model No. LDT092H4E
1Voltage - 60Hz 208/230V-3ph 460V-3ph 575V-3ph
Compressor 1
Rated Load Amps
105 62 39
Compressor 2
Rated Load Amps
43 33
Outdoor Fan
1
15 15 20
Motor
2Maximum
50 25 20
60 30 20
3Minimum
45 23 17
47 24 18
1
2
3
Page 12
ELECTRICAL DATA 8.5 TON
Model No. LDT102H4E
1Voltage - 60Hz 208/230V-3ph 460V-3ph 575V-3ph
Compressor 1
Rated Load Amps
105 62 39
Compressor 2
Rated Load Amps 16
110 52
Outdoor Fan
1
15 15 20
Motor
2Maximum
60 30 20
60 30 20
3Minimum
48 25 19
50 26 20
1
2
3
ELECTRICAL DATA 10 TON
Model No. LDT122H4E
1Voltage - 60Hz 208/230V-3ph 460V-3ph 575V-3ph
Compressor 1
Rated Load Amps
110
Compressor 2
Rated Load Amps
136
Outdoor Fan
1
15 15 20
Motor
2Maximum
70 30 25
80 35 25
3Minimum
59 27 22
61 28 23
1
2
3
Page 13
LDT078-150 PARTS ARRANGEMENT
FIGURE 1
UNIT
CONTROLLER
INDOOR
COIL OUTDOOR FANS
(3 ON 122 & 150)
COMPRESSORS CONDENSATE
DRAIN
FILTERS
(FOUR - 20 X 25 X 2”)
ECONOMIZER
(OPTIONAL)
BLOWER
(DIRECT DRIVE)
GAS VALVE
BURNERS
COMBUSTION
AIR INDUCER
WIRELESS
BOARD
WIFI
ANTENNA
REVERSING
VALVE
LDT078-150 CONTROL BOX
FIGURE 2
W4
A55
K65
T3
T1
T18
TB13
K1
K2
S117
SHADED AREA IS A HINGED PANEL IN FRONT OF
CONTROLS AREA (OPTIONAL A173 LOCATION)
Page 14
I-UNIT COMPONENTS
The LDT unit parts arrangement are shown in figure 1. All
L1, L2, and L3 wiring is color coded; L1 is red, L2 is yellow,
and L3 is blue. See wiring diagrams in the back of this
manual for complete call out of components per LDT unit.
All 7.5 through 12.5 ton units are configure to order units
(CTO).
A-Control Box Components
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can affect elec
tronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
LDT control box components are shown in figure 2. The
control box is located in the upper portion of the com
pressor compartment.
1-Disconnect Switch S48 or Circuit Breaker
CB10 (field installed)
LDT units may be equipped with an optional disconnect
switch S48 or circuit breaker CB10. S48 and CB10 are tog
gle switches, which can be used by the service technician
to disconnect power to the unit.
2-Transformer T1
All LDT series units use a single line voltage to 24VAC
transformer mounted in the control box. Transformer sup
plies power to control circuits in the unit. The transformer is
rated at 92VA and is protected by a 6 amp circuit breaker
(CB8). The 208/230 (Y) voltage transformers use two pri
mary voltage taps as
shown in figure 3, while
460 (G) and 575 (J) volt
age transformers use a
single primary voltage
tap.
3-CAI Transformer T3 (575V Units)
All LDT 575(J) voltage units use transformer T3 located in
the control box. The transformers have an output rating of
0.5A. T3 transformer supplies 230 VAC power to the com
bustion air inducer motor (B6).
4-Transformer T18
T18 is a single line voltage to 24VAC transformer used in all
LDT units. T18 is rated at 70VAC and is protected by a 3.5
amp circuit breaker (CB18).
5-Compressor Contactor K1 & K2
All compressor contactors are three‐pole‐double‐break
contactors with a 24VAC coil. In all LDT units, K1 and K2
energize compressors B1 and B2 respectively in response
to first, second or third stage cooling demands. The auxil
iary N.C. contacts are opened to disable the crankcase
heaters when compressor is energized.
6-Power Exhaust Relay K65 (PED units)
Power exhaust relay K65 is a N.O. DPDT relay with a
24VAC coil. K65 is used in all LDT units equipped with the
optional power exhaust dampers. K65 is energized by the
economizer control panel (A6), after the economizer
dampers reach 50% open (adjustable on control A6).
When K65 closes, the exhaust fan B10 is energized.
7-Terminal Block (TB13)
TB13 terminal block distributes line voltage power to the
line voltage items in the unit.
FIGURE 3
RED
230 VOLTS
208 VOLTS
PRIMARY
SECONDARY
208/230V TRANSFORMER
Page 15
PLUMBING COMPONENTS
FIGURE 4
Condenser Coil
Evaporator Coil
Compressor 1
Compressor 2
Reversing Valve
Reversing Valve
LDT078-102
LDT122-150 Condenser Coil
Evaporator Coil
Reversing Valve
Compressor 2 Compressor 1
Accumulators
Page 16
B-Cooling Components
LDT units use independent cooling circuits consisting of
separate compressors, outdoor coils and indoor coil (with 2
separate stages). See figure 4..Units are equipped with two
or three draw-through type condenser fans. and direct-
drive blowers. The blower draws air across the indoor coil
during unit operation.
Cooling may be supplemented by a factory‐or-field‐in
stalled economizer. The indoor coils are slab type and are
stacked. Each indoor coil uses a thermostatic expansion
valve as the primary expansion device. Each indoor coil is
also equipped with enhanced fins and rifled tubing. In all
units, each compressor is protected by a crankcase heater,
high pressure switch and low pressure switch. Additional
protection is provided by by thermistors for low ambient
control and freezing prevention.
1-Compressors B1 and B2
Units use two scroll compressors and two independent
cooling circuits. Compressor capacity may vary from stage
to stage. In all cases, the capacity of each compressor is
added to reach the total capacity of the unit. See “SPECIFI
CATIONS” and “ELECTRICAL DATA” (table of contents)
or compressor nameplate for compressor specifications.
WARNING
Electrical shock hazard. Compressor must be
grounded. Do not operate without protective cover
over terminals. Disconnect power before removing
protective cover. Discharge capacitors before ser
vicing unit. Failure to follow these precautions could
cause electrical shock resulting in injury or death.
Each compressor is energized by a corresponding com
pressor contactor.
NOTE-Refer to the wiring diagram section for specific unit
operation.
IMPORTANT
Some scroll compressors have an internal vacuum
protector that will unload scrolls when suction pres
sure goes below 20 psig. A hissing sound will be
heard when the compressor is running unloaded.
Protector will reset when low pressure in system
rises above 40 psig. DO NOT REPLACE COMPRES
SOR.
2-Freezestats S49 and S50
Each unit is equipped with a low temperature switch
(freezestat) located on the return bend of each indoor coil.
S49 (first circuit) and S50 (second circuit) are located on
the corresponding indoor coils.
Each freezestat is a SPST N.C. auto-reset switch which
opens at 29F + 3F (‐1.7C + 1.7C) on a temperature drop
and closes at 58F + 4F (14.4C + 2.2C) on a temperature
rise. To prevent coil icing, freezestats open during com
pressor operation to temporarily disable the respective
compressor until the coil warms sufficiently to melt any ac
cumulated frost.
If the freezestats are tripping frequently due to coil icing,
check the unit charge, airflow and filters before allowing
unit back in operation. Make sure to eliminate conditions
which might promote indoor coil ice buildup.
3-High Pressure Switches S4 and S7
The high pressure switches is a manual reset SPST N.C.
switch which opens on a pressure rise. The switch is locat
ed in the compressor discharge line and is wired in series
with the compressor contactor coil.
S4 (first circuit) and S7 (second circuit) are wired in series
with the respective compressor contactor coils.
When discharge pressure rises to 640 ± 10 psig (4412 ± 69
kPa) (indicating a problem in the system) the switch opens
and the respective compressor is de-energized (the econ
omizer can continue to operate)..
4-Low Pressure Switches S87, S88
The low pressure switch is an auto‐reset SPST N.O. switch
(held N.C. by refrigerant pressure) which opens on a pres
sure drop. All units are equipped with this switch. The
switch is located in the compressor suction line.
S87 (compressor one) and S88 (compressor two) are
wired to A55 Unit Controller. A55 governs the low pressure
switches by shunting the switches during start up until pres
sure is stabilized. After the shunt period, the control has a
three‐strike counter, during first thermostat demand, be
fore the compressor is locked out. The control is reset by
breaking and remaking the thermostat demand or manual
ly resetting the control.
When suction pressure drops to 25 + 5 psig, (indicating low
pressure), the switch opens and the compressor(s) is(are)
de-energized. The switch automatically resets when pres
sure in the suction line rises to 40 + 5 psig due to many
causes such as refrigerant being added.
When discharge pressure reaches 450 + 10 psig (3102 $
69 kPa) in either circuit (indicating defrost is completed) the
appropriate switch opens. The switches automatically re
set when pressure in the suction line drops to 300 + 20 psig
(2068 $138 kPa).
Page 17
5-Reversing Valve L1 and L2
A refrigerant reversing valve with a 24 volt solenoid coil is
used to reverse refrigerant flow during unit operation in all
LDT units. The reversing valve is connected in the vapor
line of the refrigerant circuit. The reversing valve coil is en
ergized during cooling demand and during defrost.
Reversing valve L1 and L2 are controlled by the M4 con
troller in response to cooling demand or by defrost.
6-Defrost Pressure Switch S46 and S104
The defrost pressure switch S46 and S104 are auto‐reset
SPST N.C. pressure switches which open on a pressure
rise. All LDT units are equipped with these switches. The
switches are located on the discharge line. S46 and S104
are wired in series with the CMC1 control board.
When discharge pressure reaches 450 + 10 psig (3102 $
69 kPa) in either circuit (indicating defrost is completed) the
appropriate switch opens. The switches automatically re
set when pressure in the suction line drops to 300 + 20 psig
(2068 $138 kPa).
7-Defrost Temperature Switch S6 and S9
Defrost thermostat switches S6 and S9 have S.P.S.T. N.O.
contacts which close on a temperature fall (initiating de
frost). The switches are located on the expansion valve dis
tributor assembly at the inlet to the outdoor coil. The switch
monitors the outdoor coil suction temperature to determine
when defrost is needed. When the outdoor coil suction tem
perature falls to 35F + 4F (1.7C + 2.2C) the switch clos
es (initiating defrost after minimum run time of 30, 60, or 90
minutes). When the temperature rises to 60F + 5F
(15.6C + 2.8C) the switch opens.
8-Filter Drier (all units)
LDT units have a filter drier located in the liquid line of each
refrigerant circuit at the exit of each condenser coil (outdoor
coil in LDT units). The drier removes contaminants and
moisture from the system.
9-Condenser Fan Motors B4, B5, B21
See specifications section of this manual for specifications
of condenser fans B4 , B5, and B21 (B21 on 122 and 150
units only). All LDT motors are electrically commutated
condenser fan motors (ECM). The ECM motors are wired
directly to 230VAC power but do not operate until a pulse
width modulated (PWM) control signal is sent from the M4
controller. All outdoor fans will run at the same speed when
the appropriate PWM signal is received. The fans may be
removed for servicing and cleaning by removing the fan
grilles.
10-Crankcase Heaters HR1, HR2
Heater HR1 is installed around compressor B1 and heater
HR2 is installed around compressor B2. Crankcase heater
wattage varies by compressor manufacturer.
11-Temperature Sensors RT46, RT47, RT48
& RT49
Units are equipped with four factory-installed thermistors
(RT46 / RT49) located on different points on the refrigerant
circuit.
The thermistors provide the Unit Controller with constant
temperature readings of four specific locations on the re
frigeration circuit. These temperatures are used as feed
back in certain modes of unit operation.
Each thermistor must be specifically placed for proper unit
operation and to initiate valid alarms. See figure 5 and fig
ure 6 proper locations.
Page 18
LDT078, 092, 102, 122, 150
INDOOR COIL
RT46, RT47
DETAILS NOT TO SCALE
BLUE
RT47
YELLOW
RT46
22J06
22J06
FIGURE 5
Page 19
LDT078, 092, 102, 122, 150
OUTDOOR COIL
RT48, RT49
DETAILS NOT TO SCALE
BLUE
RT49
YELLOW
RT48
22J08
22J08
FIGURE 6
Page 20
C-Blower Compartment
The blower compartment in all LDT078-150H units is locat
ed between the indoor coil and the outdoor coil section. The
blower assembly is accessed by disconnecting the blower
motor and all other plugs and removing the screws in front
of the blower housing.
1-Blower Wheels
Units are equipped with a backward inclined blower wheel.
See "SPECIFICATIONS" at the front this manual for more
detail.
2-Indoor Blower Motor B3
Units are equipped with a direct drive blower assembly with
a three-phase, variable speed, direct drive blower motor.
All motor specifications are listed in the SPECIFICATIONS
(table of contents) in the front of this manual. Units may be
equipped with motors manufactured by various manufac
turers, therefore electrical FLA and LRA specifications will
vary. See unit name plate for information specific to your
unit.
A-Blower Operation
Refer to the Unit Controller Setup Guide to energize blow
er. Use the mobile service app menu; see SERVICE >
TEST.
In both thermostat and zone control mode, the Unit Con
troller will stage the blower between low and high speed.
WARNING
1-Make sure that unit is installed in accordance with the
installation instructions and applicable codes.
2-Inspect all electrical wiring, both field‐ and factory‐
installed, for loose connections. Tighten as required.
3-Check to ensure that refrigerant lines do not rub against
the cabinet or against other refrigerant lines.
4-Check voltage at disconnect switch. Voltage must be
within range listed on nameplate. If not, consult power
company and have voltage condition corrected before
starting unit.
5-Make sure filters are new and in place before start‐up.
Initiate blower only (G) demand at thermostat according to
instructions provided with thermostat. Unit will cycle on
thermostat demand. The following steps apply to applica
tions using a typical electro-mechanical thermostat.
1- Blower operation is manually set at the thermostat sub
base fan switch. With fan switch in ON position, blow
ers will operate continuously.
2- With fan switch in AUTO position, the blowers will cycle
with demand. Blowers and entire unit will be off when
system switch is in OFF position.
NOTE - Blower operation mode can also be initiated by the
mobile service app.
Direct-drive motor may not immediately stop when power is
interrupted to the Unit Controller. Disconnect unit power
before opening the blower compartment. The Controller's
digital inputs must be used to shut down the blower. See
Unit Controller manual for operation sequences.
B-Blower Access
The blower assembly is secured to a sliding frame which
allows the blower assembly to be pulled out of the unit. See
figure 8.
1- Loosen the reusable wire tie which secures the con
trols and high voltage blower wiring to the blower hous
ing. Disconnect the pressure sensor low voltage wire
harness.
2- Remove and retain screws on either side (and on the
front for direct drive) of sliding frame. Use the metal
handle to pull frame toward outside of unit.
3- Slide frame back into original position when finished
servicing. Reattach the blower wiring in the previous lo
cation using the wire tie. Reconnect pressure sensor
low voltage wire harness.
4- Replace retained screws.
The supply CFM can be adjusted by changing the percent
age of motor output using the Unit Controller settings Refer
to table 1 for menu paths and default settings. Record any
RPM% changes on the parameter settings label located on
the inside of the compressor access panel.
CAUTION
The BLOWER CALIBRATION process starts the indoor
blower at operational speeds and moves the economizer
damper blades. Before starting this process, replace any
access panels and close all unit doors except com
pressor compartment door.
Blower calibration is required only on units that are newly
installed or if there is a change in the duct work or air filters
after installation. Use the mobile service app to navigate to
the SETUP>TEST & BALANCE>BLOWER menu. After
the new CFM values are entered, select START CALIBRA
TION. The blower calibration status is displayed as a %
complete. Upon successful completion, the mobile service
app will display CALIBRATION SUCCESS and go back to
the blower calibration screen.
IMPORTANT - The default value for Cooling Low CFM is
lower than a traditional singe- or two-speed unit. If operat
ing the unit with a 2- or 3-stage controller (2- or 3-stage
thermostat, DDC controller, etc.), it is recommended to in
crease the Cooling Low CFM default value to a suitable lev
el for part load cooling (typically 60% of full load CFM).
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