System Operation - Lennox Merit 14HPX Installation Instructions Manual

Table 5. Normal Operating Pressures − Liquid +10 and Vapor +5 PSIG*
Use table 5 as a general guide when performing maintenance checks. This is not a procedure for charging the unit (Refer
to Charging / Checking Charge section). Minor variations in these pressures may be expected due to differences in instal-
lations. Significant differences could mean that the system is not properly charged or that a problem exists with some
component in the system.
14HPX−018
5F (5C)**
Liquid / Vapor
65 (18) 226 / 140
70 (21) 244 / 141
75 (24) 263 / 142
80 (27) 283 / 143
85 (29) 302 / 144
90 (32) 328 / 145
95 (35) 351 / 146
100 (38) 376 / 147
105 (41) 402 / 148
110 (38) 430 / 149
115 (45) 465 / 150
60 (15) 346 / 139
50 (10) 323 / 117
40 (4) 306 / 98
30 (−1) 278 / 84
20 (−7) 273 / 66
*IMPORTANT These are most−popular−match−up pressures. Indoor match up and indoor load cause pressures to vary.
**Temperature of the air entering the outside coil (outdoor ambient temperature).

System Operation

UNIT COMPONENTS
IMPORTANT
Some scroll compressor have internal vacuum protector
that will unload scrolls when suction pressure goes
below 20 psig. A hissing sound will be heard when the
compressor is running unloaded. Protector will reset
when low pressure in system is raised above 40 psig. DO
NOT REPLACE COMPRESSOR.
Bi−Flow Liquid Line Filter Drier
The unit is equipped with a large−capacity biflow filter drier
which keeps the system clean and dry. If replacement is
necessary, order another of the same design and capacity.
The replacement filter drier must be suitable for use with
HFC−410A refrigerant.
High Pressure Switch (S4)
The 14HPX is equipped with an auto-reset high pressure
switch (single−pole, single−throw) which is located on the
liquid line. The switch shuts off the compressor when
discharge pressure rises above the factory setting. The
switch is normally closed and is permanently adjusted to
trip (open) at 590 + 15 psig (4068 + 103 kPa).
506649−01
IMPORTANT
14HPX−024 14HPX−030
Liquid / Vapor Liquid / Vapor
233 / 137 238 / 138
252 / 138 263 / 139
271 / 140 279 / 139
292 / 141 299 / 140
314 / 142 324 / 141
338 / 143 340 / 142
361 / 145 375 / 145
387 / 146 397 / 145
412 / 147 424 / 147
441 / 148 454 / 150
471 / 151 485 / 150
352 / 138 338 / 137
331 / 114 334 / 112
304 / 99 312 / 93
299 / 80 302 / 74
283 / 66 280 / 53
14HPX−036 14HPX−042
Liquid/ Vapor Liquid / Vapor
Cooling
220 / 138 223 / 125
236 / 140 241 / 130
256 / 141 261 / 134
276 / 142 282 / 138
298 / 143 302 / 139
321 / 144 326 / 140
344 / 144 349 / 141
369 / 146 374 / 142
394 / 147 399 / 143
421 / 148 428 / 145
449 / 149 455 / 146
Heating
350 / 134 373 / 139
331 / 117 363 / 117
313 / 97 348 / 97
298 / 83 336 / 74
284 / 66 322 / 64
Thermal Protection Switch (S173)
Some XC13 units are equipped with a compressor
mounted normally closed temperature switch that
prevents compressor damage due to overheating caused
by internal friction. The switch is located on top of the
compressor casing (see figure 1). This switch senses the
compressor casing temperature and opens at 239−257°F
(115°C−125°C) to shut off compressor operation. The
auto−reset switch closes when the compressor casing
temperature falls to 151−187°F (66°C−86°C), and the
compressor is re−energized. This single−pole, single−throw
(SPST) bi−metallic switch is wired in series with the 24V Y
input signal to control compressor operation.
Crankcase Heater (HR1) and Thermostat Switch
(S40) (−036 through −060 models only)
All models sizes are equipped with a belly band type
crankcase heater. HR1 prevents liquid from accumulating
in the compressor. On Y voltage units, the HR1 is
controlled by a single pole, single throw thermostat switch
(S40) located on the liquid line (see figure 1 for location).
On all other units, the heater is on when there is no
compressor operation.
Page 28
14HPX−048 14HPX−060
Liquid / Vapor Liquid / Vapor
231 / 136 243 / 136
248 / 139 263 / 137
271 / 140 282 / 138
291 / 142 306 / 139
312 / 143 327 / 140
335 / 144 351 / 141
359 / 145 376 / 142
384 / 146 401 / 143
411 / 148 426 / 145
439 / 149 452 / 146
468 / 150 484 / 148
355 / 130 351 / 117
336 / 113 333 / 105
315 / 88 316 / 88
296 / 72 308 / 70
286 / 64 300 / 61
Compressor
Mounted