Lennox 14HPX Unit Information page 18

Temp.
80 24 24 24 23 23 22 22 22 20 19 18 17 16 15
of air
entering
78 23 23 23 22 22 21 21 20 19 18 17 16 15 14
indoor
76 22 22 22 21 21 20 19 19 18 17 16 15 14 13
coil ºF
74 21 21 21 20 19 19 18 17 16 16 15 14 13 12
A 72 20 20 19 18 17 17 16 15 15 14 13 12 11 10
70 19 19 18 18 17 17 16 15 15 14 13 12 11 10
Wet−bulb ºF
57 58 59 60 61 62 63 64 65 66 67 68 69 70
T
Drop
C
19º
53º
air flow
DRY
BULB
All temperatures are
expressed in ºF
C − Pre− Charge Maintenance Checks
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 installations. Significant differences could mean that the system is not properly charged or that
a problem exists with some component in the system.
14HPX−018
Liquid / Vapor
5F (5C)**
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).
DT
B
A
72º
B
air flow
64º
DRY BULB
INDOOR WET
BULB
COIL
IMPORTANT
Normal Operating Pressures − Liquid +10 & Vapor +5 PSIG*
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
Step 1. Determine the desired DT Measure entering air tempera-
ture using dry bulb (A) and wet bulb (B). DT is the intersecting value
of A and B in the table (see triangle).
Step 2. Find temperature drop across coil Measure the coil's dry
bulb entering and leaving air temperatures (A and C). Temperature
Drop Formula: (T
Drop
Step 3. Determine if fan needs adjustment If the difference be-
tween the measured T
+3º, no adjustment is needed. See examples: Assume DT = 15 and
A temp. = 72º, these C temperatures would necessitate stated ac-
tions:
DT
Cº T –
Drop
53º 19 – 15
58º 14 – 15
62º 10 – 15
Step 4. Adjust the fan speed See indoor unit instructions to in-
crease/decrease fan speed.
Changing air flow affects all temperatures; recheck temperatures to
confirm that the temperature drop and DT are within +3º.
FIGURE 18
Table 5
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
Page 18
) = A minus C.
and the desired DT (T
Drop Drop
=
ºF ACTION
=
4 Increase the airflow
=
−1 (within +3º range) no change
=
−5 Decrease the airflow
14HPX−048
Liquid / Vapor
231 / 136
248 / 139
271 / 140
291 / 142
312 / 143
335 / 144
359 / 145
384 / 146
411 / 148
439 / 149
468 / 150
355 / 130
336 / 113
315 / 88
296 / 72
286 / 64
–DT) is within
14HPX−060
Liquid / Vapor
243 / 136
263 / 137
282 / 138
306 / 139
327 / 140
351 / 141
376 / 142
401 / 143
426 / 145
452 / 146
484 / 148
351 / 117
333 / 105
316 / 88
308 / 70
300 / 61