Lennox International Inc CONDENSING UNITS Superheat Rfc, Use Weigh-Inmethod, ABOVE or, Below

START: Measure outdoor ambient temperature																		1.		Confirm proper airflow across coil using figure 19.
													39ºF						2. Compare unit pressures with table 4, Normal
												(3.8ºC) and								Operating Pressures.
USE WEIGH-IN METHOD													Below					3.		Use SUPERHEAT to correctly charge unit or to
Weigh-in or remove refrigerant										ABOVE or										verify the charge is correct.
																			4.	Set thermostat to call for heat (must have a cooling
based upon line length										BELOW
							40ºF													load between 70-80ºF (21−26ºC)
					(4.4ºC) and														5.	Connect gauge set.
SUPERHEAT RFC						Above													6.	When heat demand is satisfied, set thermostat to
																				call for cooling.
																			7.	Allow temperatures and pressures to stabilize.
				SHº (Superheat) Values (+/−5ºF)															8.	Measure the suction line pressure and use the use
																				value to determine saturation temperature (table
				Wet Bulb (air entering indoor coil)
																				3):
		ºF*	50	52	54		56	58	60	62	64	66	68	70	72	74	76
																				SATº =_________
		40	15	18	20		23	26	29	32	34	38	41	43	46	48	51
																			9.	Record suction line temperature:
		45	13	16	18		21	24	27	30	33	36	39	41	44	46	49
																				VAPº =_________
		50	11	14	16		19	22	25	28	31	34	37	39	42	44	47
		55	9	12	14		17 20 23			27	30	33	36	38	40	42	44		10.	Subtract to determine superheat (SHº):
		60	7	10	12		15 18 21			24	27	30	33	35	38	40	43			VAPº − _____ SATº ______ = SHº______
		65	-	6	10		13	16	19	21	24	27	30	33	36	38	41		11.	Record the wet bulb temperature (air entering
		70	-	-	7		10	13	16	19	21	24	27	30	33	36	39			indoor coil):
		75	-	-	-		6	9	12	15	18	21	24	28	31	34	37			WB =_______
		80	-	-	-		-	5	8	12	15	18	21	25	28	31	35		12.	Record outdoor ambient temperature.
		85	-	-	-		-	-	-	8	11	15	19	22	26	30	33		13.	Compare results with table to the left.
		90	-	-	-		-	-	-	5	9	13	16	20	24	27	31
		95	-	-	-		-	-	-	-	6	10	14	18	22	25	29
		100	-	-	-		-	-	-	-	-	8	12	16	21	24	28
		105	-	-	-		-	-	-	-	-	5	9	13	17	22	26		NOTE − Do not attempt to charge system where a
If refrigerant	is
		110	-	-	-		-	-	-	-	-	-	6	11	15	20	25		dash appears, system could be overcharged.
REMOVED, retest to
																			Superheat is taken at suction line service port.
		115	-	-	-		-	-	-	-	-	-	-	8	14	18	24
confirm that unit	is
																			Suction line superheat must never be less than 5ºF
properly charged.		* Dry−bulb temperature (ºF) of entering outdoor ambient air.																	at the suction line service port.

If value is LESS than shown, then REMOVE refrigerant.

MORE or

LESS

If value is MORE than shown, then ADD refrigerant.

If refrigerant is ADDED, retest to confirm that unit is properly charged.

		Figure 24. HFC−410A Superheat RFC Method
		Table 3. HFC−410A Temperature Pressure (Psig)
°F	°C		Psig	°F	°C	Psig
−40	−40.0		11.6	60	15.6	170
−35	−37.2		14.9	65	18.3	185
−30	−34.4		18.5	70	21.1	201
−25	−31.7		22.5	75	23.9	217
−20	−28.9		26.9	80	26.7	235
−15	−26.1		31.7	85	29.4	254
−10	−23.3		36.8	90	32.2	274
−5	−20.6		42.5	95	35.0	295
0	−17.8		48.6	100	37.8	317
5	−15.0		55.2	105	40.6	340
10	−12.2		62.3	110	43.3	365
15	−9.4		70.0	115	46.1	391
20	−6.7		78.3	120	48.9	418
25	−3.9		87.3	125	51.7	446
30	−1.1		96.8	130	54.4	476
35	1.7		107	135	57.2	507
40	4.4		118	140	60.0	539
45	7.2		130	145	62.8	573
50	10.0		142	150	65.6	608
55	12.8		155

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