Saturation Pressure-Temperature

Saturation Defined

• Saturation is the point at which a substance can exist as a liquid and a gas at the same time within a sealed container.
• Comparison: Saturation temperature for water at sea level is 212 degrees (boiling)

Uses in the HVAC Field

• Saturation exists in most parts of evaporators and condensers while cooling systems are in operation
• As pressure rises, the saturation temperature rises
• As pressure falls, the saturation temperature falls
• Engineers speak of a refrigerant's P/T to refer to saturation conditions
• If you know the pressure of a saturated substance, you can use a P/T Chart to find its saturation temperature

Using the Chart Below

1. Turn unit on; monitor system running approximately 15 to 30 minutes.
2. Take a reading of your refrigerant system pressure (PSIG).
3. SUPERHEAT (for Fixed Metering Device)
   
   
   1. Determine Temperature from Chart below
   2. Subtract from actual suction line temperature before compressor
   3. Use Manufacturers recommended superheat if available
   4. If not available use 10-15 degrees
4. SUBCOOLING (for TXV)
   
   
   1. Determine Temperature from Chart below
   2. Subtract from liquid temperature entering TXV
   3. Use Manufacturers recommended superheat if available
   4. If not available use 12 degrees

PSIG	R-22	R-134A	R-410A		PSIG	R-22	R-134A	R-410A
0	-41	-15	-60		78	46	75	20
2	-37	-10	-58		80	48	76	21
4	-32	-5	-54		85	51	79	24
6	-28	-1	-50		90	54	82	26
8	-24	3	-46		95	56	85	29
10	-20	7	-42		100	59	88	32
12	-17	10	-39		105	62	90	34
14	-14	13	-36		110	64	93	36
16	-11	16	-33		115	67	96	39
18	-8	19	-30		120	69	98	41
20	-5	22	-28		125	72	100	43
22	-3	25	-26		130	74	103	45
24	0	27	-24		135	76	105	47
26	2	30	-20		140	78	107	49
28	5	32	-18		145	81	109	51
30	7	35	-16		150	83	112	53
32	9	37	-14		160	87	116	57
34	11	39	-12		170	91	120	60
36	13	41	-10		180	94	123	64
38	15	43	-8		190	98	127	67
40	17	45	-6		200	101	131	70
42	19	47	-4		210	105	134	73
44	21	49	-3		220	108	137	76
46	23	51	-2		225	110	139	78
48	24	52	0		235	113	142	80
50	26	54	1		245	116	145	83
52	28	56	3		255	119	148	85
54	29	57	4		265	121	151	88
56	31	59	6		275	124	153	90
58	32	60	7		285	127	155	92
60	34	62	8		295	130	158	95
62	35	64	10		305	133	161	97
64	37	65	11		325	137	167	101
66	38	66	13		355	144	173	108
68	40	68	14		375	148	177	112
70	41	69	15		405	155	182	118
72	42	71	16		500	173	202	134
74	44	72	17		600	N/A	N/A	149
76	45	73	19		700	N/A	N/A	159