SERVICING
196 Rev. 3
LIQUID LINE SIZING
CONDENSING UNIT ABOVE EVAPORATOR
EFFECTIVE
LENGTH
50
75
100
125
150
18
3/8
3/8
3/8
3/8
3/8
24
3/8
3/8
3/8
3/8
3/8
30
3/8
3/8
3/8
3/8
3/8
36
3/8
3/8
3/8
3/8
3/8
42
3/8
3/8
3/8
3/8
3/8
48
3/8
3/8
3/8
3/8
3/8
60
3/8
3/8
3/8
1/2*
1/2**
* If overall drop is 10 feet or more, the next smaller size
may be used.
** If overall drop is 30 feet or more, the next smaller size
may be used.
LIQUID LINE SIZING
EVAPORATOR ABOVE CONDENSING
UNIT MAXIMUM VERTICAL LIFT
EFFECTIVE
LENGTH
LINE
SIZE
50
75
100
125
150
18
3/8
47
46
45
45
42
24
3/8
45
42
40
40
35
30
3/8
43
40
37
37
30
36
3/8
40
35
30
30
20
42
3/8
37
31
25
25
12
48
48
3/8
1/2
33
47
25
45
17
43
17
43
0
40
60
60
3/8
1/2
25
45
12
45
0
40
0
40
-
35
The previous table is based on a maximum liquid line pres-
sure drop of 25 lbs. Any portions of the liquid line which will
pass through a high ambient area must be insulated to pre-
vent loss of subcooling.
5. Determine the amount of additional refrigerant the sys-
tem will require using the Refrigerant Correction Chart
and example shown.
REFRIGERANT CORRECTION CHART
Liquid Line Size, O.D.
Oz. Refrig/Ft Liquid Line
1/4
0.20
3/8
0.60
1/2
1.30
EXAMPLE: The liquid line to be used with an RCA48A2A
will have a linear length of 65 feet, an effective length of 75
feet, and a vertical lift of 30 feet, with the evaporator above the
condensing unit.
The maximum vertical lift for a 4 ton unit with an effective
liquid line length of 75 feet is 25 feet of a 3/8" line, or 45 feet
for a 1/2" line. Our lift is 30 feet, so a 1/2" liquid line must be
used.
Additional refrigerant will be -
65 feet of 1/2" line = 1.3 x 65 feet
= 85 oz.
- 25 feet of 3/8" line = 0.6 x 25 feet = 15 oz.*
(*already in condensing unit)
= 70 oz.
70 oz. charge will need to be added to the system.
6. Check the system nameplate. An accumulator must be
added to the system if-
- you are adding more than 15% to the system charge
listed on the nameplate,
-or more than 125 linear feet of liquid line of the size origi-
nally on the unit,
- or any time a non-matching indoor coil is used.
ACCUMULATOR SIZING CHART
UNIT SIZE
ACCUMULATOR
PART NUMBER
MAX. ADDED
REFRIGERANT
18 - 30
11190801
120 oz.
36
11190803
150 oz.
42 - 48
11190807
180 oz.
60
11190808
225 oz.
If the calculation in step 5 requires you to add more
refrigerant than the accumulator referenced above can hold,
you must relocate the system components so a shorter or
smaller diameter liquid line may be used.
7. Make the final charge adjustment. Subcooling at the con-
densing unit must be 14° to 18°F. If the indoor coil has a
capillary tube the superheat must also be measured. Ad-
just charge as explained in section S-103 CHARGING.
S-200 DUCT STATIC PRESSURES AND/OR
STATIC PRESSURE DROP ACROSS COIL
This minimum and maximum allowable duct static pressure
for the indoor sections are found in the specifications sec-
tion.
Tables are also provided for each coil, listing quantity of air
(CFM) versus static pressure drop across the coil.
Too great an external static pressure will result in insufficient
air that can cause icing of the coil. Too much air can cause
poor humidity control and condensate to be pulled off the
evaporator coil causing condensate leakage. Too much air
can also cause motor overloading and in many cases this
constitutes a poorly designed system.
To determine proper air movement, proceed as follows:
