18
REFRIGERANT LINES
General refrigerant line sizing:
1. The 38MVC/MVQ units are shipped with a full charge of
R410A refrigerant. All charges, line sizing, and capacities
are based on runs of 25 ft (7.6 m). For runs over 25 ft (7.6
m), consult long-- line section on this page for proper charge
adjustments.
2. Minimum refrigerant line length between the indoor and
outdoor units is 10 ft. (3 m).
3. Refrigerant lines should not be buried in the ground. If it is
necessary to bury the lines, not more than 36 --in (914 mm)
should be buried. Provide a minimum 6--in (152 mm)
vertical rise to the service valves to prevent refrigerant
migration.
4. Both lines must be insulated. Use a minimum of 1/2--in.
(12.7 mm) thick insulation. Closed--cell insulation is
recommended in all long -- line applications.
5. Special consideration should be given to isolating
interconnecting tubing from the building structure. Isolate
the tubing so that vibration or noise is not transmitted into
the structure.
S The following maximum lengths are allowed:
REFRIGERANT LINE LENGTHS ft. (m)
Unit Size
Max Line
Length
Max Elevation
(ID over OD)
Max Elevation
(OD over ID)
9K 65 (20) 35 (11) 35 (11)
12K 65 (20) 35 (11) 35 (11)
18K 100 (30) 50 (15) 50 (15)
24K 100 (30) 60 (18) 60 (18)
S The following are the piping sizes.
PIPE SIZES
Unit Size Mix Phase Vapor
9K 1/4” 3/8”
12K 1/4” 1/2”
18K 1/4” 1/2”
24K 3/8” 5/8”
Refrigerant Charge
REFRIGERANT CHARGE lb. (kg)
Unit Size Air Conditioner
Heat Pump
9K 2.3 (1.0) 2.4 (1.1)
12K 2.9 (1.3) 3.0 (1.4)
18K 4.4 (2.0) TBD
24K TBD TBD
S Above charge is for piping runs up to 25 ft. (7.6 m).
S For piping runs greater than 25 ft. (7.6 m), add 0.1 oz. of
r efrigerant per foot of extra piping up to the allowable
length.
Long Line Applications, 38MVC
Units:
1. A crankcase heater should be added for line lengths longer
than 25 ft (7.62 m) to prevent the migration of refrigerant to
the compressor during the “OFF” cycle.
2. A field fabricated wind baffle is recommended.
3. No change in line sizing is required.
4. Add refrigerant per table below.
ADDITIONAL CHARGE TABLE
Unit
Size
Total
Line Length,
ft
Additional Charge, oz.
Min. Max.
10 --- 25ft
(3.05 --- 7.62m)
>25 --- 65 ft
(7.62---19.81m)
>65 --- 100 ft
(19.81---30.48m)
9K
cool
only
10
65
none
0.1ozper
foot
9K
hp
12K
cool
only
12K
hp
18K
cool
only
100
0.1oz. per
foot
5. Reduction in capacity due to long lines can be calculated
from the chart below.
CAPACITY LOSS
Capacity,%Loss
Line Length, ft
Cooling: 25 45 65 100
9&12KBTU/Hmodels 0% 2% 5%
18 & 24 KBTU/H m odels 0% 2% 4% 7%
Heating:
9&12KBTU/Hmodels 0% 7% 11%
18 & 24 KBTU/H m odels 0% 7% 11% 15%
38/40MVC, MVQ
