38MGRBQ: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
17
REFRIGERANT LINES
General Refrigerant Line Sizing
1. The outdoor 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)
per number of zones. For runs over 25 ft. (7.6 m), consult the see “Long Line Applications:” on page 18 for proper charge adjustments.
2. The 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 36in (914 mm) should be buried. Provide a
minimum 6in (152 mm) vertical rise to the service valves to prevent refrigerant migration.
4. Both lines must be insulated. Use a minimum of 1/2in. (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 vibration or noise is not
transmitted into the structure.
IMPORTANT: Both refrigerant lines must be insulated separately.
Table 13 displays the following maximum lengths allowed.
Table 13 — Piping and Refrigerant
NOTE: The refrigerant charge included is adequate for the outdoor unit’s maximum number of zones multiplied by the standard piping
length per zone. For piping runs greater than the “Maximum Piping Length with no additional refrigerant charge per System”.
NOTE: Multi-zone outdoor unit compatibility can only support one (1) AHU per unit. When the 30K or 36K AHU is utilized in multi-zone
48K ODU applications, 500 grams (17.6 oz) of additional refrigerant charge must be added to the system
38MGRBQ Size
STANDARD HIGH HEAT HIGH HEAT STANDARD HIGH HEAT STANDARD
VAPOR
CYCLE
18R 24HH 30HH 36R 36HH 48R 48K
(208/230 V)
Min. Piping Length per
each indoor unit
ft. (m) 10 (3)
Standard Piping Length
per each indoor unit
ft. (m) 25 (7.5)
Max. outdoor-indoor
height difference (OU
higher than IU)
ft. (m) 49(15) 49(15) 49(15) 49(15) 65(20) 65(20) 65(20)
Max. outdoor-indoor
height difference (IU
higher than OU)
ft. (m) 49(15) 49(15) 49(15) 49(15) 65(20) 65(20) 65(20)
Max. height different
between indoor units
ft. (m) 32 (10)
Max. Length per each
indoor unit
ft. (m) 82 (25) 98 (30) 115(35) 115(35) 115(35) 115 (35) 115 (35)
Max. Piping Length with
no additional refrigerant
charge per System
(Standard Piping length
x No. of Zones)
ft. (m) 49 (15) 74 (22) 98 (30) 98 (30) 98 (30) 123 (37.5) 123 (37.5)
Total Maximum Piping
Length per system
ft. (m) 131(40) 197(60) 262(80) 262(80) 262(80) 328(100) 328(100)
Additional refrigerant
charge (between
Standard – Max piping
length)
Oz/ft
(g/m)
0.16 (15)
Number of IDU 2 3 4 4 4 5 5
Suction Pipe (size -
connection type)
in 3/8*2 3/8*3 1/2 *1+ 3/8*3 1/2 *1+ 3/8*3 1/2 *2+ 3/8*2 1/2 *2+ 3/8*3 1/2 *2+ 3/8*3
(mm) 9.52*2 9.52*3 12.7*1+9.52*3 12.7*1+9.52*3 12.7*2+9.52*2 12.7*2+9.52*3 12.7*2+9.52*3
Liquid Pipe (size -
connection type)
in 1/4*2 1/4*3 1/4*4 1/4*4 1/4*4 1/4*5 1/4*5
(mm) 6.35*2 6.35*3 6.35*4 6.35*4 6.35*4 6.35*5 6.35*5
Refrigerant Type
Heat Pump Models
Charge Amount
R410A
Lbs
(kg)
4.08(1.85) 5.73(2.6) 8.38(3.8) 8.38(3.8) 10.14 (4.6) 10.14 (4.6) 10.14(4.6)
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