Service manual
SERVICING
161
LONG LINE SET APPLICATION R-410A
This long line set application guideline applies to all AHRI listed R-410A air conditioner and heat pump split system
matches of nominal capacity 18,000 to 60,000 Btuh. This guideline will cover installation requirements and additional
accessories needed for split system installations where the line set exceeds 80 feet in actual length. The long line sets can
have three different configurations (1) Outdoor unit and Indoor unit are at the same level, (2) Outdoor unit is above the Indoor
unit coil, (3) Outdoor unit is below the Indoor unit.
This guideline is meant to provide installation instructions based on most common long line set applications. Installation
variables may affect the system operation.
SECTION 1. GENERAL REQUIREMENTS FOR ALL LONG LINE SET APPLICATIONS
1. Equivalent length must be used to determine acceptability of any long line set application. See Section 5 for equivalent
length calculations.
2. For any residential split system installed with a long line set, 3/8” liquid line size must be used.
Limiting the liquid line size to 3/8” is critical since an increased refrigerant charge level from having a larger liquid line
could possibly shorten a compressor’s life-span.
a. Exceptions for air conditioning (cooling only) applications, 1/4" liquid line may be used in:
i. 1.5 ton applications for up to 100 equivalent feet with maximum 40’ vertical lift
ii. 2.0 ton applications for up to 75 equivalent feet with maximum 20’ vertical lift
b. Exceptions for air conditioning (cooling only) applications, 5/16" liquid line may be used in:
i. 1.5 ton applications for up to 250 equivalent feet with maximum 60’ vertical lift
ii. 2.0 ton applications for up to 200 equivalent feet with maximum 40’ vertical lift
iii. 2.5 ton applications for up to 175 equivalent feet with maximum 30’ vertical lift
3. Most refrigerant tubing kits are supplied with 3/8” thick insulation on the suction line. For long line installations over 80
feet, if the line set passes through a high ambient temperature zone, 1/2” thick suction line insulation is required to
reduce loss of capacity. The liquid line must be insulated if more than 50 feet of liquid line will pass through an area that
might reach temperatures of 30°F or higher than outdoor ambient. Never attach a liquid line to any uninsulated portion
of the suction line.
4. A crankcase heater must be installed on any compressor (if crankcase heater is not already factory installed).
5. Hard start assist kit is required.
6. Use of a thermostatic expansion valve (TXV) is required in all long line set applications. Unit must be charged to 7 to 9ºF
subcooling at the indoor unit.
7. Maximum equivalent length of line set is:
a. 250 feet for single stage units with scroll or reciprocating compressors.
b. 150 feet for single stage units with rotary compressors.
c. 150 feet for two stage units.
8. Maximum linear length of line set is:
a. 200 feet for single stage units with scroll or reciprocating compressors.
b. 150 feet for single stage units with rotary compressors.
c. 150 feet for two stage units.
9. Low voltage wiring. Verify low voltage wire gauge is adequate for the length used due to increased line set application.
10. Vibration and Noise: In long line applications, refrigerant tubing is highly prone to transmit noise and vibration to the
adjoining structure. Use adequate vibration-isolating hardware when mounting line set to structural members. See Figures
1-1, 1-2 and 1-3 for example of proper mounting.