Carrier line set sizes
The right line set diameter for your Carrier mini-split by capacity — across the Performance and Infinity ductless lines — plus the length limits and Carrier's move to R-454B Puron Advance. Prefer to size by run length too? Use the size calculator.
Carrier line set size by capacity
Line set diameter is set by your system's capacity. Match your Carrier unit's BTU rating to the typical liquid-and-suction pair below — sizes shift between Carrier's R-410A and R-454B generations, so confirm against your manual.
| Carrier system size | Typical line set (liquid × suction) |
|---|---|
| 9,000 BTU | 1/4" × 3/8" or 1/4" × 1/2" (by generation) |
| 12,000 BTU | 1/4" × 3/8" or 1/4" × 1/2" (by generation) |
| 18,000 BTU | 1/4" × 1/2" or 3/8" × 5/8" (by generation) |
| 24,000 BTU | 3/8" × 5/8" |
| 36,000 BTU | 3/8" × 5/8" |
The interesting shift is at the small end: Carrier's older R-410A 38MAQ and 40MAQ units run a 1/2" suction line at 9k and 12k, while the newer R-454B 37MARA steps that down to 3/8". Carrier's single-zone ductless units are OEM-built (by GD Midea) but carry Carrier-labeled specs, so the installation manual for your exact model is the authority. Always confirm the diameters there before buying.
Carrier moved to R-454B Puron Advance
Carrier's older ductless units — the 38MAQ and 40MAQ Performance and Comfort series — use R-410A. The current Performance (37MARA) and Infinity (37MAHAQ) lines use R-454B, which Carrier brands as Puron Advance. The copper line set is the same either way, but your vacuum pump, gauges, and any field charge must match your unit's refrigerant — check the model and data plate before you buy tools or add refrigerant.
Field-flared, not quick-connect
Carrier mini-splits use standard field-flared line sets, not pre-charged quick-connect. You flare the copper ends and pull a vacuum before opening the service valves — work that typically needs a vacuum pump and EPA 608 certification. Shop standard line sets for a Carrier install, or see pre-charged line sets if you want the no-vacuum route on a compatible system.
Carrier line set length limits
Diameter is only half the spec. Your Carrier system also limits how long the line set can run and how far the indoor and outdoor units can sit apart in height, and those limits depend on the generation. Plan your run to the figures below, then confirm the exact limits for your model in its installation manual.
| Minimum line length | Maximum line length | Max vertical separation | Pre-charged for |
|---|---|---|---|
| 10 ft (3 m) | 82–213 ft by capacity | 32–98 ft by generation | 25 ft |
Carrier's limits depend on capacity and generation. The R-410A 38MAQ and 40MAQ units allow about 82 ft of line on 9,000–18,000 BTU models and about 164 ft on 24,000–36,000 BTU models, with up to 32 ft of vertical separation. The newer R-454B lines reach further — the Performance 37MARA 24,000 BTU is rated for about 213 ft, with up to 49–98 ft of lift. The factory charge covers about the first 25 ft; beyond that an HVAC pro adds about 0.16–0.32 oz per foot. Carrier lists a minimum run of about 10 ft.
How to find your Carrier model's line set size
- Identify the model and generation. Note the model number — a 38MAQ or 40MAQ prefix is the R-410A line, while a 37MARA (Performance) or 37MAHAQ (Infinity) prefix is the newer R-454B line.
- Check the installation manual. It lists the exact liquid and suction diameters, the maximum line length, the vertical lift, the pre-charge distance, and the refrigerant for your model — the final word.
Common questions
What size line set does a Carrier 12,000 BTU use?
It depends on the model. Carrier's R-410A 38MAQ and 40MAQ 12,000 BTU units use a 1/4" liquid line with a 1/2" suction line, while the newer R-454B 37MARA 12,000 BTU steps the suction down to 3/8". Confirm against your model's installation manual.
What refrigerant do Carrier mini-splits use?
Carrier's older ductless units (38MAQ and 40MAQ Performance and Comfort) use R-410A, while the current Performance (37MARA) and Infinity (37MAHAQ) lines use R-454B, which Carrier brands as Puron Advance. Match your line set, tools, and any added charge to your unit's refrigerant.
What is the minimum line set length for a Carrier mini-split?
Carrier specifies a minimum line set length of about 10 feet (3 m) to limit noise and vibration. Keep your run at or above that and confirm the figure in your model's manual.
What is the maximum line set length for a Carrier mini-split?
It depends on capacity and generation. Carrier's R-410A units allow about 82 ft on 9,000–18,000 BTU models and 164 ft on 24,000–36,000 BTU models; the newer R-454B Performance 24,000 BTU reaches up to about 213 ft, with 32–98 ft of vertical separation. The factory charge covers about the first 25 ft; beyond that an HVAC pro adds refrigerant. Confirm your unit's maximum in its manual.
This page provides general guidance on Carrier mini-split line set sizing based on published Carrier specifications. Exact line diameters vary by series and model, and lengths, maximum line length, vertical lift, and refrigerant (R-410A or R-454B) differ by unit — always verify against your unit's official installation manual before purchasing or installing.