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Construction glossary · MEP

What is refrigerant pipingin construction?

Refrigerant piping in construction is the ACR copper line set that carries refrigerant between the outdoor unit and the indoor coil of an air conditioning or heat pump system, made up of a small liquid line and a larger, insulated suction line. Estimators take it off in linear feet per circuit, pulling the line sizes from the equipment manufacturer's tables rather than scaling them off the drawings. The joints are brazed, and the work belongs to the mechanical contractor's piping scope.

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Updated August 2026 · Reviewed by the Ruh construction team

Pair liquid + suction lineMaterial ACR copperMeasured in LF of line-set
The definition

Refrigerant piping, explained.

Refrigerant piping connects split system condensing units, heat pumps, and VRF outdoor units to their indoor coils, and it lives in the Division 23 mechanical scope. The drawings usually show the routing diagrammatically at best: the floor plan locates the equipment, the schedule names the model, and the actual pipe sizes come from the manufacturer's line sizing tables based on capacity, total length, and the vertical lift between units. The material is ACR copper (air conditioning and refrigeration grade), which ships cleaned, dehydrated, and capped, and every joint is brazed with dry nitrogen flowing through the pipe to keep oxide scale from forming inside. New estimators get burned three ways: they measure the horizontal plan run and forget the vertical riser between floors or up to the roof, they price both lines at the same diameter when the suction line is always larger than the liquid line, and they skip the elastomeric insulation the suction line needs to prevent condensation and capacity loss. Long line sets also trigger extra refrigerant charge beyond what the factory ships inside the unit.

How it is measured

Refrigerant piping is measured in linear feet (lf) per line, broken out by diameter, because the liquid and suction lines carry different sizes and prices. A 3 ton split system might pair a 3/8 in liquid line with a 3/4 in suction line, but the only authoritative source is the manufacturer's table for that exact model, length, and lift. The takeoff carries the copper, the suction line insulation as a separate lf line, a brazed joint count or labor allowance, and the nitrogen, pressure test, evacuation, and charging labor per circuit. Cost drivers are diameter, run length, riser height, and accessibility. Quantities come from the mechanical floor and roof plans for routing, the equipment schedule for tonnage, and the manufacturer's engineering data for sizes and charge adders.

Is refrigeration piping the same as refrigerant piping?

Refrigeration piping and refrigerant piping name the same scope on air conditioning and heat pump work: the ACR copper line set between the outdoor unit and the indoor coil, one liquid line paired with a larger suction line. The material is the same under either name, ACR copper, air conditioning and refrigeration grade. So is the takeoff, linear feet per line broken out by diameter, with the suction line insulation carried as its own lf line.

What a refrigerant piping system includes

A refrigerant piping system is one circuit, not one pipe: an outdoor unit, the indoor coil it serves, and the liquid line, suction line, insulation, and brazed joints between them. The takeoff keeps each piece on its own line and rolls the circuit up, so the bid shows what one complete line set costs rather than one copper total.

The refrigerant pipe riser is the length a plan view hides. The vertical run is picked up in lf and added to the horizontal run on the same line, and the suction line insulation is measured over that riser at the same lf as the copper it covers. Riser height is a cost driver in its own right, so a tall riser belongs on the face of the line rather than buried in a plan length.

What is DX piping?

DX piping, short for direct expansion, is another name for the refrigerant piping on this page. A DX system feeds refrigerant from the outdoor unit straight to the indoor coil, so the pipe between them is a copper line set rather than the chilled water piping a chiller plant would run to the same coil. On the equipment side the same split shows up as a DX coil in an air handler instead of a chilled water coil.

DX piping and chilled water piping stay different takeoff lines even when they land on the same coil: one is copper line set measured in lf per line by diameter, the other is hydronic piping measured in lf by size, material, and service. Keep them apart so the insulation and the per-circuit test and charge labor land on the right scope.

Worked example

Refrigerant pipe riser and line set takeoff

Worked example

Price the line set for a rooftop condensing unit serving a second floor air handler. The plan shows 60 lf of horizontal run, the riser scales at 25 ft, and you carry 10 lf for offsets and fittings: 60 + 25 + 10 = 95 lf per line. The circuit needs 95 lf of 3/8 in liquid line, 95 lf of 3/4 in suction line, and 95 lf of elastomeric insulation on the suction side. At illustrative installed rates of $9 per lf for the liquid line, $14 per lf for the suction line, and $4 per lf for insulation: 95 x $9 = $855, 95 x $14 = $1,330, and 95 x $4 = $380. The unit ships charged for the first 25 ft, so 95 - 25 = 70 ft draws an illustrative 0.6 oz of refrigerant per ft: 70 x 0.6 = 42 oz, which is 42 / 16 = 2.625 lb, and at an illustrative $20 per lb that adds 2.625 x $20 = $52.50. The circuit totals $855 + $1,330 + $380 + $52.50 = $2,617.50.

How Ruh handles it

How Ruh handles refrigerant piping.

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Refrigerant piping: frequently asked questions

What type of copper is used for refrigerant piping?+

ACR copper, a grade cleaned, dehydrated, and capped at the mill specifically for air conditioning and refrigeration service. It comes as soft annealed coils in smaller diameters and hard drawn straight lengths in larger ones. Joints are brazed with a high temperature alloy rather than soft soldered, and good practice flows dry nitrogen through the pipe during brazing so oxide scale does not form inside and foul the expansion valves.

Does refrigerant piping need to be insulated?+

The suction line always gets closed cell elastomeric insulation; without it the cold line sweats, drips onto ceilings, and loses capacity to heat gain. Cooling-only liquid lines usually run bare, but heat pump and VRF manufacturers often require insulation on both lines because either can run hot or cold depending on mode. Check the manufacturer's installation manual and the project spec, and carry the insulation as its own lf line in the takeoff.

How are refrigerant line sizes selected?+

From the equipment manufacturer's line sizing tables, which key off the unit capacity, the total equivalent length of the run, and the vertical separation between the outdoor and indoor units. Bigger is not safer: an oversized suction line slows the refrigerant velocity that carries compressor oil back to the compressor, which can kill it. Long or tall runs may also require traps and a larger refrigerant charge, both of which belong in the estimate.

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Related terms

Condensate drainVRF systemHeat pumpHydronic pipingSmoke damperDuct insulation

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Figures on this page are illustrative. Construction estimates depend on project-specific conditions, source documents, market pricing, and professional judgment. Ruh's AI assists the estimator and does not replace professional review: your team reviews, validates, and approves every estimate, bid, and pricing decision.

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