Air conditioner refrigerant lines (C) Daniel Friedman Air Conditioning Refrigerant Line Installation Procedure
Refrigerant Piping Specifications & Piping Mistakes to Avoid

  • REFRIGERANT PIPING INSTALLATION - CONTENTS: Air conditioning refrigerant line defects. Refrigerant line insulation requirements & common temperatures; Refrigerant line mounting requirements & mechanical damage risks; Air conditioning refrigerant piping distances and diameters required; Allowable distances between air conditioning compressor and air handler; Why & where you will see refrigerant line brazing or soldered together at the Low Pressure & High Pressure lines
  • REFRIGERANTS & PIPING - separate article
  • POST a QUESTION or READ FAQs about HVAC system refrigerant piping or tubing routing, connections, materials, charging

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Refrigeration equipment piping for air conditioners & heat pumps: this air conditioning repair article discusses the refrigeration piping requirements, insulation, mechanical fastening, and allowable distances as well as errors in air conditioning refrigerant piping installations that risk future refrigerant leaks or malfunction in the cooling equipment.

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Air Conditioner Refrigerant Line Installation Requirements & Refrigerant Line Defects

Refrigerant line leak points (C) Carson Dunlop Associates

According to Carson Dunlop Associates Home Reference Book,

The copper refrigerant lines move the refrigerant between the condenser and the evaporator. Refrigerant lines are normally arranged in pairs, with the larger diameter line carrying gas and the smaller one carrying liquid. The larger refrigerant pipe containing cool gas is typically insulated to prevent condensation and increase efficiency.

The most common problems with refrigerant lines are mechanical damage, leakage and corrosion. Refrigerant lines are frequently damaged where they pass through the house wall. Leaking refrigerant lines are usually identified by oil deposits on the line.

Illustration, left, courtesy of Carson Dunlop Associates.

Refrigerant Line Mounting Requirements

Absence of slack in the air conditioning system coolant lines at the compressor units can cause leaks: should the compressor move, perhaps because its supporting pads settle, there will be likely leaks at these lines. You should review this question with your HVAC service person. This item may be deferred until next maintenance or service.

Our refrigerant line photo (below left) shows worn insulation and a crimped condensate drain line. Our photo of a pair of outside compressor units (below right) shows what looks like a neat installation, but the mounting of the refrigerant piping against the building wall and absence of slack is just asking for a refrigerant leak in these systems.

Refrigerant line fastener (C) Daniel Friedman Refrigerant line slack (C) Daniel Friedman

Refrigerant piping slope illustration Carson Dunlop Associates Carson Dunlop Associates' sketch (left) illustrates the installation of the refrigerant suction and liquid lines and points out that the refrigerant lines should slope downwards towards the condensing unit - a detail that helps direct refrigerant oil back towards that component.

Also notice that the extra length of refrigerant piping that may be found both indoors at the air handler and outdoors at the condenser / compressor unit should be coiled and positioned properly as well.

According to McQuay International, a large producer of refrigeration equipment,

Refrigerant lines need to be securely installed to minimize vibration that causes noise and damages piping. Reciprocating compressors, in particular, cause vibration. Steel braided flexible refrigerant lines (a must for spring isolated reciprocating compressors) minimize this vibration. ...

Refrigerant lines that rub against solid objects wear holes through copper and create a leak. For this reason, when refrigerant lines pass through walls, the line should pass through sleeved openings in such a manner that the lines do not touch. There are several commercially available pipe clamping systems that allow pipes to be held rigid without causing damage to them. Most include some form of rubber grommet around the pipe, which is then secured within a bracket. Many building codes specify minimum support spacing.

Piping should also be protected from mechanical damage. Where piping is exposed to possible damage, the lines should be routed out of the way or be protected in some form of chase.

Burying refrigerant lines should be avoided.

Refrigerant Line Installation in Buildings: Nail Protection Requirements

Use Nail and Screw Plates to Protect Refrigerant Tubing

Refrigerant piping routing (C) D FriedmanWhere refrigerant piping (or condensate drains) are routed through building walls, floors, or ceilings, if the holes drilled through framing members place the tubing too close to an interior or exterior wall surface, there is a risk that a drywall nail or screw, or an exterior siding nail will puncture the refrigerant lines.

We protect against this hazard by nailing standard nail plates across the face of each stud, joist, or rafter where this risk is present.

Our refrigerant line photo (left) shows liberal use of these nail plates on the interior face of wall studs where the routing of refrigerant lines was close to the interior wall surface.

Because the builder had not yet completed the exterior siding (just the OSB sheathing was in place), we also had to watch out for use of long siding nails that might puncture one of these lines.

Outside the building in areas where this was a concern, because the sheathing was already in place, we simply marked "no-nail" areas on the OSB.

Refrigerant Line Insulation Requirements & Proper Installation Details

Air conditioner refrigerant line insulation mistakes (C) Daniel FriedmanRefrigerant piping should be insulated

Manufacturers also recommend wrapping the insulated refrigerant lines exposed to outdoor weather, using an appropriate weatherproof tape.

For details about proper installation of insulation on HVACR refrigerant lines or piping please see REFRIGERANT PIPING INSULATION.

Crimped Refrigerant Line or Tubing Insulation

Air conditioner manufacturers include installation instructions with each unit. It's worth taking the time to read all of those details as the manufacturer has the same desire for a successful and trouble-free installation as the home or business owner or the HVAC installer.

Among these instruction details you'll read how the manufacturer wants the refrigeration lines installed, including the following:

When installing insulation over the refrigerant tubing, do not over-tighten the foam insulation (typically held in place with plastic ties or tape). Crimping the insulation along its refrigerant tubing pathway creates points of less and possibly inadequate insulation.

Missing or inadequate refrigerant piping insulation means a system that operates at a lower efficiency and it risks condensate drips into problem areas such as wall or ceiling cavities - a mold risk.

Air Conditioner Refrigerant Line Diameters & Lengths vs. Distance Between Compressor/Condenser and Air Handler/Evaporator Coil

How Far Apart Can I Separate the Air Conditioner Compressor/Condenser from the Air Handler/Evaporator Unit?

I live in a townhouse and have a split air conditioner system. The compressor is currently on the roof, but it may need to be relocated to ground level. The other unit is in the attic. How far away from the house can the compressor be (maximum, not minimum). I do not want to put the unit on my terrace, which is next to the house, because it would diminish our ability to use the terrace due to noise, etc. Could the unit be located approximately 37 feet away from the house without affecting it's function? This would place it at the back of the garden, either behind a fence or obscured by a shrub. - Anon.

Answer: Almost any A/C equipment separation distance can be made to work, but the installer will need to take a look at refrigerant piping diameter guides

Moving an air conditioner compressor to a distance of about 40 feet from a building wont' prevent it from working, but the installer might need to adjust the diameter of the refrigerant lines to be sure that the equipment is working at 100% of its capacity.

A more careful answer to your question is not so much that there is a specific distance limit between the A/C compressor and A/C evaporator coil so much as a need to get the size (diameter) of refrigerant lines and amount of refrigerant charge correct - that is, if we exceed some distance, probably like 100', we may need to increase the refrigerant piping diameter as well as the refrigerant charge for the system to work properly.

There is a more subtle technical concern with refrigerant velocity in the line. If the velocity is too low, refrigerant oil may not be properly distributed in the system. In addition to total length of refrigerant piping, the number of elbows, bends, fittings, also affect flow and have to be taken into account.

Each A/C manufacturer offers their installer technicians equipment installation instructions that include how to size refrigerant piping properly. The instructions may include complex calculations, or simply a chart of separation distances between the outside compressor/condenser unit and the inside air handler/evaporator unit.

If there is not a "table" of distances and pipe diameters for a specific air conditioning system, then the manufacturer will expect the installer whose layout is different from the usual distances to make some measurements on the system and to adjust it accordingly.

Diameter of Refrigerant Piping & Tubing

In a nutshell, the size in diameter of the refrigerant suction and supply piping needs to be determined by the installer based on the distances involved, the equipment tonnage, changes in elevation between compressor and evaporator coil, the number and type of fittings in the refrigerant piping system, ambient operating temperature ranges, and other cooling equipment specifications given by the manufacturer.

If the installer places the equipment far enough apart that s/he should have used a larger (or smaller) diameter piping system, the A/C system will still work, but its cooling capacity may be reduced.

A cooling line that is too big in diameter OR too small in diameter can cause the equipment not to work properly or efficiently.

Copper Tubing ID versus OD: internal diameter versus outside diameter

It's easy to get confused about pipe sizes or diameters when discussing flexible copper tubing. Refrigeration technicians often refer to flexible copper refrigerant tubing by its outside diameter or "OD" while plumbers usually refer to any piping by its inside diameter or "ID".

A 1/4" OD (outside diameter) flexible copper refrigerant line actually has about a 1/8" ID (inside diameter). So when you are measuring or ordering piping, make sure you and your supplier are talking about the same size by using "OD" or "ID" in your measurements.

Swaging copper tubing procedure (C) D Friedman

Storage of Refrigerant Piping or Tubing

Unused refrigerant piping or tubing should be stored with its ends capped to keep dirt and moisture out of the piping.

Refrigerant Piping or Tubing Connections

Most HVAC systems that we have inspected and all that we have installed or repaired used soldered or brazed connections for copper refrigerant piping on both suction and high pressure lines.

Some manufacturers, codes, and procedures also allow flare fittings - something we have used on some LP gas lines but in our opinion flare fittings are more leak prone than soldered connections. (We do not use compression fittings on refrigeration and air conditioning systems.)

Soldering or Brazing Copper Refrigerant Tubing or Capillary Tube Connections

In the opinion of some HVAC instructors, half of the leaks found in refrigerant piping are traced to defective soldered or flared connections so it's important to make these connections as close to perfect as you can during system installation or repair. [1]

Sections of flexible copper tubing to be soldered or brazed together are connected using a procedure called swaging.

Copper tubing swaging tool (C) Daniel FriedmanA swaging tool (see our sketch above and our photograph at left) is used to join similar-sized sections of refrigerant piping without requiring an additional coupling fixture. Swaging tools come in a range of sizes - two of mine [DF] are shown at left.

Typical swaging tools used for refrigerant piping connections handle tubing sizes 3/16", 1/4", 5/16", 3/8", 1/2" and 5/8" O.D. (Refrigerant tubing sizes are specified in O.D. or outer diameter).

The advantage of this approach is that we eliminate at least one soldered joint, increasing the reliability of the refrigerant piping system (or other piping) against leaks.

The swaging tool is inserted into the end of the copper tubing through a flare block or, if the installer is experienced, the tubing may be hand-held.

The swaging tool is carefully hammered until it has expanded the copper tubing internal diameter (ID) sufficiently to permit it to slip over the connecting copper tubing section.

The interior of the enlarged end of tubing and the exterior of the factory-sized tubing that will insert into the enlarged mate are both cleaned, primed, or fluxed and soldered according to the manufacturer's instructions, typically using silver solder, or in some applications, brazing.

Guide to Soldering Materials & Temperatures for Refrigerant Piping & Tubing

This article describes three different temperature ranges for soldering copper piping or tubing along with some general copper pipe or tubing soldering advice.

General Soldering Advice for Copper Piping or Tubing

  • Clean oxidation off of the copper tubing inside and outside before soldering, using emery cloth or wire brushes. Meticulous cleaning is necessary to get reliable solder connections and leak proof joints.
  • Use anti-corrosion soldering paste. This prevents oxidation of the copper surface when you heat the tubing or piping in the course of soldering the materials together.
  • Don't use more heat than necessary to make a soldering connection. Too much heat boils away the flux and oxidizes the copper. If you see this happening you'll have to stop, cool the copper tubing or piping, and start over at the cleaning step.

Temperature Ranges of Copper Soldering

  • 300 degF copper soldering: uses a 50:50 solder that requires little heat. The solder flows like water - it's easy. (50:50 lead solder is no longer used in plumbing applications out of concern for lead in water supplies).
  • 500 degF copper soldering: using 95:5 solder to get more heat to get the solder to flow.

Capillary tube soldering advice (C) D Friedman

  • 1150 degF copper soldering: silver solder, use on big refrigeration systems, use when there are wide temperature variations (to withstand the expansion/contraction); can cause flaking inside the copper line, so in refrigeration applications, good practice flush the lines with nitrogen and flush them with nitrogen too while soldering; silver soldering is also used when there are variations between the two metals joined, e.g. steel to copper.

    The joint has to be red hot. Watch out to avoid using this process too close to 95-5 solder joints or they will melt.

The copper tubing ends to be connected are cleaned, sanded, treated with soldering or brazing flux, and soldered or brazed.

When a capillary tube is to be soldered take are not to place soldering flux too far into the joint or the solder may flow over and close the end of the capillary tube. (see our sketch).

Advice for Making Flare Fitting Connections with Copper Tubing or Piping

Flare fitting (C) D Friedman

Watch out: in our OPINION (and that of other HVAC technicians) compression fittings should never be used and in best practice flare fittings should also not be used on refrigerant gas or liquid piping. Soldered connections are much less likely to leak under the harsh conditions to which refrigerant piping is subjected: vibration, high pressures, high temperature swings, and outdoors, weather exposure.

  • When you cut copper piping or tubing using a saw (rare) or a copper pipe or tubing cutter (the usual practice) the cutting wheel may leave a lip of copper on the inside of the copper pipe or tubing.

    For soldering or flaring copper piping, you will want to remove this lip (to be sure that the full diameter of the pipe is available to avoid a flow restriction, and when making a flare fitting in particular, be sure also to remove burrs in the copper pipe or tubing end before attempting to create the flare end of the tubing using your flaring tool.

    Plumbing and HVAC supplies sell special reaming tools used for this purpose. Don't over-do the reaming or you may create an over-thinned tapered edge of your flare that will crack during expansion, but be sure that all burrs are removed.
  • Put the flare nut onto the tubing before making the flare - you'll only make this mistake once.
  • For 1/4" OD tubing, the end of the tube extends about 1/8" above the flaring block at the start of the flaring procedure.
  • The flare that you create should fit snugly inside of the nut, extending to fully cover the tapered seat inside the nut, and it should exactly cover the face of the flare fitting.
  • Also see "Identifying Sources of Leaks at Brass Flare Fittings ..." found at GAS LEAK DETECTION, LP / NG where we illustrate examples of causes of leaks in flare fitting connections

Refrigerant Piping Sizing and Run Length: refrigerant pressure drop and temperature loss

For example, measuring the refrigerant gas line pressure drop (or temperature change) on the suction line (return to the compressor) will show (typically) that a 4 degree temperature loss through the refrigerant line will result in an 8 percent loss in cooling capacity of the system.

Or on the discharge line (output from the compressor) will show (typically) that a 4 degree temperature loss through the refrigerant line will result in a 2 percent percent loss in cooling capacity of the system.

So it's not that the air conditioner won't work at all if the compressor/condenser is located at an unusual distance from the air handler/evaporator coil, it's more that it may lose some capacity and have to work harder - meaning higher electrical bills and in extreme cases, shorter equipment life.

Equivalent Refrigeration Piping Length to Include Fittings, Controls Devices

ASHRAE[7] and some air conditioner manufacturers such as McQuay[6] provide a refrigeration piping guide that gives complete, detailed guidance and charts on refrigerant line sizing (diameter) as a function of length of run. The company points out that the entire liquid refrigerant line is composed of more than just piping, and includes

  • The length of refrigerant piping itself
  • The elbows or other fittings used to joint refrigerant piping between the cooling coil/evaporator and the compressor/condenser unit
  • Any filter driers installed (one or in some cases two)
  • Any isolating devices, control valves, etc.

Each of these devices or components contributes volume to the refrigerant piping system and must be considered in designing the "equivalent length" of the entire refrigerant piping system in order to determine the proper refrigerant charge. For example,

  • A 1/2" nominal diameter globe valve or solenoid valve contributes an equivalent of 17 feet of refrigerant piping
  • A 1/2" nominal diameter filter drier contributes an equivalent of 12 feet of refrigerant piping
  • A 1/2" nominal diameter suction line filter contributes an equivalent of 15 feet of refrigerant piping

Technical Note on Refrigerant Piping: HVAC economizer detail using refrigerant line brazing or soldering together of the Low Pressure & High Pressure lines for deliberate heat exchange

In some refrigeration system designs, a low-temperature (heat laden) vapor line (suction line) is soldered alongside the high-temperature, high-pressure liquid refrigerant line. This conjoining of the two refrigerant lines is likely to be done where the vapor line is entering the compressor/condenser unit.

The purpose of this line-to-line soldering is to act as a heat exchanger, to reduce the temperature of the liquid refrigerant that is going to enter the metering device (TEV or cap tube), gaining some benefit to system operation - we want a lower refrigerant temperature at the point where the liquid refrigerant is about to be metered or released into the cooling coil (evaporator coil in the air handler).

A second benefit of this heat exchange is that in the larger suction line entering the compressor, the refrigerant enters at a higher temperature, easing the compressor's job of compressing and raising the refrigerant temperature on the condenser side, so that the refrigerant is (by being hotter) better able to transfer heat to ambient air in the environment around the condensing coil.

Other forms of air conditioner and heat pump economizers and economizer tricks of the trade are discussed at AIR CONDITIONING HEAT PUMP SAVINGS

Continue reading at REFRIGERANT PIPING INSULATION or select a topic from the More Reading links shown below.

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