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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.

Also see REFRIGERANT LEAK DETECTION and INSTALLATION ERRORS, COMPRESSORS. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

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Air Conditioner Refrigerant Line Installation Requirements & Refrigerant Line Defects

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.

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 Insulation & Nail Protection Requirements

Use Nail and Screw Plates to Protect Refrigerant Tubing

Protect Refrigerant Lines & Their Insulation Outdoors

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

Effects of Missing, Damaged, Crimped Refrigerant Line 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

Question: 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.

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

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 leakproof 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.
• 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 fils 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.

Advice for Making Flare Fitting Connections with Copper Tubing or Piping

• 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 where we illustrate examples of causes of leaks in flare fitting connections

More Details about 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.

Some air conditioner manufacturers such as McQuay provide a refrigeration piping guide that gives complete, detailed guidance and charts on refrigerant line sizing (diameter) as a function of length of run.

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

Questions & Answers about HVAC system refrigerant piping or tubing routing, connections, materials, charging

Question: can I use standard 3/4" diameter copper piping instead of flexible 3/4" copper tubing for the refrigerant suction line?

I am running the piping for my central air unit. I will have a qualified HVAC technician make the connections.

I have no problem bending the smaller 3/8 tubing. However, I am having a difficult time installing the ¾ line without crimping the pipe.

My question is can I use standard ¾ inch cooper piping instead of the ¾ in tubing? I’m good at plumbing.

I could then neatly run the pipe to within a foot of the condenser and coil and have the technician complete the install. Thanks for your help and the great website. Steve

Reply: Yes but ...

Certainly I've seen [DJF] commercial HVAC installations where larger diameter soldered-joint copper piping was used for refrigeration liquid or gas movement - there is no conceptual problem with that approach but

• more solder joints rather than flexible tubing bends increases the risk of a leaky joint, so choice of high quality copper (type M?) and joint soldering or brazing workmanship and proper soldering materials will be important
• as with any new air conditioner or heat pump installation, the amount of refrigerant charge may need to be adjusted to accommodate the volume within the refrigerant piping system.

Bending copper tubing - tips for

Incidentally, among my plumbing tools I keep a set of tightly coiled springs of appropriate inner-diameter to slip over flexible copper tubing that needs to be bent without crimping or kinking. These springs, sold at HVAC suppliers, slip over the tubing in the area where you want to make the bend, and the steel of the spring holds the copper tubing keeping it round so that you can make a bend without any crimps.

Also you may have noticed that even smaller diameter flexible copper tubing can become increasingly difficult to bend and re-bend in the same area of tubing. That's because as you bend the tubing the heat of the bending process alone is sufficient to anneal the copper, making it harder. So we try to get the bends nice and neat and right the first time.

Question: Are exposed copper refrigerant lines ok outdoors?

Is it safe to have all copper refrigerant lines installed on the outside of the house? Thank you, Caren

Reply: Yes but refrigerant piping should ben insulated, supported, and where outside, wrapped

A competent onsite inspection by an expert usually finds additional clues that help understand whether or not there are problems with your air conditioning system or its installation details. If you see signs of amateur workmanship on one part of the system it's appropriate to raise a question about other installation details that may not have been noticed, and thus to take a closer look.

That said, it is perfectly normal for copper air conditioner or heat pump piping to continue outside the house in order to connect to and from the compressor/condenser unit.

However air conditioner manufacturers and other expert sources include installation instructions that specify that the refrigerant lines should be insulated, supported, and wrapped with a weatherproof protective tape. Also be sure that the opening in the building wall where the refrigerant lines emerge has been properly sealed against leaks and insect pests.

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AIR CONDITIONING & HEAT PUMP SYSTEMS

A/C - HEAT PUMP CONTROLS & SWITCHES
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• Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• Thanks to reader Anon. for discussing the allowable distance between air conditioner compressor and a building or from the air handler - July 2010
• ASHRAE Handbook Refrigeration, Chapter 2, 2006. © American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., www.ashrae.org
• Refrigerant Piping Design Guide, McQuay Corporation, Americans HQ: 13600 Industrial Park Blvd., Minneapolis, Minnesota 55441, 800-432-1342 (Toll Free) 763-553-5330 (Direct), 763-553-5177 (Fax). Web search 07/15/2010 original source: http://www.mcquay.com/mcquaybiz/literature/lit_systems/AppGuide/AG_31-011_120407.pdf - quoting:
  McQuay International delivers engineered, flexible solutions for commercial, industrial and institutional HVAC requirements with reliable products, knowledgeable applications expertise and responsive support. As part of Daikin Industries, a Fortune 1000 company, McQuay is the second largest air conditioning, heating, ventilating and refrigeration company in the world. 
• [1] "Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.

• Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
• Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
• "Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
• Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
• Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
• Air Conditioning Inspection, Diagnosis, Repair, Efficiency all the basics for home owners, inspectors, new repairmen
• Air Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard
• Asbestos HVAC Ducts and Flues field identification photos and guide
• Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation