Air conditioner refrigerant line insulation mistakes (C) Daniel Friedman Refrigerant line insulation installation
for air conditioners, heat pumps, refrigeration equipment

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Guide to proper installation of insulation on refrigerant piping:

Why is refrigerant piping insulation needed, what problems occur if the insulation is incomplete, missing, crimped, or otherwise improperly installed, and how do we fix these problems.

What types of insulation are used on refrigerant tubing sytsems & where can the insulation be purchased? How is the insulation secured to the refrigerant tubing? Is it necessary to insulate refrigerant piping where it runs through ceilings and walls?

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Proper Method for Installing Insulation on Air Conditioning & Heat Pump Refrigeration Lines & Condensate Drains

Refrigerant line insulation (C) Daniel FriedmanHere we describe defects in refrigerant piping insulation, problems caused by defective refrigerant piping insulation, recommended installation practices for refrigerant tubing insulation in building walls or cavities as well as outdoors where exposed to the weather, and interior leaks on & in wall below a split system air conditioner wall-mounted unit traced to missing insulation.

Avoid gaps and missing insulation along the refrigeration lines

Proper placement and securing of insulation on air conditioner or heat pump refrigeration lines is important to avoid condensation leaks into the building. One, or on some systems both refrigeration lines can be cool or cold under some operating conditions.

The cold copper tubing in contact with warm humid air causes moisture in the air to condense onto and then drip off of the refrigration lines.

The result can be leaks into the building, as our photo at left illustrates.

Missing or damaged refrigerant line insulation insulation On the refrigerant lines, particularly on the larger suction line, will cause condensation and drips from the lines in humid areas.

Air conditioner refrigerant lines exposed outdoors (C) Daniel Friedman

In our photo at above left where refrigerant line insulation is incomplete, the drip stains on the attic floor may well indicate a point at which leak stains or even mold appear on the ceiling below.

In our photo at left none of the refrigerant lines are insulated where they emerge from the building wall.

If the lines were also uninsulated within the wall, depending on their location and the wall's dew point properties, a condensation, leak, mold, rot, or insect problme can ensue.

We have seen very costly building damage where lines were not properly insulated indoors: condensate drips wet gypsum board walls, leading to a costly mold remediation project.

Missing refrigerant line insulation also may increase system operating cost or in addition to a condensation worry, uninsulated high pressure refrigerant lines may result in unwanted heat transmission into some building areas..

Insulated refrigerant lines (C) Daniel Friedman

Here we illustrate a neat insulation job visible on the outdoor portion of refrigerant piping for a split system ductless air conditioner installlation.

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

Suction lines are cold – 40°F (4.4°C) SST – and cause condensation, even in conditioned spaces. In addition, any heat that enters the refrigerant adds to the superheat and reduces system efficiency.

For these reasons, suction lines should be insulated with a vapor proof insulation. This is a requirement of many building codes. Rubatex is the most common form of refrigerant line insulation.- Thanks to professional home inspector Stephen Stanczyk in Washington State ( for editing assistance.

Liquid lines generally are insulated. They are warm to hot (110°F (43.3°C) for air-cooled). If liquid lines pass through a space that is warmer than the refrigerant (i.e. the roof of a building at roof level), or if they could be considered hot enough to pose a safety risk, then insulation should be added.

Discharge lines are generally uninsulated. They may be very hot, in excess of 150°F (66°C), so insulation may be warranted as a safety consideration, or if the heat loss from the discharge gas line would be considered objectionable to the space.

Hot gas bypass lines should be insulated, especially if the runs are long or if the piping is exposed to cold temperatures.

Watch out: condensation on the suction line and at the bottom of the compressor could be an indication of excess liquid refrigerant returning to the compressor via the suction line. This liquid slugging of the compressor can damage or destroy the motor. We discuss refrigerant flooding and six common causes of liquid refrigerant slugging the compressor


Do Not Compress Insulation on A/C or Heat Pump Refrigeration Lines

Compressed AC refrigerant line insulation leaks (C) Daniel Friedman

The same split system air conditioner installer we described above

at A/C CONDENSATE DISPOSAL for Ductless or Split System Air Conditioners

violated the manufacturer's recommendations against compressing the insulation on the refrigerant lines - one more picky issue that we decided to let go since the wall was to be insulated with blown-in foam.

But he made the same mistake on the insulation on the refrigeration lines and condensate drain where they extend outdoors between the building wall and the compressor/condenser unit.

Our photographs illustrate that the importance of not compressing refrigeration line insulation is no joke.

In our photo below, notice those drip stains below the condensate lines at each location where the insulation was compressed by a too-tight plastic tie?

Air conditioner refrigerant line insulation mistakes (C) Daniel Friedman

And in the two photos at below, notice the incomplete insulation on the refrigeration line?

It leaves me worried about condensation and water accumulation inside the wall cavity as well. Since I know this installer is not stupid we're left thinking he has a bit of contempt for his customers, or a limited concept of workmanship.

Air conditioner refrigerant line insulation mistakes (C) Daniel Friedman

Imagine that same dripping and accumulation of water where the installer made the same mistake in a fiberglass-batt insulated wall or a wall or ceiling inside which the dew point may be reached on the refrigeration lines?

The accumulation of water in a building cavity is asking for a costly mold, insect, or rot damage problem later on.

Air conditioner refrigerant line insulation mistakes (C) Daniel Friedman

Missing insulation on the refrigeration lines outdoors is not a catastrophe - at least for a short un such as at this split system compressor/condenser unit.

Perhaps a little loss in efficiency of the system operation in some weather conditions.

Air conditioner refrigerant line insulation mistakes (C) Daniel Friedman

On a long refrigeration line run, say between an attic air handler and a ground level compressor/condenser, the effects may be more significant.

We removed the leaky, incomplete, and ugly squashed insulation on the refrigeration lines for this system (above left), replacing the squashed foam insulating tubing with new insulation (shown below)

.Air conditioning refrigerant line insulation squashed (C) Daniel Friedman

Below you can see the new refrigerant tubing insulation being installed: we're peeling out the edge tape so that the split foam insulation sides can adhere to one another.

Air conditioner refrigerant line insulation mistakes (C) Daniel Friedman

Incidentally, just clipping off the old plastic wire ties to "release" the squashed refrigerant line foam insulation won't work: after a few months the insulating foam remains permanently squashed, as you can see in our photo at left.

We paid particular attention to sealing and insulating the refrigeration line at the exit point from the building wall, reducing the chances of leaks into the wall at that point.

To keep the refrigeration line insulation in place you can still use a plastic tie if you like - just don't tighten it so far as to squash the insulation.

Air conditioner refrigerant line insulation mistakes (C) Daniel Friedman

The manufaturer (Sanyo) recommends covering the foam insulation on the refrigeration line with weatherproof tape which we did at the end of this job.

I admit that we "over-designed" the final insulation job shown in our last photo with that extra layer of foam that surrounds both lines, as we used more thickness of insulation than necessary. We did so to end with a neat, weather-protected job that, combined with the application of black weatherproof tape, should last for a long time.

Notice that the aluminum or plastic ties used to hold components in place were left loose - we did not squash the new refrigerant line insulation, and we made sure it was continuous, neat, and protected from the weather.

A neat installation takes what, maybe five minutes longer than a sloppy one, but it took about an hour to buy the replacement refrigerant line insulation, remove the original sloppy installation, and do the job right the second time.

Protect outdoor refrigerant line insulation from the weather

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

Interior Leaks On & In Wall Below a Split System Air Conditioner Wall-Mounted Unit Traced to Missing Insulation

Split system A/C wall unit condensate leak (C) Daniel Friedman

Watch out: The split system air conditioner installer we described

at A/C CONDENSATE DISPOSAL for Ductless or Split System Air Conditioners

violated the manufacturer's recommendations against compressing the insulation on the refrigerant lines not just outside or in the walls, but also inside the wall-mounted unit itself.

During the first season of use of the newly-installed Sanyo split system air conditioner the building occupants noticed water stains and rippled wall paint extending down the wall below the indoor air handler cooling unit.

Our photo (left) shows where the refrigerant lines rise in the wall to enter the wall-mounted half of the split system air conditioner (that larger white area below the left end of the unit) and the blue tape marks where we first saw condensate water dripping from the unit.

On inspection we ran the air conditioner for an hour or so on a hot humid day, then inspected the wall surface for moisture. Simply touching or pressing on the plastic bottom of the wall-mounted cooling unit sent a cascade of water droplets down the building wall interior surface.

We gave our A/C installer a call and asked for help. To his credit, the tech came immediately to the job site.

Disassembling and inspecting the indoor cooling unit by removing its plastic cover and then lifting it carefully away from the wall mounting bracket (watch out to avoid bending refrigerant lines and causing a refrigerant leak), he found that there was no insulation whatsoever on the refrigeration lines that ran horizontally along the rear bottom of the unit.

The result was condensation on the refrigeration lines that did not drip into the unit's condensate tray but rather fell into the plastic bottom where water leaked out onto and into the building wall.

The condensate tray in a wall-mounted split system air conditioner or heat pump unit is designed to catch water condensing on the cooling coils, directing it to a drip pan and then to the condensate drain line.

But depending on routing of the refrigerant lines, these may provide another source of condensation that does not fall into the tray.

The "fix" for this condensate leak was the installation of foam insulation along the refrigerant lines inside the unit, from their point of exit from the building interior wall surface to their point of connection to the cooling coil. The leak was stopped.

Reader Question: is it OK for an air conditioner or heat pump installer to substitute the brand of copper refrigerant line insulation?

PDM insulated refrigerant line set - source: 2016I’m having a Mitsubishi ductless mini split installed. The contractor uses PMD Gelcopper insulation instead of the Mitsubishi type. Is making the switch a good idea?

Thanks,M.A. [private email], 2016/03/24

[Click to enlarge any image]

Shown at left: PDM Gelcopper insulated copper refrigerant-tubing line set from PDMUS. This product provides pre-insulated copper refrigerant tubing.

The insulation is polyethylene closed-cell foam on copper tubing. Detailed technical specifications and the ASTM Standards with which this product complies are provided by the manufacturer at the web page we cite below.


Fair question, M.A., I don't know for sure what insulation you are asking about. Insulation on what

? I presume you refer to PDM (not PMD) foam insulation on refrigerant tubing on a split system A/C or heat pump. As long as the insulating properties and weather and damage resistance of the alternative insulation meet the original Mitsubishi specifications I doubt that there is a concern with the change you cite.

You can of course contact Mitsubishi directly to ask if they have an opinion.

PDM Gelcopper is a polyethylene closed-cell foam refrigeration tubing insulation. I'm doubtful that changing the insulation choice affects system operation. Of course depending on where the insulation is installed its life may vary. For example insulation products vary in durability where exposed to sunlight and weather. Here is what the manufacturer says:

R410a approved: Gelcopper can be used in applications where high-pressure gases are used as refrigeration source. UV resistant: Gelcopper is UV resistant Paintable: the insulation can be painted to match the surroundings.

PDM US recommends product installation under plastic duct to protect it from severe weather conditions, accidental damages or theft.


Continue reading at REFRIGERANT PIPING INSTALLATION or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see REFRIGERANT PIPING INSULATION FAQs - questions and answers about insulation on refrigerant pipes or tubing, posted originally at the end of this page.

Or see REFRIGERANT PIPING UNDERGROUND, BURIED where we note proper insulation & protection for buried refrigerant tubing

Or see these

Air Conditioning & Heat Pump Refrigerant Articles

Suggested citation for this web page

REFRIGERANT PIPING INSULATION at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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