Refrigeration equipment piping questoions & answers for installing air conditioners & heat pumps:

How-to and diagnostic questions & answers about the installation of HVAC refrigerant system piping or tubing.

These questions add details about selecting, mounting, and connecting refrigeration tubing or piping used in air conditioner & heat pump systems.

This air conditioning repair article series 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.

Air Conditioner Refrigerant Line Questions & Answers

These questions & answers about refrigerant gas piping installation, repair, troubleshooting were posted originally at REFRIGERANT PIPING INSTALLATION - be sure to review that article.

On 2016-10-21 by (mod) - support the refrigerant line below the mobile home floor

Mike, I'd support the refrigerant line below the mobile home floor or if it is going to be in ground contact I'd use plastic-coated copper refrigerant tubing.

On 2016-10-21 by mike

hi, running a/c line from a/c unit out back to blower on side of house/ old one leaked / under mobile home can it be laid on ground or do they have to have hangers ? thanks

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: what kind of fitting is used on a Carrier Air conditioner that attaches freon line to condensing unit -

Need to know what kind of fitting is used on a Carrier Air conditioner that attaches freon line to condensing unit - VInce

Reply:

Vince the two common piping attachment on refrigeration lines are soldered/brazed copper tubing at which a female connecting end is prepared using a swaging tool, and in some communities, carefully-prepared flare fittings. Details are in the article above.

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.

 

Question: why are the refrigerant lines vibrating noisly - it sounds like a freight train!

(July 5, 2011) Maura said:

What would cause the refrigerant lines to vibrate so loudly it sounded like a freight train? What is considered normal vibration of the gas line? Because now causes copper line to vibrate very loudly. The new unit was installed last year, but problem just started. Thank you for any advice you can offer

Reply:

Maura:
Refrigerant lines don't normally cause vibration noises, since they are expected to be covered with foam insulation and thus wouldn't transmit vibration to the building; but if the equipment to which the lines are attached is itself vibrating it is certainly possible that the copper tubing carrying refrigerant could pick up that motion and where the tubing is in contact with the building it could transmit vibration noises.

Don't "solve" the problem by just isolating the piping from the building with foam - that's treating the symptombut not an underlying problem.

I'd start by looking for the source of vibration - it's more likely to be a compressor that is not mounted properly, has some loose component, or if originating indoors, a loose fan motor mount or blower assembly. Let us know what you find as it may help other readers.

Reader follow-up:

Thank you Dan I will try to explain exactly what happened. Had a power outage about 2 weeks ago, when the power came back on an extremly loud noise was coming from basement. It was the lines coming from ac unit. Noise was very loud! Turned circuit breaker off than back on it stopped. Unit was also working. Called ac guys said it was a power surge, I don't know.

Then a few days later the lines started to make a similar noise but not as loud turning power off did not stop it. Realized copper pipe was vibrating up against insulated pipe.

Called ac guys again because noise would not stop all they did was tape the copper wiring to stop the vibrating not really addressing why it is happening in first place. I asked if it might be a problem with compressor. Asked them check they put a hardstarter on which I know I don't need because that is not the problem.

Then again last night air cycled on, the very very loud noise started again only lasted 10 seconds and stopped.

AC guys just left still telling me possible brown outs from electric co. I don't think so. Have you ever heard of anythin like this? Shoul I have them replace compressor it is still under warranty. Thank you very much any advice would be helpful.

Reply:

We need to know if the vibration originates with the outside compressor/condenser or the indoor air handler unit. If it's outside in origin, and because replacing a compressor is costly, you'd sure want that done (if needed) under warranty.

A power surge can damage a control board - in fact more likely than damaging the compressor itself. I'd ask for some more careful testing of the equipment that is buzzing.

Reader Follow-up:

Thank you Dan, it is definitely coming from the compressor/ condenser unit and much more than a buzzing noise. If you email your phone# I will call you and play back the recordings of the noise they are extremely loud!!! I am not sure if what ac guys are telling is accurate. Again thank you for your expertise, I greatly appreciate.

Reply:

Having just arrived on an assignment out of the U.S., a phone playback is probably not practical, but certainly from what you have described, an accurate diagnosis of just what part(s) is (are) failing is in order; call the service co and ask them to send a senior technician.

You might point out that the first tech, who taped the lines, appears not to have the experience to recognize that there is a problem.

You can also ask your electric company if they have been reducing voltage or if there have been brownouts in your area - explaining that you are diagnosing an electrical question, and making clear you aren't coming to them with a claim.

Question: I can't use copper refrigerant piping in my facility

(Apr 10, 2012) Joe said:

I am installing a 'mini-split' style 3 ton a/c unit. I absolutely can not use copper lines in my facility. It has been done previously using hoses and connectors. What is the max PSI on a typical split 3 ton units refridg. lines?

Reply:

Joe: take a look at the specifications for operating pressure of the equipment you are installing. Typically you could be looking at a safe pressure rating of 200-400 psi. And the rating for hoses protected with metal braiding.

See REFRIGERANT PRESSURE READINGS & CHARTS

Question: what is the effect of short refrigerant piping

(Apr 24, 2012) MHND said:

what is the effect of short pipes between indoor & outdoor split AC unit

Reply:

MHND maybe you need to send me a photo - I don't understand the question. The refrigerant charge on a system with long piping could require adjustment, and of course the pipes have to be supported and insulated, but they don't impact the system operation in either direction of length other than computing the proper charge quantity.

Now if you mean that a compressor/condenser was installed with no slack or loop to allow the piping to tolerate vibration, that's asking for a refrigerant leak.

Question: buried refrigerant lines

(June 6, 2012) Soo said:

We just bought a new home and discovered that the home inspector and the county inspector both missed the fact that the refigerant lines outside the house going to the compressor are buried underground.

There is a concern now that we have a freon leak in that 30 foot section of pipe that is outside and under a foot of dirt. If the lines were insulated prior to being buried, is the concern of a leak valid?

Reply:

Soo,

The diagnosis of a refrigerant leak will center around the operation of your system and refrigerant charge measurement, not the refrigerant pipe routing. However depending on your climate and the insulating materials used, your piping insulation may not be effective.

Burying refrigerant lines was probably done to avoid damage that might occur to lines routed over ground for the distance you describe, though we don't understand why there was a need for 30 feet of separation distance.

Happily the shallow depth means it's trivial to excavate and replace leaky piping, perhaps using a protected conduit for the replacement to make service in the future easier.

Question: ice on the refigerant line

(June 9, 2012) Cliff said:

I had a small block of ice around the the refrigerant line coming from ac unit outside after running it. What does this indicate?

Reply:

Cliff:

Ice on a short exposed section of refrigerant line most often means that insulation is missing at that location. Persistent icing at the coil or other locations can indicate low charge and a refrigerant leak.

Question: ok to run the A/C for a long time?

(June 11, 2012) Zev said:

Can running a central A/C unit set for 66F for along periods of time damage the unit. I live in Washington, DC where it's frequently hot and humid.

Reply:

Zev, running a central A/C for "long periods" - even several days at a time should not damage the unit, though it may damage your wallet when the electrical bill arrives. The equipment and its wiring and overcurrent protection, if properly installed, is designed to safely operate continuously for extended intervals.

Question: compressor is tripping the circuit breaker

(June 22, 2012) Bobby said:

I live in Denver and keep my a/c set around 65-67F degrees. Recently, with the hotter temps and moderately higher humidity, the compressor has been tripping the breaker, causing the unit to blow warm air. I just moved from New Orleans 6 months ago and am not familiar with differences in a/c performance/limitations between NO and Denver.

My landlord's a/c tech says that the higher altitude will cause the a/c system to be overworked if the thermostat is set below 72F. I have been unable to find any information to substantiate his assertion. Is there any truth to this?

Reply:

Bobby if the circuit breaker is tripping the compressor motor or some other component is drawing abnormally high current - a sign of trouble. It's possible that a failing compressor motor doesn't show up until it's been working extra hard.

In sum Bobby, I have not come across your landlord's claim. more likely the compressor is failing and drawing overcurrent, or is hard starting.

Question:

(June 24, 2012) david said:

I have received quotes from different companies to replace my 20 year old 4 ton central a/c system. The existing system has 3/4 inch copper tubing for the refrigerant. I am looking at replacing the unit to a 4 ton Infinity or Performance series Carrier or a XR or XLi series Trane system.

One company said that it would be necessary to run a new 7/8" line. Another company said the existing line would be fine as the newer refrigerant flows easier. The esimated lentgh of the run between the air handler (inside the house) and the compressor (outside of house)is about 50'. What is the correct answer.

Reply:

David, I don't know why the piping needs replacement unless it's damaged or leaky. A larger pipe just means a larger refrigerant charge, right? Please ask the first co why a new line is needed. The "flow easier" argument sounds nonsensical to me but probably that's because the fellow speaking with you was not an English major.

Perhaps what was meant was that to achieve adequate refrigerant flow rate in a high capacity system larger diameter piping is required.

Question: solder suction and high pressure refrigerant lines together?

(June 29, 2012) JohnSmith said:

My refrigerant lines go about 10' vertically down the outside wall of my house. They are right next to each other. If I solder them together would it increase the efficiency of my unit? It's a 3.5 ton R22 heat pump. Thanks.

Reply:

In general I think the answer is yes. How about giving the manufacturer of your unit a call at their tech support number for confirmation that you're not creating any problem.

I wouldn't do it, however. I'd worry about creating oxidized crud inside the piping - which then fouls the refrigerant metering equipment, as well as increasing line rigidity, perhaps increasing damage risk, and certainly making future refrigerant line replacement more costly.

Question: will the AC unit work with extra length of refrigerant line?

(July 28, 2012) Steve said:

If the tech left more coolant line than needed but still charged the unit for the amount of line he had will the unit still work as it is supposed to.

Reply:

Steve I'm not sure "more coolant line than needed" is quite the case - good practice leaves some slack, even an extra coil, so that vibration and slight movement don't rip open a brazed refrigerant piping joint.

The refrigerant charge used by the HVAC tech normally includes an allowance for the total length (and diameter) of piping in the system. If the charge is too low you'll probably discover it as frosting at the cooling coil.

Question: re-use refrigerant lines

(Aug 19, 2012) Tom D said:

I have concealed 1/4 and 1/2 inch copper lines that feed my existing split case heat pump that recently died. Can I reuse these lines for a larger size heat pump system that says is needs 3/8 and 5/8 inch lines? My existing lines are embedded in the wall

Reply:

Generally if the refrigerant piping is larger in diameter than needed that's not an issue except for having to calculate the refrigerant charge correctly. Lines that are too small may limit the system's operating capacity.

Question: cut and cap unused refrigerant lines

(Oct 2, 2012) John said:

I am demoing my ac unit. its old and i do not use it anymore. I wanted to know if i could just cut the copper lines and cap them in case i want a new on in the future.

Reply:

I agree that soldering a cap in place on the refrigerant lines makes sense to keep them clean for possible future use.

Question:

(Nov 18, 2012) Dave said:

After meeting EPA requirements for demolition of a system, it is best to totally remove all system piping and not reuse it due to unkown conamminants which could damage a new system.

Reply:

Thanks for the opinion Dave. But of course when a new system is installed, a filter/drier is installed as a matter of course. And previously used, clean copper tubing that was kept sealed ought to be as clean as copper tubing that was sitting somewhere in a warehouse.

I'd agree however that if older copper refrigerant piping was damaged, corroded, or had previously leaked I'd junk all of it rather than use suspect piping on a new installation.

Dan

Question:

(May 5, 2014) vm said:

I am told that a wire rubbed against the copper pipe on the out door unit. They said the vibrating caused the wire casing to wear off and cause the bare wire to puncture the copper pipe. Now the home warranty company is not covering it claiming that it is not "normal wear and tear". Is this correct? or are they just trying to get out of paying?

Reply:

VM

My opinion is of course the insurer wants to avoid paying on a claim. You need help from an attorney familiar with home warranty policies to review the terms of your policy. A wire rubbing that causes a refrigerant leak sounds like an installation error or a product defect.

Keep us posted.

Question: using running boards to support refrigerant piping

(May 31, 2014) Petra said:
We have to install refrigerant lines in the attic. Could we use running boards (e.g. 2x4 lumber) which would run at an angel to the trusses to shorten the distance between coil and condenser?

Reply:

Petra

That sounds quite reasonable. Don't cut or modify trusses.

Question: covers for refrigerant piping for a heat pump

Where can I find the plastic covers for my heat pump lines that run on an exposed wall.

Reply:

Your local HVAC supplier carries piping covers and insulation. You may also find these products at building suppliers such as Loews or Home Depot.

Question: damaged refrigerant piping insulation

(Oct 30, 2015) shankar guggari said:
The acis parts deteles sinds

(Nov 1, 2015) Daniel said:
Rats have chewed all the black insulation off the copper refrigerant line in my mother's split system, it's the type of insulation that is actually bonded to the pipe somehow, what is best way to repair this? thank you.

Reply:

Bummer. I think you'll have to pull off enough of the remaining insulation that you can install slip-over add on insulation; you'll buy insulation in lengths that have a split along one side to just open and slip onto the existing refrigerant lines.

Question: Distance from roof deck to have A/C or other lines?

(Nov 19, 2015) Alex D said:

Any building code experts here? Distance from roof deck to have A/C or other lines?

I'm trying to find if there is a code that states how far away from the residential roof deck items can be placed. Namely A/C and gas lines. There's no way a roofer can know if there is an A/C line or gas line buried under insulation next to the roof deck. I've heard it's anywhere from 6" to 3 '.

I was just curious if anyone had a code number and description for that. Most cities subscribe to the different international building codes.

Thanks for you help!

(June 24, 2016) Lou gallegos said:
How far away does the refrigerant supply line have to be off roof deck osb

Reply:

Alex:

I can't cite a specific code provision on refrigerant line piping placement in roof decks, but generally with any piping or wiring it is run in the center of joists or studs (or rafters in a flat roof) and if lines are run close to the surface of the wood framing member they must be protected with steel plates.

You can see examples of this protection at

inspectapedia.com/aircond/Refrigerant_Piping_Insulation.php - REFRIGERANT PIPING INSULATION (see the page top photo)

The following excerpt

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.

is from inspectapedia.com/aircond/AC_Guide_McQuay.pdf Refrigerant piping design guide by McQuay

Lou:

I think there's a trick lurking in this question, Lou. In some circumstances there's no harm in refrigerant piping touching OSB, but

- a hot roof deck may affect HVAC system operation by raising piping temperatures abnormally

- routing that permits the piping to touch the underside of a roof deck makes me think someone is drilling holes through the tops rather than center of rafters in a construction where finish-ceiling surfaces prevent attaching to rafter underside.

Question: use fiberglass insulation on refrigerant piping lines?

(May 2, 2016) Cole said:
I am a retired plumber, not an HVAC Tech.

I am planning to install a condenser on a flat roof just outside of my attic-installed FAU. The distance between the two is only about 15-20ft.

I happen to have some extra fiberglass insulation I had bought for my Potable Hot Water piping system. Will this work to insulate the liquid and vapor lines between the coil and the condenser? It's approx. 1" wall thickness; and I would use a weather proof jacket where it runs outdoors.
Thanks, Cole.

Reply:

Cole:

I would hesitate to try fiberglass insulation on outdoor HVAC refrigerant piping: it will pick up and hold moisture, not insulate, deteriorate, and in freezing weather, freeze and ultimately fall apart. Instead I'd use slip-on or split-and-clip foam insulation designed for use on refrigerant tubing.

In the article links above see REFRIGERANT PIPING INSULATION for details.

Question: run refrigerant piping above ground or under-ground?

(May 23, 2016) Reynan said:

Refrigerant piping between ACCU and AHU (big units) should be underground or above ground installation?

Reply:

Not specified.

(May 27, 2016) Reynan said:
Meaning either above or below ground is acceptable?

Mod said: yep. Adequate protection from damage, insulation, and corrosion are of course required.

Question:

(June 7, 2016) Bill Paxton said:
What are the requirements for line set support in the attic? Type and spacing?

(June 21, 2016) Rosemarie Greaser said:
I live in an outside unit of a four-plex.

My air condenser and the next door neighbor's air condenser are outside my unit. My neighbor had to have a new condenser installed and the company is telling him that the copper piping that runs under my part of the building to his part of the building are leaking.

They want to run piping up my side of the wall outside, through my attic and then down to his air handler in his garage. I don't think the piping is leaking and don't really want freon pipes through my attic. Is this a safe alternative or is there another solution? Anxious for your answer.

Reply:

Rosemarie,

Refrigerant piping run through building attics and walls is not normally considered a danger; most likely it'll run with no joints or fittings, as continuous tubing (thus reducing the risk of a leak).

Refrigerant leaks are really bad for the environment but the gases are pretty inert and at low levels such as leaking out of a residential A/C system, not likely to be a hazard to neighbours.

If it were my place I'd let them install solid piping where needed.

(June 22, 2016) Rosemarie Greaser said:
Thank you danjoefriedman for your suggestion.

I'll see if I can request the company do the solid piping. I think I will need to see some evidence that there is indeed a leak first in the underground piping and not just some poor installation techniques. I've read some reviews on this company and they don't seem to be very good.

(mod) said:
That sounds reasonable.

Question: freon leaking from plastic refrigerant lines?

(July 30, 2016) KJWaddell said:
I have an older HVAC system, and my repairman tells me the freon is leaking from "plastic" refrigerant lines used at installation(that were only manufactured for a few years). He indicated I'd need to replace the entire system because these lines leak. Is it possible to replace these lines and keep the existing system?

Reply:

(mod) said:
Yes, though if your system uses R22 that is no longer used in AC systems it may make sense to change it

(July 31, 2016) Anonymous said:
Thanks for responding! Is there any reason it would be impossible to replace the lines without replacing the entire system?

(They say I'd also have to replace the furnace if I replace the outside AC unit...because the old furnace "couldn't handle the new AC output". so I would love to replace the lines and keep my existing system to save cost.

(mod) said:
"Impossible" is a bit encompassing; as I don't know what might be encountered. But in general, refrigerant lines can be replaced without changing the equipment. If your tech wants to replace the entire system I'd like to understand what s/he has seen. Sometimes a very competent tech is indeed working in your interest but is not good at explaining. Press for details.

To replace refrigerant lines one has to evacuate the system, remove the old piping, install new piping along with new filter/driers, then re-charge the system and test it for leaks.

(July 31, 2016) Anonymous said:
Thank you, again. The system is quite old, and they always point that out...but it runs very well with the exception of the freon leak, which has worsened in the past 2 years and is now at the point of failure. Planning to move in the near future, so trying to avoid a $6k investment in a whole new system if I can. I appreciate your insights.

(mod) said:
I understand wanting to eschew putting money into the next owner's A/C system.

...

Continue reading at REFRIGERANT PIPING INSTALLATION - topic home, or select a topic from the More Reading links just below or see the ARTICLE INDEX.

Or see REFRIGERANT PIPING INSTALLATION FAQs-2 - more-recent questions and answers about refrigerant piping installation

REFRIGERANT GASES & PIPING - home

Or see these

Air Conditioning & Heat Pump Refrigerant Piping Articles

• REFRIGERANT GASES & PIPING - home
• REFRIGERANT PIPING INSTALLATION
• REFRIGERANT PIPING DAMAGE & LEAKS
• REFRIGERANT PIPING GURGLING
• REFRIGERANT PIPING INSULATION
• REFRIGERANT LINE MOUNTING
• REFRIGERANT LINE NAIL PROTECTION
• REFRIGERANT PIPING LENGTH vs DIAMETER
• REFRIGERANT TUBING BRAZING & SOLDERING
• REFRIGERANT TUBING FLARE CONNECTIONS
• REFRIGERANT TUBING ECONOMIZER & HEATING TRICKS
• REFRIGERANT PIPING UNDERGROUND, BURIED
• REFRIGERANT PIPING CODES & STANDARDS
• REFRIGERANT PRESSURE DIAGNOSIS

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REFRIGERANT PIPING INSTALLATION FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

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