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.

Photo: the author's (DF) swaging tools used as one method to connect and braze refrigerant piping sections together or to connect a refrigerant filter/drier.

Refrigerant leak from cracked flare fittings on the refrigerant piping?

A friend of mine is having some problems with a room sized split air conditioner in his home. The unit is about three years old.

A few months ago the unit stopped cooling and an air conditioning technician confirmed that the gas had leaked out.

To inspect the lines some drywall had to be removed form a lowered ceiling, and upon inspection a cracked flare nut was found. The technician said that this is a not uncommon occurrence.

Have you ever come across cracked flare fittings in small air conditioners? It seems to me that it's just a case of poor quality fittings. What do you think?

Anyway, the damaged fitting was replaced and the unit again functioned properly.

now my friend is having more trouble with the same unit, and the technician says that now there is leaking in the copper tubing itself.

This is also a new on one me. The tubing was professionally installed and there are few bends. Unfortunately the tubing is in the wall, and partly behind a tiled bathroom wall, so revealing all of it to find the point of failure will be serious undertaking.

My friend is thinking of rerouting for convenience though the result will not be as aesthetic and the rerouted tubing will inconveniently routed on the roof of his home, where the compressor is located.

Do you have any experience with leaks in copper tubing except at bends or points of "trauma?" Is the kind of cheap Chinese Fe-Al contaminated Cu tubing mentioned in Robert W Porter's post prone to leaking?

Thanks for any insights. On 2018-08-26 7 by YossiD

Answer by (mod) - We never use flare fittings in refrigeration piping

Yossi

We do not ever use flare fittings on refrigerant piping as they're not likely to withstand the pressures involved on the high side.

I think you probabaly mean swaged connections: one end of the copper tubing is enlarged to permit joining two sections of copper piping.

The swage joint is then soldered or brazed. Some swaging tools are shown in my photo.

Swage joints are discussed

at REFRIGERANT PIPING INSTALLATION

Chinese cu tubing made with Fe-Al contaminated Cu tubing: warning

Our house was built 2000-2001 when cheap Chinese cu tubing made with Fe-Al contaminated Cu tubing was first imported, especially in FL. Our CA house had a single such water line leak which was fixed with a 4-in line insert.

Now one of two AC units has a seasonal leak, the one with a longer run of Cu tubing. Leak sealant was tried unsuccessful.

The run to and from the evaporator (replaced a few years ago) is long, 50-75 feet in attic under insulation.

Should we try to find lead (how?) or replace it all, including vertical runs? On 2018-07-04 by Robert W Porter

 

Safety: is there an explosion risk when soldring halon refrigerant lines?

While installing an outdoor unit and prepare it for service, found leak after opening hex ports for the first time, wanted to solder but don't know if there are dangers to me or the equipment? On 2018-06-21 by James

by (mod) -

James

Halogen based A/C or heat pump refrigerants are not explosive, though lubricants and oils might be flammable.

The danger to the equipment is contaminating the refrigerant system, clogging the expansion valve, or damaging the compressor motor.

A tech would evacuate the system, do the soldering, install a burnout dryer, maybe two of them, then change out the dryer again after a few months - all trying to avoid contamination clogs.

 

Is there a code on routing of refrigerant lines?

My question is about the route of the freon line from the outdoor AC unit to the indoor air handler:

This goes up the side of my house and under the roof line.

The last time I had a new roof, the roofers punched a hole in the freon line.

Is there a code on whether the line should be installed low enough to prevent this from happening? On 2018-08-28 by Des de Souza

by (mod) - Yes, given here, and also, Refrigerant piping should be protected from physical or mechanical damage

Refrigerant piping should be protected from physical or mechanical damage by either routing or shielding.

For example where a line runs through a wooden stud you'd use nail plates to keep someone from driving a nail through the line.

See details and source citation documents at

REFRIGERANT PIPING INSTALLATION

Will a "too short" refrigerant line cause problems?

I just installed Sharp brand split system air conditioner (photo above).

The product leaflet says that the minimum refrigerant pipe length is 3m,

but my final pipe seem only less then 50cm between the outdoor and indoor unit.

Do this short pipe length cause any trouble to the indoor unit or outdoor condenser?

Hope to get reply to release my worry On 2018-06-24 by Walter Sui

Answer by (mod) -Yes: missing vibration dampening loop in refrigerant piping

Yes the short pipe is likely to risk refrigerant leaks because it doesn't allow The extra length which would accommodate vibration and movement.

Can new condenser unit use old refrigerant lines?

I have an old Lennox A/C unit: it finally died. Can a new outside unit be replaced and still use all the existing lines that go into house? On 2018-06-24 by john

Answer by (mod) - Yes if ...

Yes if they are in good condition and are the right size for the new system.

Do I still want a sight glass on a replacement refrigerant line?

Just changed my entire ac system .
Now have a matching 14seer 4ton Rheem system.

I had a sightglass in the old 3/8 freon line.
Do I still use the sightglass since I changed from freon22 to r410a ? ( yes it's an expansion valve coil ) On 2017-07-10 by Johnny P

Answer by (mod) - signs of low refrigerant

sure, Johnny.

The sight glass will show bubbles of gas and loss low refrigerant in the liquid line of the refrigerant piping system for virtually all refrigerant types.

What's the right refrigerant line diameter for a new 3-zone split system A/C?

Hi,
I’m installing mini split tri zone condenser unit with 3 ducted airhandler units. They are same brand. All 3 zones on condenser unit has 1/4” for suction and 3/8” for discharge lines.

Two airhandler units match line sizing, but one unit has 1/4” for suction and 1/2” for discharge.

What line size should I use 3/8” or 1/2"? On 2017-05-20 by Alex

by (mod) -

Alex, thank you for asking I'm sorry but I'm not sure what is the right answer. We would need to find the brand and model and check with manufacturers technical support. Something sounds strange to me. unless we are talking about a heat pump., as I am sure you know usually the suction line is the larger diameter

note by Alex

Sorry for confusion suction line is 3/8 on condenser unit, but ducted airhandler unit has 1/2". I was going to use 1/2" but wasn't sure. I could find any manufacture instructions. Brand is Midea.
Thanks

Answer by (mod) - ok to use larger diameter refrigerant piping

My opinion And I'm surely not the last word on this, is that you're always safer with a larger-diameter refrigerant line. However don't forget that you will need to adjust the refrigerant charge accordingly

Watch out: there may be increased leak risks with larger diameter refrigerant piping in locations subject to mechanical stress from vibration or settlement or movement of the equipmenbt as it's more difficult to include an extra loop of tubing or piping to permit movement without breaking connections.

Service tech came 3 times to add refrigerant at new A/C unit, now says have to run new lines in the attic: why there?

1 1/2 years ago a friend installed an a/c unit, brand new. In the 1,1/2 years he had come three times to add freon; he said the main lines are leaking and so must be replaced with new lines run through the attiv. Why not underneath the house?On 2017-09-28 by Miguel

Explanation by (mod) -

Miguel,

I agree that it sounds like the air conditioning refrigerant system is leaking. It might be possible to use a leak detection device to find the leak. That would be a happier approach and less costly approach than simply replacing everything.

Routing refrigerant lines through the attic may be enormously less expensive than trying to dig or bore beneath a building's basement or crawl space or slab to run lines there.

Wrong refrigerant line size for new refrigerant may have destroyed the new compressor motor

AC tech replaced outside unit due to compressor failure. After three weeks not cooling got somebody else to look at it.

He said that the piping was the wrong size due to the new freon and that the unit was the wrong size. Compressor started making nosie and died. How can I tell if the piping and unit are the right size. On 2017-09-17 by marroquinsevastian

Notes by (mod) -

Marroq

Start by looking at the brand and data tag on your equipment.

Then call the manufacturer's service support line for an opinion about minimum refrigerant line size, or get a copy of the installation and operation manual for your unit.

There you'll see that the refrigerant line size required might depend on the total system capacity and also the length of piping runs.

But normally changing refrigerant itself wouldn't require new refrigerant piping.

A mis-match between the outdoor compressor/condenser unit and the indoor air handler and cooling coil could be a problem.

None of these would explain a sudden death of a new compressor unit. More likely there was an installation error. Something as simple as the wrong quantity of refrigerant charge or an improperly-functioning refrigerant metering valve can send liquid refrigerant to a compressor - killing it.

What are the average number and type of COPPER fittings that go inside a commercial rooftop unit refrigeration piping system?

I wanted to know the average number of COPPER joints inside a commercial rooftop unit (avg size 25 tons of refrigeration)
OR
I was looking to understand the average number and type of COPPER fittings that go inside a commercial rooftop unit... I'm specifically looking at the fittings used for connecting the refrigerant piping inside the AC equipment itself.

I can count between 20 to 30 odd joints in this diagram...The number of fittings would help to arrive at an average number for joints, is my assumption.

Anybody who could throw some light on this...I would really appreciate. Thank you On 2017-07-28 by Jyo Gupta -

Comments by (mod) -

Jyo

Are you asking about all of the copper fittings in the rooftop unit or just the connections between the refrigerant piping to the unit itself? The latter is trivial.

The former depends on the manufacturer's design and the A-coil design. There is not a standard one-off design nor number. We'd need to answer the latter question by looking at a specific rooftop unit design.

Meanwhile, sure it's reasonable to count fittings in the *theoretical* drawing you found of a rooftop HVAC unit and to use 20-30 piping joints as common.

In part the higher number may be due to the illustrator's presumption that larger-sized copper pipes are more-likely to be in use in a commercial rooftop HVAC unit, so she assumed that the design would not use flexible copper tubing to make some of the bends and thus to avoid some of the elbows.

I'm not sure that a manufacturer would accept that in practice.

Followup by Jyo Gupta

Thanks for the insights, Daniel! That really helps.

I actually wanted to get a basic idea about the minimum number of copper fittings (connections) used to joint refrigerant piping between the cooling coil/evaporator and the compressor/condenser unit in an average-sized commercial rooftop unit.

And if possible to understand the break-up share by type (tee’s, elbows, caps) would be great.

I understand this number is rather trivial given that flexible tubing (to reduce no of fittings) would possibly be preferred by a rooftop unit manufacturer, but any idea nevertheless would be greatly appreciated.

Thanks for your help.

 

Is it ok to run air conditioner coolant line through the clothes chute?

Can air conditioner coolant line be run down a clothes shoot? On 2018/05/25 by Elsene -

Answer by (mod): beware of the limits on vertical rise of refrigerant piping

Can you run A/C refrigerant piping through a laundry chute?

Physically possible, sure. Within very specific total vertical height limits and refrigerant pipe diameters that need to be reviewed with the manufacturer of the air conditioning equipment.

Watch out: Good idea?

Maybe not: dumping clothes down a laundry chute risks damaging lines, causing a leak, or knocking off insulation. If there is room to route the refrigerant lines through the clothes chute I'd expect the installing contractor to make sure the piping is protected from damage, perhaps enclosing it in a suitable conduit.

There are vertical height limits for refrigerant piping. That's because vertical refrigerant piping can run into limits on its ability to move droplets

The minimum velocity required to carry oil droplets up a vertical riser is higher for a larger diameter pipe than it is for a smaller diameter pipe. This is due to the velocity profile of the refrigerant flowing inside the pipe. In a smaller diameter pipe, the higher-velocity refrigerant is closer to the inner walls of the pipe than it is in a larger-diameter pipe.

For instance, while the minimum allowable velocity in a 2 1/8 in. (54 mm)-diameter suction riser is approximately 1,000 fpm (5 m/s), the minimum velocity in a 1 1/8 in. (28 mm)-diameter riser is only 700 fpm (3.6 m/s).

While the old minimum-velocity limits were easy to remember, they may lead to the unnecessary use of double suction risers.

The recommended maximum-velocity limit of 4,000 fpm (20 m/s) has not changed. A higher velocity inside the suction line may cause objectionable noise for those nearby. -

Source: TRANE AIR CONDITIONING REFRIGERANT PIPING MANUAL [PDF], Trane Belgium, retrieved 2018/05 25, original source: http://www.tranebelgium.com/files/book-doc/20/en/20.aqerykdx.pdf

Will cooling capacity be impacted by using a larger diameter refrigerant pipe

Hi copper pipe of 5/8 was installed few months back. Now I have bought 1 ton split. Pipe with the split is 3/8 . Fitting is concealed I can't change will it effect the cooling

Explanation by (mod) - no but get the refrigerant charge right

Rav

No, not as long as the refrigerant charge volume is correct.

When there is a larger refrigerant piping than factory specifications, depending on the total length of that tubing and thus its total volume, the refrigerant charge may need to be increased accordingly. On 2017-06-12 by Ravinder

Diagnose Hissing and condensation on refrigerant line after installing a split system A/C unit

After installing my 1HP split AC, on testing, it gives a low hissing soung along the length of the pipes.

I also noticed condensate and water droplets along the whole length of the pipe. I had to extend the pipe as a result of the distance from the room to where the outdoor unit is to be located.

On 2017-05-18 by Shehu

Suggestions by (mod) re: hissing sound along refrigerant pipes

I'm not sure what's happening Shehu. If there was a refrigerant leak that you heard hissing, the system will very quickly stop cooling.

Or is the noise coming from the expansion valve?

Refrigerant bubbles inside of piping usually mean the refrigerant charge is too low (or there is a sticky TEV).

The condensate along the refrigerant piping suggests that it is not insulated where it should be.

Can I add R410A to my R32 refrigerant system to make up for long refrigerant line run?

I have just installed an air con with a long pipe run and as such I need to add some extra refrigerant (50 grams to be exact).

The system uses R32 refrigerant, however I only have R410A refrigerant, would it be ok to add the extra 50g of R410A into the system or will this not be comparable with the R32 refrigerant already in the system?

I know the proper solution is to just buy a tank of R32 but I don't do much work with this refrigerant and it is hard for me to get. On 2017-05-02 by Sam

Reply by mod:

I wouldn't do it. Mixing refrigerants, even if it doesn't rapidly do serious harm to the system, changes the operating properties, pressure, temperature, cooling capacity in ways that can make adjustment and repair difficult.

Perhaps you can find a service tech who'll generously let you have the small amount of R32 you need.

Is it OK to route refrigerant lines up through the attic?

Hi,
I am installing a split air conditioner onto a block wall and the only way to run the pipes without having to have ducting going half way around my room is to take the pipes up into the ceiling through the attic and then down the other side of the building.

This means the pipes will go up about 2.6m, across the attic about 7m then about 3m down the other side of the building to the compressor.

Will this piping arrangement be ok, will there be any major downsides to this approach. P.S. The drain can be taken outside another way so this is not a concern.
Thanks. On 2017-05-01 by Tyrone

Answer by (mod) re: yes but don't forget to calculate the volume of refrigerant needed when increasing piping lengths

Don't forget to calculate the additional refrigerant that will be needed, and be meticulous about insulating the suction line so that you don't have condensate drips into the ceiling.

Note by Tyrone

Yes I will be sure to add the extra refrigerant and insulate the pipes. I was just concerned about the two vertical runs playing havoc with the refrigerant oil or the performance of the system.

Problem with vibration in HVAC equipment

new unit installed almost 2 years ago. cools great but I am also getting vibration and when the unit kicks on, I get a louder than normal thud sound inside the house, and when it shuts off, I get another sound that is impossible to describe, like a ping pong ball bouncing on the floor(twice).

the return line coming out of the unit into the house is not that long, about 18 inches but it has a 90 degree elbow to angle it into the house. Is that correct and could that be causing some of my noise On 2017-04-25 by tim

by (mod) re:

Tim:

Vibration that is new in an existing HVAC installation suggests loose or lost mounting bolts or perhaps a failing electric motor.

I would not expect refrigerant piping to itself be a cause of noise except where it's not secured and is telegraphing mechanical equipment vibration.

Is it proper to have a loop in the refrigerant line?

Just had a Lennox split system installed. The refrigerant line and the condensation line were installed on the outside of the air handler cabinet in a loop. The air handler is in a closet in my home. It looks very strange.

Is this an acceptable installation?
Thank you. On 2017-01-26 by Donna

by (mod) re: refrigerant piping loop: probably ok

Donna,

I really can't guess from just the information in your message.

But a loop in refrigerant tubing, particularly outside at the compressor/condenser unit may be proper and good practice to give flexibility against vibration damage.

But an excessive loop might be a bit odd - multiple coils, for example - at least unnecessary and possibly subject to more vibration or movement than we want. Post a photo if you can.

See

REFRIGERANT PIPING INSTALLATION

and

Carlyle MINIMIZING REFRIGERANT LINE VIBRATION [PDF] (2021 >

OK to braze a larger pipe onto the indoor and outdoor units?

I have a 1 HP AC installed already whose high and low side use 1/4 and 3/8 inch pipes respectively but would like to change it to 1.5 HP AC of 1/4 and 1/2 inch pipes.

Would it be right to just braze a short lenght of 1/2 inch pipe to the indoor and outdoor units of the existing 3/8 inch pipe or should the 3/8 inch pipe be replaced entirely? Thanks 2016-11-29 by Ezema Solomon

by (mod) re: probably not

Ezema,

Probably not, unless the total piping distance is small. What does the manufacturer say is their recommended pipe size for your A/C brand and model?

Can I run 2 parallel refrigerant lines instead of changing to a larger diameter?

I had a 3 ton split system and I am upgrading to 5 ton. Based on the length of the run 50 feet the vendor says to use a 1 1/8 suction line. The old line is fine and is 3/4. Rather than run a new 1 1/8 line can I run a second 3/4 line and with the two parallel lines be ok. On 2016-11-25 by Greg Lane

by (mod) - not a great idea and your calculations are off

Sounds messy to me. You'll still have to join the 2 lines at either end, plus you're increasing risk of failure wight more components.

Finally, see

CYLINDER VOLUME CALCULATION to see that the recommended larger line is not equal to what you propose in volume.

...

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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 GASES & PIPING - home

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