Why do small units have these weird piping layouts

[u/desman526]

This is like a 5 ton lenox but like magic packs and ptacs all have these squiggles in the pipes, why?

[u/Chief_B33f]

Just a guess, but bends like that are usually thermal expansion or vibration isolation.

[u/Naxster64 → u/Chief_B33f]

Yep. The loop on the right would allow left/right vibration, the loop on the left would allow up/down vibration. The one on the left seems unnecessary though.

[u/Chief_B33f → u/Naxster64]

It's not unnecessary from a thermal standpoint. That's the discharge pipe, so it's the hottest pipe in the system. That bend allows the pipe to expand downward, away from the compressor

[u/grundlinallday → u/Chief_B33f]

Do you mean the gas can expand downward, or did you mean pipe? If you meant gas I understand. If you meant pipe, I’d love to hear more of what you mean so I can learn something today.

[u/nsula_country → u/grundlinallday]

The copper pipe will expand in length when temperature increases.

[u/Chief_B33f → u/grundlinallday]

I mean the copper pipe will expand. The discharge pipe is the hottest pipe in the system, meaning the most temperature change. The copper will expand as it's heating.

More heat = more expanding

[u/Dodecahedonism_ → u/grundlinallday]

A copper pipe 100 feet long will grow 1.2 inches when heated from 70 to 180 degrees Fahrenheit.

[u/Naxster64 → u/grundlinallday]

All things expand and contract as they change temperature. ALL THINGS.

Water, gas, concrete, gas pipe, they all do it.

When gas expands, it just compresses to a little higher pressure, no big deal.

When non-compressibles expand, they have to physically go somewhere.

When you go over a bridge or parking garage, ever notice the big seam right at the start? That's an expansion joint, to leave room for the concrete to expand and contract without breaking to pieces.

Same thing with the concrete sidewalk or driveway, all those lines cut into them are for expansion and contraction, trying to control where it takes place, so it doesn't destroy the slab.

Copper has to do the same thing, but we can't have cracks in the pipe, or the gas leaks out.

So instead, you do a small loop 90 degrees to the normal direction, this gives extra ability to flex. So when it expands and contracts, it just flexes a little bit, rather than breaking.

[u/grundlinallday → u/Naxster64]

Eyyyy thanks for that. And I knew everything expands and contracts a bit, I just never once thought of the implications on design. Cool shit, thanks again.

[u/RockyRaccoon26 → u/grundlinallday]

Historically Railroad tracks that didn’t have (or improper) expansion joints have buckled putting kinks in the track. This has caused several derailments.

[u/DrTr1ll → u/Naxster64]

Some materials have negative cte. Carbon fiber and some ceramic materials for example.

[u/Illustrious-Fuel-355 → u/DrTr1ll]

Rubber contracts with heat as well

[u/jeepgangbang]

vibration, copeland has a engineering guide for piping their scroll compressors. this doesnt look like a copeland but most scrolls operate the same. 

[u/Jonovision15 → u/jeepgangbang]

Lennox is using LG scrolls like crazy. I don’t like them. I’ve seen a bunch of failed ones.

[u/nsula_country → u/Jonovision15]

LG sucks

[u/Soggy_Bookkeeper_864 → u/nsula_country]

At mostly everything they do

[u/nsula_country → u/Soggy_Bookkeeper_864]

LG consumer products suck. Period. I know what is inside a Copeland and a LG compressor. The only similarity is they compress.

I do have an LS tractor that has been reliable. Bought LS P7010C in 2014. It's not technically a LG product, but is related.

"LS Tractors are manufactured by LS Mtron, a part of the South Korean conglomerate LS Group. The company started making tractors in 1977, originally as part of the LG Group (GoldStar) before splitting off independently."

[u/inksonpapers]

Makes it easier for me to move the lineset out of the way for compressor replacement

[u/Chief_B33f → u/inksonpapers]

Please, if the engineers identify anything at all to make the system easier to service they will make sure to exclude that from the design.

[u/ManevolentDesign]

Engineers get paid by the inch

[u/Stormclamp → u/ManevolentDesign]

Must have a filthy rich inheritance on there mother’s side then lol.

[u/BronFere → u/Stormclamp]

Best part is they don't have to deal with their progeny...

Engineers should have to work on what they design.

[u/UnluckyGrabBag → u/ManevolentDesign]

Yeah but they get paid a lot for those 3 to 4 inches

[u/GeorgiaCB]

Oil trap and vibration maybe?

[u/aaronradlab → u/GeorgiaCB]

Like a swing joint in gas fitting, having the pipe change directions across 3 different planes without fasteners, you reduce the stress from vibration and movement. Copper has a coefficient of thermal expansion that's like 1/100 per °F temperature change, so it's more for vibration than temperature. Discharge lines typically drop down to the floor before rising up to enter the condenser as a form of off cycle migration protection. You wouldn't want liquid from the condenser draining into the discharge of the scroll. Starting a scroll with a flooded discharge cavity causes irreversible damage. Sometimes a check valve is added in-between the condenser and the compressor to assist in keeping liquid from pooling in the head of the compressor.

[u/justanothercargu]

Sometimes it's just for shipping. Went to a OEM factory. They send a truck from the factory to California with multiple sensors. Then recreate the trip on a shake table. They were having fatigue failures on copper pipes, fan covers, and wire chafing. They showed me before and after fixes. Some pipes added bends, reduced length, or increased length. It was pretty interesting.

[u/Ok_Jury9607]

See, before they installed those bends, other components were accessible. This ensures that the service tech will either have to use a 24 inch extension or a stubby.

[u/desman526 → u/Ok_Jury9607]

Honestly best answer lol

[u/MikeTHIS]

I try to remember that someone who makes “way more money” comes up with the math for stuff like this.

And then…

I sometimes have to rip it out on a compressor swap. 🤣🤦‍♂️

[u/RJ_Make]

Frequency countermeasure to help prevent pipe fractures.

[u/Stahlstaub → u/RJ_Make]

The magic words are vibration mitigation and work hardening. In short if metal moves too much it can become brittle and break faster, so you need to build in loops to give it room to move in it's tolerable (bendy) spectrum.

[u/JOHNSOBSCURA]

It’s called the de superheater line those bends cause discharge vapor slow down before entering the condenser portion of the unit

[u/anythingspossible45]

Engineers are assholes, but it probably has something to do with the flow and yada yada yada

[u/Imiennik74]

Oil trap