question for an HVAC pro !

[theoldwizard1]

I have recently heard that some mini-split manufacturers are saying that what ever their supplied tubing length is (25') it can not be shortened or lengthened.

Lengthening beyond "reasonable" (50'?) makes sense, but why not shorten to say 10' ?

 

[bonneyman]

The units are pre-charged with the correct amount of refrigerant for the condensing unit, evap unit, and that amount of interconnecting pipe. Perhaps they were getting too many warranty calls with failed comps from people adjusting the tubing length without adjusting the charge?

Anyway - other than maybe them denying warranty if they find the piping not factory-prepped - there isn't any reason why you can't adjust it so long as you don't go overboard and adjust the charge when installing. IIRC there's an overall max length limit (60') and vertical difference limit (15').

 

[justinjoyal]

I guess they want people to use the provided flares/fittings so they dont **** up the install ? Or maybe they just know most people will want to use the proper lenght for the job and thus they can void the warranty stating they did not follow the guidelines.

 

[yeldogt]

The specifications are all in the literature ... there is a minium. I believe it was 10' for the Mitsubshi. It's total length -- so -- 10' is 5' of seperation.

They weigh in the extra charge based on length. A direct instalation (wall with unit on ground outside) ends up being within the 25' total length .. 12.5 feet seperation

 

[oldgoaly]

Years ago they made 15', 25', 35', 50' precharged with aeroquip fittings. been out of the business little more than 10 years. Funny how mini-splits came back. I have a Afco "mini-split" condensing unit from the early 1960's in the shed. still the box. Inside blower coil is from the 1970's.

 

[theoldwizard1]

Anyway - other than maybe them denying warranty if they find the piping not factory-prepped - there isn't any reason why you can't adjust it so long as you don't go overboard and adjust the charge when installing. IIRC there's an overall max length limit (60') and vertical difference limit (15').

Kind of what I thought. I am NOT talking a DIY installation. Kind of a pain in the ****, but you could install the long tubing, test the system, remove the refrigerant, cut and splice the tubing in the middle, re-insulate and then charge to the correct amount.

 

[SALIV8]

I have recently heard that some mini-split manufacturers are saying that what ever their supplied tubing length is (25') it can not be shortened or lengthened.

Lengthening beyond "reasonable" (50'?) makes sense, but why not shorten to say 10' ?

The manufacturer of both of my systems don't supply tubing. What manufacturer are you talking about, out of curiosity?

 

[bonneyman]

Kind of what I thought. I am NOT talking a DIY installation. Kind of a pain in the ****, but you could install the long tubing, test the system, remove the refrigerant, cut and splice the tubing in the middle, re-insulate and then charge to the correct amount.

You'd be surprised how many installs of those I went on, and the installer didn't know (or want to mess with) the pre-fabbed piping. So, if the two units were only separated by 8 feet (i.e through a wall), all the extra piping was just left coiled up and tucked outside along the wall! Sometimes neat, mostly just shoved. And after a few years in the sun the insulation starts roting....and there goes the superheat and efficiency!
Of course the owner is not aware of any of this. But he's noticing the system ain't cooling like it once did - and "soak 'em and run" Joe installer ain't answering the phone!

 

[Jackfre]

The solution to that issue is to buy another brand. There are mins and maxes on line sets. When Fujitsu first came out with the inverter units we were warned about to short a line set. That first year we, as the reps, were told that it could create a harmonic issue and turn the evap. into a speaker and you may not like what it is singing. The following year I caught one of the Japanese engineers and asked what was the actual cause of the harmonics. He said it was the compressor tearing itself apart.
The actual problem today is the line sets. I spoke with an old customer back east who has had to replace line sets on 75 units. The insulation had a chemical in it that was eating the copper. Minuscule leaks that just drive you nuts and cost a fortune. I would never use a factory supplied flare on a 410a line set or the flare nuts on them. Compare the supplied fittings on the equipment vs those supplied with the line set and you will see why.

 

[Jim greengo]

The solution to that issue is to buy another brand. There are mins and maxes on line sets. When Fujitsu first came out with the inverter units we were warned about to short a line set. That first year we, as the reps, were told that it could create a harmonic issue and turn the evap. into a speaker and you may not like what it is singing. The following year I caught one of the Japanese engineers and asked what was the actual cause of the harmonics. He said it was the compressor tearing itself apart.
The actual problem today is the line sets. I spoke with an old customer back east who has had to replace line sets on 75 units. The insulation had a chemical in it that was eating the copper. Minuscule leaks that just drive you nuts and cost a fortune. I would never use a factory supplied flare on a 410a line set or the flare nuts on them. Compare the supplied fittings on the equipment vs those supplied with the line set and you will see why.