Fujitsu ductless minimum line set runs

Ron Jr._3

Installed 2 indoor units / 1 outdoor at my home over the weekend . Cannot believe I waited so long to do this ! Amazingly quiet compared to the window shakers .



Found out there's minimum runs to each unit , and I'm well below the minimums . Is there minimum runs because of the refrigerant charge ?  Will I need to recover some of it ? Add more lineset and coil it behind the unit ?  The system is working flawlessly so far . Thanks in advance !

Techman

minimum

I beleave it has more to do w/ controlling the refrig flow and allowing the "sensors" to control comp/ fan speed and TXV throttling and a little space(line set)to let the throttling begin.

don_9

Charge

Yes that would be why.But it kinda tuff to adjust the charge unless you get inside the unit to install your temperature probe.The two lines going to the indoor unit i hear is part of the metering device so checking temps in that area will throw you off.

I would not even sweat it if the subcooling is under 20 degree.

Jack

When the inverter units first came out

We were introduced to the min line set length. I was representing them at that point. We were told initially that the line set had the min of 9' for those systems 15kbtu and under & 15' for 18 and above. We asked why this was the case and were told that with the minimums not met you could possibly create a resonance that would turn the evap into a speaker, and you might not like the song it sings. Digging further with one of the engineers we asked what created the noise and he replied that it was the compressor stressing out.



I'd suggest you recover the refrigerant and do a serpentine coil up the wall behind the condensing unit to achieve the minimum. DO NOT coil the line set as it will trap oil and that won't be pretty either.



They are pretty neat systems!

Ron Jr._3

Thanks guys for the replies !

Sorry , forgot about this thread till yesterday  . The system worked amazing on a 95 degree day . Had both the 1st and 2nd floor units on the " Quiet " setting and in economy mode and both had no problem keeping the temps at 72 .



One more question which I didn't see addressed in the literature . Can you take one indoor unit out temporarily and have the other run ? I might need to remove the 2nd floor unit for a good chunk of time . Worse comes to worse I can relocate it temporarily but I'd like to avoid it !

Jack

Sorry, but no

You cannot disconnect one evap on a dual system. If you are remodeling, build the unit onto a temporary but secure support or leave this until the end. The condensing unit is looking for both evaps and will fault if two are not connected and recognized. Wait til you run it for heat;)

Ron Jr._3

Thanks Jack

There was a Fujitsu class at a local Sid Harvey's a few weeks ago after work . Couldn't make it . Had a ton of questions , but thanks for answering a few on here .



Yep , it's a remodel in a year or 2 . The wall it's on will not be removed , but the ceiling and roof nearby will be . So I didn't want to take a chance .



Tried it on heat once , when it dropped into the 50s one night . It can really crank out some warm air ! I'm just glad I have some supplemental heat for when my oil tank runs dry . Which has happened 3 times in one year !

Jack

Actually you mis-state the case

What you should be doing is using the oil as a back-up to your mini-split. I think you will find you will save a lot doing so.

Ron Jr._3

At Long Island electric rates

I'm not quite sure of that !



I think we're at 23 cents a KWh

MikeyB

Fujitsu

Hey Ron, you can check out Wales-Darby's website, they give training on the Fujitsu units at their place in Islandia NY, I was there last summer for John Barbas training and I wanted to make a Fujitsu traing over the winter but never made it, hopefully i can make one this year, they look like real nice units.

Ron Jr._3

Hey Mikey

I was there too , for John's pm class . That place is great . Thanks for the heads up ! I heard they came out with different indoor units . With an optional motion sensor ? To deactivate when no ones in the room . 

Ron Jr._3

Coil like this ?

Not my house ! lol  . This was a house next door where we were doing a central air changeout . Either they actually read about the minimum run or they just didn't want to re-flare the fittings ! 

Jack

Not like that

Putting the line set in a coil like that will trap oil and toast the compressor. Should be laid off in a serpentine fashion