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  1. #1

    Question/advice on split ductless unit

    Hello,

    I own a condo in a converted 3 family home; it's the 3rd and 4th level. The 4th level is a converted attic to studio. The house has a steep pitch roof, so there's no regular windows in the 4th floor, just skylights.

    Have a friend, who works for a commercial HVAC company, come look and told me the best solution was to install the split ductless indoor unit(Sanyo CL 1872, 1.5 ton), inside a crawl space that's up against the ceiling of the 4th floor. The crawl space area is somewhere around 9x9 feet, with the ceiling just about 5 feet high in the middle...not a lot of space, not any ventilation beyond the ridge vents. His solution was for me to have someone come in after the install and put an exhaust fan cut into the roof to suck out the hot air. It sounded reasonable at the time and they did the install(sans exhaust fan).

    Made a call to someone to come do the exhaust fan...he wanted to check with another HVAC person before doing that, didn't think it sounded "right"...long story short, have talked to 3 other HVAC people who all told me that application wasn't correct, and I ran the risk of it not working efficiently, and the fan could burn out quickly, ect.

    Now my last issue/question: if I put the condenser off the ground outside(NOT DYI, I'm having someone come actually tomorrow to start the work), I believe the line set will go beyond the max 35ft the unit is designed for....so what happens if the line set is 40, 45, or 50 feet? The 4th floor is probably 35 feet in itself, then running the line inside to the control unit will go beyond that.

    I'm at my wit's end with this, and seems like even with different HVAC people I've spoken with, I'm getting different opinions. Thanks!

  2. #2
    Join Date
    Oct 2010
    Location
    Baton Rouge, LA
    Posts
    1,114
    So...
    It is a ductless split system, with both the condenser and the evaporator inside?
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  3. #3
    Quote Originally Posted by XcelTech View Post
    So...
    It is a ductless split system, with both the condenser and the evaporator inside?
    That's the way they originally installed it; telling me to just put an exhaust fan in the roof above the crawl space. So re-reading my post, I'm referring to the condenser inside the crawl space. The evaporator was installed in a good spot already on the wall inside the apt.

    I've been told by a few others the condenser really needs to go outside(ventilation issues, poor reliability of the exhaust fans, and more), so now I'm wondering what happens if the line set goes beyond the specs(someone said they can just add extra refrigerant?)?

    I might just have them mount it somewhere higher along the outside of the house so the line set length is within spec, but I don't want the house to look bad from the outside.

  4. #4
    Join Date
    Jun 2006
    Location
    Plano,TX
    Posts
    10
    I suspect thats too much rise for that mini-split. You have to consider oil migration and liquid refrigerant migration (compressor killer) I would read the IOM (installation,operation,maintenance) personally. Have your contractor call the manufacturer and ask for application assistance

  5. #5
    Join Date
    Oct 2010
    Location
    Baton Rouge, LA
    Posts
    1,114
    I think your gonna have a lot of trouble with the condenser unit exchanging heat since it will already be pulling in hotter then normal air.

    The purpose of the condensers coils is to take high pressure, high temperature vapor and turn it into high pressure, high temperature liquid(AKA use latent heat to create a change in state and remove heat). By starting with a hot crawl space attic heat you are gonna have issues with that change in state.

    Every manufacture has requirements for the length of the line set. There are several reason for these requirements.

    To name just a couple:
    1.) Heat transfer to/from the refrigerant in the copper lines increases as the length increases.
    2.) Lines that are too long or have too much of an incline will cause stress on the compressor and/or cause reduced FPM causing a lack of oil return to the compressor.

    A more precise answer to your question is not so much that there is a specific distance limit between the compressor and the evaporator so much as a need to get the size of refrigerant lines and amount of refrigerant charge for that distance correct. If the distance exceed a certain point you may need to increase the refrigerant piping diameter as well as the refrigerant charge for the system to work properly.

    But the biggest concern is velocity. If the velocity is too low, oil may not make it back to the compressor. In addition to total length of refrigerant piping, the number of elbows, bends, fittings, and so on also affect the flow and have to be taken into account. Which is why following the OEM specs are always the better way to go.

    So let me kinda whittle this down a bit:

    Not following the OEM will void your warranty.

    It will also increase the risk of a damage prone system that doesn't work well when it is running.

    There is little to no chance with the condenser in the attic that it will be able to cool the space during 100 degree weather.

    An better solution would be to build a platform on the slant of the roof were the top of the unit sits below the apex so that it is only visible from one side of the building.
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  6. #6
    Join Date
    Oct 2009
    Location
    Finland
    Posts
    117
    Have your tech read the installation manual. There he will find the limits of installation lenght and height difference between units. Also what has to be done to extend those limits to maximum.

  7. #7
    Join Date
    Aug 2008
    Location
    S. Grand Prairie
    Posts
    244
    Quote Originally Posted by slaps76 View Post
    Now my last issue/question: if I put the condenser off the ground outside(NOT DYI, I'm having someone come actually tomorrow to start the work), I believe the line set will go beyond the max 35ft the unit is designed for....so what happens if the line set is 40, 45, or 50 feet? The 4th floor is probably 35feet in itself, then running the line inside to the control unit will go beyond that.
    The lineset isn't limited to 35ft, that's the length of lineset that the unit comes precharged to use. The installer can adjust that and it's listed in the install manual on how to do this...it's no big deal, we do it all the time. There is a maximum, it varies with the brand/unit but it's usually way more than 50'. So you don't have anything to worry about...
    Originally Posted by ladyfire3374:

    "I used to wake up excited about the challenges of the day. Now the anticipation level is somewhere between a root canal and a colonoscopy."

  8. #8
    Thanks everyone. The installer is here, he just found on the manual where it says "if total tubing length becomes 25 to 98 ft(max), charge addtl refrigerant by .27oz/ft. No additional charge of compressor oil is necessary." I'm going to still call the customer support when it opens in a few minutes to double check, I'm still paranoid! It's probably no more than 50 feet from condenser to evaporater.

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