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Mini split total pipe length calculation

Posted by ylmzm (My Page) on
Thu, Feb 20, 14 at 13:56

We are trying to select a mini split system for our house. I was reading the Fujitsu Halcyon system manuals, and there is something not clear to me in copper pipe length calculations. Each connection from an outdoor unit to indoor unit (or branch box) is composed of two copper tubes: A liquid pipe (1/4"), and a gas pipe (3/8").

The maximum allowed pipe length between a branch box and an indoor unit is 50 ft. Does it mean that the pipe distance between the branch box and indoor unit should be less than 50 ft, or should it be less than 25 ft ( 25 ft for each pipe) ?

[BranchBox] <--------------------------------> [IndoorUnit]

So, the question is: Do we add the length of all copper pipes between two units while calculating the total pipe length distance?


Follow-Up Postings:

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RE: Mini split total pipe length calculation

Here is an image of the manual page


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RE: Mini split total pipe length calculation

What model are you using. If you are not doing the Hybrid Flex Inverter 4 ton unit you will not use a branch box.

Assuming you are using a single unit the 9&12 kbtu units use 1/4 & 3/8" line sets I will tell you that the maximum line set length (both vert and horiz) is 66'. The maximum vert rise allowed is 49' and the units are pre-charged for up to 49'.

The HFI units are a bit more complicated on line sets, so are you doing an HFI system or a single?


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RE: Mini split total pipe length calculation

Oh, and another thing, if you go to Fujitsugeneral.com and select Contractor, on the left side it will give you their entire catalog for download. All this info is there.


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RE: Mini split total pipe length calculation

Thanks, Jackfre. I will install a 4 ton outdoor unit (AOU48RLXFZ) with 6 indoor units (12 and 9 BTU units). There will be two branch boxes. In the Fujitsu manual, it tells the maximum distance from branch box to indoor unit is 49 ft. Does it mean that each pipe (1/4" and 3/8") can have a max of 49 ft length? Or, does it mean that the total length of 1/4" pipe + 3/8" pipe needs to be less than 49 ft ( in this case each pipe becomes max ~ 25 ft length) ?


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RE: Mini split total pipe length calculation

Both lines are 49' each. It's a given that distance will be spaned by 2 lines.


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RE: Mini split total pipe length calculation

As Klem said, Point A to Point B. Don't feel like the Lone Ranger on this. I cannot tell you how often people ask this question.
FYI, I met a contractor up in the N CA area a couple years ago who did two houses. they were virtually identical. One owner chose to go conventional ductedhigh efficiency LP and AC. The other chose the HFI system you are looking at. The contractor opined that both systems were almost identical in installed cost. When asked about the operating costs he said that the HFI system was running at about 45% of the cost of the conventional system. I think it a good choice on your part.


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RE: Mini split total pipe length calculation

Thanks everyone!


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