A/c Total Line Set Distance

[brianubaldo]

hello

is there a general data about total line set distance for airconditioning?

what is the maximum distance of pipes for a certain capacity of aircon?

[fridge doctor]

Hi, this Q has been asked before - by me actually.

The answers came back that there were no hard and fast rules.

As a general rule, I had always considered that 15 metres would be about the upper limit of run before performance is lost.

Trevor

[paul_h]

Depends on the size unit, ie the compressor and the pipe sizes.
Small units (ie 2.5kw with 1/4" and 3/8" lines are good for 7m, unit's that are 3.5kw with 1/4" and 1/2" in are good for 10m, units that are 4.5kw with 3/8" and 1/2" are good for 15m, larger units are good for 20m and so on)
All the good brands have this info in the install manuals anyway.

[brianubaldo]

thanks for the replies.

im looking in the internet for the general data for line set distance. but its very hard to find one..

many aircon service manuals has no specified total line set distance of pipes.. im just thinking of the maximum allowable for every cooling capacity.. i just need a hard copy of data for future reference.

im thinking of oil migration if i exceed the maximum allowed distance.

bro's is there a general data about this? or just a technical peoples trial and error method?

[BritCit_Juve]

The line size is restricted by the capacity of the system, the fluid velocity and the pressure drop of the line.
If the suction line is too large then the velocity through it willbe low so oil return will be too low.
If its too small the velocity will be too high giving a high pressure drop and this will result in a loss of capacity and excessive wear on the compressor.
Likewise if the liquid line is too large the compressor wont be able to fill it with a steady column of liquid for the tev etc and iff its too small the expansion assy will be starved of refrigerant causing the system to under perform.
The manufacturers take the relative system capacity (which is directly related to refrigerant volume flow) and make a selection based on permitted parameters (lift, drop and temperature range) they then select a pipe size that will work comfortably at these conditions and still give the design capacity.
To simplify matters on the world stage they usually select 15m for the residential product as they can then comfortably select a cheaper compressor and more basic control scheme.
For industrial / light commercial products the select heavier duty components and selet a line size that will give a longer run (typically around 50m)
Sometimes they have to limit the minimum length or give a change in size to acheive the upper limits.
Although it will destroy any chances of warranty a competent refrigeration engineer could size the pipework to acheive the required flow rate over longer than permissable piperuns while still maintaining the required duty by selecting a suction line that will give a pressure drop over its total length of between 1° and 2°C.
A full description and a lot more detail can be found in DOSSAT.
BritCit

[brianubaldo]

thank for the replies..

can you give any links for the general rules of a/c pipe length starting from 1hp to large split systems..

if some installers exceeds the maximum line set distance the condesing unit will suffer. the efficiency of the unit maybe will lessen by 20%?