Sizing new pack

[friging hell]

my boss has got me installing a refrigeration system with 11 cabinets on it totalling 9.5kw, there is 40m of pipework 7/8 and 1/2 (smaller on riser) but with the amount of tees and elbows (90 + 45) the total is about 70m this is without tails and shut off value's.
Is there a point at which pipe size needs to change or the work load of condensing unit changes!
I normally work on smaller singular unit's, this is first pack i've put in and don't want any problems and have to go back again and again and again!

Cheers fella's

[US Iceman]

Is there a point at which pipe size needs to change or the work load of condensing unit changes!


Yes, but it depends on a lot of different factors.

The capacity and performance of the compressors can be affected if the suction line is too small. What happens is the total length of the pipe increases the pressure loss. The total length is usually called total equivalent length.

The total equivalent length is comprised of: total lineal feet of pipe + the equivalent length of the fittings and valves. What this tries to provide is that the valves or fittings will have specific losses associated with them. This loss is provided as an equivalent length of pipe for that fitting or valve size/type.

This has to be done for each evaporating temperature and each suction line!

A similar method has to be done for the liquid lines to prevent the liquid from flashing off into a vapor, which does not effective cooling.

Discharge line sizes to the condenser are also found this way.

If the combination of the pipe, valves and fittings is greater than the pressure losses allowed for selecting the compressor capacity you CAN affect the compressor performance in a bad way.