Problem With Condenser Pipe Length

Manufactures generally recommend 5 to 10 mts for split units. More the pipe length larger pressure drop and it will have its effect on its system performance. For theoretical calculation any book on refrigeration will give details on refrigerant piping design.

With a 30 kw compressor that is a serious capacity which may well cope with 50mts of run. Cooline or the compressor manufacturer would have some detail dependant on advice if a lift to the condenser or if its a horizontal pipe run, Its a rise to the condenser, roof mounted or just higher by four meters, form an oil trap with elbows if you haven't bought one, preferably buy one. My rule of thumb and it works, an oil trap every 3 mts lift, always play safe, compressors are too valuable to abuse the engineering. If its a perfectly horizontal run ensure the run either has a series of oil traps, 3 or 4 mts to ensure the oil is drawn back or the oil runs back to the compressor by the natural fall of gravity. Its worked for me and I've broken some manufacturer's rules by being cautious and ensuring there were oil traps. Compressors are rremarkably resilien if they have a goodly supply of oil. So add additional oil to ensure the traps are filled and the compressor will work well but never starve the oil the life blood, be nosey. The liquid line, always use a filter drier and a sight glass, maybe called a liquid eye to see the action of the liquid in the system. Low cost 3kw units will be short runs assuming back to back installations through the wall. Better quality branded manufacturer's have longer runs, you get what you pay for. Once the capacity starts to increase, 7.5kw, certainly 10kw the pipe run has a serious gas flow and the action takes off, to a practical man, me, it's WHERE THE DUTIES AND THE ENGINEERING WANT TO WORK FOR THE ENGINEER, much more satisfying to observe, test, maintain. Check your tables for increasing the pipe sizes over longer distances to cope with pressure drops and don't break those rules, ever.

As per O&E manual recommended length 25 ft, but we want to extend 45 ft, 30 ft vertical and 15 ft horizontal. Increase pipe diameter may help us but what will be the other factors?

If It was my plant I would go for it!!!!! However, I'm not responsible for your decision and would wish you every success in whatever you choose or you stick with the operating manual. For reference, I always found the same common sense with installing oil lines for oil burners in th e70's and to use solenoids to prevent oil moving or loosing prime in the system. Refrigerants are similar, (but easier to work with) my observation and don't always listen to the Softies or the Consultants. However, we all have to put our money where our mouth is if we add an additional 50% of pipework, your choice.

I believe compressor manufacture's are very conservative and as before as long as there is sufficient oil always to stop the compressor running "dry."

Although I see very few solenoids fitted on other installers systems, I believe in the protection of the solenoid. Solenoids prevent migration of liquid refrigerant to the wrong places when the system stops operating. I have a wish never to loose a compressor for the want of a drier, a solenoid, oil traps, use common sense is the watchword!

I'm presuming the condensing unit is at the low level? Evaporator at the top? My scheme would include a liquid line solenoid before the expansion valve. If there is a possibility of liquid migrating to the fill the drop to the suction line into the base of the system, a solenoid at the top of drop or the outlet (return) of the evaporator. This will prevent any liquid slugging into the cold static compressor when it's turned off, maybe for hours or weeks(?). I have been told I use solenoids when they aren't specified, I play safe and don't replace many compressors unless it's wear an because of old age! That is my justification and I did maintain some important main frame computer sites, 80's-90's where A/C failure was a major problem for the system computers, banks and defence. Best wishes