vacuum pump sizing 1

[thelobster]

Ill be pulling a vacuum on a 240 ton self contained chiller, it has two circuts. My rule of thumb in the past has been 1 cfm per 7 tons of cooling. Looking at the physical size of the expansion valves this could be a 1/3-2/3 set up.IF my rule of thumb is correct, two 10 cfm pumps should be big enough for one circut, but if I use two pumps of equal size will they pull the vacuum oil out of each other and into my refrigeration system.

 

[absrbrtek]

1 10 CFM pump will be plenty. Id be more concerned with the size hoses or copper your going to use between the vp and chiller. If your using 1/4" hoses youll never get the full benefit of the 10 cfm, the hoses will restrict your pumps ability to pull out of the chiller. Use a 1/2 hose if you can. Ive pulled down many a centrifugal with a 10 CFM pump with no problems using 1/2" hose/copper.

 

[thelobster]

thanks I also use 1/2 inch braided hoses.I just wasnt sure of my rule of thumb calculations ,this is one of the biggest machines Ive worked on.We have bigger and with the prices of some of the bigger contractors my company is keeping a little more work in house.Thanks again for the input Ill keep my eyes and ears open in this forum.