Calculating glycol lines

[Higgins]

I've read here that a trunk with 4 glycol lines in it (10 product and up) is only calculated as 1.5 times as much as a 2 glycol trunk. Just wondering if this is true and what the principle of it is.

We are about to install 4 trunk lines with 10 products in each. They are serving 2 locations from beer Y's off the kegs.
I would love to use a 10 product trunk with only 2 glycol lines but I'm not sure if this would be wise.
The runs are
2 @ 30'
2 @ 50'

Without factoring the 1.5 theory of the 4 line glycol this system would have 120' of glycol per 30' run and 200' per 50' run!
Thats 640' of glycol line!!!
This can't be the proper way to calculate as this would require a 1 horse deck with a few pumps.

What is the proper calculation and can this system be cooled by a 1/2 horse unit with 2 pumps (With either 2 or 4 lines of glycol per trunk)

Thanks

[Beer Dr]

Ten product lines with only two glycol lines would be unwise. Glycol lines should always touch your product lines, with 10 lines this wouldn't be possible. Your figures are incorrect, the trunkline length is what you need to go by. Your trunkline total is 160 ft., x 1.5 equals 240 ft. You can use a 250 ft. unit with two pumps or two 125 units.

[Higgins]

Thanks for the help that's good news!
I would however like to know WHY the 1.5 rule works.
2 pumps sounds like the way to go.
Wonder if you can use more pumps than that or if it's redundant.

Thanks again

[Scott Zuhse]

The reason for the 1.5 rule is that the piece of refrigeration (glycol power pack) is required to pull the heat out of a larger conduit. To accomplish this most efficiently, the unit must be sized correctly.

Scott Zuhse, Instructor Micro Matic Dispense Institute