Your Own

Four-Product Draft System

A cold plate based system design by Pat Babcock

My system came about through a combination of the curved surface of my beer refrigerator and dumb luck.  Let me explain…

My old beer refrigerator is a late ‘50s GE with a slightly rounded top and a curved door.  The compressor on this old gal would freeze Lucifer’s mustache.  For years, I pondered various methods for mounting a stainless steel splash and catch I got from a friend, but the thick walls and curved surfaces pose one hell of a challenge.  I once considered mounting an air-cooled box to the side of the refrigerator or some wooden contrivance to allow me to use my four-faucet stainless steel backsplash and catch on the door, but nothing appealed to me.  Then, one day while thumbing through a Rapids catalog in search of ideas, I spotted a gleaming four-product cold plate.  “This, I thought to myself, “is my holy grail! But how to use it…”

I was still wrestling with the problem of getting the splash onto the refrigerator door, when I heard that my sister had traded her old pop-up trailer in for a new one.  This new one had a built in refrigerator.  Bingo! Her old dorm refrigerator might now be available!  Sure enough: I now had a project. 

To support the refrigerator and house the CO2, the kegs and the spill collector, I built a 25”x25”x36” “services cabinet”.  This cabinet is open at the rear, and has castors for mobility.  It was built of ¾”CDX plywood for no other reason than that’s what I had laying about.

On to the preparation of the refrigerator!  First, I removed the inner shield from the door and replaced it with a piece of plexiglass.  A pattern of small holes was drilled in the bottom right of the panel to help keep the insulation dry.  A hole saw was used to bore through the plexiglass and the refrigerator door for the faucet shanks.  Sections of 1-½” diameter PVC pipe were cut to fit between the plexiglass and the door to prevent the section from collapsing when tightening down the faucets.

A piece of ½” plywood was cut to fit behind the splash.  Holes were drilled for the faucet shanks, and the board was mounted to the door using stainless steel machine screws.  The splash was then mounted to the board using stainless wood screws.

A 2” diameter hole was cut through the floor of the refrigerator to carry the tubing. To protect the tubing from the metal edge, a section of 2” PVC pipe was cut long enough to drop into the hole and the hole cut in the top of the services cabinet below.  This served as the beer line conduit.  To prevent the pipe from simply dropping through, PVC electrical tape was wrapped around the pipe to form a stop. 

With the refrigerator on the cabinet where I expected it to stay, the line conduit installed between the cabinet and the refrigerator, and the refrigerator door closed, the top of the cabinet was marked for the location of the hose for the spill tray drain.  The hole was cut into the top, and a section of fresh water feed line (solid, chromed copper such as used under an exposed bathroom sink) was fed through the hole.  The tube was then flanged over a nut and connected to the spill drain.  Plumber’s putty is used to seal the drain to the base of the pan of the splash.  A length of tubing was connected to the other end and put into an empty 2 liter pop bottle.  This assembly contains any beer which may spill into the pan during use.

Next, four 7’ lengths of  5/16” beer hose were fed up into the conduit.  Swivel nuts were installed on the cabinet end to accept the cornie keg fittings and labels were placed on each end to identify them.  The other ends were connected to the inlets of the cold plate set onto the refrigerator’s shelf.  Four 3’ lengths of 3/16” beer hose were connected to the outlet side of the cold plate.   Permanent “ear clamps” were used to secure the beer lines to the fittings.  (Note that the lengths and diameters of beer hose used are dictated by the design of the cold plate. Check with the manufacturer of your cold plate to determine the lengths and diameters to be used.)

A stainless steel flange was placed on each shank, then the shanks were installed through the refrigerator door and the jam nuts installed and tightened.  The faucet elbows were assembled and then installed onto the shanks.  Finally, the 3/16” beer hose was installed onto each faucet elbow.  The faucet were installed on the front panel to finish off the refrigerator door.

A four-position air distributor with safety relief was installed in the services cabinet.  CO2 hose was installed on each valve of the distributor and on the distributor main.  Swivel fittings were installed on the ends of each of the four keg pressure lines, and the inlet line was installed on one tee of a teed regulator. 

Finally, an eye-screw was installed inside the cabinet to hold the tip-chain for the gas cylinder.  One end of the tip chain slips over the eye.  The chain is wrapped around the neck of the cylinder, then the other end is slipped over the eye. A partially open link of the chain is then passed through the eye to prevent the chain from coming off unexpectedly.

Pieces of foam were placed between the cold plate and the freezer element to help prevent the top of the plate from icing up.  A 1/8” hole was drilled into the side of the refrigerator, and a bi-metal thermometer was installed to monitor the internal temperature.  Finally, the drain of the spill pan was connected to the drain line.

Due to the lengths of hose and the restriction of the plate itself, fairly high pressure is required to drive the system – 35psig!  Since the kegs are stored at cellar temperature while on line, this pressure would spell disaster for any reasonably carbonated beer.  To prevent overcarbonation, the physical law of partial pressures is exploited to mix N2 (virtually insoluble in beer) with CO2 to provide appropriate carbonation pressure at the high line pressure.  In my system, I use 70% CO2 (or 24.5 psia) and 30% N2.  With the kegs at 70’F, the 24.5 psia yields approximately 2.3 volumes of CO2 in the beer – suitable for most styles, and my preferred level.

The system performed admirably.  With the thermostat set to its lowest setting, the interior of the refrigerator stayed at or slightly below freezing – ideal for a cold plate which is designed to be used under ice and water (pretty constant 32’F).  Thermal variation due to the keg being stored warm was evident as occasional foaming during continuous use, but this was never excessive and never a problem.  Serving soda through the system was problematic in two regards: without alcohol, the soda had a tendency to freeze inside the plate and, particularly with aromatic sodas such as root beer and ginger ale, it’s nearly impossible to get the odor and flavor out of the lines.  In hindsight, I’d also use check valves in all the gas lines to prevent “cross contamination” of the flavors. 

Approximate cost to build:  $525 including cabinet, refrigerator and all fasteners.