The refrigerant solution is a mixture of distilled water and liquid anhydrous ammonia. Although
anhydrous ammonia is not illegal to possess in a closed refrigeration system, it is
sometimes difficult to obtain. In some states (especially in the Midwest) laws have
recently been passed restricting the transfer of anhydrous ammonia due to its use in the
manufacture of crystal meth. Be sure to check the situation in your state before you
attempt to build one of these units! Companies that service commercial air
conditioners and refrigeration systems usually have stockpiles of ammonia. Also municipal
maintenance facilities have access to liquid anhydrous ammonia. Anhydrous ammonia must be
stored in large metal cylinders under pressure. So to receive it, you must have a pressure
vessel such as an 11 lb. propane tank ready to go. Showing these folks who service these
commercial cooling units the plans or the absorption refrigerator unit that you have
constructed usually gets them to give or sell you the 7 lb. of ammonia that you need. As a
last resort, you might try someone who repairs camper refrigerators. These people rarely
give anything away.
The generator vessel for this system is an 11lb. propane tank in new or excellent
condition. The condenser vessel is a 5 lb. CO2 fire extinguisher bottle. A stainless steel
(SS) charging valve, a SS shut-off valve, and a SS pressure relief valve also need to be
obtained. The same people that have the ammonia usually have the valves also. Some
commercial machine shops also might be able to order these valves.
One word of caution here. Don't scrimp on the vessels and the valves.
You cannot use the brass valves available in building supply stores. Pressures of up to
250 lb. will be produced within the system. FREON CONTAINERS MUST NOT BE USED
UNDER ANY CIRCUMSTANCES. Since even small quantities of ammonia gas can be
lethal, the entire system must be absolutely gas tight. All testing, charging and bleeding
must be done outside in the open air. Defective or corroded components must not be used.
When completed, the fully charged system weighs about 47 lb. Smaller and lighter systems
can be built by scaling down the sizes of the various components.
The total cost of the system will depend on your scrounging abilities and the local
availability of the various components. The unit shown in the photograph cost the author
about $ 100.00 to build. If you end up buying all the components new, you could spend
about $ 250.00. Liquid ammonia costs about $ 2.00/lb. The 26% ammonia available in
janitorial supply stores can be used to test the unit but it is not concentrated enough to
produce ice. Once the system has been completed and charged, the only additional expense
to produce ice will be the cost of fuel used to heat the unit and the plastic bags for the
ice. Detailed plans and operating instructions may be purchased for $15.00 US.
Detailed plans and operating instructions may be
purchased for $15.00 US.
Download the plans HERE