UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA CIRCULAR 329 September, 1933 CONSTRUCTION AND OPERATION OF MECHANICAL REFRIGERATORS FOR FARMS^ JAMES E. TAVEENETTI2 As a refrigerator on the farm may be desirable for any of several reasons, the kind or size recommended depends on the requirements to be met. Small household refrigerators (ranging in size from 3 to 18 cubic feet), are satisfactory for storing small quantities of food for daily consumption. In utility refrigerators (ranging in size from 25 to 150 cubic feet) and used like the small household type, the farmer may store, for home consumption, relatively large quantities of food such as a hog or a quarter of beef, either home-grown or purchased, and may keep limited quantities of produce such as eggs and cream until sufficient is accumulated for marketing. Special refrigerators are rec- ommended for cooling and storing relatively large quantities of a particular product such as milk,^ fruit, and vegetables until marketed. Refrigerators consist of two parts : the cabinet or room, comprising the storage space for the refrigeration, and the refrigerating unit, by which it is cooled. Refrigerating units are supplied by various manu- facturers in practically any size desired, and a farmer generally cannot construct his own or have it built to order. Cabinets may also be pur- chased ready made in sizes up to 100 cubic feet, but a farmer skilled in carpentry can sometimes economically construct his own refrigerator cabinet or room or have it built to order, when a size larger than the small household type is desired. 1 This publication is the tenth of a series reporting results of investigations con- ducted by the California Agricultural Experiment Station in cooperation with the California Committee on the Eelation of Electricity to Agriculture. 2 Associate in Agricultural Engineering and Field Engineer of the California Committee on the Eelation of Electricity to Agriculture. 3 More specific information on dairy refrigeration may be found in Bulletin 495, "Milk Cooling on California Dairy Farms." University of California — Experiment Station DESIGN OF REFRIGERATOR CABINETS AND ROOMS Types. — The type of cabinet or room — namely walk-in, non-walk-in, or semi-walk-in — depends upon the size and use. With the non-walk-in types (figs. 14 and 15), a person standing outside the door can reach in to place the produce in the refrigerator. In size these usually range up to 60 cubic feet, although one or two manufacturers construct them with capacities up to 100 cubic feet. Depth and height are limited, an increase in volume being obtained by increasing the width. The depth is usually about 24 inches and should not be over 30. The height varies with the height of storage space desired plus the height necessary for the coil and baffle if the latter are installed across the top. The storage space should not be over 6 feet high ; the over-all height of the cabinet, not over 8 feet. The walk-in types (fig. 17) are those which one may enter. In size they range from 100 cubic feet up. The semi-walk-in type (fig. 16) combines the first two: besides a walk-in door there is also a small reach-in door through which a portion of the inside may be reached. The size usuall}^ ranges from 75 to 125 cubic feet, although a large walk-in refrigerator sometimes has a small door opening upon shelves in a corner. Household refrigerators are all of the non-walk-in type, while the special refrigerators are generally of the walk-in variety. Utility refrig- erators may be any one of the three, but are usually non-walk-in, semi- walk-in, and walk-in for small, medium, and large sizes, respectively. Size. — The size of a refrigerator may be expressed in two ways: either as the total inside volume or as the volume available for storage. The latter is equal to the total volume less that occupied by the coil, baffle, and clearances for air circulation ; it is usually about 75 per cent of the total. Sizes mentioned in this circular refer to the net storage capacity. Household and utility refrigerator sizes are somewhat arbitrary because the quantity of produce to be stored cannot be determined exactly. A refrigerator larger than seems necessary is usually best, for the amount stored increases when space is available. The size of the special refrigerator may be rather accurately determined, since the amount to be stored can usually be estimated. Table 1 gives the approxi- mate storage space required for difi:erent individual units of farm products, and for containers in which they are stored. CiR. 329] Mechanical Refrigerators for Farms Location of Cooling Coil. — The cooling coil may be placed at one side, in the center, or overhead. If it is on the side (figs. 1, a and c) , as usually in small household refrigerators, the air first circulates downward TABLE 1 Approximate Storage Space Necessary for Various Sizes and Types of Farm Produce and Containers Article Apple box.. Berry crates . 12-pint 15-pint 24-pint shallow. 24-quart 32-quart Cantaloupe crates Cauliflower crate Celery crate Standard Pony Jumbo Standard flat. Pony flat Jumbo flat Cherry boxes.. Eastern... Lambert, Orange box Lemon box Grape box Lettuce crate Los Angeles lug Egg crate — 30-dozen.. Milk cans.. Bottle crates / 10-gallon. \ 5-gallon. / 12-quart... \ 20-pint Beef carcass — 600 pounds Rear quarter of beef— 150 pounds ... Front quarter of beef— 150 pounds Hog carcass— 150 pounds Lamb carcass — 50 pounds Veal carcass— 100 pounds Turkey — 12 pounds Chicken — 4 pounds Length, inches Width, inches Height, inches 20 12 13 20 15 5 23 15 5 24 18 7 24 12 13 24 16 13 24 13 13 24 12 12 24 14 14 24 15 6 24 13 5 24 16 6 25 19 10 25 22 23 20 10 4 20 11 5 26 13 13 27 12 15 18 15 6 25 19 14 18 14 8 27 13 14 15 15 24 12 12 20 20 15 11 20 15 9 48 30 120 20 15 60 48 15 60 18 15 60 12 12 48 18 12 60 12 10 20 8 6 12 through the cooling coil and the space below, and then upward through the main storage compartment. The advantage of this arrangement is that the box can be made lower and is more easily constructed. The disadvantage is that the coldest part of the refrigerator is the rela- University of California — Experiment Station tively small space directly below the cooling coil, while the warmest part is usually at the top of the main storage compartment, where meat is hung. With the cooling coil in the center (fig. 1,1)), the construction is the same as at the side except that large storage spaces are on both sides of the coil. ^^ N \ /- K>ni \ COIL A / S .nWWWWWWW^^ NX\\\\\\\\\\\Y\\\\\\\\\\\\\\\\\\\\\^^^^ ^ /-"/^t COIL \ / $\\\\\\\\\\\\\ \\\\\\\\\\\\\\\\\\\^^^ Fig. 1. — Location of the cooling coil: a, side coil in non-walk-in refrigerator; b, center coil in non-walk-in refrigerator; c, side coil in walk-in refrigerator. Arrows indicate the direction of air currents. With the overhead construction (figs. 2, a and h), the cooling coil is located across the top of the box. The air circulates either downward in the center and upward along the front and back walls, or downward along the back wall and upward along the front wall, according to the type of baffling. This location has the advantage that the circulation of the air is uniform across the box, so that there can be separate com- CiR. 329] Mechanical Refrigerators for Farms partments, each cooled by separate air currents. The disadvantages are greater over-all height and more difficult construction. Baffling. — The main purpose of baffling in the refrigerator is to direct the air currents and catch the drip from the cooling coil. As the air circulation is of prime importance, one must be careful to construct the baffle correctly and to allow sufficient clearance. In the overhead type of construction the baffling may be of either the L or the V type. With the L type baffling (fig. 2, a), the clearance around the baffle for air circulation should be about ^ the depth of the refrigerator, the Coil \'i\']j ^ / N N kWWWWWW^ \\\\\\\\\\\\\X\\\\\\\\\\\V^V^\N 10 ^ r X ^ Coil Coil \ Lss^a^^-^^ S2 c c o 8 ft \ ''' W jv^ ^^\\\\\\\\\\\\\\\\\\\\\\\\\\\ d b Fig. 2. — Location of the cooling coil and type.s of baffles: a, over- head coil with L type baffle ; ft, overhead coil with V type baffle. top of the baffle should be on a level with the top of the cooling coil, and approximately 3 inches clearance should be allowed between the bottom of the cooling coil and the baffle. With the V type baffle (fig. 2, 5), the clearance in the center for air circulation should be approxi- mately ^ the depth of the refrigerator ; that on the two sides and top, approximately %o the depth. With the side and center type coils, the clearance for air circulation should be the same as for the L and V type baffles, respectively. Portability. — On some farms, particularly those that are rented, the refrigerator should be portable. If small, it can be moved as a unit. If relatively large — from 25 to 150 cubic feet, — it can be made in sec- tional construction and taken apart at will. In this type, each wall and the top and bottom are separate sections, held together with lag screws when assembled. Such construction has another advantage : the sections can be built in a convenient place and then assembled in a room whose doors are too small to admit the complete cabinet. 6 University of California — Experiment Station With large refrigerators — 150 cubic feet and up — the box is usually made solid, either as a separate cabinet or as an entire room in a building. Although this type is more easily constructed, it has the dis- advantage of not being portable. MATERIALS USED IN REFRIGERATOR CABINETS AND ROOMS Insulation. — Insulation serves to decrease the quantity of heat con- ducted through the refrigerator walls. It should have a low heat transfer factor and low moisture absorption ; it should also be odorless, Fig. 3. — Various kinds of insulating materials: a, corkboard; h, vegetable fiber board ; c, granulated fill insulation ; d, felted sheet insulation ; e, fiber fill insulation. vermin and rodent proof, not easil}^ settled or disintegrated, reason- able in cost, and easily obtained and installed. On the market are many different kinds of insulations made from various materials (fig. 3 and table 2). Some are available in the sheet form, the material being pressed into sheets, quilts, or felts ; and some in loose form, the individual fibers being loose or the material coarsely ground. The first forms are known as sheet insulation, and the latter as fill insulation. The former have the advantages of being more easily made moisture-proof, of not settling, and of usually having a lower heat transfer factor. They have the disadvantages of being relatively high in first cost, of being harder to install, and of requiring the framing to be of a definite width. Fill insulations have the advantages of being low in first cost, of being easily installed, and of fitting into any space. CiR. 329] Mechanical Refrigerators for Farms 7 They have the disadvantages of not being easily made moisture-proof and of tending to settle. Vegetable cork in the sheet form (sheet cork or corkboard), one of .the best insulations, is usually recognized as standard. For refrigerators up to 125 cubic feet, it is generally considered economical to use the equivalent of 3 inches of sheet cork : above 125 cubic feet, the equivalent TABLE 2 Various Insulating Materiai.s and the Thickness Equivalent to One Inch of Corkboard Trade name Description Thickness, in inches, equivalent to one-inch corkboard Balsa wood Bark from Balsa tree 1 11 1.00 Cabot's Quilt 1.00 Celotex Matted cane fibers 1 05 20.00 Corkboard 1.00 Fibrofelt Felted vegetable fibers 1 09 Fla.'flinTiTTi Felted vegetable fibers 1 06 1.33 Hair-felt Felted cattle hair Aerated cellular gypsum 1 00 Insulex 2 00 1.10 Kapok 1.00 Linofelt Confined vegetable fiber 1 00 1.25 1.05 Mineral wool Fibers blown from slag 1 00 Pressed fibers blown from limestone 1.00 Redwood fiber 1.00 Wood 3.00 of 4 inches of sheet cork. If fill insulation is used, the thicknesses should be increased to 4 and 6 inches, respectively. Sheet insulations such as corkboard and rock cork are available in sheets 12 or 18 inches wide, 36 inches long, and 1, 1^/2, 2, 3, and 4 inches thick. Vegetable fiber sheet insulations are usually available in sizes 3 to 5 feet wide, 8 to 12 feet long, and about i/o inch thick. Structural Materials. — Wood and poured concrete are the common structural materials used for farm refrigerators. Concrete is quite generally used for large walk-in refrigerators and for milk storage rooms on dairies, but cannot be used for sectional construction. Wood will serve for any type and size refrigerator, although in places subject to wear or moisture it must be protected by a covering of galvanized iron. 8 University of California — Experiment Station Concrete has certain advantages : (1) it is relatively permanent ; (2) it is fire-resistant; (3) it may be w^ashed without injury; (4) it needs no paint or varnish. The disadvantages are : (1) its high initial cost and (2) its limitation to use in nonportable refrigerators. The advantages of wood are : (1) it can be used on any type or size of refrigerator; (2) it has a lower initial cost; (3) it makes construc- tion easier. The disadvantages are: (1) it is not permanent; (2) it is easily damaged and must be protected in places of wear; (3) it is not fire-resistant ; and (4) it must be painted or varnished. Other materials such as concrete blocks, hollow tile, and brick are sometimes used. They have approximately the same properties as TABLE 3 Grades of Various Kinds* of Lumber Suitable for Eefrigerators Use Douglas fir Ponderosa pinef Redwood Maple No. 1 common "B" flooring Moisture proof No. 1 select No. 1 common "B" select, and bet- ter T & G Moisture proof Heart, common standard T & G Moisture proof Matched sheathing Shelves and meat hook bars Firsts and seconds * Spruce is commonly used for the inside sheathing of ready-made refrigerators because it does not give an odor, but it is not generally stocked by lumber yards and is relatively expensive, t Often sold commercially as mountain pine or California pine. poured concrete, though a material such as hollow tile increases the insulating value of the wall. The initial costs of these materials in most localities lie between those of wood and poured concrete. In small refrigerators (125 cubic feet or less), moisture-proof ply- board (1/2 inch or more) is sometimes used for the inside sheathing. It has the advantages of easier construction and no cracks, but the dis- advantage of higher cost. Lumber used in the construction of a refrigerator must be straight and dry. The kind will depend upon the local stock available and the price. Grade-marked lumber (table 3) is recommended because it will be of the quality specified. Doors. — Being subject to hard usage, refrigerator doors must be well made. Otherwise, they are liable to warp, swell, and lose their shape; they may become hard to open and close and may allow air leakage. Preferably, therefore, they should be bought from a manufacturer familiar with refrigerator construction. When doors are purchased, the jambs and sills are included. Choice among the three types of sills available depends upon the type of CiR. 329] Mechanical Refrigerators for Farms refrigerator constructed. Where the refrigerator floor is above the surrounding floor, the high sill (fig. 4, &) is used. Where the two floors have approximately the same level, one may use either the bevel wood sill (fig. 4, a) or the angle-iron sill (fig. 4, c) . The latter is recommended if the sill will be subjected to moisture or hard wear, as in dairies. AMQLt lR.0Id6 HOLDIM^ --•/■•v---. ::'.Il:>:■:•;•■:-> JAME)5. JAM5 WALL 6TUJ)57 (3A5K.E.T5^ E^Tnm^ ^ Fig. 4. — Various types of door sills and a horizontal section of an installed door : a, bevel wood sill ; b, high sill ; c, concrete sill ; d, horizontal section of an installed door. The number and size of the refrigerator doors will depend upon the type of construction. The non-walk-in cabinet should have enough doors to give easy access to the whole interior. The usual practice is to have each door a little smaller than the compartment into which it opens. With the semi-walk-in and walk-in refrigerators, one walk-in door is usually sufficient. The sizes of walk-in doors run from 2 feet by 6 feet for small refrigerators up to any dimensions desired. For openings over 5 feet in width, double doors are used. The most common size for a door is 21/2 X 6 feet. Certain sizes considered as standard should be used whenever possible because they are usually stocked by the manufac- 10 University of California — Experiment Station turers and cost less. If a special size or type of door is desired, it may be purchased made to order. Standard doors may usually be obtained in widths of 2, 2V2, 3, 3Vi>j 4, 4I/2, and 5 feet ; and in heights of 2, 3, 5, 6, 6l^, and 7 feet. These dimensions are those of the clear opening. In ordering standard doors, specify the clear opening desired, the type of sill, and the method of opening, whether right or left hand. Right-hand doors swing to the right ; left-hand, to the left. In ordering special doors, specify also the type and thickness of insulation. All locks on walk-in doors should open from both inside and outside. As the wall opening necessary for the jambs of a door varies in size with different manufacturers, it should not be made until the door has been obtained. For walk-in doors, it is usually about 5 inches higher and 7 inches wider than the clear opening. For non-walk-in refrigerators where the front is made up almost entirely of doors, the whole front including the doors had better be made to order. Miscellaneous Materials. — Asphaltum, which is generally used for moisture-proofing the insulation, should be of a grade suitable for this job and should have a melting point of between 150° and 200° F. A heavy grade of moisture-proof building paper should be used between the insulation and the sheathings. Galvanized iron for covering the baffle and floor should be No. 20 gauge. If used on the walls and backs of tlie doors, it shouhl be No. 24 gauge. Lag screws should be galvanized, and wood screws should l)e either brass or nickel-plated. CONSTRUCTION OF REFRIGERATOR CABINET AND ROOMS Walls. — With concrete and sheet insulation the wall construction is usually as shown in figure 5, c. It consists of an outside concrete wall, approximately 4 inches thick, against which the insulation is placed and held by either hot asphalt or mortar, and an inside finish of approxi- mately 14 inch of cement plaster. The procedure in construction is to build the foundation, outside walls, and top, and then to install the insulation, cement plaster, door, refrigerating units, baffle, racks, and shelves in the order named. The insulation should be in two layers with staggered joints, the inside layer being fastened to the layer adjoining the concrete by wood skewers driven at an angle. Either mortar or asphaltum will hold the insulation in place and seal the joints. When using the latter, do not coat the Cm. 329] Mechanical Refrigerators for Farms 11 surface on which the cement plaster is to be placed, for the plaster does not adhere well to asphaltnm. With wood and sheet insulation the usual type of wall construction (figs. 5, a and h) consists of insulation between the framing members with moisture-proof building paper and tongue-and-groove sheathing ln5ufdiior)-0' ro5^-ry>5tud5 y\yM.w)j}j%ii\ymu»jMKKK k v»})m.KKKKiiin»».KK «■«.^l^^^At«■^^^^^ -Cro3S-rdil3-2"x.6" Z\6' corner ^tudi Moisture-ppoo/ \ buildinq paper iNSbealhinq (vertical) d iitJIIIH.\K\^})}>MJM^tj>tj,mif)>»m,> ■\\W\MlllllK\i~f1tl/fa Fig. 8. — Construction features of refrigerator walls using fill insula- tion : a, solid studs and horizontal sheathing ; h, staggered studs and horizontal sheathing; c, corner sections of a wall, top, and floor using horizontal framing and vertical sheathing; d, corner section of two walls using horizontal framing and vertical sheathing. With fluffy insulation such as redwood bark fiber and mineral wool, the framing members and sheathing may be either horizontal or vertical, for the insulation will stay in position. In nonportable refrigerators with insulation such as ground cork, the framing members must run vertically and the sheathing horizontally, for the insulation must ])e CiR. 329] Mechanical Refrigerators for Farms 15 poured into place as the sheathing is nailed on. With the knock-down construction where the walls are built as individual units and may be laid flat for installing and insulation, the framing members and sheath- ing may run in either direction. Moislure-proo^ buildinq paper ■In5ul<3fion-5" 'Cro5C> roil- I Jx^i Insulaiion-E" /Concrete /loor~2' ';;:.'! •-•5 bea t h i n(^ - ("x 4" T.4. G. -Moisture-proo/* buildincj poper ln5uldiion-4" ^^ * ~Cro55 - r<3 i I - 2"x4" ^','/ \ ; /ln5U laf ion - 2" y. rConcrcte fioor-Z" ik.:^. ... an n/[r NAoisturc- proo/' fill in«3ulatior) 2'k4"5ll' b. Cement planter- •|'' Obcet inouldtion-^" Oneatmn<3 Conc^et^ ^^^^^^^^^^-^^^ i G. Fig. 9. — Corner sections of wall and floor using combination of structural materials: a, wood and sheet insulation with concrete floor; b, wood and fill insulation with concrete floor; c, concrete foundation and floor with wood, sheet, and fill insulations. Construction with these materials proceeds as with sheet insulation except that the insulation is packed into place as the inside building paper and sheathing are being put on. With a combination of wood, concrete, and sheet or fill insulation, another method is shown in figures 9, a and h. It consists of ordinarj^ 16 University op California— Experiment Station wood construction with provision for a concrete floor and a cement- plaster inside wall up to approximately 1 foot above the floor. Figure 9, c shows a combination consisting of a foundation, floor, and inside finish of concrete and cement plaster, and double walls of wood with both sheet and fill insulations. The framing members are in the outside wall, with moisture-proof building paper and sheathing on either side and with fill insulation between. The sheet insulation is Q I van i zed iron fx.4" l^Q; Wdl<3r-pro buildin<^ pcvp Fig, 10. — Section of a baffle, showing construction features. Tlie vertical section should be attached to tlie horizontal section by screws so that it can be easily removed. asphalted, nailed to tlie inside sheathing of the outer Avail, and finished with cement plaster. This type of construction is often used in refrig- erators built in as part of a room Avhose walls may serve as the outer wall of the refrigerator. Baffle Construction. — Figure 10 shows a good baffle construction. It consists of two parts : a horizontal section in which two layers of matched lumber run in opposite directions with building paper between and in which a covering of 20-gauge galvanized iron is bent into a trough on the lower edge; and a vertical section of a single layer of matched lumber. The vertical section should be 3 inches greater from the top surface of the horizontal section to its top than the height of the cooling coil to be used. The approximate over-all width of the baffle should be % the inside width of the refrigerator for L type baffles, and 1/8 the inside width for the V type baffle. The vertical section should be easily removable in order to permit access to the cooling coil. CiR. 329] Mechanical Refrigerators for Farms 17 Fig. 11. — Types of meat hook racks: a, rails around the walls; &, inclined bars; c, removable bars. 18 University of California — Experiment Station Racks and Shelves. — When meat is hung in the refrigerator, a rack is desirable. The most common types are shown in figure 11, a and h. One consists of an incline with bars in different horizontal and vertical planes ; the other, of a rail around the wall. These racks have the advan- tage of convenience in hanging the produce but the disadvantages of not being easily removable and of wasting space. — Z" Fig. 12. — Various types of meat hooks: a, for two-inch wood bar; &, for one-half inch steel bar; c, screw; d, "S" hook. Another type of rack (fig. 11, c) consists of individual horizontal bars across the refrigerator, held in place by brackets on the ends. It has the advantages that any portion or all of the bars are easily removed and that all the storage space may be utilized because as many bars as desired can be put in position to accommodate any particular produce. If, for example, poultry is being stored, one set of bars can be placed across the top, another below this set, and perhaps another below that, so that three carcasses can be hung one above the other. In placing car- casses in the refrigerator, remove the bars and start at the rear; as each bar is loaded, insert another until the entire refrigerator is full. In storing carcasses such as of hog or veal that will require the entire height of the storage space, one can remove the lower bars and use only the top set. CiR. 329] Mechanical Refrigerators for Farms 19 The type and size of bars varies with the kind of meat hook used. Figure 12 shows the various meat hooks available. The bars for the wood-bar type of hooks should be a full 2 inches in width to prevent the hooks from twisting on the bar and injuring the corners. The depth of the bars will depend upon the distance between supports, as shown in table 4. Shelves in the refrigerator are for convenience in placing produce and for utilizing as much storage space as possible. They may be ready- made of metal or specially made of wood, but should be so constructed that air will pass through. Metal shelves have the advantage of less bulk, easier cleaning, and greater durability ; the disadvantages of not TABLE 4 Dimensions of Bars for Various Distances Between Supports Distance between supports, feet Up to 3 3 to 5 5 to 8 Dimensions of wood bar, inches 2x2 2x3 2x4 Dimensions of steel bar, inches ^xl ^^x2 '2X3 being readily available and of b6ing made in certain sizes that necessi- tate fitting the storage space to the shelves. Wood shelves, though easily made in any size and shape* desired, have the disadvantage of being subject to wear, not easily cleaned, and less sanitary. Hardwood such as maple is desirable for shelves ; but when it is not available, spruce or Oregon pine may be used. The size of the slats should be not more than 1x2 inches nor less than % x 1 inch ; and the space between slats should be from % to 1 inch. All shelves should be removable both for cleaning and for making the storage space available for produce that requires more height than that between the shelves. Ice Making and Water Cooling. — Ice making, though desirable, re- quires extra equipment and extra initial and operating expense. In small household refrigerators, ice is made by the main cooling coil. In large refrigerators, this arrangement is not practicable, because coils with ice-making facilities are limited in size and cannot be operated on a defrosting cycle. In the latter case, therefore, the usual method is to have two coils, one the main cooling coil and one an ice-making coil in a small compartment insulated from the rest of the refrigerator (fig. 14). Both coils are operated from the same compressor, but the temper- ature of each is separately regulated by a special valve arrangement. 20 University of California— Experiment Station Cold drinking water may be provided by one of three methods: (1) A container of water 'may be placed in the refrigerator. This plan, though least expensive, is inconvenient because the container must be removed from the refrigerator for filling and for obtaining the cool water. (2) The refrigerator may contain a permanent tank, which is filled either from inside or outside and from which water may be obtained through a faucet either on the inside or outside. This, though more convenient than the first method, costs more. (3) Inside the refrigerator there may be a coil, connected to a water main, and to a TABLE 5 Length in Feet of Various Sizes of Pipes to Contain a Given Quantity of Water Gallons of water ■ Size of pipe, inches 0.5 1.0 1.5 2.0 2.5 3.0 H 16 3 10 5.8 4 3 2.6 20 11 6 8 3 5 2 3.6 17.4 12 8 7.8 5 4 3 5 23.2 17 10 4 7 2 4 6 ; 21 5 13 9 6 1 IM IH 2 15 6 2H 10 8 3 ... 6.9 faucet on the outside. As cold water is witlidrawn from tlie faucet, the coil is automatically refilled. Table 5 gives the approximate lengtlis of various sizes of j)ipes neces- sary to hold a given quantity of water. Finish. — Concrete requires no finish other than a smooth surface, but wood must be either painted or varnished as desired. If painted, it should have two coats of aluminum paint as a primer and one or more coats of enamel paint of the desired color for the finish. If varnished, it needs two coats of shellac as the primer and two coats of spar varnish as the finish. The shelves and meat hook bars should not be painted or varnished, but should be given a coat of hot paraffin. All metal coming in contact with the stored produce should be gal- vanized ; and all other metal, such as bars for the meat hooks, should be coated with aluminum paint. General Construction Notes. — A refrigerator must be carefully con- structed in order to look well and work efficiently. All joints and corners should be tight to prevent air leakage either into the insulation or from outside to inside of the refrigerator and vice versa. Particularly Cm. 329] Mechanical Refrigerators for Farms 21 with sectional construction, the dimensions must be exact and the corners right angled so that the sections will fit together properly. The framing members for sheet insulation must be of a definite and uniform width (% inch wider than the thickness of insulation) ; they are usually ripped from stock sizes. When possible, the lumber should be ripped at the lumber yard or a mill, wiiere a better job can be done and labor saved. In spacing the framing members with sheet insulation, two methods may be used. According to the first, the members are spaced so that standard-sized insulation sheets will fit between without cutting, Vs inch extra being allowed for the asphalt. Waste and cutting of the insulation are thus saved, though more accurate work and more time are required. The other method is to space the members any desired distance and cut the insulation to fit the spaces. Construction is easier because a variation in the spacing is immaterial, but the required cutting of the insulation causes a certain amount of waste. In no case should the members to which matched lumber sheathing is nailed be over 2 feet apart. Because refrigerator doors are much heavier than the ordinary and are often severely jarred, the framing around them should be extra heavy. For doors up to 2 ft. 6 in. x 6 ft. 6 in., the framing (fig. 4, d) holding the side jambs should be not less than 4 inches wide and should be securely fastened at the top and bottom. For doors larger than the above, the side framing should be not less than 6 inches wide. If spikes are used to hold the frame together, holes should be bored to prevent splitting of the lumber. The building paper under the sheathing should be lapped at least 6 inches, or a double layer used. Coating the insulation with asphalt may be accomplished by painting with or dipping in hot asphalt. Painting is more tedious, more difficult, and less satisfactory than dipping. Do not coat the surface of the insula- tion on w^hich plaster is to be applied. After installing the insulation, fill all holes or cracks with asphalt. Iron bands ^4 x 1^4 inches on the outside of the sheathing, lag- screwed to the framing of the top and bottom, may be used for holding the sections of a portable refrigerator together instead of the lag screws placed as in figure 5, h. Concrete floors should slope toward the door or toward a drain in the refrigerator so that water will not stand on the floor. 22 University of California— Experiment Station REFRIGERATING UNIT The refrigerating unit is composed of two main parts, the compressor and the cooling coil. Both contain a substance known as the refrigerant which is liquid during part of the refrigerating cycle and vaporous the ^ LEGEND " <\ |v-- • : -M Lo\^ pressure ^■^ vapor. M^mm^ H/gh pressure ^opor. Y/////A Lo^ pressure . //gu/'d. H/gh pressure //(^uid . Fig. 13. — Kcfrigerating unit showing the parts and condition of the refrigerant in each: a, compressor; &, condenser; c, float valve regu- lating flow of refrigerant into cooling coil; d, cooling coil; e, sylphon bellows operating motor switch. rest of the time. It acts as a medium for transferring heat. Figure 13 shows the parts of a complete refrigerating unit and the condition of the refrigerant in each. The operating cycle of the unit is as follows : (1) the vaporous refrigerant is raised to a high pressure in the com- pressor cylinder, a; (2) the refrigerant is cooled in the condenser, hy Cm. 329] Mechanical Refrigerators for Farms 23 either by air or by water, and is changed from vapor to liqnid ; (3) the liquid refrigerant is released throngh a valve c into the cooling coil d in the refrigerator, where it is under a low pressure; (4) the change in pressure lowers the boiling point of the refrigerant to a temperature below that surrounding the coil, heat is consequently absorbed from the interior of the refrigerator, and the refrigerant boils; (5) the vaporous refrigerant is drawn out of the coil by the compressor, and the cycle is repeated. The sylphon bellows, e, expanding or contracting as the tem- perature of the cooling coil increases or decreases, closes or opens the electric circuit to the motor. Compressors with water-cooled condensers have the advantages of lower pressures and more capacity per horsepower ; the disadvantages of requiring both a flow of water (when the compressor is operating) and some means of disposing of the water. They are recommended where extra warm air temperatures occur or where water is readily obtained and disposed of. Compressors with air-cooled condensers have the advantages of not requiring water and of being easily installed; the disadvantage of less capacity per horsepower. The efficiency of both water and air- cooled condensers decreases with increased temperatures of the cooling medium. The size of the compressor and cooling coil required for a refrigerator varies with the outside area, the temperatures inside and outside, and the amount of produce cooled. Since the type of produce stored in household and utility refrigerators does not differ greatly on different farms, definite figures can be given for the size of refrigerating unit necessary. The equivalent pounds'* or refrigerating capacity necessary per square foot of outside area every 24 hours for each degree temperature dift'erence (Fahrenheit) between inside and outside is 0.02 and 0.016, respectively, for the equivalent of 3 and 4 inches of sheet cork insula- tion. This holds for both household and utility refrigerators under conditions of ordinary farmers. The air circulating in the refrigerator absorbs moisture from the stored produce. When passing over the cooling coil, this moisture is condensed and frozen, forming frost that tends to decrease the efficiency of the coil. When the refrigerating unit operates on a defrosting cycle, the temperature of the coil between the time the compressor stops and starts is allowed to rise above 32° F : the frost is then melted, caught by 4 An equivalent pound of ice-melting effect is the quantity of heat necessary to melt one pound of ice. 24 University of California — Experiment Station the baffle, and drained out of the refrigerator. The compressor must not operate more than a total of 16 hours per day in order for the refrigerat- ing unit to run on a defrosting cycle. The following example shows how to figure the size of refrigerating unit necessary for household and utility refrigerators : Assume a refrig- erator cabinet with outside dimensions of 4 x 5 x 8 feet, insulated with the equivalent of 3 inches of corkboard and operating with a difference of 45° F between the temperature of the refrigerator and that of the surrounding air. The outside area is 2 (4x5) +2 (4x8) +2 (5x8), or 184 square feet. The capacity necessary per square foot per degree for 3 inch insulation is 0.02, so that for 184 square feet and 45° differential the capacity necessarj^ would be 184 times 0.02 times 45, or 166 equiva- lent pounds of ice-melting effect. The cooling coil necessary for the re- frigerator would, therefore, need a capacity of 166 pounds per 24 hours. The compressor operating on a defrosting cycle cannot run over 16 hours a day, so that its capacity must be 166 pounds per 16 hours, or 166 times %, or 249 pounds per 24 hours. Table 6 shows that a i/^-horsepower com- pressor, either air or water cooled, would be satisfactory. Because the type and quantity of produce stored in special refrig- erators may vary greatly on different farms, no definite figures for the size of refrigerating unit can 1)e given. The size necessary must, however, be large enough to extract the heat conducted through the walls plus the heat given off by the produce cooled. The heat conducted through the walls is constant for a given thickness of insulation and is equal to 0.016 and 0.012 pounds of ice-melting effect per square foot per degree temperature difference for the equivalent of 3 and 4 inches of corkboard insulation, respectively. The following example shows how to calculate the size of refrigerat- ing unit necessary for a special refrigerator. Assume a refrigerator with outside dimensions of 5 x 6 x 9 feet, operating with a 50° temperature differential, insulated with the equivalent of 4 inches of corkboard, and cooling 120 gallons of milk per day from 90° to 40°. The heat conducted through walls equals 258 times 0.012 times 50, or 155 pounds of ice- melting effect. The heat extracted from the milk is equal to 120 times 8.6 (the weight of a gallon of milk) times 0.9 (the specific heat of milk) , times 50, divided by 144 (the heat required to melt one pound of ice), or 322 pounds of ice-melting effect. The capacity of the refrigerating unit must be equal to 155 plus 322 times %, or 715 equivalent pounds of ice-melting effect per 24 hours. From table 6, either a 1-horsepower air-cooled or a %-horsepower water-cooled compressor would be satis- factory. CiR. 329] Mechanical Refrigerators for Farms 25 The two most important items to consider when buying a refrigerating unit are the proper size and the service available. The latter is important because a farmer cannot repair his own unit unless he is thoroughly familiar with it and has the proper tools and replacement parts. TABLE 6 Approximate Capacities of Compressors per Horsepower per 24 Hours IN Equivalent Pounds of Ice-Melting Effect Horsepower of motor Capacity, pounds of ice- melting effect per 24 hours V5 H y%- % 1 . 2 . 3 . 5 , 10 . 350 500 750 1,000 1,500 2,000 3,000 5,000 7,500 10,000 COSTS Initial Costs. — The initial costs of a refrigerator vary widely with the use, size, type, materials used, and whether the cabinet or room is built on the farm, made to order, or purchased ready-made. Table 7 gives approximate total costs per cubic foot of various types of refrigerators. The large sizes of each type approach the lower limit in cost ; the smaller sizes, the upper limit. The cost of the refrigerating unit usually ranges from 50 to 75 per cent of the total cost of a refrigerator. For household refrigerators, the refrigerating unit cost is approximately 75 per cent of the total, and usually no saving made by constructing the cabinet will justify the trouble and poorer product. If one must estimate the cost of a refrigerating unit, several dealers should be consulted. Operating Costs. — The cost of electricity for operating the refriger- ating unit varies with the use, the amount of produce cooled, the thick- ness of insulation, and the temperature differential between inside and outside. 26 University of California— Experiment Station The operating costs for special refrigerators will be more than those for household and utility refrigerators when a large quantity of produce is cooled each day, and less when the produce is left in storage for rela- tively long periods. With electricity at 11/2 cents per kilowatt hour, the estimated average cost per month throughout the year for household and utility refrig- TABLE 7 Approximate Cost per Cubic Foot of Storage Space for Various Types OF Refrigerators* Type of refrigerator Built on farm by hired carpenter Ready-made or built to order Household dollars 10-15 G- 8 5- 2-5 dollars 25-50 12-20 8-10 1 Walk-in 6- 8 Sn(¥>inl Tvalk-in * Includes cost of both cabinet or room and rcfriKcraliuK unit. erators is ^1S)() and $1.25 ])er 100 s(|ii;ii-c iVct <»!' outside i-ct'i-igerator area for the equivalent of 3 and 4 inch corkhoard insulation, resi)ec- tively. With electricity at 31/2 cents, tlie estimated average montlily cost is $3.50 and $2.90 for the equivalent of 3 and 4 inch corkboard insiihi- tion, respectively. OPERATION OF THE REFRIGERATOR Location. — The refrigerator cal)inet or room must usually be located where convenient space is availa))le. It should, liowevcM-, I)e in as cool a place as possible, never in direct sunlight. The compressor should have a cool environment such as the basement or space under the house, but should ])e easily accessible for servicing. Air-cooled compressors should not be enclosed or ])bK'e(l in a location that will interfere with the circulation of air over the condenser. Care. — Though the interior of the refrigerator should l)e kept clean, free water should never be used on wood construction. Washing at least once every two weeks with a clean s])()nge or rag and a solution of washing soda, followed by wiping with pure water, is recommended. Repainting or varnishing when necessary' will help ])r()long the life. Instructions should be obtained from the manufacturer as to the care and adjustments of the refrigerating unit. Cm. 329] Mechanical Refrigerators for Farms 27 The doors should not be opened oftener than necessary, lest the operating cost be increased. They had better be opened a few times for relatively long periods, however, rather than a nnmber of times for short periods. TABLE 8 Approximate Cold Storage Temperatures of A^arious Farm Products* Article Apples Apricots Asparagus Bacon Beans, string Beef Blackberries.. Butter Cabbage Cantaloupe .. Carrots Cauliflower... Celery Cherries Cheese Cream Cucumbers... Currants Dates Eggplants Eggs Figs Fish Fruit, dried . Grapefruit Grapes Ham Tempera- ture, degrees Fahrenheit 32-40 32-36 32-40 35-40 35-45 33-38 32-40 30-40 35-45 32-40 32-40 32-40 32-40 32-40 35-45 35-45 40-45 32-40 50-60 35-45 32-40 45-55 25-35 35-45 32-40 32-40 32-40 Article Honey Lamb Lettuce Lemons Salt meat Melons Mushrooms.. Nuts Milk Onions Oranges Peaches Pears Persimmons. Plums Pork Potatoes Poultry Prunes Rabbits Radishes Raisins Raspberries . Sausage strawberries Tomatoes Turnips Veal Tempera- ture degrees Fahrenheit 35-45 32-38 32-40 35-45 40-45 35-45 32-40 35-45 35-45 35-45 32-45 35-45 32-40 32-40 32-40 32-38 35-40 30-35 32-40 30-35 35-45 40-50 32-40 32-40 32-40 32-40 35-45 32-40 * The figures given in this table are an approximate average of the temperatures given by tables by several different authorities en refrigeration. The values for the specific heats of the various products also varied in the different tables. In general the specific heat of milk, fruits, berries, and vegetables is approxi- mately 0.9; that of meats, eggs, cream, and cheese approximately 0.75. The specific heat is the quantity of heat that must be extracted to cool one pound 1° F. Dividing the specific heat by 144 gives the equivalent pounds of ice-melting effect to cool one pound 1° F. A thermometer should be kept available for checking the temperature in the refrigerator. Temperatures. — A temperature of 40° to 45° F for household refrig- erators, and 36° for utility refrigerators, is usually satisfactory. For a special refrigerator, the best temperature will depend upon the product stored and the length of the storage period. Table 8 gives the storage temperatures of various farm products. The lower limit should be used for relatively long storage periods; the upper, for short ones. 28 University of California — Experiment Station Placing Food in a Befrigerator. — When separate compartments are available, odor-giving foods such as onions, lemons, cantaloupes, and cabbage, and odor-absorbing foods such as milk, butter, meat, and eggs, should be kept in different compartments. If the interior is a single compartment, the odor-giving foods should be placed where the air current will strike them just before returning to the cooling coil ; the odor-absorbing foods, where the air current will strike them in coming from the cooling coil. Milk and butter should be kept in closed containers. Vegetables keep best if they are washed and placed in a closed con- tainer such as the hydrater in household refrigerators. Fruits keep best if wrapped in tissue paper, which keeps them from drying out rapidly. Meats should be placed in the coldest portion of the refrigerator and should not be enclosed or wrapped. There must be sufficient room around the products and containers for the circulation of air. REFRIGEEATOR TROUBLES AND THEIR CAUSES The temperature is too high : This condition may be caused by im- proper setting of the temperature control which is not probable if the temperature was correct when first installed ; by trouble in the refrig- erating unit ; or by blocking of air circulation. The temperature is too low: The refrigerating unit is improperly adjusted or the motor, switch is stuck shut. The cooling coil is frosted, but the air temperature is too high : Air circulation is blocked either by the stored products or by excessive frost on the coil. The refrigerating unit operates continuously ])ut does not cool the refrigerator : The trouble lies in the refrigerating unit. The motor fuses blow out : There is trouble in the unit or motor. Never replace the fuses with a larger size. There is odor in the refrigerator or the food has a peculiar flavor : This trouble may be caused by a particular product stored, by improper cleaning, or by a refrigerant leak. If ammonia or sulfur dioxide is the refrigerant, a leak can be detected by the odor or by the smoke test. Sulfur burned in the presence of ammonia, or ammonia fumes in the presence of sulfur dioxide, forms white smoke. For other refrigerants, information should be obtained from the manufacturer as to the method of determining leaks. If the refrigerating unit is at fault, a service man should be called to repair it, unless the owner is thoroughly familiar with the unit, knows how to remedy the trouble himself, and has the proper tools. Cm. 329] Mechanical Refrigerators for Farms 29 REFRIGERATOR PLANS AVAILABLE FROM THE COLLEGE OF AGRICULTURE, UNIVERSITY OF CALIFORNIA The California Committee on the Relation of Electricity to Agricul- ture, cooperating with the Division of Agricultural Engineering, University of California, has designed four mechanical refrigerators of the general utility type, ranging in size from 35 to 125 cubic feet, in an effort to meet the requirements of the average farm. Two of the refrigerators are of the non-walk-in type, one is semi- walk-in, and one is a walk-in. The two non-walk-in refrigerators are identical in size, but one has an ice-making coil and the other a water- cooling coil. Perspectives, brief descriptions, and estimated costs of each refriger- ator are given in the following pages. The complete working drawings and specifications of these plans may be secured from the Agricultural Extension Service, University of California, Berkeley, for 50 cents per set. Fig. 14. — Perspective of refrigerator for plan C-152. 30 University of California — Experiment Station Plan C-152, Thirty-jive Foot Mechanical Refrigerator. — This refrig- erator (fig. 14) was designed to meet farm requirements where it is desired to store relatively large quantities of perishable foodstuffs and to make ice or frozen desserts. This type is particularly adapted for storing meats slaughtered on the farm or bought in wholesale quantities. The cabinet is a non-walk-in type made in six sections that can be taken apart for transporting. There are three separate storage compart- ments, each accessible by an individual door, and a coil compartment accessible by a removable panel. On the left side is the meat comjiart- ment, large enough to hold two medium-sized sheep, two small hogs, a large veal or a quarter of beef. On the riglit center is a compartment with three removable shelves. On tlie lower right is a compartment which contains an ice-making coil and which may be kept at freezing tempera- tures to provide storage for limited quantities of perishables. The coil compartment is located across the top. The detailed description follows : Gross volume 5.'^ cu. ft. Net storage capacity 3.") cu. ft. Food shelf area 11 sq. ft. Exterior dimensions 4' 9" wide, 2' 10" dee]), 7' f)" liigli Interior dimensions 3' 10%" wide, 2' deep, 6' 8" high Exterior finish V'd T & G, painted or varnished Interior finish Plvboard, painted or varnished Insulation 3" of eorkboard or its equivalent Door openings in clear : Meat compartment 1' 8" x 5' Shelf compartment 1' 6" x 3' Freezing compartment 1' 0" x 1' (5" Ice-making capacity 7 to 13 lbs. twice a day Estimated operating cost $2 to $3 per montli (average tliroughout the year with electricity at 2 cents per kw-l.r.) Estimated initial cost of both cabinet and refrigerating unit $5r)0 to $700 Flan C-153, Forty Cubic Foot Mechanical Refriyeralor. — This refrig- erator (fig. 15) was designed to meet farm requirements where it is desired to store relatively large quantities of perishable foodstuffs, particularly meats slaughtered on the farm or bought in wholesale quantities. The cabinet is a non-walk-in type made in six sections that can be taken apart for transporting. It is divided into two food-storage com- partments, each accessible through an individual door, and a cooling-coil compartment accessible through a removable panel. On the left side is Cm. 329] Mechanical Refrigerators for Farms 31 a meat compartment large enough to hold two medium-sized sheep, two small hogs, a large veal, or a quarter of beef. On the right side is a compartment with four removable shelves. By removing the bottom shelf, one obtains sufficient room to store a 10-gallon milk can or several boxes of fruit or vegetables. The coil compartment is located across the top. On one side of the meat compartment is a water-cooling coil that may be connected to the water main and to a faucet on the front. Fig. 15. — Perspective of refrigerator for plan C-153. The detailed description follows : Gross volume 53 cu. ft. Net storage capacity 40 cu. ft. Food shelf area 17 sq. ft. Exterior dimensions 4' 9" wide, 2' 10" deep, 7' 5" high Interior dimensions 3' 10%" wide, 2' deep, 6' 8" high Exterior finish Vd T & G, painted or varnished Interior finish Plyboard, painted or varnished Insulation 3" of corkboard or its equivalent Door openings in clear : Meat compartment 1' 7" x 5' Shelf compartment 1' 7" x 5' 32 University of California — Experiment Station Capacity of Avater coil li gallons Estimated operating cost $2 to $3 per month (average throughout the year with electricity at 2 cents per kw-hr.) Estimated initial cost of both cabinet and refrigerating unit $500 to $650 Plan C-154, Eighty Cubic Foot Mechanical Refrigerator. — This re- frigerator (fig. 16) was designed to meet farm requirements where it is desired to store relatively large quantities of perishable foodstuffs or limited quantities of farm produce such as eggs, fruit, berries, milk, and cream until marketed. Fig. 16. — Perspective of refrigerator for plan C-154. Cm. 329] Mechanical Refrigerators for Farms 33 The cabinet is a semi-walk-in type made in six sections that can be taken apart for transporting. On the right side, a small door opens upon two removable shelves. On the left side, a walk-in door gives access to the entire interior of the cabinet. Under the shelves is sufficient room to store four 10-gallon milk cans. With the shelves in place there is room to hang half a beef or several hogs, sheep, or veals. With the shelves removed the meat-storage capacity is approximately doubled. Along the right wall just under the lower shelf is a water-cooling coil that may be connected to a water main and to a faucet on the front. The cooling coil is located across the top. The detailed description follows : Gross volume 112 cu. ft. Net storage capacity 80 cu. ft. Food shelf area 11 sq. ft. Exterior dimensions 5' 6" wide, 3' 10" deep, 8' 9" high Interior dimensions 4' 9" wide, 3' deep, 8' high Exterior finish Vd T & G, painted or varnished Interior finish Plyboard, painted or varnished Insulation 3" of corkboard or its equivalent Door openings in clear : Walk-in door 2' x 6' Eeach-in door V 4" x 2' Capacity of water coil 2 gallons Estimated operating cost $2.50 to $3.50 per month (average throughout year with electricity at 2 cents per kw-hr.) Estimated initial cost of both cabinet and refrigerating unit $550 to $700 Plan C-155, One Hundred and Twenty-five Cubic Foot Mechanical Refrigerator. — This refrigerator (fig. 17) was designed to meet farm requirements where it is desired to store large quantities of perishable foodstuffs or a limited quantity of farm products such as eggs, fruit, vegetables, milk, and cream until marketed. The cabinet is a walk-in type made in six sections that can be taken apart for transporting. One walk-in door opens in the center of the front. Within are four removable shelves on each side of the door, and three bars for meat hooks across the box just under the baffle. By remov- ing the lower shelves one can make room for three 10-gallon milk cans on each side of the box. With the shelves in place, there is room to store a half of beef or several hogs, sheep, or veals. With the shelves removed the meat capacity is approximately doubled. The cooling coil is located across the top. 34 University of California— Experiment Station Fig. 17. — Perspective of refrigerator for plan C-155. The detailed description follows : Gross volume 167 eu. ft. Net storage capacity 125 cu. ft. Food shelf area 35 sq. ft. Exterior dimensions 5' 9" wide, 4' 10" deep, 9' 3" higli Interior dimensions 4' 10%" wide, 4' deep, 8' C" high Exterior finish V'd T & G, painted or varnished Interior finish Plyboard, painted or varnished Insulation 3" of corkboard or its equivalent Door opening in clear 2' x 6' Estimated operating cost $3 to $4 per month (average throughout the year witli electricity at 2 cents per kw-hr.) Estimated initial cost of both cabinet and refrigerating unit $600 to $750 Cm. 329] Mechanical Refrigerators for Farms 35 ACKNOWLEDGMENTS The author expresses appreciation to Professor B. D. Moses, Professor J. D. Long, and Mr. H. L. Belton, of the Agricultural Engineering Division, and to Mr. A. F. Kessing, of the Frigidaire Company, for their cooperation in obtaining the material for this circular and also to the other members of the Agricultural Engineering Division who assisted in the preparation of the manuscript. 14to-9,'33