Document jGD4w5wKbp6p9KkKrXkJ4V0y

566 CHAPTER 24 1955 Guide coils and piping. It is recommended that a medium temperature solder of 95 percent tin--5 percent antimony, or capillary brazing alloys, be used. All piping is, generally, subjected to a hydrostatic test of at least three times the working pressure, but not less than -150 psig. The more common forms of application of panel heating fall into the following general categories: (1) embedded piping for ceilings; (2) em bedded piping for walls; (3) embedded piping for floors; (4) air heated ceilings, walls or floors; (5) electrically heated ceilings, walls or floors. Embedded Piping for Ceilings When piping is embedded in ceilings, the construction used is generally one of the following: a. Pipe or tube is embedded in the lower portion of a concrete slab, generally very close to its lower surface. If plaster is to be applied to the concrete, the piping `t.... -VVy VrA- ^tOMCBlTC : .>' ' 4 ' ^ :* a, b.-y.n.Yvyi-- - - Fiq. 1. Coins in Structural Concrete Sear HEATING AORTA SUPPORTING MtilUW 1CAATCH COAT 0*14 OB A fT CENTER* CHBtDOWO Altt RIBC OB ITttL /sTOtrCTUHAL MIXBCR* FINISHED nASTCB <tOJNC Suspended Plaster Ceiling SCRATCH COAT FtNJSHEO BLASTER CEILING Fig. 3. Coins in Plaster Below Lath Plaster Ceiling Below Joists Fio. 2. Coils in Plaster Above Lath may be placed directly on the wood forms. If the slab is to be used without plaster finish, then the piping.is installed about I in. above the undersurface of the slab. Fig. 1 shows this method of construction. It is important that any local construc tion codes which may affect the position of the piping be consulted. b. Pipe or tubing is embedded in a metal lath and plaster ceiling. If the lath is suspended to form a hung ceiling, both the lath and the heating coils are secured wired to the supporting members in such a way that the lath is below, but in good contact with the coils, as shown in Fig. 2. Plaster is then applied to the metal lath, care being taken to embed the coil, as shown in Fig. 2. c. Copper tubes of the smaller diameters are attached to the underside , lath or gypsum lath. Plaster is then applied to the lath to embed the tube, as sho in Fig. 3. d. Other forms of ceiling construction utilise prefabricated panels of met*! composition board, wood paneling, etc., having warm water piping, tube or cbanne built into the panel sections. Coils are usually of the sinuous type, although some header or grid typ* coils have been used in ceilings. Coils may be of either ferrous or non-fer- Panel Heating 567 rous pipe or tube, with coil pipes spaced from 4 to 9 in. on centers, de pending on the required output, pipe or tube size, and other factors. Where plastering is applied to pipe coils, a standard three-coat gypsum plastering specification1 is followed, with a minimum of f in. of cover be low the tubes when the tubes are installed below the lath. Generally, the surface temperature of plaster panels should not exceed 120 F, and this is usually met by limiting the water temperature in the pipes or tubes in contact with the plaster to a maximum temperature of 140 F. Insulation should be placed above the coils to reduce the reverse loss which is the difference between the heat supplied to the coil and the net useful output to the heated room. In order to protect the plaster installation and to assure proper air dry ing of the plaster, it is recommended that no heat be applied to the panels for two weeks after all plastering work has been completed. When the system is started for the first time, the water supplied to the panels should be at a temperature not more than 20 deg above the prevailing room temperature at that time (but not in excess of 90 F). Water should be circulated at this temperature for about two days. Then the water tem perature should be increased to 140 F at a rate of approximately 5 deg increase per day. During the air-drying and preliminary warming-up periods, adequate ventilation should be provided to carry off moisture from the panels. No paint or paper should be applied to the panels until these periods have been completed. No paint or paper should be applied while the panels are being operated. After paint and paper have been applied, a further shorter warm-up period, similar to that for the first time starting, is also recommended. Embedded Piping for Walls Although not so universally used as ceiling panels, wall panels may be constructed by any of the methods outlined for ceilings. Fig. 5. Warm Air Plaster Ceiling Construction