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612 CHAPTER 23 1957 Guide Table 1. Thermal Resistance of Plaster and Metal Ceiling Panels Spac ing id. Thermal. Resistance to Down ward Heat Flow (rd) --fF_deg)(hr)(sq ft) per Btu Heat Flow Ratio, au/9d 0 0.2 0.4 0.6 0.8 1.0* Plaster Paneu^ Standard Gypsum Plaster, Three ' Coats' H in.- (nom.) non-ferrous tube or Yi in. (nom.) fer rous pipe above metal lath tied at 8-inch intervals with good tube embed ment,or H in. (nom.) nonferrous tube below metal or gypsum lath. 4H 0.30 0.34 0.38 0.42 0.48 0.50 6 0.45 0.51 0.57 0.63 0.69 0.75 9 0.75 0.85 0.95 1.05 1.15 1.25 12 1.15 1.29 1.43 1.57 1.71 1.85 Aluminum Panel* >6 in. Minimum Thickness TUBES |- l spacing pipe or tube installed so lr* A aa ** that excellent heat jeon- 7 \ duction to ceiling surfaoe flange 'aluminum obtained. 3 0.07 0.07 0.07 0.07 0.07 0.07 a Any ceiling panel also acts as a floor panel to the extent of its upward heat flow. If the upward heat flow is high and the space above is occupied, check floor surface temperature for possible foot discomfort (see Reference 7). Also check effect on heating requirements of the space above. It is not' good practice to have the major portion of the upper room's hating requirements supplied by .the upward neat flow of a ceiling panel below. . , . b Recommended maximum inlet water temperature (<max) 140 F. 0 Recommended maximum inlet water temperature (fmax) 220 F. quired. Also in Table 1 find the resistance of each panel (rd), using heat flow ratios calculated from the flow rates determined in Steps 2 and 4, interpolating as required. Room A B C Spacing (Inches) 9 9 Heat Flow Ratio 12.5 4--7.7 = 026 6 --19.7 = -30 5----- = 0.19 26.1 Resistance (r<i) 0.35 0.90 0.85 Step 6. Mean Water Temperature For the required panel output (gd) found in Step 2, the panel resistance (fa) found in Step 5, and the room air temperature (fa), find the mean water temperature ({mw) from Fig. 15. This use of Fig. 15 is illustrated in Fig. 15B. 15B.'Fig. Determination, of Mean Water Temperature for Room A from Fig. A from Fig. 15 Panel Heating 613 Values of fmw for Rooms A, B and C as determined from Fig. 15 are as follows: Room A 13 131 F, Room B tmw = 110.5 F, Room C tmw = 119 F Step 7. Design Mean Water Temperature Select a single design mean water temperature (fdmw) for each group of rooms which is to comprise a zone, choosing the highest mean water temperature (fmw) of the group subject to the following: a. If tmw + g is equal to or less than tmax (see Nomenclature and Table 1, this mean water temperature (fmw) is an acceptable design mean water temperature (fdmw). Proceed to Step 8. b. If tmw 4* 2 is greater than fmax , go back to Step 5 and select a panel con struction which has a lower panel resistance (rd). This can be accomplished by either or both of the following: 1. Reducing the tube spacing, 2. Decreasing the upward heat flow (gn) by providing additional insulation above the panel. If the required mean water temperature is still too high apply either or both of the following: 1. Reduce the heat loss of the room, 2. Provide supplementary heating. In Example 1, assume tx -- tQ = 15 F deg and fmax = 140 F. Then since fmw = 131 F, tmw 4- H (ti -- t0) = 138.5 F and is less than fmax . Thus 131 F can be used as the design mean water temperature fdmw Step 8. Design Panel Output From Fig. 15, find the panel output (gd) for design mean water temperature - vdmw), room air temperature (fa) and panel resistance (rd). Fig. 15C shows how Fig. 15 is used to find q& for Room B in this step. 15C.Fig. Determination of Design Panel Output for for Room B from Fig. 15 The mean water temperature (tmw) found for Room A in Step 6 was used as the design mean water temperature (<dmw). The panel output for.Room A which was determined in Step 2 is therefore the design panel output for this room. Design Panel outputs for Rooms B and C can be found from Fig. 15 using the design mean water temperature (Idmw). Room A B Design Panel Output (gd) . BTU per (hr)(sq ft) 47.7 32.5