V-Class Thermal Factors & Procedures Checking Thermal Rating Checking the thermal rating is extremely important. If the gear drive’s capacity to dissipate thermal energy is insufficient, it will overheat, and severe damage may occur. Gear drive basic thermal ratings are defined on page 2. A discussion of the application-adjusted thermal rating, and when it is applicable, is found on page 3. Thermal Rating Factors Thermal horsepower ratings published herein are based on a 68°F (20°C) ambient temperature at an altitude up to 2460 feet above sea level. For other conditions, the thermal horsepower rating must be multiplied by the factors shown in Tables 1 & 2 (see right). Application-Adjusted Thermal Rating Once a mechanically adequate gear drive selection has been made per Steps 1-4 on page 6, determine the application-adjusted thermal rating of the gear drive. The application-adjusted thermal rating of the gear drive selected must equal or exceed the actual motor horsepower. In most cases, the nameplate power rating of the motor is assumed to equal the actual power transmitted. It is not necessary to apply the mechanical service factor when determining thermal adequacy of a gear drive. Use the following formula to determine application-adjusted thermal rating: PTA = PT x B1 x B2 x B3 x B4 x B5 where: PTA = Application-Adjusted Thermal Rating PT = Basic Thermal Rating B1 = Ambient Temperature Factor (Table 1) B2 = Altitude Factor (Table 2) B3 = Ambient Air Velocity Factor for no auxiliary cooling (Table 3) B4 = Duty Cycle Factor (Table 4) B5 = Alignment-Free Package Factor (Table 5) Basic Thermal Ratings for parallel shaft gear drives are found on pages 48 thru 107. Basic Thermal Ratings for right angle shaft gear drives are found on pages 162 pages 213. Once a gear drive satisfies mechanical requirements, select an auxiliary cooling method with an application-adjusted thermal rating that equals or exceeds the actual power transmitted. If no listed cooling method is adequate, contact the Factory for selection of an optional heat exchanger, or consider a larger gear drive with greater thermal capacity. Table 5 — Alignment-Free Package Factor* – B5 Size 117 Motor RPM All 127 133, 137 143, 147 153, 157 163, 167 173, 177 187 193, 197 203, 207 213, 217 223, 227 237, 243, 247 253, 257 263, 267 273, 277 All All All All All All All All All All All All ≤ 1500 >1500 1200 ≤ 1500 >1500 ≤ 1200 1200 ≤ 1500 >1500 ≤ 1200 Close Coupled Alignment-Free Drive 0.88 … 1.13 … … 0.95 0.94 … 0.76 0.76 0.66 0.65 0.74 0.56 0.73 0.53 0.57 0.75 0.55 0.59 0.76 * Factor to be applied to shaft fan cooling only. Not applicable for other cooling types. NEMA 447T/IEC 280M and Smaller Motors NEMA 449T/IEC 315S and Larger Motors 8 Catalog 171-110 Table 1 — Ambient Temperature Factor – B3 (For all cooling methods) Ambient Temperature ★ Ambient Adjustment 59F (15C) 68F (20C) 77F (25C) 86F (30C) 95F (35C) 104F (40C) 113F (45C) 122F (50C) 1.00 0.91 0.82 0.74 0.65 0.56 0.48 ★ Factors for other ambient temperatures can be interpolated. Table 2 — Altitude Factor – B2 Altitude Above Sea Level – Feet 0 12300 14760 17225 2460 4920 7380 9840 Table 3 — Ambient Air Velocity Factor † (For no auxiliary cooling) Sustained Ambient Air Velocity † 1.6 to 4.6 4.6 to 12.1 > 12.1 ft/sec < 1.6 Large Indoor Room Large Indoor Room Outdoors Environment Confined Space Installed – B3 Factor for No Auxiliary Cooling 0.75 1.00 1.40 1.90 † The sustained ambient air velocity must be a continuous flow of air directly onto the gear drive. If the air flow cannot be relied upon to be continuous, an ambient air velocity factor of 0.75 must be used. Table 4 — Duty Cycle Factor ‡ % Operating Time Per Hour 100% 80% 60% 40% 20% – B4 Factor With or Without Auxiliary Cooling 1.00 1.05 1.15 1.35 1.80 ‡ The duty cycle factor must be based on the percentage of each hour that the drive is operating. For example: a gear drive operating for 48 minutes of every hour of the day has an 80% duty cycle, but a drive operating for four hours and resting for four hours has a 100% duty cycle. Where the % Operating Time Per Hour falls between values tabulated above, use the next higher % Operating Time. Fluid Couling 1420HFDD 1.14 1.00 0.89 1.00 1.14 0.88 … … … … … … … … … … 1480HFDD … 1.13 1.00 1.13 1.27 1.00 0.74 0.74 … … … … … … … … 1584HFDD … 1.41 1.26 … … 1.27 0.95 0.95 0.76 0.76 … … … … … … 1660HFDD … … … 1.18 1.18 0.76 0.76 … … … … … … 1.55 1.56 … VFD / Floating Shaft Coupling All Sizes (NEMA & IEC) 1.14 0.89n, 1.41s 0.88n 1.00n 1.00 1.14 0.95 0.95 0.76 0.76 … … … … … … , 1.26s , 1.27s Factor at 180°F Sump 1.09 Ambient Adjustment Factor at 200°F Sump 1.08 1.00 0.92 0.85 0.78 0.70 0.63 0.56 Factor 1.00 0.95 0.90 0.85 0.81 0.76 0.72 0.68
