Mike Dolt Enterprises
Mike Dolt Enterprises
User: curious george, Location: Lockport, IL
Asked on: Wednesday, March 30, 2011 at 10:50 am EDT
Answered on: Tuesday, May 14, 2024 at 3:29 am EDT
Question: 2008 NECSection 400.5I have a situation where STOW or STOOW chord is going to be in ambient temperatures exceeding the 86 degree F default.Section 400.5 states " Where cords are used in ambient temperatures exceeding 86 degrees F, the temperature correction factors from Table 310.16 that correspond to the temperature rating of the cord shall be applied to the ampacity from table 400.5(B).How do I find the temperature rating of the cord? Table 310.16 is for conductors, not cords, and the conductors do not correspond to cords.Table 400.4 gives me the insulation type and it uses for cords, but not the temperature rating.Any help would be appreciated.Thanks -
Determining the Temperature Rating of Cords
The NEC does not provide a specific method for determining the temperature rating of cords. However, you can use the following steps to estimate the temperature rating based on the insulation type: Refer to Table 400.4
This table lists the insulation types used for cords and their respective temperature ratings.
Identify the insulation type of the STOW or STOOW cord
Examine the cord's markings or consult its data sheet.
Estimate the temperature rating
Based on the insulation type, estimate the corresponding temperature rating from Table 400.4.
Example
If the STOW or STOOW cord has a PVC insulation (Type SV), its estimated temperature rating would be 75°C (167°F).
Applying the Ambient Temperature Correction Factor
Once you have estimated the temperature rating of the cord, use Table 310.16 to determine the ambient temperature correction factor. For a cord with a 75°C temperature rating, the correction factor for an ambient temperature of 90°F (32.2°C) would be 0.
91.
Adjusting the Ampacity
Multiply the ampacity from Table 400.5(B) by the ambient temperature correction factor to adjust for the elevated ambient temperature.
Example
If the ampacity from Table 400.5(B) for a 14 AWG STOW or STOOW cord is 30 amps, the adjusted ampacity for an ambient temperature of 90°F would be:30 amps 0.91 = 27.3 amps
Note: The adjusted ampacity should not exceed the rating of the overcurrent protective device (e.g., circuit breaker or fuse). Always consult the manufacturer's instructions for the specific cord being used. Flag for review