Due to the construction of Leviton’s Hydraulic-Magnetic branch circuit breaker, current flows closer to the face of the breaker than some competitive breakers. Temperatures up to 40°C (104°F) can be measured at the face of the breaker near the handle, which is far below UL temperature limit of 60°C (140°F). In some competitive circuit breakers, the current path is located more toward the back plane. Due to this, these breakers will feel cooler toward the front. Based on Leviton’s testing, overall internal temperatures are very similar.
Does this affect performance?
This doesn’t affect performance at all. As defined by UL in the UL489 standard dated June 2011, the following applies:
- Handles, knobs and other user surfaces: UL489, paragraph 7.1.4.1.6 states that the maximum temperature on handles, knobs, and other surfaces subject to user contact during normal operation shall not exceed 60°C (140°F) on metallic and 85°C (185°F) on nonmetallic surfaces.
Table 1: Summary of temperature rise and maximums for a standard rated breaker (breakers are calibrated in 40°C ambient)
| Surface | Temp. rise above ambient | Temp. max at 40°C ambient (104°F) |
| Termination on standard rated breaker | 50°C (90°F) | 90°C (194°F) |
| Termination on 100% rated breaker | 60°C (108°F) | 100°C (212°F) |
| Handles, knobs, other user contact surfaces – Metallic | N/A | 60°C (140°F) Maximum |
| Handles, knobs, other user contact surfaces – Nonmetallic | N/A | 85°C (185°F) Maximum |
For more information on the differences between Thermal Magnetic and Hydraulic Magnetic circuit breakers, please review our Technical Application Note.