O&M Manual –90E1720004
Section 9 Maintaining the Bypass-Isolation Transfer Switch Page 45 of 52
Absence of dust or debris either airborne or settled.
Relative humidity averaging less than 70%.
Absence of vibrations or seismic activity.
Circuit Loading
Continuous loading (with 100% rated devices) is between 20- 80% of the equipment
ratings.
Average loading not exceeding 70% of the equipment rating.
Only resistive or continuous motor loads, no welding or jogging loads.
Transfer switching less than 52 cycles annually.
Maximum of two circuit breaker trips due to overload or fault annually.
Equipment Installation
Torque all bus bar joints, lugs, and bolts to their appropriate tightness at installation.
Securely tighten all control and communications wiring at installation.
Follow pre-energizing checkout rigorously.
Normal Operating Conditions
When the equipment is operating under the “normal operating conditions” outlined below, it
should be inspected and maintained every 1–3 years, or more frequently, based on the user’s
experience.
Environmental
Ambient room temperature is between -22 °F (-30 °C) and 104 °F (40 °C).
Altitude is less than 6600 ft (2012 m).
The effect of solar radiation is not significant.
Note: Refer to the principles outlined in IEEE Standard C37.24-1986 for additional
information.
Circuit Loading
Transfer switching is no more than 104 cycles annually.
Welding or jogging loads represents less than 15% of a circuit and/or equipment
loading.
Equipment Installation
Torque all bus bar joints, lugs, and bolts to their appropriate tightness at installation.
Securely tighten all control and communications wiring at installation.
Follow pre-energizing checkout rigorously.
Harsh Operating Conditions
When the equipment is operating under the “harsh operating conditions” outlined below, it
should be inspected and maintained every 6 months, or more frequently, based on the user’s
experience.
Environmental
Ambient room temperature is less than -22 °F (-30 °C) or greater than 104 °F (40 °C).
Altitude exceeds 6600 ft (2012 m).