The general information in this guide is intended to assist in evaluating the effect of solar radiation on outdoor metal-enclosed switchgear@ and is@ for example@ applicable to outdoor metal-enclosed circuit breaker power switchgear@ metal-clad switchgear@ metal-enclosed interrupter switchgear@ metal-enclosed gas insulated switchgear@ control switchboards@ metal-enclosed bus@ and pad-mounted switchgear. Specific data are given in current-temperature relationship@ and tabulation form for its application to outdoor metal-enclosed lowvoltage power circuit breaker switchgear@ outdoor metal-clad switchgear@ and outdoor metal-enclosed interrupter switchgear. Purpose Switchgear will perform satisfactorily and have a reasonable life expectancy when operated within the temperature limits established; for example@ in the following standards: ?? IEEE Std C37.20.1?2@ 3@ 4 ?? IEEE Std C37.20.2? ?? IEEE Std C37.20.3? ?? IEEE PCC37.20.9?/D3 ?? IEEE Std C37.21? ?? IEEE Std C37.23? ?? IEEE Std C37.74? ?? IEEE Std C37.100.1? These standards specify the temperature rise limits above a standard (maximum) ambient temperature of 40 ?? This is satisfactory for indoor applications where the temperature rise is due entirely to heat release (internal losses). In outdoor applications@ the limiting temperatures result from the net effect of internal losses and external influences@ principally the sun@ wind and local ambient temperatures. All of these must be considered in determining the current-carrying capability of outdoor metal-enclosed switchgear. The magnitude of these factors will vary geographically and from season to season. The time relationship of maximum circuit loads with respect to maximum ambient temperature is important. It is not practical to design switchgear on the basis that all adverse factors reach their maxima coincident with maximum loads. If this does not occur@ full current ratings may be realized. Recommendations are made to point out the cumulative effect of these various influences. 2Information on references can be found in Clause 2. 3IEEE publications are available from the Institute of Electrical and Electronics Engineers (http:// standards .ieee .org/ ). 4The IEEE standards or products referred to in Clause 2 are trademarks owned by the Institute of Electrical and Electronics Engineers@ Incorporated.