A delta connected transformer high leg voltage = ( Line voltage /2 ) * 1/732 High leg voltage = 230/2 * 1.732 High leg voltage = 199 Volts
According to the NEC, continuous loads are those where the maximum current is expected to last for three hours or longer at full rated load. Examples of continuous loads include heating equipment, lighting fixtures, and certain motors that run continuously for extended periods.
Wireway area = 4 * 4 = 16 sq. in. Refer NEC [376.22(A)] The conductor fill area should be maximum 20% of wireway area. WireWay conductor fill = 16 * 0.2 = 3.2 sq. in. Area of 500 kcmil THHN = 0.7073 sq in. [Chapter 9, Table 5] Number of 500 kcmil THWN conductors = 3.2 / 0.7073 = 4.5 ( 4 conductors)
Branch circuit conductor size should 125% of continuous load [ NEC 422.10(A)] Electric water heater current = 4000 / 240 = 16.6 Amperes Branch conductor size = 16.6 * 1.25 = 20.75 amperes As per branch conductor next size up rule 10 AWG with rating of 30 A at 60 C is suitable [ Refer NEC Table 310.15(B)(16)]
The maximum overcurrent protection for a 12 AWG (American Wire Gauge) copper conductor is typically 20 Amperes. This means that the circuit breaker or fuse protecting the 12 AWG copper conductor should not have a rating higher than 20 Amperes.
The National Electrical Code (NEC) in the United States specifies that the overcurrent protection device for non-motor appliances must not exceed 20 amperes if the overcurrent device rating is not marked on the appliance.
Type AC (Armored Cable) cables, also known as "BX" cables, must be supported and secured at intervals not exceeding 4.5 feet, according to the National Electrical Code (NEC) in the United States.
Feeder conductors are responsible for carrying electrical power from the source (service equipment, transformer, etc.) to various distribution points within a building or facility. These distribution points can be panelboards or other load centers where the final branch circuit overcurrent devices (circuit breakers or fuses) are located.
Wireway Area = 4 in. * 4 in. = 16 sq. in. Refer : NEC 376.22(A) The conductor fill area should be maximum 20 % of the total wireway area. Wireway conductor fill = 16 * 0.2 = 3.2 sq. in.
As per NEC Table 220.12 , The unit general lighting load for hospital is 2 VA per sq ft. So total lighting load of hospital = 80,000 * 2 = 1,60,000 VA As per NEC Table 220.42 The lighting load demand factors are as follows First 50000 or less 40% i.e 50,000 * 0.4 = 20000 Reaming is 20% 1,10,000 * 20 = 22000 So total lighting load after demand factor is applied = 20000 + 22000 = 42000 VA
The size of branch circuit conductor to protect against over current must be more than 125 % of continuous load. 22 * 1.25 = 27.5 amperes. Refer : Table 310.15(B)(16). No 10 THWN with 35 amperes at 75 0C is suitable
Answer: 4/0 AWG Note: Feeder conductors that supply entire load of dwelling unit can have the rating of 83% of service disconnect of dwelling unit. The service conductor ampacity for 250 A service disconnect = 0.83 * 250 = 207.5 amperes Refer : NEC Table 310.15(B)(16) 4/0 AWG with ampacity 250 amperes ( 75 C) is suitable as service conductor
The National Electrical Code (NEC) in the United States does not permit underground wiring under a pool or within 5 feet horizontally from the inside wall of a pool.
The total underground conductor size = 3 * 400 = 1200 kcmil .Refer NEC Table 250.166 .The required GEC is 3/0 AWG for 1200 kcmil size
Answer : 8 AWG The over current device 25 A is less than 10 percent of the rating of the feeder breaker (400A.) As per code it cannot be less than 40 A. Refer : NEC Table 310.15(B)(16) 8 AWG at 40A 60 C is the minimum size required.
According to NEC Article 680.22, audio system equipment supplied by a branch circuit must not be located within 5 feet horizontally of the inside wall of a pool, spa, hot tub, fountain, or within 5 feet horizontally of the prevailing tidal high water mark.
