ELECTRICAL LOAD COMPUTATION POWER
CURRENT SIZE OF WIRE Using the I computed, refer to TABLE A1(Allowable Ampacities of Insulated Conductors Rated 0 through 2000 Volts, 60 degree Celsius Through 90 degree Celsius not more than Three Current-Carrying Conductors in Raceways, Cable, Based on Ambient Temperature of 30 degree Celsius) for the type and size of wire. Refer to the first load ampere greater than the iComputed and get the recommended size of wire to be used. To check: Table given ampere x 80% = value grater than IComputed wire size is accepted Value lower than the IComputed wire size is rejected; use the second higher value to determined the wire size Note: Philippine Electric Code state that: For general lighting use 15A CB for protection and wire size 2.0 sqmm For convenience Outlet use 20A CB for protection and wire size 3.5 sqmm For larger motors use 3.5 sqmm etc… SIZE OF PROTECTION From TABLE A2 (Standard Ampere Rating for Fuses and Circuit Breaker) Refer to the first maximum load ampere greater than IComputed and get the corresponding size of recommended ampere for fuse or circuit breaker. SIZE OF CONDUIT For General lighting use 15mmØ Flexible Conduit For Appliances and motor use 20mmØ Flexible Conduit SIZE OF MAIN PROTECTION WIRE ITOTAL= PT/230V Using the computed ITOTAL , refer to TABLE A1(Allowable Ampacities of Insulated Conductors Rated 0 through 2000 Volts, 60 degree Celsius Through 90 degree Celsius not more than Three Current-Carrying Conductors in Raceways, Cable, Based on Ambient Temperature of 30 degree Celsius) for the type and size of wire. Refer to the first load ampere greater than the computed ITOTAL and get the recommended size of wire to be used.. To check: Table given ampere x 80% = value grater than ITOTAL ,wire size is accepted
Value lower than the ITOTAL ,wire size is rejected; use the second higher value to determined the wire size MAIN PROTECTION ITOTAL X 2= I From TABLE A2 (Standard Ampere Rating for Fuses and Circuit Breaker) , get the recommended size of fuse or circuit breaker. FARM STORAGE Electrical loading computation CKT 1: GENERAL LIGHTING OUTLET No. of outlet= 10 POWER P= 10 x 100 P= 1000VA CURRENT ICOMPUTED= 1000VA/230V ICOMPUTED= 4.35A SIZE OF WIRE From Table A1, for 4.35A refer to 20A use 2.0 mm2 TW, CU wire. PROTECTION I= 4.35A From TABLE A2, for 4.35A use maximum load of 8A therefore the size of protection is 15A CB CKT 2: CONVENIENCE OUTLET No. of outlet= 6 POWER P= 6X180X2 P= 2160VA CURRENT ICOMPUTED= 2160VA/230V ICOMPUTED= 9.39A SIZE OF WIRE From Table A1, for 9.39A refer to 20A use 2.0 mm2 wire size (TW, CU) or 3.5 mm2 TW, CU as stated by the Philippine Electric Code for convenience outlet.
PROTECTION I= 9.39A From TABLE A2, for 9.39A use maximum load of 12A with 30A CB or 20A CB as specify by the Philippine Electric Code for convenience outlet. CKT 3: ACU OUTLET No. of outlet= 1 POWER P= 1000VA P= 1000VA CURRENT ICOMPUTED= 1000VA/230V ICOMPUTED= 4.35A SIZE OF WIRE From Table A1, for 4.35A refer to 20A use 2.0 mm2 TW, CU or 3.5 mm2 TW, CU as stated by the Philippine Electric Code for special purpose outlet. PROTECTION I= 4.35A From TABLE A2, for 4.35A use maximum load of 8A with 15A CB or 20A CB as specify by the Philippine Electric Code for special purpose outlet. CKT4: ACU OUTLET REFER TO CKT 3 CKT 5: MOTOR OUTLET No. of outlet= 1 POWER P= 373VA P= 373VA CURRENT ICOMPUTED= 373VA/230V ICOMPUTED= 1.62A SIZE OF WIRE Use 3.5 mm2 TW, CU as stated by the Philippine Electric Code for special purpose outlet. PROTECTION I= 1.62A
From TABLE A2, for 1.62A use maximum load of 8A with 15A CB or 20A CB as specify by the Philippine Electric Code for special purpose outlet. CKT 6: MOTOR OUTLET REFER TO CKT 5
MAIN PROTECTION PTOTAL=5906 ITOTAL= 5906/230V ITOTAL = 25.68A From Table A1, for 25.68A refer to 30A use 5.5 mm2 TW, CU Check: 30A x 80% = 24A >>>rejected Use the next higher value therefore use 8.0mm2 TW, CU 25.68 X 2= 51.36A From Table A2, for 51.36A use 50A CB for the size of the Circuit breaker.
