Hi all,
we are assembling an industrial control panel which consists of 4 branch circuits supplied from panel feeder as follows:
Panel feeder : #12 AWG , which is connected directly to fused-distribution block (i will call it FDB) (200KA , 1 in - 8 out ) no other devices are connected to the feeder (no breaker , no disconnects , and so on).
(1) Branch 1 (Main circuit) : supplied from the above FDB , then Fused disconnect switch then power supply (3PH-in , 24vdc-out,5A) then supplementary breaker number 1 (3A) then PLC & I/O
(2) Branch 2 (Heater) : supplied from the above FDB , then Fused disconnect switch then power supply (3PH-in , 24vdc-out,20A) then supplementary breaker number 2 (20A) then Heater
(3) Branch 3 (Lighting) : supplied from the above FDB , then Fused disconnect switch then power supply (1PH-in , 24vdc-out , 3A) then supplementary breaker number 3 (2A) then LED
(4) Branch 4 : supplied from the above FDB , then Fused disconnect switch then Receptacle outlet
My questions:
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(Q1) : At first , all the above " Fused disconnect switches " were circuit breaker , but since max interrupt capacity we found was 10 kA , that was a small value since it always lowers the global SCCR of the panel , so we thought to replace the breakers with Fused disconnect switches which dramatically increased the SCCR of all branches upstream all the power supplies at almost small acceptable cost. Now , what about the breakers downstream the power supplies ,
(a) Branch 1 : the is control circuit class 1 fed by power supply (which is similar to control transformer rules - i guess ) hence the supplementary breaker number 1 will be neglected , is that correct ?
(b) Branch 2 : the supplementary breaker number 2 has interrupt capacity of 7.5 kA and since the power supply is less than 5 kVA and less than 120 v secondary output (i will treat it as power transformer - can i do that ?) then the primary protector of the power supply applies its SCCR to the entire branch circuit hence it is ok to use the supplementary breaker number 2 , is that correct ?
(c) Branch 3 : same as Branch 2 , is that correct ?
OR , should we take all supplementary breakers into account while estimating SCCR of the panel because a power supply cannot be treated as a power transformer nor a control transformer ?
(Q2) If it is required to install SPD for the panel feeder , it will be another branch (number 5) in parallel to the above branches and supplied from FDB , is that correct ?
Thank you all for helping
we are assembling an industrial control panel which consists of 4 branch circuits supplied from panel feeder as follows:
Panel feeder : #12 AWG , which is connected directly to fused-distribution block (i will call it FDB) (200KA , 1 in - 8 out ) no other devices are connected to the feeder (no breaker , no disconnects , and so on).
(1) Branch 1 (Main circuit) : supplied from the above FDB , then Fused disconnect switch then power supply (3PH-in , 24vdc-out,5A) then supplementary breaker number 1 (3A) then PLC & I/O
(2) Branch 2 (Heater) : supplied from the above FDB , then Fused disconnect switch then power supply (3PH-in , 24vdc-out,20A) then supplementary breaker number 2 (20A) then Heater
(3) Branch 3 (Lighting) : supplied from the above FDB , then Fused disconnect switch then power supply (1PH-in , 24vdc-out , 3A) then supplementary breaker number 3 (2A) then LED
(4) Branch 4 : supplied from the above FDB , then Fused disconnect switch then Receptacle outlet
My questions:
----------------
(Q1) : At first , all the above " Fused disconnect switches " were circuit breaker , but since max interrupt capacity we found was 10 kA , that was a small value since it always lowers the global SCCR of the panel , so we thought to replace the breakers with Fused disconnect switches which dramatically increased the SCCR of all branches upstream all the power supplies at almost small acceptable cost. Now , what about the breakers downstream the power supplies ,
(a) Branch 1 : the is control circuit class 1 fed by power supply (which is similar to control transformer rules - i guess ) hence the supplementary breaker number 1 will be neglected , is that correct ?
(b) Branch 2 : the supplementary breaker number 2 has interrupt capacity of 7.5 kA and since the power supply is less than 5 kVA and less than 120 v secondary output (i will treat it as power transformer - can i do that ?) then the primary protector of the power supply applies its SCCR to the entire branch circuit hence it is ok to use the supplementary breaker number 2 , is that correct ?
(c) Branch 3 : same as Branch 2 , is that correct ?
OR , should we take all supplementary breakers into account while estimating SCCR of the panel because a power supply cannot be treated as a power transformer nor a control transformer ?
(Q2) If it is required to install SPD for the panel feeder , it will be another branch (number 5) in parallel to the above branches and supplied from FDB , is that correct ?
Thank you all for helping
