ozkan
Member
- Location
- Berlin, CT, USA
Hi,
We have a pump application which we are planning to replace with bigger pump motor. The new motor is 60 HP, 3 phase, 480 V, 68.3 Amps and SF=1.15 on the nameplate.
The current power and control wires(motor start-stop wires) are in the same conduit which size is 1 1/4 inches. And, we will replace 6 AWG THWN current power wires with 3 AWG THHN wires. The control wires will be 14 AWG THHN, the quantity is 4 and the voltage is 120 V.
So, the total wires in the conduit will be 3( 3 AWG) + 4 (14 AWG) wires. According to my calculations, the conduit fill will be about 21.67% which is less than 40%.
The ambient temperature is 36-40 degree celcius and I can do ampacity correction because of the ambient temperature. But, I got confused for the number of the wires in the same conduit because of different voltage levels in the same conduit.
For instance, NEC 2017 Article 310.15.(B)(3)(a) says that "Where conductors of different systems, as provided in 300.3, are installed in a common raceway or cable, the adjustment factors shown in Table 310.15(B)(3)(a) shall apply only to the number of power and lighting conductors (Articles 210, 215, 220, and 230)."
In this case;
My question is, what will the derating factor be for the wires if they are for different voltage levels ?
Is my current derating factor "1"? Or, is it "0.7 (70%)" which is for 7-9 wires and should be applied to all power and control wires?
Thanks.
We have a pump application which we are planning to replace with bigger pump motor. The new motor is 60 HP, 3 phase, 480 V, 68.3 Amps and SF=1.15 on the nameplate.
The current power and control wires(motor start-stop wires) are in the same conduit which size is 1 1/4 inches. And, we will replace 6 AWG THWN current power wires with 3 AWG THHN wires. The control wires will be 14 AWG THHN, the quantity is 4 and the voltage is 120 V.
So, the total wires in the conduit will be 3( 3 AWG) + 4 (14 AWG) wires. According to my calculations, the conduit fill will be about 21.67% which is less than 40%.
The ambient temperature is 36-40 degree celcius and I can do ampacity correction because of the ambient temperature. But, I got confused for the number of the wires in the same conduit because of different voltage levels in the same conduit.
For instance, NEC 2017 Article 310.15.(B)(3)(a) says that "Where conductors of different systems, as provided in 300.3, are installed in a common raceway or cable, the adjustment factors shown in Table 310.15(B)(3)(a) shall apply only to the number of power and lighting conductors (Articles 210, 215, 220, and 230)."
In this case;
My question is, what will the derating factor be for the wires if they are for different voltage levels ?
Is my current derating factor "1"? Or, is it "0.7 (70%)" which is for 7-9 wires and should be applied to all power and control wires?
Thanks.
