MatthewM
Member
- Location
- Phoenix, Arizona
Hello Electrical Gurus,
Bottom Line Up Front:
I am installing equipment and am concerned that the calculated service requirements far exceed the manufacturers recommended install requirements.
History:
I am the maintenance supervisor for a manufacturing facility. I have worked here for eight months and before coming here had very little experience in the electrical industry. I am currently assigned to a project in which I am working on the installation of several pieces of CNC equipment. Specifically my guys are installing several HAAS CNC machining centers. We have an electrician at the facility; however, he is not a licensed electrical contractor (there are no certifications for electricians in the state of Arizona outside of a contractor's license).
My degree is in mechanical engineering, but through research and study I have developed an extremely rudimentary understanding of the code and electrical systems. I did my best at calculating the requirements for our equipment and what I calculated far exceeds the manufacturers recommended installation instructions. I am here to seek counsel from experienced electricians. I would like to know if I made incorrect assumptions in my calculations, and if not why the code differs so much from what the manufacturer recommends.
The System:
The machines run on 240V, 3 pahse power. Each machine will have its own run of conduit with 3 current carrying wires and a ground wire. Runs are no longer than 50 ft total. Busway switches are rated at 75 deg C.
Machine Type 1 - HAAS VF1
Feed: 3 Phase Power at 240V off of a bus bar (Bus bar is fed from a 175kVA transformer)
Peak Load: 20 kVA
Continuous Load: 14 kVA
Manufacturers recommended wire size @ 240V: #8 AWG
My calculated wire size @240V:#3 AWG
Machine Type 2 - HAAS TL-2
Feed: 3 Phase Power at 240V off of a bus bar (Bus bar is fed from a 175kVA transformer).
Peak Load: 14 kVA
Continuous Load: 20 kVA
Manufacturers recommended wire size @ 240V:#8 AWG
My calculated wire size @ 240V:#6 AWG
Machine Type 3 - HAAS ST-20SS
Feed: 3 Phase Power at 480V to individual transformer.
Peak Load:40 kVA
Continuous Load:28 kVA
Manufacturers recommended High Voltage wire size @ 480V: 8 AWG
Manufacturers recommended Low Voltage wire size @ 240V: 4 AWG
My calculated wire size (primary side of transformer): #3 AWG
My calculated wire size (secondary side of transformer): 3/0 AWG
I have included a basic spreadsheet with the results of my calculations. I used the following website to calculate wire size because it seemed to be the most thorough, taking into account temperature ratings of terminals and number of conductors in a raceway in its calculations:
http://www.electrician2.com/calculators/wireocpd_ver_1.html
Please check my work and provide any insight you may have on this matter.
Thanks,
Matt
Bottom Line Up Front:
I am installing equipment and am concerned that the calculated service requirements far exceed the manufacturers recommended install requirements.
History:
I am the maintenance supervisor for a manufacturing facility. I have worked here for eight months and before coming here had very little experience in the electrical industry. I am currently assigned to a project in which I am working on the installation of several pieces of CNC equipment. Specifically my guys are installing several HAAS CNC machining centers. We have an electrician at the facility; however, he is not a licensed electrical contractor (there are no certifications for electricians in the state of Arizona outside of a contractor's license).
My degree is in mechanical engineering, but through research and study I have developed an extremely rudimentary understanding of the code and electrical systems. I did my best at calculating the requirements for our equipment and what I calculated far exceeds the manufacturers recommended installation instructions. I am here to seek counsel from experienced electricians. I would like to know if I made incorrect assumptions in my calculations, and if not why the code differs so much from what the manufacturer recommends.
The System:
The machines run on 240V, 3 pahse power. Each machine will have its own run of conduit with 3 current carrying wires and a ground wire. Runs are no longer than 50 ft total. Busway switches are rated at 75 deg C.
Machine Type 1 - HAAS VF1
Feed: 3 Phase Power at 240V off of a bus bar (Bus bar is fed from a 175kVA transformer)
Peak Load: 20 kVA
Continuous Load: 14 kVA
Manufacturers recommended wire size @ 240V: #8 AWG
My calculated wire size @240V:#3 AWG
Machine Type 2 - HAAS TL-2
Feed: 3 Phase Power at 240V off of a bus bar (Bus bar is fed from a 175kVA transformer).
Peak Load: 14 kVA
Continuous Load: 20 kVA
Manufacturers recommended wire size @ 240V:#8 AWG
My calculated wire size @ 240V:#6 AWG
Machine Type 3 - HAAS ST-20SS
Feed: 3 Phase Power at 480V to individual transformer.
Peak Load:40 kVA
Continuous Load:28 kVA
Manufacturers recommended High Voltage wire size @ 480V: 8 AWG
Manufacturers recommended Low Voltage wire size @ 240V: 4 AWG
My calculated wire size (primary side of transformer): #3 AWG
My calculated wire size (secondary side of transformer): 3/0 AWG
I have included a basic spreadsheet with the results of my calculations. I used the following website to calculate wire size because it seemed to be the most thorough, taking into account temperature ratings of terminals and number of conductors in a raceway in its calculations:
http://www.electrician2.com/calculators/wireocpd_ver_1.html
Please check my work and provide any insight you may have on this matter.
Machine | Voltage | Continuous (KVA) | Peak (KVA) | Continuous Current (Amps) | Peak Current (Amps) | Conductor Size | Ground Wire Size |
VF1 | 240 | 14 | 20 | 34 | 48 | #3 AWG THHN | #8 AWG THHN |
TL-2 | 240 | 9 | 14 | 22 | 34 | #6 AWG THHN | #8 AWG THHN |
ST-20SS (Primary) | 480 | 28 | 40 | 34 | 48 | #3 AWG THHN | #8 AWG THHN |
ST-20SS (Secondary) | 240 | 28 | 40 | 67 | 96 | 3/0 AWG | #6 AWG THHN |
Thanks,
Matt