1. Structure dimensions and unit space
Scroll table left / right →Sources: Schneider catalog 8998CT9701R07/09 pp. 7-15; Rockwell 2100-IN012M p. 9 and 2100-SG003G pp. 27-28 ("Each 90 in. vertical section can accommodate up to 6.0 space factors or 78 in."); Eaton catalog V3-T3 and RP04304003E; GE GEH-4961 and BuyLog Section 15; Siemens Speedfax Section 16. Only Allen-Bradley uses the term space factor, and its half space factor is 6.5", not 6". Square D reduced-height structures: 79.5"/73.5"/67.5" giving 60"/54"/48" of unit space.| Line | Section H x W | Depths | Usable unit space | Unit increment |
|---|
| Square D Model 6 | 90" x 20" (4" vertical wireway) | 15" / 20" | 72" | 6" units; stab openings every 3" |
| A-B CENTERLINE 2100 | 90" x 20" (4.38" wireway); 25"-35" options | 15" / 20" / 25" | 78" (6.0 space factors) | 0.5 SF = 6.5" |
| Eaton Freedom / Series 2100 | 90" x 20" | 16" / 21" | 72" | 6" |
| GE 8000 / Spectra | 90" x 20" (+4.5" sills and lifting angles) | 13" / 20" / 22" | 72" | 6" |
| Siemens tiastar | 91.125" x 20" (24"-60" options) | 15" / 20" | 72" | 6" |
2. Bus ratings and the plug-in ceiling
Scroll table left / right →Sources: Schneider 8998CT9701 pp. 13-14 and typical spec 2.08.A; Rockwell 2100-IN012M pp. 9-10 ("Standard, center-fed, 300 A rated vertical bus... for an effective 600 A capacity") and 2100-SG003G p. 28 ("Unit plug-in power stabs are rated 225 A"); GE GEH-4961 p. 4 ("stabs rated 225 amperes maximum"); Eaton catalog V3-T3; Siemens Speedfax 16. Square D publishes no per-stab ampere rating; its 300 A figure is the vertical bus rating, and the plug-on limit is stated by frame class. Bus ampacity under UL 845 is based on 65 C maximum rise over 40 C ambient (Schneider 8998CT9701 p. 13).| Line | Horizontal bus | Vertical bus | Plug-in (stab) limit | Bracing |
|---|
| Square D Model 6 | 600-2500 A | 300 A std, 600 A opt. | Breakers and fusible through the 400 A frame; larger units cable to horizontal bus | 42 kA std; 65/85/100 kA opt. |
| A-B CENTERLINE 2100 | 600-3200 A | 300 A std center-fed (600 A effective), 600 A opt. (1200 A effective) | Stabs rated 225 A; breaker feeders plug-in through 225 A, frame-mounted from 400 A | 65 kA; ArcShield to 65 kA |
| Eaton Freedom | 600-3200 A | 600/800/1200 A options listed | per catalog | 42-100 kA |
| GE 8000 / Spectra | 600 A std (higher unverified) | 300/450/600 A | Stabs rated 225 A maximum; plug-in units to Size 5 and 600 A feeders | 65 kA std package |
| Siemens tiastar | 600-2500 A | 300/600/800 A | per catalog | 42/65/100 kA |
3. Unit height by NEMA starter size, FVNR with circuit breaker
Scroll table left / right →Sources: Schneider 8998CT9701 p. 36; Rockwell 2100-SG003G pp. 31-32 (Bulletins 2112/2113); Eaton RP04304003E; Siemens Speedfax p. 16-17. Fusible versions run taller in every line. Reversing starters run roughly 1.5x FVNR height. Electronic overloads, oversized control transformers, and ground fault options add one increment in all lines per the same tables. n/p: not published in the retrieved document.| NEMA size | Square D Model 6 | A-B 2100 (space factors) | Eaton Series 2100 | Siemens tiastar |
|---|
| Size 1 | 6" (Compac 6) or 12" | 0.5-1.0 SF (6.5"-13") | 12" (18" alt.) | 12" (6" compact) |
| Size 2 | 12" | 1.0 SF (13") | 12" / 18" | 12" (6" compact) |
| Size 3 | 18" | 1.5-2.0 SF (19.5"-26") | 18" / 24" | 18" (12" compact) |
| Size 4 | 21" | 2.0-2.5 SF (26"-32.5") | 18" / 24" | 24" (18" compact) |
| Size 5 | 42" (48" with thermal-mag breaker) | 3.5 SF (45.5") | 36" | 36" |
| Size 6 | 72", full 20" x 20" section | 6.0 SF, 25" wide, frame-mounted, no vertical wireway | n/p | 48" or 72" |
The Size 5 and 6 rows are why large motors leave the bucket: a Size 5 FVNR consumes 36 to 48 inches, half a section, and a Size 6 is a full frame-mounted section in every line that offers one at all. A 200 HP motor at 460 V is Size 5 territory by the NEMA rating table; the equivalent breaker feeder unit for a wall-mounted drive is 18 to 24 inches (see the VFD feeder reference).
4. Unit height by breaker feeder frame
Scroll table left / right →Sources: Schneider 8998CT9701 p. 34 (breaker feeders) and p. 35 (fusible; only one disconnect 400 A or larger per section); Rockwell 2100-SG003G 2193F tables; GE BuyLog Section 15. Square D unit extenders add 3-24 inches; total unit height cannot exceed 72 inches.| Feeder rating | Square D Model 6 | A-B 2100 (space factors) | GE 8000 / Spectra |
|---|
| 15-150 A | 6" (Compac 6) or 12" plug-on | 0.5-1.0 SF (125 A frame) | 6" or 12" (150 A SE frame) |
| 175-250 A | 6" Compac or 18" plug-on | 0.5-1.5 SF (250 A frame, plug-in to 225 A trip) | 12" (250 A SF frame) |
| 300-400 A | 27" plug-on (400 A frame) | 2.0 SF, frame-mounted (400 A TK) | 24" (SG frame) |
| 450-600 A | 36" | 3.5 SF (1200 A TN frame class) | 24" (600 A SG) |
| 800-1200 A | 18"-21" top-entry, cabled | 2.0-3.5 SF | n/p |
5. NEMA wiring classes and types
Scroll table left / right →Definitions per Schneider catalog 8998CT9701 pp. 9-10 (NEMA/EEMAC wiring classes); NEMA ICS 18 adds subtypes C-S (structure-mounted master terminal blocks) and C-M (separate marshaling compartment). Factory defaults worth knowing: Allen-Bradley ships Class I Type B-T standard (2100-SG003G); GE standard is Class I Type B (BuyLog Section 15).| Designation | Definition |
|---|
| Class 1 | Independent units: manufacturer completes wiring within each unit; no wiring between units. |
| Class 2 | Class 1 plus manufacturer-furnished interlocking and wiring between units per the purchaser's control system diagrams. |
| Type A | Field wiring lands directly on device terminals inside the unit. Provided only on Class 1 MCCs. |
| Type B-D | Control wiring to unit terminal blocks; load wiring for Size 3 and smaller lands directly on device terminals adjacent to and accessible from the vertical wireway. |
| Type B-T | As B-D, but load wiring lands on factory-wired power terminal blocks in or adjacent to each unit. |
| Type C | Control and load wiring for Size 3 and smaller land on master terminal blocks at the top or bottom of the section, factory-wired to the units. Size 4 and larger load wiring lands on device terminals in every type. |
6. Standards notes
Scroll table left / right →| Fact | Source |
|---|
| MCCs are listed to UL 845 (tri-national with CSA C22.2 No. 254). 6th edition, June 2021, extends scope to 1000 V; 5th edition covered 600 V ac. | UL 845 scope pages; ANSI listing |
| Sections and units are listed independently: a UL-listed vertical section can legally contain non-listed units. | Schneider 8998CT9701 p. 9 |
| Bus ampacity is rated at 65 C maximum temperature rise over 40 C ambient. | Schneider 8998CT9701 p. 13, typical spec 2.05.B |
| NEMA ICS 18-2001 (R2007) is the NEMA MCC standard, scope 600 V ac; effectively frozen, with application content carried in UL 845 Annex H. | ANSI webstore listing; manufacturer citations |
| Wire bending space at MCC terminals is governed by NEC 430.10(B); manufacturers sell 12-24 inch pull boxes specifically to meet it. | Siemens Speedfax 16-6; Rockwell 2100-SG003G lug notes |
Sources
1. Schneider Electric, Model 6 Motor Control Centers catalog, 8998CT9701R07/09, Class 8998.
2. Rockwell Automation, publication 2100-IN012M-EN-P (April 2024); 2100-SG003G-EN-P (July 2025); 2100-CA004K-EN-P (Sept 2025).
3. Eaton, catalog Volume 3 Tab 3, Motor Control Centers, Freedom; renewal parts RP04304003E.
4. GE/ABB, GEH-4961, Spectra Series / 8000-Line Installation and Maintenance; GE BuyLog, Section 15.
5. Siemens, Speedfax product catalog Section 16, tiastar; tiastar instruction manual CCIM-TIAST-1115.
6. UL 845 scope documents; ANSI/NEMA ICS 18-2001 (R2007) listing.
