NEC Chapter 9 Table 4 — Conduit Dimensions & Percent Fill Areas

MetricDesignator	Trade Size	Over 2 Wires40%	60%	1 Wire53%	2 Wires31%	NominalInternalDiameter	Total Area100%
16	1/2	78	0.122	118	0.182	104	0.161	61	0.094	15.8	0.622	196	0.304
21	3/4	137	0.213	206	0.320	182	0.283	106	0.165	20.9	0.824	343	0.533
27	1	222	0.346	333	0.519	295	0.458	172	0.268	26.6	1.049	556	0.864
35	114	387	0.598	581	0.897	513	0.793	300	0.464	35.1	1.380	968	1.496
41	112	526	0.814	788	1.221	696	1.079	407	0.631	40.9	1.610	1314	2.036
53	2	866	1.342	1299	2.013	1147	1.778	671	1.040	52.5	2.067	2165	3.356
63	212	1513	2.343	2270	3.515	2005	3.105	1173	1.816	69.4	2.731	3783	5.858
78	3	2280	3.538	3421	5.307	3022	4.688	1767	2.742	85.2	3.356	5701	8.846
91	312	2980	4.618	4471	6.927	3949	6.119	2310	3.579	97.4	3.834	7451	11.545
103	4	3808	5.901	5712	8.852	5046	7.819	2951	4.573	110.1	4.334	9521	14.753
129	5	5220	8.085	7830	12.127	6916	10.713	4045	6.266	128.9	5.073	13050	20.212
155	6	7528	11.663	11292	17.495	9975	15.454	5834	9.039	154.8	6.093	18821	29.158

MetricDesignator	TradeSize	Over 2 Wires40%	60%	1 Wire53%	2 Wires31%	NominalInternalDiameter	Total Area100%
16	1/2	73	0.114	110	0.171	97	0.151	57	0.088	15.3	0.602	184	0.285
21	3/4	131	0.203	197	0.305	174	0.269	102	0.157	20.4	0.804	328	0.508
27	1	215	0.333	322	0.499	284	0.441	166	0.258	26.1	1.029	537	0.832
35	114	375	0.581	562	0.872	497	0.770	291	0.450	34.5	1.36	937	1.453
41	112	512	0.794	769	1.191	679	1.052	397	0.616	40.4	1.59	1281	1.986
53	2	849	1.316	1274	1.975	1125	1.744	658	1.020	52	2.047	2123	3.291
63	212	—	—	—	—	—	—	—	—	—	—	—	—
78	3	—	—	—	—	—	—	—	—	—	—	—	—
91	312	—	—	—	—	—	—	—	—	—	—	—	—

MetricDesignator	TradeSize	Over 2 Wires40%	60%	1 Wire53%	2 Wires31%	Nominal Internal Diameter	Total Area100%
12	3/8	30	0.046	44	0.069	39	0.061	23	0.036	9.7	0.384	74	0.116
16	1/2	81	0.127	122	0.190	108	0.168	63	0.098	16.1	0.635	204	0.317
21	3/4	137	0.213	206	0.320	182	0.283	106	0.165	20.9	0.824	343	0.533
27	1	211	0.327	316	0.490	279	0.433	163	0.253	25.9	1.020	527	0.817
35	114	330	0.511	495	0.766	437	0.677	256	0.396	32.4	1.275	824	1.277
41	112	480	0.743	720	1.115	636	0.985	372	0.576	39.1	1.538	1201	1.858
53	2	843	1.307	1264	1.961	1117	1.732	653	1.013	51.8	2.040	2107	3.269
63	212	1267	1.963	1900	2.945	1678	2.602	982	1.522	63.5	2.500	3167	4.909
78	3	1824	2.827	2736	4.241	2417	3.746	1414	2.191	76.2	3.000	4560	7.069
91	312	2483	3.848	3724	5.773	3290	5.099	1924	2.983	88.9	3.500	6207	9.621
103	4	3243	5.027	4864	7.540	4297	6.660	2513	3.896	101.6	4.000	8107	12.566

MetricDesignator	TradeSize	Over 2 Wires40%	60%	1 Wire53%	2 Wires31%	NominalInternalDiameter	Total Area100%
12	3/8	—	—	—	—	—	—	—	—	—	—	—	—
16	1/2	89	0.137	133	0.205	117	0.181	69	0.106	16.8	0.660	222	0.342
21	3/4	151	0.235	226	0.352	200	0.311	117	0.182	21.9	0.864	377	0.586
27	1	248	0.384	372	0.575	329	0.508	192	0.297	28.1	1.105	620	0.959
35	114	425	0.659	638	0.988	564	0.873	330	0.510	36.8	1.448	1064	1.647
41	112	573	0.890	859	1.335	759	1.179	444	0.690	42.7	1.683	1432	2.225
53	2	937	1.452	1405	2.178	1241	1.924	726	1.125	54.6	2.150	2341	3.630
63	212	1323	2.054	1985	3.081	1753	2.722	1026	1.592	64.9	2.557	3308	5.135
78	3	2046	3.169	3069	4.753	2711	4.199	1586	2.456	80.7	3.176	5115	7.922
91	312	2729	4.234	4093	6.351	3616	5.610	2115	3.281	93.2	3.671	6822	10.584
103	4	3490	5.452	5235	8.179	4624	7.224	2705	4.226	105.4	4.166	8725	13.631
129	5	5455	8.528	8183	12.792	7229	11.30	4228	6.610	131.78	5.210	13639	21.32
155	6	7878	12.304	11817	18.456	10439	16.302	6106	9.536	158.36	6.258	19696	30.76

MetricDesignator	TradeSize	Over 2 Wires40%	60%	1 Wire53%	2 Wires31%	NominalInternalDiameter	Total Area100%
12	3/8	50	0.077	75	0.115	66	0.102	39	0.060	12.6	0.495	125	0.192
16	1/2	80	0.125	121	0.187	107	0.165	62	0.097	16.0	0.630	201	0.312
21	3/4	139	0.214	208	0.321	184	0.283	107	0.166	21.0	0.825	346	0.535
27	1	221	0.342	331	0.513	292	0.453	171	0.265	26.5	1.043	552	0.854
35	114	387	0.601	581	0.901	513	0.796	300	0.466	35.1	1.383	968	1.502
41	112	520	0.807	781	1.211	690	1.070	403	0.626	40.7	1.603	1301	2.018
53	2	863	1.337	1294	2.006	1143	1.772	669	1.036	52.4	2.063	2157	3.343

MetricDesignator	TradeSize	Over 2 Wires40%	60%	1 Wire53%	2 Wires31%	NominalInternalDiameter	Total Area100%
12	3/8	49	0.077	74	0.115	65	0.102	38	0.059	12.5	0.494	123	0.192
16	1/2	81	0.125	122	0.188	108	0.166	63	0.097	16.1	0.632	204	0.314
21	3/4	140	0.216	210	0.325	185	0.287	108	0.168	21.1	0.830	350	0.541
27	1	226	0.349	338	0.524	299	0.462	175	0.270	26.8	1.054	564	0.873
35	114	394	0.611	591	0.917	522	0.810	305	0.474	35.4	1.395	984	1.528
41	112	510	0.792	765	1.188	676	1.050	395	0.614	40.3	1.588	1276	1.981
53	2	836	1.298	1255	1.948	1108	1.720	648	1.006	51.6	2.033	2091	3.246

A fixed industrial process heating unit uses a hermetic refrigerant motor-compressor and also incorporates equipment covered by another NEC article. Which section directs the installer to the table listing those other applicable articles?

A 425.4
B 425.1
C 425.3
D 425.6

Show answer & explanation

Correct: C — 425.3

425.3 is the section that hosts Table 425.3, directing the installer to other NEC articles that apply to fixed industrial process heating equipment with a hermetic refrigerant motor-compressor. 425.1 only states the article's scope, 425.6 covers listed equipment requirements, and 425.4 covers branch-circuit sizing — none of these point to the cross-reference table.

An installer has two non-hermetic motors of different horsepower feeding a common branch circuit and needs to determine which one governs as the largest motor for 430.53(B) grouping rules. Neither nameplate lists rated-load current directly usable for comparison, so the tech must pull equivalent full-load current values from Table 430.248 based on horsepower. Which section directs this method of finding the highest rated motor?

A 440.6(B)
B 440.12(B)(2)
C 440.7
D 440.4(B)

Show answer & explanation

Correct: C — 440.7

440.7 specifically instructs that, for motors other than hermetic compressors or 440.6(B) multimotor equipment, full-load current for comparison purposes is taken from Table 430.248, 430.249, or 430.250 based on horsepower rating. 440.6(B) covers ampacity marking for multimotor equipment generally, not the largest-motor determination method, and 440.12(B)(2) deals with combination-load short-circuit protective device sizing instead.

An electrician is installing EMT to carry stage lighting circuit conductors and wants to know the conductor fill table that applies, along with confirmation that the usual 30-conductor cap on other raceway types doesn't apply here. Which section addresses this?

A 520.21
B 520.6
C 520.10
D 520.5(A)

Show answer & explanation

Correct: B — 520.6

520.6 directs use of Table 1 of Chapter 9 for percentage fill in metal conduit or EMT and expressly states the 30-conductor limitation of 366.22 and 376.22 does not apply. 520.5(A) only covers general wiring methods permitted for stage equipment, not conductor fill calculations.

Chapter 9, Table 4 — conduit & tubing areas

EMT

Table 9.4

FMC

IMC

Table 9.4

Table 9.4

Race your codebook — 3 lookups on this table

Every table. Timed lookups. Spaced repetition.

MetricDesignator	Trade Size	Over 2 Wires40%		60%		1 Wire53%		2 Wires31%		NominalInternalDiameter		Total Area100%
MetricDesignator	Trade Size	mm2	in.2	mm2	in.2	mm2	in.2	mm2	in.2	mm	in.	mm2	in.2
16	1/2	78	0.122	118	0.182	104	0.161	61	0.094	15.8	0.622	196	0.304
21	3/4	137	0.213	206	0.320	182	0.283	106	0.165	20.9	0.824	343	0.533
27	1	222	0.346	333	0.519	295	0.458	172	0.268	26.6	1.049	556	0.864
35	114	387	0.598	581	0.897	513	0.793	300	0.464	35.1	1.380	968	1.496
41	112	526	0.814	788	1.221	696	1.079	407	0.631	40.9	1.610	1314	2.036
53	2	866	1.342	1299	2.013	1147	1.778	671	1.040	52.5	2.067	2165	3.356
63	212	1513	2.343	2270	3.515	2005	3.105	1173	1.816	69.4	2.731	3783	5.858
78	3	2280	3.538	3421	5.307	3022	4.688	1767	2.742	85.2	3.356	5701	8.846
91	312	2980	4.618	4471	6.927	3949	6.119	2310	3.579	97.4	3.834	7451	11.545
103	4	3808	5.901	5712	8.852	5046	7.819	2951	4.573	110.1	4.334	9521	14.753
129	5	5220	8.085	7830	12.127	6916	10.713	4045	6.266	128.9	5.073	13050	20.212
155	6	7528	11.663	11292	17.495	9975	15.454	5834	9.039	154.8	6.093	18821	29.158

Chapter 9, Table 4 — conduit & tubing areas

EMT

Table 9.4

FMC

IMC

Table 9.4

Table 9.4

Race your codebook — 3 lookups on this table

Keep going

Every table. Timed lookups. Spaced repetition.