Section 13—Thermal Overload Unit Selection

This section identifies the thermal overload units needed for the starters specified in an order. Tables are based on motor full-load amps and provide the catalog number for the appropriate thermal units to be used at that current rating.

Melting Alloy Overload Selection Tables for Combination Starter Units

Size 1
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
0.56–0.63	B 0.81	4.12–4.70	B 6.90
0.64–0.68	B 0.92	4.71–5.21	B 7.70
0.69–0.77	B 1.03	5.22–5.53	B 8.20
0.78–0.85	B 1.16	5.54–6.17	B 9.10
0.86–0.97	B 1.30	6.18–7.02	B 10.2
0.98–1.09	B 1.45	7.03–7.92	B 11.5
1.10–1.21	B 1.67	7.93–8.61	B 12.8
1.22–1.33	B 1.88	8.62–9.17	B 14
1.34–1.53	B 2.10	9.18–10.0	B 15.5
1.54–1.73	B 2.40	10.1–11.0	B 17.5
1.74–1.89	B 2.65	11.1–11.8	B 19.5
1.90–2.17	B 3.00	11.9–13.5	B 22
2.18–2.53	B 3.30	13.6–15.3	B 25
2.54–2.87	B 3.70	15.4–17.4	B 28
2.88–3.22	B 4.15	17.5–19.4	B 32
3.23–3.49	B 4.85	19.5–22.2	B 36
3.50–3.85	B 5.50	22.3–25.1	B 40
3.86–4.11	B 6.25	25.2–27.0	B 45

Size 2
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
3.94–4.45	B 6.90	14.0–15.8	B 25
4.46–4.97	B 7.70	15.9–17.9	B 28
4.98–5.28	B 8.20	18.0–19.9	B 32
5.29–5.97	B 9.10	20.0–22.8	B 36
5.98–6.89	B 10.2	22.9–25.4	B 40
6.90–7.92	B 11.5	25.5–28.9	B 45
7.93–8.71	B 12.8	29.0–30.8	B 50
8.72–9.27	B 14.0	30.9–32.5	B 56
9.28–10.2	B 15.5	32.6–34.9	B 62
10.3–11.4	B 17.5	35.0–39.7	B 70
11.5–12.3	B 19.5	39.8–44.7	B 79
12.4–13.9	B 22

Size 3
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
14.0–14.9	CC 20.9	36.9–39.8	CC 59.4
15.0–16.2	CC 22.8	39.9–42.3	CC 64.3
16.3–17.2	CC 24.6	42.4–45.7	CC 68.5
17.3–18.7	CC 26.3	45.8–49.2	CC 74.6
18.8–20.2	CC 28.8	49.3–52.8	CC 81.5
20.3–21.7	CC 31.0	52.9–56.8	CC 87.7
21.8–23.3	CC 33.3	56.9–61.2	CC 94.0
23.4–25.2	CC 36.4	61.3–66.1	CC 103
25.3–27.1	CC 39.6	66.2–71.2	CC 112
27.2–29.4	CC 42.7	71.3–76.7	CC 121
29.5–31.6	CC 46.6	76.8–82.9	CC 132
31.7–34.0	CC 50.1	83.0–90.0	CC 143
34.1–36.8	CC 54.5

Size 4
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
44.0–46.8	CC 64.3	73.0–78.1	CC 112
46.9–50.6	CC 68.5	78.2–83.9	CC 121
50.7–54.5	CC 74.6	84.0–91.1	CC 132
54.6–58.4	CC 81.5	91.2–97.5	CC 143
58.5–62.9	CC 87.7	97.6–104	CC 156
63.0–67.7	CC 94.0	105–113	CC 167
67.8–72.9	CC 103	114–133	CC 180

Size 5 without CT Type Overloads
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
88.2–95.1	DD 112	171–180	DD 220
95.2–101	DD 121	181–197	DD 240
102–111	DD 128	198–204	DD 250
112–119	DD 140	205–213	DD 265
120–131	DD 150	214–237	DD 280
132–149	DD 160	238–243	DD 300
150–170	DD 185	244–266	DD 320

Size 5 with CT Type Overloads and Circuit Breakers
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
40.8–45.5	B 1.03	115–128	B 3.00
45.6–49.9	B 1.16	129–140	B 3.30
51.0–57.5	B 1.30	141–160	B 3.70
57.6–65.9	B 1.45	161–193	B 4.15
66.0–73.1	B 1.67	194–209	B 4.85
73.2–81.5	B 1.88	210–232	B 5.50
81.6–92.3	B 2.10	233–248	B 6.25
92.4–104	B 2.40	249–266	B 6.90
105–114	B 2.65

Size 5 with CT Type Overloads and Fusible Switch Disconnects
Motor Full-Load Current (A)	Thermal Unit Number	Max. Fuse Rating (A)	Motor Full-Load Current (A)	Thermal Unit Number	Max. Fuse Rating (A)
40.8–45.5	B 1.03	90	115–128	B 3.00	250
45.6–49.9	B 1.16	100	129–140	B 3.30	250
51.0–57.5	B 1.30	110	141–160	B 3.70	300
57.6-65.9	B 1.45	125	161–193	B 4.15	350
66.0–73.1	B 1.67	125	194–209	B 4.85	400
73.2–81.5	B 1.88	150	210–232	B 5.50	400
84.6–92.3	B 2.10	175	233–248	B 6.25	400
92.4–104	B 2.40	200	249–266	B 6.90	400
105–114	B 2.65	225

Size 6
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
133–148	B 1.30	272–308	B 2.65
149–174	B 1.45	309–348	B 3.00
175–195	B 1.67	349–397	B 3.30
196–219	B 1.88	398–429	B 3.70
220–239	B 2.10	430–495	B 4.15
240–271	B 2.40	496–520	B 4.85

Melting Alloy Overload Selection Tables for Part Winding Combination Starter Units

Size 1
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
1.12–1.27	B 0.81	8.24–9.41	B 6.90
1.28–1.37	B 0.92	9.42–10.43	B 7.70
1.38–1.55	B 1.30	10.44–11.07	B 8.20
1.56–1.71	B 1.16	11.08–12.35	B 9.10
1.72–1.95	B 1.30	12.36–14.05	B 10.2
1.96–2.19	B 1.45	14.06–15.85	B 11.5
2.20–2.43	B 1.67	15.86–17.23	B 12.8
2.44–2.67	B 1.88	17.24–18.35	B 14
2.68–3.07	B 2.10	18.36–20.1	B 15.5
3.08–3.47	B 2.40	20.2–22.1	B 17.5
3.48–3.79	B 2.65	22.2–23.7	B 19.5
3.80–4.35	B 3.00	23.8–27.1	B 22
4.36–5.07	B 3.30	27.2–30.7	B 25
5.08–5.75	B 3.70	30.8–34.9	B 28
5.76–6.45	B 4.15	35.0–38.9	B 32
6.46–6.99	B 4.85	39.0–44.5	B 36
7.00–7.71	B 5.50	44.6–50.3	B 40
7.72–8.23	B 6.25	50.4–54.0	B 45

Size 2
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
7.88–8.91	B 6.90	24.8–27.9	B 22
8.92–9.95	B 7.70	28.0–31.7	B 25
9.96–10.57	B 8.20	31.8–35.9	B 28
10.58–11.95	B 9.10	36.0–39.9	B 32
11.96–13.79	B 10.2	40.0–45.7	B 36
13.80–15.85	B 11.5	45.8–50.9	B 40
15.86–17.43	B 12.8	51.0–61.7	B 45
17.44–18.55	B 14.0	61.8–65.1	B 50
18.56–20.5	B 15.5	65.2–69.9	B 56
20.6–22.9	B 17.5	70.0–79.5	B 62
23.0–24.7	B 19.5	79.6–89.4	B 70

Size 3
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
28.0–29.9	CC 20.9	73.8–79.7	CC 59.4
30.0–32.5	CC 22.8	79.8–84.7	CC 64.3
32.6–34.5	CC 24.6	84.8–91.5	CC 68.5
34.6–37.5	CC 26.3	91.6–98.5	CC 74.6
37.6–40.5	CC 28.8	98.6–105.7	CC 81.5
40.6–43.5	CC 31.0	105.8–113.7	CC 87.7
43.6–46.7	CC 33.3	113.8–122.5	CC 94.0
46.8–50.5	CC 36.4	122.6–132.3	CC 103
50.6–54.3	CC 39.6	132.4–142.5	CC 112
54.4–58.9	CC 42.7	142.6–153.5	CC 121
59.0–63.3	CC 46.6	153.6–165.9	CC 132
63.4–68.1	CC 50.1	166.0–180.0	CC 143
68.2–73.7	CC 54.5

Size 4
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
105–112	CC 74.6	170–181	CC 132
113–122	CC 81.5	182–195	CC 143
123–131	CC 87.7	196–209	CC 156
132–142	CC 94.0	210–227	CC 167
143–153	CC 103	228–247	CC 180
154–157	CC 112	248–266	CC 196
158–169	CC 121

Size 5 without CT Type Overloads
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
176–190	DD 112	342–361	DD 220
191–203	DD 121	362–395	DD 240
204–223	DD 128	396–409	DD 250
224–239	DD 140	410–427	DD 265
240–253	DD 150	428–475	DD 289
254–299	DD 160	476–487	DD 300
300–341	DD 185	488–532	DD 320

Size 5 with CT Type Overloads and Circuit Breakers
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
81.6–91.1	B 1.03	230–257	B 3.00
91.2–101	B 1.16	258-281	B 3.30
102–115	B 1.30	282–321	B 3.70
116–131	B 1.45	322–387	B 4.15
132–146	B 1.67	388–419	B 4.35
147–163	B 1.84	420–465	B 5.60
164–184	B 2.10	466–497	B 6.25
185–209	B 2.40	496–532	B 6.90
210–229	B 2.65

Size 5 with CT Type Overloads and Fusible Switch Disconnects
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
81.6–91.1	B 1.03	230–257	B 3.00
91.2–101	B 1.16	258–281	B 3.30
102–115	B 1.30	282–321	B 3.70
116–131	B 1.45	322–387	B 4.15
132–146	B 1.67	388–419	B 4.35
147–163	B 1.88	420–465	B 5.60
164–184	B 2.10	466–497	B 6.25
185–209	B 2.40	498–532	B 6.90
210–229	B 2.65

Ambient-Compensated Bimetallic Overload Selection Tables for Combination Starter Units

Size 1
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
0.57–0.60	AR 1.05	3.46–3.81	AR 5.8
0.61–0.66	AR 1.15	3.82–4.20	AR 6.4
0.67–0.73	AR 1.26	4.21–4.65	AR 7.0
0.74–0.81	AR 1.39	4.66–5.29	AR 7.7
0.82–0.90	AR 1.53	5.30–5.84	AR 8.5
0.91–1.05	AR 1.68	5.85–6.27	AR 9.3
1.06–1.15	AR 1.85	6.28–6.97	AR 10.2
1.16–1.25	AR 2.04	6.98–7.59	AR 11.2
1.26–1.35	AR 2.24	7.60–7.89	AR 12.4
1.36–1.47	AR 2.46	7.90–8.95	AR 13.6
1.48–1.58	AR 2.71	8.96–10.3	AR 15.4
1.59–1.74	AR 2.98	10.4–11.7	AR 17.6
1.75–1.94	AR 3.28	11.8–13.3	AR 20.5
1.95–2.20	AR 3.62	13.4–15.2	AR 23
2.21–2.47	AR 3.98	15.3–17.2	AR 27
2.48–2.76	AR 4.37	17.3–19.7	AR 30
2.77–3.07	AR 4.80	19.8–22.4	AR 35
3.08–3.45	AR 5.3	22.5–26.0	AR 40

Size 2
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
4.24–4.62	AR 8.5	16.5–18.9	AR 35
4.63–5.05	AR 9.3	19.0–21.6	AR 40
5.06–5.54	AR 10.2	21.7–23.3	AR 44
5.55–6.13	AR 11.2	23.4–24.9	AR 47
6.14–6.44	AR 12.4	25.0–26.9	AR 51
6.45–7.48	AR 13.6	27.0–29.1	AR 55
7.49–8.55	AR 15.4	29.2–31.3	AR 60
8.56–9.74	AR 17.6	31.4–33.5	AR 66
9.75–11.1	AR 20.5	33.6–36.9	AR 72
11.2–12.7	AR 23	37.0–39.1	AR 79
12.8–14.4	AR 27	39.2–40.9	AR 86
14.5–16.4	AR 30	41.0–45.0	AR 94

Size 3
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
27.1–30.0	E 67	47.0–51.5	E 74
30.1–33.2	E 69	51.6–57.0	E 76
33.3–35.7	E 70	57.1–62.8	E 77
35.8–39.4	E 71	62.9–69.1	E 78
39.5–43.4	E 72	69.2–75.0	E 79
43.5–46.9	E 73	75.1–83.3	E 80

Size 4
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
50–55.9	E 88	82–86.9	E 96
56–60.9	E 89	87–92.9	E 97
61–65.9	E 91	93–97.9	E 98
66–69.9	E 92	98–107.9	E 99
70–75.9	E 93	108–113.9	E 101
76–81.9	E 94	114–125.9	E 102

Size 5
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
105–116	AR 3.28	166–184	AR 4.80
117–132	AR 3.62	185–207	AR 5.3
133–148	AR 3.98	208–229	AR 5.8
149–165	AR 4.37	230–266	AR 6.4

Size 6
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
146–169	AR 1.68	280–311	AR 3.28
170–185	AR 1.85	312–353	AR 3.62
186–201	AR 2.04	354–396	AR 3.98
202–217	AR 2.24	397–442	AR 4.37
218–236	AR 2.46	443–492	AR 4.80
237–253	AR 2.71	493–520	AR 5.3
254–279	AR 2.98

Ambient-Compensated Bimetallic Overload Selection Tables for Part Winding Combination Starter Units

Size 1
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
1.14–1.21	AR 1.05	6.92–7.63	AR 5.8
1.22–1.33	AR 1.15	7.64–8.41	AR 6.4
1.34–1.47	AR 1.26	8.42–9.31	AR 7.0
1.48–1.63	AR 1.39	9.32–10.59	AR 7.7
1.64–1.81	AR 1.53	10.60–11.69	AR 8.5
1.82–2.11	AR 1.68	11.70–12.55	AR 9.3
2.12–2.31	AR 1.85	12.56–13.95	AR 10.2
2.32–2.51	AR 2.04	13.96–15.19	AR 11.2
2.52–2.71	AR 2.24	15.20–15.79	AR 12.4
2.72–2.95	AR 2.46	15.80–17.91	AR 13.6
2.96–3.17	AR 2.71	17.92–20.7	AR 15.4
3.18–3.49	AR 2.98	20.8–23.5	AR 17.6
3.50–3.89	AR 3.28	23.6–26.7	AR 20.5
3.90–4.41	AR 3.62	26.8–30.5	AR 23
4.42–4.95	AR 3.98	30.6–34.5	AR 27
4.96–5.53	AR 4.37	34.6–39.5	AR 30
5.54–6.15	AR 4.80	39.6–44.9	AR 35
6.16–6.91	AR 5.30	45.0–52.0	AR 40

Size 2
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
8.48–9.25	AR 8.5	33.0–37.9	AR 35
9.26–10.11	AR 9.3	38.0–43.3	AR 40
10.12–11.09	AR 10.2	43.4–46.7	AR 44
11.10–12.27	AR 11.2	46.8–49.9	AR 47
12.28–12.89	AR 12.4	50.0–53.9	AR 51
12.90–14.97	AR 13.6	54.0–58.3	AR 55
14.98–17.11	AR 15.4	58.4–62.7	AR 60
17.12–19.49	AR 17.6	62.8–67.1	AR 66
19.50–22.3	AR 20.5	67.2–73.8	AR 72
22.4–25.5	AR 23	74.0–78.3	AR 79
25.6–28.9	AR 27	78.4–81.9	AR 86
29.0–32.9	AR 30	82.0–90.0	AR 94

Size 3
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
54.2–60.1	E 67	94.0–103.1	E 74
60.2–66.5	E 69	103.2–114.1	E 76
66.6–71.5	E 70	114.2–125.7	E 77
71.6–78.9	E 71	125.8–138.3	E 78
79.0–86.9	E 72	138.4–150.1	E 79
87.0–93.9	E 73	150.2–166.6	E 80

Size 4
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
100–111.9	E 88	164–173.9	E 96
112–121.9	E 89	174–185.9	E 97
122–131.9	E 91	186–195.9	E 98
132–139.9	E 92	196–215.9	E 99
140–151.9	E 93	216–227.9	E 101
152–163.9	E 94	228–251.9	E 102

Size 5
Motor Full-Load Current (A)	Thermal Unit Number	Motor Full-Load Current (A)	Thermal Unit Number
210–233	AR 3.28	332–369	AR 4.8
234–265	AR 3.62	370–415	AR 5.3
266–297	AR 3.98	416–459	AR 5.8
298–331	AR 4.37	460–532	AR 6.4