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 with CT Type Overloads

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 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 with CT Type Overloads

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	—	—