A.O. Smith 100 Series Service Handbook page 22

MCB - SECTION A
See Figure 12 on page 19 for location of this section on the MCB.
The upper right corner of the MCB contains the following sockets/components:
• Red LED (illuminated when the F1 fuse is open or not installed)
• F1 Fuse (7.5 amp automotive fuse - transformer secondary [24 VAC] winding protection)
• J3 Socket (24 VAC power supply from transformer)
• Pin 1 - 24 VAC from PDB J2 Socket Pin 1
• Pin 2 - 24 VAC from PDB J2 Socket Pin 2
• Pin 3 - Ground from PDB J2 Socket Pin 3
20
RED LED
F1 FUSE
J3
1 2 3
Figure 13
Servicing should only be performed by a Qualified Service Agent
A