A.O. Smith TC-099 - Manual (Page 28)

AOS WPC - Tech Training 27 of 72 Ashland City, TN © 2007
Servicing should only be performed by a Qualified Service Agent
VF BOILER SERVICE MANUAL
MCB - SECTION A
The upper left corner of the MCB contains the following sockets/components:
Red LED (illuminated when the F1 fuse is open or missing)
F1 Fuse (7.5 amp automotive fuse - 24 VAC transformer protection)
J3 Socket (24 VAC power supply from transformer)
• Pin 1 - 24 VAC line
• Pin 2 - 24 VAC line
• Pin 3 - Ground
A
Red LED
Illuminated when
F1 fuse is blown
F1 Fuse
24 VAC
7.5 amp
J3 Socket
24 VAC power supply
from transformer
3
2
1
The MCB circuit board is mounted upside down on VF boilers compared to the illustrations below.