A.O. Smith BFM - 120 - Manual (Page 5)

BFM
Electrical diagram
A = Jacket
B = Isolating transformer
C = APDS (Air pressure
differential switch)
C = Filter
E = Reset button
F = Frost thermostat
G = Control thermostat
H = ON/ OFF switch
K = Safety thermostat
L = High-limit thermostat
M = Burner control
N = Connector clip strip
P = Earthing strip
R = Clock (optional)
S = Relay
T = Potentiostat (optional)