A.O. Smith BTH 150 - Page 29

A. O. Smith Water Products Company Service Handbook
Irving, Texas 2000© Training Department
28
STEP 11. 24 VAC CHECK –
Each terminal of pressure switch to ground; bottom (B) first then top (T) to ground next.
IF… THEN
blocked inlet (B) to gnd does not have 24 VAC check
w
blocked inlet (B) to gnd does have 24 VAC continu
e
blocked inlet (T) to gnd does not have 24 VAC replace
blocked inlet (T) to gnd does have 24 VAC continu
e
blower prover (B) to gnd does not have 24 VAC check
w
blower prover (B) to gnd does have 24 VAC continu
e
blower prover (T) to gnd does not have 24 VAC
g
o to S
t
blower prover (T) to gnd does have 24 VAC replace
TROUBLESHOOTING
STEP 11 - 24 VAC CHECK
STEP 12 - 24 VAC CHECK THROUGH PRESS SWITCHES
STEP 12. CONTINUATION OF 24 VAC CHECK THROUGH PRESS SWITCHES
• Tank calling for heat
• Blower on (See Table on Page 32 for Opening/Closing Pressures).
IF... THEN
• check for po
s
• air tubin
g
is
c
• replace swit
c
blower prover (T) to gnd does have 24 VAC continue.
low gas press (B) to gnd does not have 24 VAC check wire co
n
low gas press. (B) to gnd does have 24 VAC continue.
• check suppl
y
• connection t
u
• replace swit
c
low gas press (T) to gnd does have 24 VAC continue.
• check wire c
o
• blower prove
r
blocked outlet (B) to gnd does have 24 VAC continue.
• check for blo
• check for po
s
• replace swit
c
blocked outlet (T) to gnd does have 24 VAC continue to St
e
blocked outlet (B) to gnd does not have 24 VAC
blocked outlet (T) to gnd does not have 24 VAC
• if BTH 120 o
r
blower prover (T) to gnd does not have 24 VAC
low gas press (T) to gnd does not have 24 VAC
(BTH 120 and 250 only)