A.O. Smith BTH 120 Service And Parts Manual page 29

STEP 11. 24 VAC CHECK –
Each terminal of pressure switch to ground; bottom (B) first then top (T) to ground next.
IF...
blocked inlet (B) to gnd does not have 24 VAC
blocked inlet (B) to gnd does have 24 VAC
blocked inlet (T) to gnd does not have 24 VAC
blocked inlet (T) to gnd does have 24 VAC
blower prover (B) to gnd does not have 24 VAC
blower prover (B) to gnd does have 24 VAC
blower prover (T) to gnd does not have 24 VAC
blower prover (T) to gnd does have 24 VAC
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...
blower prover (T) to gnd does not have 24 VAC
blower prover (T) to gnd does have 24 VAC
(BTH 120 and 250 only)
low gas press (B) to gnd does not have 24 VAC
low gas press. (B) to gnd does have 24 VAC
low gas press (T) to gnd does not have 24 VAC
low gas press (T) to gnd does have 24 VAC
blocked outlet (B) to gnd does not have 24 VAC
blocked outlet (B) to gnd does have 24 VAC
blocked outlet (T) to gnd does not have 24 VAC
blocked outlet (T) to gnd does have 24 VAC
A. O. Smith Water Products Company
Irving, Texas 2000©
TROUBLESHOOTING
STEP 11 - 24 VAC CHECK
THEN
check w
continue
replace
continue
check w
continue
go to St
replace
THEN
• check for pos
• air tubing is c
• replace switc
continue.
check wire con
continue.
• check supply
• connection tu
• replace switc
continue.
• check wire co
• blower prover
• if BTH 120 or
continue.
• check for blo
• check for pos
• replace switc
continue to Ste
28
Service Handbook
Training Department