A.O. Smith 960 through 967 - Manual (Page 25)

BTH S E R V I C E H A N D B O O K
T R O U B L E S H O O T I N G
PRESSURE SWITCH CONTINUITY
STEP 7 PRESSURE SWITCH CONTINUITY TEST
Notes:
Low Gas Pressure Switch
(BTH 120 & 250 only)
is instailed on the iniet
side of the Gas Valve.
N.O. = Normally Open
N.C. = Normally Closed
Blocked Inlet Switch
N. C. Contacts
Gas Valve - Top View
Blower Prover Switch
N. O. Contacts
Blocked Outlet Switch
N. C. Contacts
STEP 7: CHECK FOR CONTINUITY BETWEEN PRESSURE SWITCH TERMINALS WITH
WIRES REMOVED.
Condition:
• On/Off switch is off.
• All wires are disconnected from all pressure switches.
• Multimeter is set to lowest ohms scale.
IF... THEN
blocked inlet switch does not show continuity replace switch.
blocked inlet switch does show continuity continue.
blower proving switch does show continuity replace switch.
blower proving switch does not show continuity continue.
low gas pressure switch does not show continuity
check for minimum supply gas
pressure of
5.0” W.C. natural gas
9.0” W.C. LP gas
replace switch if gas pressures
are above these minimums.
low gas pressure switch does show continuity continue.
blocked outlet pressure switch does not show continuity replace switch.
blocked outlet pressure switch does show continuity
reconnect all wires to pressure
switches; continue to Step 8A.
Technical Training Department
TC-044 Revision 6
24
A. O. Smith Water Products Co.
Ashland City, Tennessee © 2004