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A.O. Smith 120 trough 500 User Manual

Page 37

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BTR TANK TYPE HEATERS

SERVICE HANDBOOK

A.O. Smith Water Products

Service Handbook

Irving, Texas ©2000

Training Department

36

STEP 14B

PILOT VALVE TEST – BTR 500 ONLY

STEP 14B.

PILOT VALVE TEST – BTR 500 ONLY.

Testing the two coils of the

Honeywell VR8404P 5004 gas valve used on the model BTR 500 only. Because of built
in diodes, it is difficult to test for ohms resistance through these coils. The following is a
DC amperage check of the main and pilot coils.
Condition:

Tank calls for heat

PV terminal of module has 24 Vac

No Pilot flame

Test Procedure:

Turn off power to heater

Meter set to test for DC amperage (on AOS meters, the black wire is in the
“com” port, the red wire is in the “10A” port, the dial is set to 20M/10A in the DC
AMP test area).

Blue “PV” wire is disconnected from the ignition PV terminal.

Install meter in series between gas valve and ignition module – 10A wire to
blue gas valve lead, common wire to PV module terminal.

Turn power on to heater, after module receives 24V

Test DC Amperage through Pilot coil of gas valve
IF

THEN

.75 to .85 DCA is not present:

• Replace the gas valve

.75 to .85 DCA is present

• Pilot should work if gas (not air) is present to pilot

Power off, reattach blue gas valve wire to PV terminal of module.

RED

WHITE

BLUE

MANIFOLD

PRESSURE

TAP

MANIFOLD

PRESSURE

TAP

PILOT GAS

MANIFOLD

GAS

The MV/PV wire on the IID is connected to the white wire

The MV wire on the IID is connected to the red wire.