A.O. Smith TC-049R3 Service Handbook page 14

RESIDENTIAL GAS AND ELECTRIC WATER HEATER
Residential Gas - continued
Electrical Testing– continued
Millivolt dropout test
Move meter probe to upper ECO solder joint and ground
Procedure:
If ...
reading of at least 10 MV is not present
reading of more than 10 MV is present but,
gas to the pilot shuts off each time knob is
released
Safety drop out test
Procedures:
Meter still connected to upper ECO solder joint and
ground.
Turn Top Knob to "off" position
Millivolt output will decrease as thermocouple cools
If...
internal safety does not activate between 1
and 3 MV (you will hear a "click" inside the
valve)
*internal safety does activate between 1 and
3 MV
*Note: A "click" sound should be heard from the valve as the main gas interrupter snaps up to the
"closed" position.
Condensation
Flue gas products contain moisture. If these flue gas products are cooled to their "dew point",
they become visible moisture – condensation.
Flue gas may become cooled by:
•
Cold supply air temperatures
•
Cool surfaces – generally, if tank water temperatures drop below 110°F, the flue pipe surface
and/or bottom tank head will be cool enough to cause condensation.
•
Increased combustion efficiency – higher thermal efficiency means that an increased amount
of heat is transferring from the flue gas into the water. If you transfer (approximately) 87.5%,
or more, the moisture in the flue gas will condense.
A.O. Smith Water Products Company
©2005
SERVICE HANDBOOK
through copper magnet winding and ECO (Emergency Cut Off)
– the safety gas shutoff
should interrupt gas through
the valve when MV current
drops to 1-3 MV.
... then
replace the control valve.
replace the control valve.
... then
replace the control valve.
valve is within tolerance and will interrupt gas
flow if pilot looses heat or ECO opens.
Technical Training Department
13
TO GROUND
Ashland City, TN