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Some people are more likely to be permanently injured
by hot water than others. These include the elderly,
children, the in
fi
rm and the physically/mentally disabled.
Table 1 (published by U.S. Government Memorandum,
1978) shows the approximate time-to-burn relationship
for normal adult skin. If anyone using hot water provided
by the water heater being installed
fi
ts into one of these
groups or if there is a local code or state law requiring a
certain water temperature at the point of use, then special
precautions must be taken.
Water
Temperature
°F
Time for 1st
Degree Burns
(Less Severe Burns)
Time for Permanent
Burns 2nd & 3rd
Degree (Most
Severe Burns)
110
(normal shower temp.)
116 (pain
threshold)
116
35 minutes
45 minutes
122
1 minute
5 minutes
131
5 seconds
25 seconds
140
2 seconds
5 seconds
149
1 second
2 seconds
154 instantaneous
1
seconds
(U.S. Government Memorandum, C.P.S.C., Peter L. Armstrong,
Sept. 15,1978)
Table 1
In addition to using lowest possible temperature setting
that satis
fi
es demand of application, a mixing valve should
be installed at water heater (see Figure 7 & Figure 8) or at
hot-water taps to further reduce system water temperature.
Mixing valves are available at plumbing supply stores.
Consult a Quali
fi
ed Installer or Service Agency. Follow
mixing valve manufacturer’s instructions for installation
of the valves. Before changing the factory setting on the
thermostat, read the “Operating The Temperature Control
System” section in this manual.
WATER HEATER OPERATION
Figure 9 shows the water heater’s sequence of operation
when a call for heat is initiated. The ignition control module
will attempt to light the burner three times. If the ignition
control does not detect ignition it will enter lockout mode
and
fl
ash the corresponding error code.
HEATER CONTROL
CHECKS TO ENSURE
BLOWER EXHAUST
PRESSURE SWITCH IS
OPEN
BLOWER IS
ENERGIZED
CONTROL CHECKS
TO ENSURE:
EXHAUST PRESSURE
SWITCH CLOSES AND
INTAKE PRESSURE
SWITCH REMAINS
CLOSED INDICATING
BLOWER IS
OPERATING AND
THERE ARE NO
BLOCKAGES (INTAKE
OR EXHAUST)
TEMPERATURE
SWITCH REMAINS
CLOSED INDICATING
VENT TEMPARATURE IS
NOT ABOVE THE
ALLOWEBLE LIMIT
IGNITER IS ENERGIZED
AND GAS VALVE IS
OPENED
BURNER COMES ON
AND THE FLAME IS
SENSED BY CONTROL
BURNER CONTINUES
TILL THE WATER IN THE
TANK REACHES THER-
MOSTAT SETTING
GAS VALVE IS CLOSED
AND BURNER SHUTS
OFF
HEATER
THERMOSTAT
CALLS FOR
HEAT
HEATER
REMAINS ON
STANDBY UNTIL
NEXT CALL FOR
HEAT
BLOWER CONTINUES
FOR A POST PURGE
TIME
Figure 9
