5
AUTOMATIC GAS SHUTOFF CONTROL
The automatic gas shutoff control, fig. 1, is an automatic safety
device which activates at a water temperature of approximately
1950F (90.5°C). This limits the water outlet temperature to a
maximum of 2000F (87.7°C).
The device is wired in series with the gas valve. The control will
automatically reset when the water temperature cools to
approximately 190oF (87.7°C).
Should the automatic gas shutoff control activate during a heating
cycle, the heater’s gas valve will close; extinguishing the main
burners. The pilot burner will also be extinguished. The circulating
pump will continue operating as long as the storage tank
thermostat continues to “call for heat”. When the water
temperature in the heater drops to 1800F (82.2°C) or below the
control module will begin an ignition cycle which will relight the
pilot burner and main burners. Re-ignition of the main burners
will occur if the storage tank thermostat continues to call for heat.
Otherwise, the normal operating cycle will resume on the
thermostat’s next call for heat.
AUTOMATIC GAS SHUTOFF CONTROL
FIGURE 1
PROTECTOR SWITCH (Coil High Limit)
This heater is equipped with a manually reset protector switch,
Figure 2, located under the small cover on the side of the jacket.
This device provides positive shutdown of the heater in the event
of heater or system malfunction. Should the surface temperature
of the copper tubing heat exchanger reach 2500F (121.1°C), the
protector switch will activate. The gas valve will close, and the
pilot and main burners will be extinguished. To resume heater
operation, the protector switch must be manually reset (remove
the protector switch cover and push the reset button) after the
coil surface temperature cools to less than 2000F(93.3°C).
FIGURE 2
DO NOT RESET THIS SWITCH WITHOUT PERFORMING THE
SYSTEM CHECKS OUTLINED UNDER PROTECTOR SWITCH
IN THE SERVICE INFORMATION SECTION. ALSO, SEE CHART
ONE UNDER THE CHECKOUT SECTION. IF NECESSARY,
CALL A QUALIFIED SERVICEMAN. Once the cause of the
protector switch activation has been determined and corrected, it
will be necessary to restart the heater following the LIGHTING
AND OPERATING instructions.
THERMAL BALANCER
The thermal balancer (standard on Models HW-200M and
HW-225M, optional on Models HW-120M and HW-160M) is a
snap-acting single-pole thermal relay used only on Cer-Temp 80
Recovery systems. It gives immediate pump start but delay of
pump shutoff for approximately 2 minutes. Residual heat in the
heat exchanger is then recovered after shutdown. This improves
efficiency and balances heater temperature with tank temperature
at shutdown.
INTERMITTENT IGNITION CONTROL MODULE
The Honeywell S-8600 control module contain the electronic
components of the system and also serve as a central wiring
system for the controls mounted on the heater. The control module
performs the following functions:
1. Checks for safe-start by sensing for a flame or false flame
condition on start-up.
2. Generates a potential of 15,000 volts for spark ignition of the
pilot burner.
3. Opens the pilot valve.
FEATURES Control Device Factory Setting Field Adjustment
1950F (90.5°C) cut out temp.
Heater Automatic Gas Shutoff Control Fixed 1900F (87.7°C) cut in temp. Non-adjustable
2500F (121°C) cut out temp.
Heater Protector Switch Fixed 2000F (93.3°C) cut in temp. Non-adjustable
Tank Temperature Control Field Supplied and Installed Adjust to Requirements
Safety Flow Switch See Table 1 Field Adjustable
TABLE 4.