A.O. Smith ADM - 40, Инструкция по установке, эксплуатации и обслуживанию

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Instruction manual ADM 13
gis
2.4 Protection for the
appliance
The burner control monitors the water temperature by means of thermostats
and ensures safe combustion. This takes place using:
•
the Gas control;
• the Thermocouple;
• the Water temperature protection;
• the Flue gas backflow safeguard.
2.4.1 Gas control
The gas control has 2 valves for safety purposes:
1. The main valve, which controls the gas supply to the burner tray and which
is switched via the I/0/II switch circuit and the control, high-limit and flue gas
thermostats. This circuit is powered by the supply voltage.
2. The safety valve, which controls the gas supply to the pilot burner and which
is switched via the thermocouple circuit and the safety thermostat. This
circuit is powered by the millivoltage from the thermocouple that is located
in the pilot flame. Whenever the safety valve closes, the main valve also
closes.
2.4.2 Thermocouple
1. To prevent gas flowing when there is no combustion, a thermocouple is
fitted. As a result of the presence of the (permanent) pilot flame, the
thermocouple maintains a millivoltage which keeps the gas control's safety
valve open.
2. If the pilot flame goes out, this voltage disappears and the gas control's
safety valve closes, interrupting the gas supply to the burner tray.
2.4.3 Water temperature protection
The burner control monitors three temperatures related to safety using the frost
and high-limit thermostats. The table explains the operation of the thermostats
with sensors.
Temperature protection
2.4.4 Flue gas backflow safeguard
To prevent the flue gases from flowing back into the appliance, is flue gas
sensor (34) and flue gas thermostat (37) have been fitted to the draught diverter.
Under normal conditions, this sensor will register the ambient temperature.
However, if the chimney does not draw sufficiently (for example due to a
blockage in the chimney) then the flue gases will 'reflux' and flow back past the
flue gas sensor. The sensor will then detect an unusually high temperature and
the flue gas thermostat will open. The gas control's main circuit closes, which
interrupts the heating cycle. The flue gas thermostat is blocked and the
appliance must be restarted manually.
Protection Description
High-limit thermostat The heat demand is ended by closing the gas control. This terminates the
heating cycle. The heating cycle restarts once the high-limit thermostat closes.
This happens because the pilot light stays lit when the gas control is closed.
The high-limit thermostat prevents overheating and/or excess lime buildup.
Safety thermostat If the safety thermostat sensor (38) registers a temperature that is higher than
93 °C, the power to the thermocouple is switched off. This terminates the
heating cycle. It is then only possible to restart the appliance using the spark
igniter.