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Boiler Safety Features:
Gradient limiting:
During operation, if the boiler supply temperature is rising too quickly, the control will start to
modulate down and reduce the firing rate down to the lowest setting to prevent overheating (in
case of no flow conditions).
Reverse flow detection:
During operation, the boiler will monitor both supply and return temperatures to ensure the return
temperature is not much higher than the supply temperature (in case of reverse flow or
malfunction of either supply or return thermistors).
Water pressure monitoring
The boiler is equipped with a water pressure sensor to ensure the boiler operates safely.
The boiler will shutdown in case the water pressure is too high (>87 Psi [6 bar]) or too low (< 12 Psi
[0.8 bar]). The boiler will operate in reduced power mode in case the water pressure drops below
15 Psi [1 bar] and will return to normal once the water pressure exceeds 19 Psi [1.3 bar].
Supply Temperature, and Flue Temperature Supervision
The control monitors the boiler supply temperature thermistor, when this temperature
exceeds 190°F [88°C] the control will reduce the output power. If this temperature continues to rise
and exceeds 203°F [95°C] the control will shutdown the burner until it cools off. The control will
shutdown and lockout if the supply temperature exceeds 2008°F [98°C] - manual reset required.
The flue temperature is monitored by a sensor located on the secondary heat exchanger.
There are two settings on the controller to monitor this temperature based on the material used for
venting. The following table explains the limits and control behavior for each selection. The boiler
will modulate to maintain the flue temperature below the settings shown in the table below. In
case the temperature exceeds the maximum limit, the boiler will shutdown and run the fan in post-
purge mode. If the temperature drops within ten minutes the boiler will return to normal
operation, otherwise it will go into a lockout state.
Flue gas temperature
Vent Material
output reduction
PVC
OTHERS
Air pressure switch, Burner door limit switch, and thermal fuse
The control is equipped with a pressure switch to monitor the vent pressure and
condensate trap water level. In case the pressure in the vent exceeds 4" WC or the condensate
trap water level is 4 inches above the air pressure switch connection port the unit will shutdown
and go into an error state.
The boiler is equipped with a switch located on the burner door and thermal fuse located
on the back of the heat exchanger set to 500°F [260°C] , and 605°F [318°C], respectively. These
switches prevents overheating in case of abnormal operation of the appliance or premature
deterioration of the insulation disk located on the back of the combustion chamber.
110
Flue gas temperature
output reduction to
140°F [60°C]
198°F [92°C]
Rinnai Commercial Boiler Installation and Operation Manual
Flue gas temperature
145°F [63°C]
203°C [95°C]
switch off limit
149°F [65°C]
207°F [97°C]
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