Water Circulation Pump
A circulation pump is integrated into the heat engine for the Hybrid application. The pump serves to push water through the heat engine at a rate that supports optimum recovery time and maximum heat output.
The control provides 120Vac, 60Hz line power to the pump to enable operation.
Water Flow Measurement
1. Water Flow Sensor
The Water Flow Sensor uses a sensor for the detection of the water flow. When water flows, the sensor rotates and a transistor is switched on and off, producing a pulsing signal with a frequency related to flow rate.
2. Water Flow Detection
Flow detection is an on/off indication of whether there is sufficient flow through the heat exchanger for normal heating.
3.If the water is less than 0.58 gal/min (2.2 l/min) the unit stops and will start again when the flow is above 0.78 gal/min (2.7 l/min).
Water Flow Restriction Valve
A motorized valve is placed in series with the circulation pump and the heat exchanger of the heat engine. This valve serves to limit the amount of flow through the heat engine such that a variable rate of flow can be achieved from the
Gas Delivery Safety String
The release of gas into the combustion chamber is of critical importance to the safe operation of the heater. The control is a combination of hardware and software that measure and ensure the gas is released only when appropriate for combustion. The term “safety string” applies to those devices or components that directly control the power applied to the gas valves as well as the gas valves themselves. The components are:
•main gas valve solenoid,
•stage 1 and 2 gas valve solenoids,
•exhaust vent high temperature switch,
•energy cut out (ECO) temperature switch.
Exhaust Vent High Temperature Switch
The water heater is designed for plastic vent piping typically used in high efficiency appliances. To ensure the water heater will not release exhaust gasses at temperatures that would cause the vent piping to melt, a bimetallic switch is mounted on the assembly. The switch used is a normally- closed switch which will open when the temperature reaches the maximum design temperature for the venting used. This switch should reset to the closed position when the vent pipe temperature cools sufficiently.
•Opening Temperature is approximately 165°F (74°C) +/- 5°F (2.8°C).
•Closing Temperature is approximately 135°F (57°C) +/- 5°F (2.8°C).
The power for the main gas valve is to be routed through the Exhaust Vent High Temperature Switch causing the main gas valve to be
The status of the Exhaust Vent High Temperature switch should be continually monitored by the controller. If an open switch is detected, the control should declare a fault and respond according to the fault. The fault is a continuous lockout.
Energy Cut Out (ECO) Temperature Switch
The heat exchanger of the heat engine is equipped with a
•Opening Temperature is 185°F
•Closing Temperature is 149°F
The power from the main gas valve is to be routed through the ECO switch causing the main gas valve to be immediately
The status of the ECO switch should be continually monitored by the controller. If an open switch is detected, the control should declare a fault and respond according to the fault. This will be a continuous lockout.
Blocked (Exhaust Gas) Outlet Detection
If the exhaust air passage is obstructed, the control is to enter a fault state and initiate a controlled shut down. This is an overall safety feature of the control system.
Igniter
The control has an integrated direct spark ignition, which can turn on, by means of a relay. This feature is integrated onto the controller board.
By default, the control will allow for three ignition retries after a failed ignition.
Flame Sensor
An active flame is sensed through a flame rod located in the burner assembly in the region of the burners flame. The flame sense input will be monitored by the control and respond to the presence of the flame.
Combustion Chamber Temperature Protection (Thermal Fuse)
If in any conditions when the temperature increases over 287.6°F (142°C) the High Limit Temperature Fuse melts. This function disconnects the power supply controller, and must be replaced.
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