Temperature Regulation

Line Voltage Monitor

The control monitors the line voltage provided to the system. If the line voltage is too low, the system components may not operate properly. For diagnostic purposes, the display panel should indicate that the cause was power-related.

•If line power is below 102Vac, the water heater will enter the fault state and initiate a controlled shut-down. The fault will automatically clear if the voltage is restored to 102Vac or above.

•If line power is above 132Vac, the water heater will enter the fault state and initiate a controlled shut-down. The fault will automatically clear if the voltage is restored to 132Vac or below.

Temperature regulation is the process by which the controller determines when the water heater is to heat water as well as when to stop the heating process. This section deﬁnes how the water heater is to regulate the temperature.

Temperature Units of Measure

The water heater control will display the temperatures in either °C or °F (as per selected unit of measure). The main temperature unit is °C and all the calculations, within the control system, are done using temperature values in °C. The display has the capability to perform a conversion from °C to °F. The resulting temperatures in °F will be rounded off to the nearest degree.

Temperature Set-point

The adjustable temperature set-point is used to determine the desired outlet temperature of the water heater.

The water outlet of the heat engine feeds the outlet of the storage tank although some mixing does occur with the water at the top of the storage tank. For this reason, the temperature of water delivered is considered equivalent to the heat engine output temperature.

This value is to be set within the acceptable range of 90°F (32°C) and 158°F (70°C) when selecting the operating modes.

As a safety measure, the control is to ensure that the set- point cannot be adjusted outside of this range.

If the water ﬂow is turned off and then is turned on, the controller remembers and automatically resets to the last temperature.

If a power outage occurs or the unit is energized/de- energized by the STANDBY symbol for re-booting, the controller resets to the last temperature setting.

After clearing a continuous lockout error code the unit will always go back to the factory default temp setting and mode.

Storage Tank Set-point

The control is required to maintain a storage tank set-point differential temperature.

Storage Tank Call For Heat

The storage tank call for heat is generated when the tank thermistor temperature drops below the storage tank set- point minus the ﬁxed storage tank differential.

At the end of a call for heat the tank thermistor’s temperature is equal to or greater than the storage tank set-point.

Temperature Control Modes

The temperature control functions can operate under one of the pre-deﬁned user-selected control modes. The temperature control mode serves to limit the range of the (heat engine) temperature set-point and the storage tank differential.

Please reference the Operating Mode Selection for details of how the set-point and differentials are adjusted for the different modes. In brief, three modes are provided: Vacation Mode, Energy Saver Mode, and Boost Mode.

The temperature control mode will be maintained after a power loss. Upon restoring power, the temperature set- point is set to the last temperature.

The default setting is 105°F (41°C) in the Energy Saver Mode.

Outlet Temperature Limit Control

Your water heater is designed to provide a constant outlet water temperature. The water heater takes into account dynamic conditions of the heat engine such as the inlet water temperature, ﬂow rate, gas ﬂow adjustment, etc and establishes the optimum performance.

The control will end the call for heat if the outlet thermistor temperature exceeds the set-point by a ﬁxed amount. The call for heat may be restored if the outlet thermistor temperature drops below the set-point by 5.4°F (3°C) or more.

Inlet Temperature Limit Control

To add protection to the system, an over-temperature comparison is made on the inlet water temperature. The water heater will end the call for heat if the inlet thermistor temperature is above the set-point.

The call for heat may be restored if the inlet thermistor temperature drops below the set-point.