State GPH-90N - Manual (Page 41)

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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
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 defi nes 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 fl ow 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 fi xed 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-defi ned 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, fl ow rate, gas fl ow 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 fi xed 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.