Bradford-White ECOSTOR2 SDW2TW75T User Manual
T eshooting Guide a structions for Service
(To be performed ONLY by
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The Bradford White
Gas Water Heaters
Table of Contents
How to use this manual
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Thermistor Wiring Test Procedure
Gas Control Temperature Sensor
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Temperature Sensor and Harness Testing
Temperature Sensor Measurement
Solar Thermal Troubleshooting
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Solar Thermal Parts List (Atmospheric)
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Solar Thermal Parts List (Ultra Low NOx)
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Solar Thermal Parts List (TTW)
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How to use this Manual
It is intended for this manual to be used by qualified service personnel for the primary purpose of troubleshooting and repair of the Bradford White EcoStor2™ Solar with Gas Backup Water Heaters. Understanding the solar thermal sequence of operation section of this manual will contribute greatly to troubleshooting the water heater.
This manual serves as a water heater supplement to service and troubleshoot specifically the solar features of the water heater. Please refer to the table below to determine which base model service manual is appropriate for the
The Bradford White EcoStor2 Solar Water Heater System
The new Bradford White Solar with Gas Backup water heaters are designed to provide reliable performance with enhanced standard features. New design features include an internal
Having an immersed heat exchanger enhances heat transfer, being able to heat directly to the potable water.
Gas Control Temperature
This service manual supplement is designed to facilitate problem diagnosis and enhance service efficiency. To further promote quicker service times , the gas valve can be removed and replaced without draining the water heater. A special tool is required and will be provided with each gas valve kit shipped from our Service Parts department.
Please read the service manual supplement completely before attempting service on this new series of solar thermal models.
This section is intended to provide a better understanding of the solar thermal design application and how it varies from the base model listed on page 3.
Solar Thermistor Wiring
The solar with gas backup water heater comes provided with two sets of twisted thermistor wiring. They are color coded for ease of use.
Brown and Orange twisted thermistor wires
The solar with gas backup models come with an internal
Brown thermistor wiring is provided under an access panel between the solar heat exchanger connections. A thermistor (not included) wired to this pair can be connected to the solar control to determine the temperature differential between the tank and the solar collector. The control can then activate a circulator to heat the tank. To assist in connecting the thermistor, the end has a supplied wire nut. A bracket and plate is supplied to mechanically press the thermistor against the tank wall.
A twisted orange wire set is provided under the upper access panel. Some solar controllers have locations for a second tank temperature input. This is not used for controlling the solar thermal system, but helps the end user understand what an anticipated delivered temperature may be.
Upper Access Location
Lower Access Location
(Orange Twisted Pair)
(Brown Twisted Pair)
Thermistor Wire Testing
Step 1. Disconnect and unplug the solar control.
Step 2. Disconnect the thermistor twisted pair from the control or control sensor wiring.
Step 3. Connect a multimeter set to read ohms to the twisted wire stripped ends.
Determine the resistance value of the attached thermistor. NOTE: The thermistor is field supplied and various
thermistors have different ohm values for different temperatures. Refer to the temperature specification sheet for the thermistor installed on the water heater to determine if the resistance value is correct.
The image to the side shows a resistance value for a thermistor at ambient temperature connected under the lower access cover (brown twisted pair). The same procedure can be followed to determine if the upper thermistor value is correct.
Step 4. If the multimeter indicates a resistance that does not match the actual temperature of the thermistor, replace the thermistor. Reconnect the wiring, verify that the new thermistor does match, and reconnect to the solar control. Turn on the power to the solar control.
If the multimeter indicates a short or open, disconnect the thermistor from the connection made under the access cover. Measure the thermistor ohm value directly. If the multimeter indicates an open, replace the thermistor.
If the multimeter indicates an appropriate ohm value, determine which wire is open by measuring directly from one end of the wire to the other, or if short; verify by measuring both wire ends from the same location. If the wiring cannot be fixed, the wiring for the thermistor may have to be ran on the outside of the water heater. Replace the wiring, and reconnect it to the solar control. Turn on the power to the solar control.
The solar with gas backup water heater senses temperature from the upper portion of the tank. This allows the solar thermal heating system to maximize the ability to heat the water inside the tank. Only when the upper portion of the water heater tank reaches the water temperature to turn on the gas control, does the backup heat begin. This is achieved by placing a thermistor sensor inside a thermal well and connecting the sensor by means of a wire harness to the gas control. The thermistor well, sensor and wire harness connection is located under the top access cover.
Wire harness connected
Wire harness plug in
to the gas control
location to the gas control
NOTE: Depending on the solar with gas backup model, the gas control may vary. Refer to the base model service manual as indicated on page 3.
and Harness Testing
If the control has gone into lockout due to excessive tank temperature (four flash, 3 second pause) reset the control by rotating the gas control knob to “OFF” position. Then follow the lighting instructions and return the gas control knob to the desired setpoint.
Observe the water heater operation. If the gas control continues to lockout due to excessive tank temperature, proceed to thermal sensor and harness testing to determine the cause.
Disconnect thermal well wire harness
THERMAL SENSOR AND
HARNESS TESTING Position the gas control knob to the “OFF” position and disconnect the thermal sensor harness from the gas control.
(see caution photos at right)
DO NOT use standard multimeter probes for this test. Doing so will damage connector. Use special pin type electronic probes or small diameter wire pins inserted into connector.
Alternate the probe on the outside position to the opposite outside wire position (see photo on right).
Once the thermal sensor resistance values are
Repeat Ohm measurement at the
known, the water temperature must also be known
to determine if the resistance values are correct.
Are thermal sensor resistance
See page 9 to obtain water temperature.
Are thermal sensor and harness resistance values correct?
Replace gas control
Stored water may be HOT when performing the following steps in this procedure. Take necessary precaution to prevent personal injury.
DETERMINE THE WATER TEMPERATURE INSIDE THE STORAGE TANK
It is important to understand once the resistance for the temperature sensor is determined from the previous page, water flow through the water heater should not occur. Prior to drawing water from drain valve, turn off the cold water supply to the water heater. This will prevent cold water flow into the tank affecting the resistance value of the temperature sensor.
Step 1. Set the Gas Control knob to the “OFF” position.
Step 2. Turn off inlet water supply to water heater.
Step 3. Draw approximately 4 gallons of water from drain valve into a container, or suitable drain, and discard. Draw an additional gallon and immediately measure water temperature using an accurate thermometer. It may be necessary to open a hot water faucet to allow water heater to drain.
Step 4. Using the chart below, determine correct resistance value for the water temperature from step 3.
Example: If the temperature of the water is 84°F, then the resistance through the sensor would be 8449 (see shaded area). NOTE: Sensor resistance increases as the temperature decreases.
In Degrees F
This troubleshooting chart serves as a water heater supplement to troubleshoot specifically the solar features of the water heater. Please refer to page 3 to determine which base model service manual is appropriate for the
temperature is sensed.
Review calculations to
out of spec.
1. See service
Gas backup not
Review service manual
for base model.
Review solar thermal