What is the BWD-3K320 thermostat? What specifications should be verified before purchasing or replacing it?

The BWD-3K320 is one of the models in the dry-type transformer temperature controller series. When performing equipment maintenance, procuring spare parts, or replacing old temperature controllers, procurement personnel sometimes request quotes directly based on the “BWD-3K320” designation on the original equipment’s nameplate.

However, when it comes to this type ofDry-type transformer thermostat...Selecting a single base model is usually not sufficient to ensure accurate product selection. Models produced at different times, by different manufacturers, or with different feature sets may vary in terms of sensor inputs, fan control, alarm outputs, communication interfaces, and mounting dimensions.

Therefore, if you need to purchase or replace a BWD-3K320 thermostat, we recommend that you not only provide the model number but also confirm the functional configuration and wiring information of the original device.

• Are there any other complete model suffixes for the BWD-3K320?
• What type of temperature sensor is used?
• What is the operating voltage of the thermostat?
• Is it necessary to control dry-type transformers?Cooling Fans?
• Are over-temperature alarms and over-temperature trip outputs required?
• Does it include remote transmission capabilities such as RS-485 or 4–20 mA?
• What are the external dimensions and cutout dimensions of the original thermostat?
• Does the replacement thermostat need to be wired the same way as the original one?

What types of equipment is the BWD-3K320 thermostat primarily used for?

The BWD series temperature controllers are primarily used for temperature monitoring and control in dry-type transformers. In practical applications, the temperature controllers are typically used in conjunction with temperature sensors installed in the transformer windings to measure the temperatures of the A, B, and C phase windings.

Depending on the specific functional configuration, dry-type transformer temperature controllers may also be used for functions such as cooling fan control, over-temperature alarms, over-temperature trip protection, and remote communication.

It is important to note that,These are common features of dry-type transformer temperature controllers; they do not imply that all BWD-3K320 models have all of these features.. If the original manufacturer's technical documentation is not available, refer to the actual equipment nameplate and terminal block.

Why Shouldn’t You Just Look at the Model Number When Purchasing the BWD-3K320?

One of the most common mistakes in many spare parts procurement projects is the assumption that “if the part numbers match, the parts are definitely interchangeable.”

In fact, temperature controllers for dry-type transformers not only display temperature but may also be connected to the transformer’s cooling fans, alarm circuits, trip circuits, and backend monitoring systems. Therefore, even if the model numbers on the front panel are the same, the units may not be directly interchangeable if their internal functional configurations differ.

For example, two thermostats may both be labeled BWD-3K320; one might require only basic temperature display and alarm functions, while the other might also need fan start/stop control or a remote communication interface for the on-site system.

Therefore, when purchasing the BWD-3K320, the more important question is not “Is this model available?” but rather:

Do the inputs, outputs, control functions, and installation requirements of the new thermostat match those of the original equipment?

What specifications should be confirmed before purchasing the BWD-3K320?

Confirm Project	Items to Confirm	Why It Matters
Full Model Number	Are there any letters or numbers following "BWD-3K320"?	Different suffixes may indicate different functional configurations.
Sensor type	Verify the model number and wiring configuration of the original temperature sensor	Determine whether the temperature input is compatible
Operating power	Check the power supply specifications on the original thermostat nameplate	Cannot be used directly due to a power supply mismatch
Fan control	Should the cooling fan be set to start and stop automatically?	Impact on the Original Cooling Control Circuit
Alarm Output	Is an over-temperature alarm contact required?	Relates to the control cabinet's alarm function
Trip Output	Is an ultra-high-temperature trip signal required?	Relating to Transformer Protection Circuits
communication function	Are interfaces such as RS-485 required?	Determine whether access to the backend system is permitted
analog output	Is a 4–20 mA output required?	Factors Affecting Temperature Data Acquisition in PLCs or DCSs
Mounting Dimensions	Dimensions, Cutouts, and Mounting Methods	Determine whether the original control box needs to be modified
Pin Definitions	Photograph the terminal block on the back of the original device	To make it easier to determine whether a direct replacement is possible

Step 1: Verify the complete nameplate information for the BWD-3K320

If you are replacing an old unit, we recommend first checking the nameplate on the side or back of the original BWD-3K320 thermostat.

When purchasing, it’s best not to just note down the model number on the front panel; instead, take a photo of all the information on the nameplate, paying particular attention to:

• Full model name;
• Whether it includes the suffixes A, B, C, or other functional suffixes;
• Power supply;
• Manufacturer;
• Date of Manufacture;
• Special Feature Icon.

If the original device has been in use for many years and the model label is unclear, you may also provide photos of the front, side, and back of the thermostat so that we can further identify the model based on the number of connectors and terminals.

Step 2: Verify the temperature sensor and temperature measurement channel

Temperature controllers for dry-type transformers are typically used in conjunction with winding temperature sensors.

When replacing the BWD-3K320, if you plan to continue using the original temperature sensor, you must verify that the sensor input of the new thermostat is compatible.

Recommended checks before purchasing:

• Original temperature sensor type;
• Number of sensors;
• Are the temperatures of phases A, B, and C measured separately?
• Are there any ambient temperature or additional temperature measurement channels?;
• Sensor connector types;
• Should the sensor connection cable be kept?

If the sensor connections do not match, you may need to replace the sensor or rewire the system, even if the thermostat itself is functioning properly.

Step 3: Determine whether the cooling fan for the dry-type transformer needs to be controlled

When the load increases, the ambient temperature is high, or the temperature rise in the windings reaches a certain level, dry-type transformers typically require the cross-flow cooling fan to be activated to enhance heat dissipation.

Some thermostats automatically control the fan's start and stop based on the winding temperature.

Therefore, when purchasing the BWD-3K320, you must verify whether the original equipment performs the following functions:

• The fan starts automatically;
• The fan stops automatically;
• Manually start the fan;
• Fan status output;
• Control of multiple sets of fans.

If the original BWD-3K320 is directly involved in fan control, the replacement product must be re-verified for output capacity and terminal definitions based on the original control circuit.

Step 4: Verify the Alarm and Trip Functions

For dry-type transformers, a temperature controller is not only a device that displays temperature but may also perform important protection and alarm functions.

Common temperature control logic includes:

• Start the fan once the temperature reaches the setpoint;
• An over-temperature alarm is triggered when the temperature continues to rise;
• When a higher temperature is reached, an ultra-high-temperature trip signal is output.

However, different projects may have varying requirements regarding alarm points, the number of output contacts, and control logic.

Therefore, when replacing the BWD-3K320, you should verify the following based on the original secondary wiring diagram:

Which terminals are used for alarms, which terminals are used for tripping, and how these outputs are connected to the control cabinet.

Step 5: Determine whether RS-485 communication is required

Some temperature control systems for dry-type transformers need to transmit winding temperature data to a backend monitoring platform, PLC, DCS, or substation integrated automation system.

If the original BWD-3K320 is already connected to the backend, the following must be confirmed during the procurement process:

• Is an RS-485 interface required?;
• What communication protocol is used?;
• Can a mailing address be set?;
• What temperature data does the backend need to retrieve?;
• Is it necessary to upload data on fan operation, alarms, or fault conditions?

It is important to note that,Just because a BWD-3K320 product looks the same doesn't mean it automatically has a communication interface.. Whether communication functionality is available should be confirmed based on the original model and actual configuration.

Step 6: Determine whether a remote output (such as 4–20 mA) is required

In addition to RS-485, some older control systems may transmit temperature data via analog signals.

If you can see temperature output wires connected to a PLC, DCS, or remote transmitter on the back of the original temperature controller, you need to verify whether the original system uses:

• 4–20 mA;
• 0–20 mA;
• 1–5 V;
• Other analog output methods.

If the new thermostat does not have the corresponding output, and the original system relies on that signal to measure temperature, you will need to select a different model rather than simply replacing the existing one.

Are the installation dimensions important when replacing the BWD-3K320?

It is very important.

Many BWD series temperature controllers are mounted on the enclosures of dry-type transformers, in temperature control boxes, or on the panels of low-voltage control cabinets.

If the new thermostat has different dimensions, the following may occur:

• The original hole was too large or too small;
• The positions of the mounting screws are different;
• Insufficient wiring space;
• The cabinet doors cannot be installed properly;
• The control panel needs to be reworked.

Therefore, for equipment replacement projects, it is best to take actual measurements of the original thermostat:

Panel width × Panel height × Mounting depth × Cutout dimensions.

If you can provide on-site photos with a ruler, it’s usually easier to match the model.

Can the BWD-3K320 be replaced with another thermostat?

Whether a part is interchangeable cannot be determined based solely on the model name.

If the original BWD-3K320 has been discontinued, has a long lead time, or an identical model cannot be found, you may look for another dry-type transformer temperature controller with equivalent functionality to serve as a replacement.

However, before making the replacement, you should at least compare the following items:

Comparison Items	Is it recommended to maintain consistency?
Types of Temperature Sensors	是
Temperature Measurement Channel	是
Operating power	是
Fan Control Functions	Based on the original system's confirmation
Alarm and Trip Outputs	是
RS-485 Communication	The original system requires confirmation when necessary
analog output	The original system requires confirmation when necessary
Mounting Dimensions	It is recommended to maintain consistency as much as possible.
Pin Definitions	Must be rechecked

If all of the above functions are compatible, you can further evaluate the actual replacement options even if the brand or specific model of the thermostat is different.

What information should I provide when requesting a quote for the BWD-3K320?

If the purpose of the purchase is to repair old equipment or replace spare parts, simply sending the words “BWD-3K320 Thermostat” will make it difficult for the supplier to accurately determine the configuration required on-site.

We recommend that you submit the following documents all at once:

• Front view of the original BWD-3K320;
• Photo of the original equipment nameplate;
• Photos of the rear terminals and existing wiring;
• Photo of the temperature sensor interface;
• Dimensions and cutout sizes;
• Is fan control required?;
• Is RS-485 or other remote transmission functionality required?;
• Purchase quantity.

The more complete this information is, the easier it will be to determine whether to look for an exact match or to replace it with a thermostat that is functionally compatible.

Frequently Asked Questions About Purchasing the BWD-3K320

1. Can you provide a direct quote for the BWD-3K320 model only?

You can inquire about the model number first, but if you’re replacing an older unit, we recommend providing photos of the nameplate and wiring as well. This is because the basic model number alone isn’t sufficient to accurately confirm all functional specifications.

2. Does the BWD-3K320 definitely come with a fan control?

You cannot make a determination based solely on the model name. Configurations may vary depending on the source and version; you should verify them based on the original equipment’s terminals, control circuits, and technical documentation.

3. Does the BWD-3K320 definitely have RS485?

RS485 is not included by default. For projects that require integration with a backend monitoring system, communication requirements must be clearly specified at the time of purchase.

4. If the model numbers are the same, why do we still need to confirm the dimensions?

Older equipment may have been in use for a long time, and products from different production batches or manufacturers may differ in terms of their housings and installation methods. Verifying the dimensions can help minimize the need for on-site modifications.

5. If I can't find the original BWD-3K320, can I still replace it?

You can identify a suitable replacement based on the original equipment’s sensors, power supply, fan control, alarm and trip mechanisms, communication interfaces, and installation dimensions; however, you should not replace it simply because it looks similar or has a similar model number.

Summary: When purchasing the BWD-3K320, the most important thing is to verify the original equipment configuration.

When purchasing or replacing a BWD-3K320 thermostat, it is not recommended to select a product based solely on the model number.

For new projects, the specific configuration must be determined based on the dry-type transformer’s temperature monitoring, fan control, alarm, trip, and backend communication requirements; for equipment replacements, priority should be given to verifying the original temperature controller’s full model number, nameplate, sensor, terminal blocks, and mounting dimensions.

If the only model number currently available is “BWD-3K320” and detailed specifications are not provided, the most effective approach is to provide photos of the original equipment and on-site wiring information to further confirm the appropriate thermostat configuration.