how do you troubleshoot a bad transformer

• Separate the transformer from the input circuit. Test the input with your DMM. ...
• If the input power does not climb to the expected value, then the problem lies not with the transformer, but with the input circuitry. [6]
• The input and output on the transformer may be labeled with "input" and "output," or the input might be a black and white pigtail. [7]

Full Answer

How do I know if my transformer is bad?

Check this reading with the transformer's stated input voltage. If the voltage reading does not match the stated input voltage, troubleshoot the voltage source before continuing with the transformer. Test the transformer's output voltage with the multimeter.

What should I do if my transformer does not produce voltage?

If the input voltage has a correct reading, but the transformer does not produce any output voltage, check the transformer's secondary windings for continuity. In addition, check the secondary circuit for a short.

Can a bad transformer cause HVAC to stop working?

HVAC Not Working – With a bad transformer, your HVAC unit will not work even when it has an adequate power supply. This is a protective mechanism to save the unit from severe damage. There is no sure-shot way of confirming that the HVAC unit is malfunctioning due to a fault in the transformer.

What are the main problems of transformer?

The transformer generally is designed and is manufactured to resist the heat and the mechanical blows. However, if it is exposed to frequent and intensive mechanical blows, even a small deformation can be converted into a serious internal defect. 3.2.3 Insulation of the core.

How do you diagnose a bad transformer?

You can do a quick test for each winding for an open while the transformer is still connected in a circuit. Assuming you're using a cheap inaccurate ohm meter. Look for a reading of somewhere between one and about 10 ohms. If any winding reads higher than 10 ohms you have probably found a bad transformer.

What happens when a transformer is faulty?

An exothermic reaction due to a faulty wire or overload that causes significant surge in temperature, resulting in sparks that may cause the transformer to catch fire and explode.

Why would a transformer stop working?

Usually, a transformer fails only after another part in the electrical circuit shorts to ground or draws an unusually high amperage. In these cases, replacing the transformer without first finding and correcting the fault will only cause the transformer to fail again.

What are the common faults in a transformer?

A number of transformer fault conditions can arise practically in any time following some special situations. These include the following five most common internal faults and few external: earth faults, core faults, interturn faults, tank faults, and external factors.

How do you test if transformer is still working?

In output transformer testing, you use the voltmeter setting to check the output voltage while the transformer is connected to power. In a transformer continuity test, you disconnect the transformer from power and check resistance in both the input and output coils using the ohmmeter function.

How do I test a transformer with a multimeter?

To do this, first set your meter to read AC voltage (not DC). Then connect the black lead from your meter to one of the output terminals on the transformer and use an alligator clip or other similar device to connect it securely. Next, touch both probes together and set your meter to read resistance (ohms).

How do you reset a transformer?

Press and hold both “Volume Up” and “Power” for about 2 seconds. If you did it right, a new menu should appear. The Asus Transformer Pad will complete the hard reset process and reboot into a factory default state. Use the volume buttons to toggle the setting to “wipe data/factory reset“.

What causes a transformer to burn out?

The most common reason why transformers explode and burn is accidents caused by lightning strikes. Lightning strikes can often damage the wiring and transformer equipment. Other extreme weather conditions such as strong winds and rains can cause trees to fall on transformers, causing explosions.

When should a transformer be replaced?

The typical lifespan of an oil-filled transformer is around 20-30 years, but some high-voltage models that are kept in pristine conditions can last 50 or 60 years! Most of the time, these transformers will outlast the career of the person who ordered or installed them.

How often do transformers need to be replaced?

Transformers are designed with an expected life span of 30 years, though some in Japan have been in service for more than for 50 years.

What happens when transformer insulation fails?

The breakdown of the insulation results in the flashover of the winding turns and cause a short circuit. The windings are usually of copper. Due to the copper line resistance, thermal losses occur. These thermal losses make hotspots in the winding due to poor or lack of maintenance.

What to do if transformer does not produce output voltage?

If the input voltage has a correct reading, but the transformer does not produce any output voltage, check the transformer's secondary windings for continuity. In addition, check the secondary circuit for a short.

What to do if transformer voltage does not match?

Check this reading with the transformer's stated input voltage. If the voltage reading does not match the stated input voltage, troubleshoot the voltage source before continuing with the transformer.

What is a low voltage transformer?

A low-voltage transformer taps into a home's high-voltage power supply and produces a safe, low-voltage electrical feed. Low-voltage transformers do not wear out. A technician should troubleshoot the transformer and find the reason it failed before replacing it. Usually, a transformer fails only after another part in the electrical circuit shorts ...

What to do if multimeter does not show continuity?

If the multimeter does not show continuity across the secondary windings, inspect the secondary circuit for a short to ground -- often a bare wire. You will have to replace the transformer.

How to test a transformer?

Test the transformer's output voltage with the multimeter. Compare the reading to the stated output voltage. If the output voltage has a correct reading, the transformer works properly.

What is the label on a transformer?

Identify the transformer's terminals, using its label as a guide. Transformers contain input, known as the "primary," and output, known as the "secondary," terminals . The transformer's label identifies the input (high voltage) and the output (low voltage) sides, along with the input and output voltages -- measured as voltage-alternating-current (VAC) -- and their corresponding terminals.

How to tell if a multimeter is continuity?

Turn the multimeter to the "resistance, ohms," function. Touch the multimeter's leads together. The multimeter should beep, indicating continuity.

Why is my transformer failing?

Inspect the transformer visually. Overheating, which causes the internal wiring of the transformer to run at elevated temperatures, is a common cause of transformer failure. This often causes a physical deforming of the transformer or the area surrounding it.

Why is my transformer shorting out?

Check for overdraw on your secondary. In some cases, the secondary of your transformer may be drawing too much current, causing it to short out. If you have a multi-tap transformer and you receive the reading "OL" from the secondary, it's likely the secondary is shorted.

How to determine transformer primary?

Confirm the proper input to the transformer. Apply power to the circuitry. Use the DMM in AC mode to measure the transformer primary. If the measurement is less than 80 percent of the expected voltage, the fault could lie in either the transformer or the circuitry providing the primary with power. In that case:

How to identify transformer inputs and outputs?

Identify the transformer inputs and outputs. The first electrical circuit will be connected to the primary of the transformer. This is its electrical input. The second circuit receiving power from the transformer is connected to the transformer secondary, or the output.

What happens if the transformer's input voltage does not climb to the expected value?

If the input power climbs to the expected value, the primary of the transformer is bad. If the input power does not climb to the expected value, then the problem lies not with the transformer, but with the input circuitry.

What is the purpose of attaching capacitors to transformers?

It is common to attach capacitors and diodes to the transformer secondary to convert the AC power from the output to DC power. This information will not be available on the transformer label. Generally, you can find the transformer conversion and output filtering information on the schematic.

How to measure voltage in a transformer?

Prepare to measure the circuit voltages. Turn off the power to the circuit. Remove covers and panels as necessary to gain access to the circuits that contain the transformer. Acquire a digital multimeter (DMM) to take the voltage readings. DMMs are available at electrical supply stores, hardware stores, and hobby shops.

How to tell if transformer is good?

Doing so ensures operation within acceptable limits. Transformers are deeply critical to the reliability of the grounding system. During your transformer inspection, use temperature as a guide to check for excessive radiant heat and stay alert to the small of overheating insulation. Both are good indicators that you should check power quality. Don't forget to log data over time with a durable power quality analyzer. It's important to establish baselines, as most power quality issues are intermittent.

Why do you need to check the temperature of a transformer?

During your transformer inspection, use temperature as a guide to check for excessive radiant heat and stay alert to the small of overheating insulation. Both are good indicators that you should check power quality.

Why is my equipment distribution system unbalanced?

The most common cause of unbalance is a change in load configuration, so quickly map out your overall equipment distribution system. Overloading — If the temperatures are substantially higher than expected and the unit is not exposed to direct sunlight, then there’s most likely a problem with overloading and cooling.

What does excessive harmonics on the third or fifth level mean?

Excessive harmonics on the third or fifth level often point to interference from electronic loads. Unbalance — When you compare temperatures of terminations and coils using a thermal imager, a higher temperature on one phase may indicate unbalance.

What causes a transformer to short?

2. Wiring Problems – Loose cables or wires inside of the transformer may result in a short circuit and fry the transformer.

What happens if your HVAC contactor is bad?

When there is a bad contactor, the entire unit is placed under a great deal of stress. Once the strain or tension becomes too high for the HVAC unit to hand, this will usually result in a blown transformer.

Where Is The Transformer In An HVAC System Located?

The transformer is an HVAC unit is inside of the furnace. However, in less than 10% of cases, it may be found inside of the exterior AC unit.

Why does my AC breaker trip?

2. Tripped Circut Breaker – Whenever your HVAC unit’s transformer goes terrible, then usually the circuit breaker will trip. The reason why it trips is so there won’t be any surge of voltage. If a voltage surge does happen, it can fry parts throughout the AC and furnace, which causes a significant breakdown in the equipment.

How many ohms does a transformer read?

A faulty transformer provides a wide-open or infinite reading, and a transformer that is not faulty will read from zero up to 10 ohms that indicate a closed circuit.

What is a transformer transfer?

Transfers are utilized whenever the incoming electricity voltage must be lowered or raised to meet the requirements of certain electrical parts or components. A transformer’s job is to alter the energy traveling to the HVAC unit from the circuit board. That progression enables the fan and air conditioner to work synergistically while it is cycling ...

What is a transformer?

A transformer is a type of passive device that transfers electric energy between circuits. Electromagnetic induction is the process that accomplishes this.

What causes a transformer to fail?

2. Wiring Issues – Loose wires or cables inside the transformer can cause a short circuit due to which the transformer may fry. 3. Power Surge – An electrical failure in the form of a power surge can also cause transformer failure.

What is the difference between a transformer and a transformer without fault?

For this, you need a multimeter, as well as the basic knowledge of using it. A faulty transformer gives an infinite or wide-open reading while a transformer without any fault reads between zero to 10 ohms which is indicative of a closed circuit.

How does a transformer work?

The work of a transformer is to change the voltage that travels from the circuit board to the HVAC unit. This progression allows the air conditioner and the fan to work in synergy while cycling on and off. The usage of Electricity can be amplified or diminished depending on how much power is needed.

Why does my transformer make a humming noise?

1. Humming And Vibrating – The humming sound in transformers is normal. It is produced due to the expansion and contraction of the laminations or the iron core. However, if there is a drastic increase in this sound, accompanied by strong vibrations, it is indicative of a bad transformer in your HVAC unit.

Why is my HVAC unit blown?

Bad transformer symptoms in HVAC unit may appear due to the following reasons –. 1. Bad Contactor – More often than not, it is a bad contactor which leads to a blown transformer. A bad contactor puts the entire unit under a lot of stress. When the tension or strain becomes too much for the unit to handle it mostly results in a blown transformer. 2.

Why is my HVAC not working?

HVAC Not Working – With a bad transformer, your HVAC unit will not work even when it has an adequate power supply. This is a protective mechanism to save the unit from severe damage. There is no sure-shot way of confirming that the HVAC unit is malfunctioning due to a fault in the transformer.

What is a transformer?

A transformer is a device which can increase or decrease the voltage of an alternating current or AC. It is a passive device which transfers electrical energy from one circuit to another. This is achieved through electromagnetic induction.

What can damage a transformer?

Disturbances by earthquakes and fires can accidentally damage the transformer.

What causes deterioration of the external insulation of a transformer?

3.2.6 Deterioration of the external insulation of the transformer due to wind, snow, salt and dust. This can be prevented with the correct inspection and maintenance.

Why is my furnace core heating so hot?

There are defects due to poor insulation of the tightening screws of the core, or an oil-cooling duct obstructed, that cause excessive heating of the core. The defects on the core develop slowly.

What is the objective of transformer maintenance and inspection?

The objective of transformer maintenance and inspection is to discover the defects that occur and that may develop slowly . These defects are described below //

What is the degree of transformer maintenance?

The degree of transformer maintenance and necessary inspection for its operation depends on its capacity, on the importance within electrical system, the place of installation within the system, on the weather conditions, and the general operating conditions.

What is a transformer designed for?

The transformer generally is designed and is manufactured to resist the heat and the mechanical blows. However, if it is exposed to frequent and intensive mechanical blows, even a small deformation can be converted into a serious internal defect. 3.2.3 Insulation of the core.

What is the purpose of inspection records of relays of protection of the transformers?

However, the operating conditions in the moment of the failure, the inspection records of the relays of protection of the various parts, as well as the transformer maintenance and the regular inspection, will help to detect the cause in many occasions.