UF Capacitors Heavy Duty X2 Safety Capacitors (THB Series) are metallized polypropylene Class X2 capacitors designed for across-the-line EMI suppression in applications that require higher environmental reliability than a standard indoor X2 capacitor.

The series is especially relevant to power meters, smart meters, solar inverters, industrial power supplies and other equipment that can remain connected to the AC mains for long periods while exposed to humidity, condensation or repeated temperature changes.

UF Heavy Duty X2 products are available in 275VAC, 305VAC and 310VAC versions, depending on capacitance and part number. Current UF product listings include values such as 0.1µF, 0.33µF, 0.47µF and 0.68µF with ±10% tolerance, -40°C to +110°C operating temperature, radial through-hole construction and multiple lead-pitch options.

 

What Is a Heavy Duty X2 THB Capacitor?

 

A Heavy Duty X2 THB capacitor performs the same basic safety function as a standard Class X2 capacitor: it is connected across Line and Neutral to suppress differential-mode conducted EMI. The key difference is the additional reliability focus under combined temperature, humidity and electrical bias.

 

THB means:

 

• Temperature
• Humidity
• Bias (applied AC voltage)

 

In a THB test, these stresses are applied at the same time. This is more representative of real power-meter and outdoor-equipment operation than a simple dry-temperature or unpowered humidity test.

 

Why Power Meters Need Heavy Duty X2 Capacitors

 

Electricity meters and smart meters are often expected to operate continuously for many years. Their input circuits remain connected to the mains, and installations can experience high humidity, seasonal temperature changes, condensation and voltage fluctuations.

A standard X2 capacitor may provide the required EMI suppression and safety classification, but a power-meter design can require additional long-term stability under humidity and electrical bias. Heavy Duty THB X2 capacitors are intended for this type of service.

 

• Continuous connection to the AC mains
• Long service intervals
• High humidity or condensation risk
• Outdoor or semi-outdoor meter installations
• Repeated temperature cycling
• Stable capacitance and insulation performance over time

 

UF Heavy Duty X2 THB - Typical Specifications

 

Parameter	Typical UF Heavy Duty X2 / THB Information
Safety Class	Class X2
Dielectric	Metallized polypropylene film
Rated Voltage	275VAC / 305VAC / 310VAC
Standard Tolerance	±10%
Operating Temperature	-40°C to +110°C
Mounting	Radial through-hole
Typical Lead Pitches	10mm / 15mm / 22.5mm / 27.5mm, depending on part
Construction	Self-healing metallized film, flame-retardant plastic case, epoxy sealed
THB Principle	Temperature + humidity + applied electrical bias
Environmental Compliance	RoHS; selected product pages also list REACH, halogen-free and MSL 1
Main Applications	Power meters, smart meters, AC-line EMI filters, inverters, industrial power electronics

 

 

THB Reliability: Why Temperature, Humidity and Bias Matter Together

 

Metallized polypropylene capacitors use an extremely thin metallic electrode. This construction enables self-healing, but it also makes moisture protection important.

If humidity penetrates the package, the metallized electrode can gradually degrade. When moisture and applied AC voltage are present together, the electrical stress can accelerate the deterioration of metallization and insulation performance.

 

Potential effects include:

 

• Capacitance loss
• Increase in dissipation factor
• Reduction in insulation resistance
• Reduced long-term reliability
• Greater risk of parameter drift in continuously energized equipment

 

This is why THB qualification is a useful selection criterion for power meters and other long-life equipment that operates under humid conditions.

 

Typical Heavy Duty X2 THB Product Examples

 

Example Part	Capacitance	Voltage	Tolerance	Lead Pitch	Example Size
X2F104KA3050100B000T	0.1µF	305VAC	±10%	10mm	13 × 13 × 7mm
X2F334KA3100225B000T	0.33µF	310VAC	±10%	22.5mm	Part-specific; verify current drawing
X2F474KA3050275B000T	0.47µF	305VAC	±10%	27.5mm	31 × 20.5 × 11mm
X2F474KA2750150B000T	0.47µF	275VAC	±10%	15mm	19 × 18 × 11mm
X2F684KA2750225B000T	0.68µF	275VAC	±10%	22.5mm	26.5 × 19 × 10mm

 

The table above is intended to show the range of existing UF product configurations. Always confirm the latest drawing, approvals and THB grade for the exact part number before production release.

 

Heavy Duty X2 vs Standard X2 Safety Capacitor

 

Selection Factor	Standard X2	Heavy Duty X2 / THB
Primary Function	Across-the-line EMI suppression	Across-the-line EMI suppression
Typical Environment	Indoor / controlled humidity	Humid, condensing, outdoor or long-life installations
Humidity + Bias Qualification	Standard safety / reliability requirements	Additional THB-focused reliability
Typical Duty	General mains-connected electronics	Long energized duty / harsh environment
Typical Applications	Home appliances, standard SMPS, general EMI filters	Power meters, smart meters, solar inverters, industrial systems
Selection Priority	Safety class, capacitance, voltage, approvals	Safety + THB level + environment + long-term stability

 

Heavy Duty THB is not automatically required for every X2 position. It is most valuable where the real operating environment creates a meaningful humidity-and-bias reliability risk.

 

Typical Applications

 

Power Meters and Smart Meters

 

Power meters are the primary focus of this series. They may remain energized for many years and can be installed in humid or poorly controlled environments. Heavy Duty X2 capacitors are used in the mains-input EMI suppression network where safety, long service life and humidity resistance are important.

 

Solar Inverters

 

Outdoor photovoltaic equipment can experience condensation, humidity and large temperature swings. THB X2 capacitors can be used in AC-input or grid-side EMI filters where long-term environmental reliability is required.

 

UPS Systems

 

UPS equipment is continuously connected to the mains and may operate in industrial or infrastructure environments. Heavy Duty X2 capacitors are relevant where the EMI filter must remain stable over long duty cycles.

 

Industrial Power Supplies

 

Industrial AC/DC power supplies can be installed in locations with dust, moisture and changing temperatures. THB-rated X2 capacitors provide an additional environmental-reliability option for the AC input filter.

 

Motor Drives and Frequency Converters

 

VFDs generate significant switching noise and require input EMI filtering. In humid industrial environments, a Heavy Duty X2 capacitor can be considered for improved long-term stability.

 

EV Chargers and Wallboxes

 

Charging equipment may be installed outdoors or in semi-exposed locations. Long mains-connected operation combined with humidity and temperature cycling makes THB performance relevant to the AC-side EMI filter.

 

Safety Standards and Approvals

 

Heavy Duty X2 capacitors are still safety capacitors connected directly across the AC line. THB performance does not replace the need for X2 safety approval.

UF's X2 / THB documentation lists approval systems including:

 

• UL / cUL - UL 60384 series
• VDE - EN 60384-14
• ENEC - EN 60384-14
• KTL / KC - K 60384
• CQC
• IEC-CB for applicable configurations

 

Approvals can vary with capacitance, rated voltage and exact product configuration. Verify the current certificate for the exact part number rather than assuming the entire THB family has identical approval coverage.

 

How to Select a Heavy Duty X2 THB Capacitor

 

1. Confirm the Safety Class

Verify that the capacitor is connected across Line and Neutral and that Class X2 is appropriate for the circuit.

 

2. Select the Rated AC Voltage

Choose the correct 275VAC, 305VAC or 310VAC rating according to the mains system and applicable end-product standard.

 

3. Select Capacitance

Use the EMI-filter design or original BOM value. Do not select by case size alone.

 

4. Define the THB Requirement

Determine whether the equipment is exposed to humidity, condensation, outdoor installation or long mains-connected duty. Specify the required THB grade / duration.

 

5. Verify Safety Approvals

Confirm the exact certification required by the target market and selected capacitance/voltage combination.

 

6. Match Lead Pitch and Case Size

Check 10mm, 15mm, 22.5mm or 27.5mm pitch as well as body dimensions and PCB clearance.

 

7. Compare the Original Part

For second-source qualification, compare capacitance, voltage, safety approvals, THB test level, temperature range, dimensions and reliability requirements.

 

Cross-Reference and Second-Source Evaluation

 

UF Heavy Duty X2 THB capacitors can be evaluated as alternative sourcing options for selected X2 / high-humidity safety capacitor series from global manufacturers.

 

UF Series	Examples of Series Commonly Compared at Series Level
Heavy Duty X2 / THB	TDK/EPCOS B32921C/D-B32928C/D, Vishay MKP3382/MKP3384/MKP3392, KEMET R46/PHE840M/PHE850/PMR-209, Panasonic ECQU, Pilkor PCX2 series, Faratronic C42(E)/MKP62

 

A series-level cross-reference is only a starting point. Do not claim pin-to-pin interchangeability until the exact capacitance, rated voltage, THB grade, safety approvals, dimensions and lead pitch have been matched.

 

FAQ

 

What is a Heavy Duty X2 safety capacitor?

 

It is a Class X2 across-the-line EMI suppression capacitor designed with additional environmental reliability for applications exposed to humidity, temperature changes and long energized operation.

 

What does THB mean?

 

THB stands for Temperature, Humidity and Bias. The capacitor is exposed to heat and humidity while an electrical voltage is applied.

 

Why are THB X2 capacitors used in power meters?

 

Power meters may remain connected to the AC mains for many years and can operate in humid or uncontrolled environments. THB qualification provides a more relevant reliability measure for these combined stresses.

 

What is the difference between standard X2 and Heavy Duty X2?

 

Both perform across-the-line EMI suppression. Heavy Duty THB versions add enhanced qualification for temperature, humidity and electrical-bias stress.

 

What voltage ratings are available?

 

UF Heavy Duty X2 products are available in 275VAC, 305VAC and 310VAC versions depending on the exact part number.

 

What temperature range is published?

 

Current UF Heavy Duty X2 product listings typically specify -40°C to +110°C.

 

Does every THB capacitor have a 1000-hour 85/85 rating?

 

No. THB test duration and grade depend on the exact product. UF's current public THB datasheet includes a 500-hour 85°C/85%RH/240VAC condition, while higher-grade products can use longer qualification conditions. Verify the exact part datasheet.

 

Can a Heavy Duty X2 capacitor replace a standard X2 capacitor?

 

Potentially, but the exact capacitance, voltage, safety approvals, case dimensions, lead pitch and circuit requirements still need to match.

 

Can UF Heavy Duty X2 replace TDK/EPCOS or KEMET X2 capacitors?

 

UF provides series-level cross-reference options for selected global X2 capacitor families. Exact part-level compatibility should be confirmed before production substitution.

 

Need a Heavy Duty X2 Capacitor for a Power Meter or Harsh Environment?

 

UF Capacitors supplies Heavy Duty X2 THB capacitors for power meters, smart meters, solar inverters and other long-life mains-connected equipment.

 

To recommend a suitable part, send us:

 

• Required capacitance
• Rated AC voltage
• Required safety approvals
• THB grade / test condition
• Lead pitch
• Maximum case dimensions
• Operating temperature and humidity
• Annual quantity

 

UF engineering can then recommend an existing Heavy Duty X2 part or evaluate a suitable THB configuration for your application.