Watlow Brand Logo
  • English
    • 中文
    • Deutsch
  • Products & Services

    Products & Services

    Products Services Configure a Product Part Lookup Help Me Choose Product Documentation
    Products
    View All

    Electric Heaters
    Cartridge Insertion Heaters Circulation Heaters Immersion Heaters Air Heaters Flexible Heaters Tubular Heaters Gas Delivery and Exhaust Heaters High-Temperature Heaters Specialty Heaters View All
    Temperature & Process Control
    Multi Loop Controllers Single Loop Controllers Indicators and Alarms Limits and Scanners Operator Interfaces
    Power Control
    Power Controllers Power Switches
    Data Management
    Data Recorders
    Panels & Systems
    WATCONNECT® Control Panels POWERSAFE™ Thermal System
    Sensors
    Thermocouples Resistance Temperature Detectors (RTDs) Fiber Optic Sensing
    man with dual monitors using product selection assistant
    Not Sure? Try Our Digital Product Assistant

    Take the complexity out of product selection with our innovative Digital Product Assistant. Answer a few application questions and our interactive tool will recommend a product from our catalog.

    Launch Assistant
    Services

    thermalwatch thumbnail image of laptop with modern analytics dashboard
    THERMALWATCH™ Intelligent Analytics Solution

    THERMALWATCH leverages our deep understanding of thermal systems to provide secure data integration and management, along with expert analysis, to transform data into valuable information.

    Learn More
    Configure a Product

    vd_
    Watlow SELECT® Visual Designer™

    Quickly configure a product to meet the unique requirements of your application. Instantly access lead times, dimensional drawings, and more - at your own pace. No login required.

    Get Started

    Prefer to talk to a human? Find a Distributor or Sales Office 

    Part Lookup

    Know Your Part Number?

    Enter your part number exactly as marked.

    #
    Tip

    Many parts have lead times, dimensional, drawings, and more available on-demand. Click "Request a Quote" on the search result to access.

    Help Me Choose

    man with dual monitors using product selection assistant
    Not Sure? Try Our Digital Product Assistant

    Take the complexity out of product selection with our innovative Digital Product Assistant. Answer a few application questions and our interactive tool will recommend a product from our catalog.

    Launch Assistant
    Still need help? Locate a Rep Contact Us
    Product Documentation

    Watlow Catalogs Specification Sheets User Manuals Software and Demos Brochures
    CAD Drawings Mobile Applications Watlow Patents Certifications & Approvals
    catalog-ebook
    Try Our Interactive Catalogs

    Click Here

    Products
    View All

    Electric Heaters
    Cartridge Insertion Heaters Circulation Heaters Immersion Heaters Air Heaters Flexible Heaters Tubular Heaters Gas Delivery and Exhaust Heaters High-Temperature Heaters Specialty Heaters View All
    Temperature & Process Control
    Multi Loop Controllers Single Loop Controllers Indicators and Alarms Limits and Scanners Operator Interfaces
    Power Control
    Power Controllers Power Switches
    Data Management
    Data Recorders
    Panels & Systems
    WATCONNECT® Control Panels POWERSAFE™ Thermal System
    Sensors
    Thermocouples Resistance Temperature Detectors (RTDs) Fiber Optic Sensing
    man with dual monitors using product selection assistant
    Not Sure? Try Our Digital Product Assistant

    Take the complexity out of product selection with our innovative Digital Product Assistant. Answer a few application questions and our interactive tool will recommend a product from our catalog.

    Launch Assistant

    Services

    thermalwatch thumbnail image of laptop with modern analytics dashboard
    THERMALWATCH™ Intelligent Analytics Solution

    THERMALWATCH leverages our deep understanding of thermal systems to provide secure data integration and management, along with expert analysis, to transform data into valuable information.

    Learn More

    Configure a Product

    vd_
    Watlow SELECT® Visual Designer™

    Quickly configure a product to meet the unique requirements of your application. Instantly access lead times, dimensional drawings, and more - at your own pace. No login required.

    Get Started

    Prefer to talk to a human? Find a Distributor or Sales Office 

    Part Lookup

    Know Your Part Number?

    Enter your part number exactly as marked.

    #
    Tip

    Many parts have lead times, dimensional, drawings, and more available on-demand. Click "Request a Quote" on the search result to access.

    Help Me Choose

    man with dual monitors using product selection assistant
    Not Sure? Try Our Digital Product Assistant

    Take the complexity out of product selection with our innovative Digital Product Assistant. Answer a few application questions and our interactive tool will recommend a product from our catalog.

    Launch Assistant
    Still need help? Locate a Rep Contact Us

    Product Documentation

    Watlow Catalogs Specification Sheets User Manuals Software and Demos Brochures
    CAD Drawings Mobile Applications Watlow Patents Certifications & Approvals
    catalog-ebook
    Try Our Interactive Catalogs

    Click Here

  • What We Do

    What We Do

    The Thermal Loop Industry Solutions Electrification Industry 4.0
    The Thermal Loop
    Learn More

    icon representing a thermal loop system
    The Thermal Loop

    For Watlow, the underlying concept behind everything we do is that of the thermal loop. Every product we offer, and every project we work on, is ultimately about the creation and control of a thermal loop in an application. 

    Learn More
    Industries

    Heat Treatment Energy and Environmental Technologies Life Sciences
    Clinical Equipment Semiconductor Processing Foodservice Equipment
    Electrification

    thumbnails of white papers relating to electrification and decarbonization
    Electrification

    Over 100 years ago, Watlow began designing and manufacturing electric heating elements to replace steam in the shoe industry. We've been electrifying equipment and processes ever since. Wherever thermal is critical, no one is better equipped to help you reach your energy transition goals. Learn why leading companies partner with us.

    Learn More
    Industry 4.0

    thumbnail of industry 4.0 white paper on tablet and print
    The Thermal Loop & Industry 4.0

    Industry 4.0 technology enables the capture and processing of data in real time, both where its generated and where it is needed, to implement effective improvements to industrial processes. Capturing data, though, is not enough. The advantage Watlow® brings to an Industry 4.0 project are its thermal experts, who understand both the important role thermal loop systems play in key applications and industry 4.0 implementations.

    Learn More

    The Thermal Loop
    Learn More

    icon representing a thermal loop system
    The Thermal Loop

    For Watlow, the underlying concept behind everything we do is that of the thermal loop. Every product we offer, and every project we work on, is ultimately about the creation and control of a thermal loop in an application. 

    Learn More

    Industries

    Heat Treatment Energy and Environmental Technologies Life Sciences
    Clinical Equipment Semiconductor Processing Foodservice Equipment

    Electrification

    thumbnails of white papers relating to electrification and decarbonization
    Electrification

    Over 100 years ago, Watlow began designing and manufacturing electric heating elements to replace steam in the shoe industry. We've been electrifying equipment and processes ever since. Wherever thermal is critical, no one is better equipped to help you reach your energy transition goals. Learn why leading companies partner with us.

    Learn More

    Industry 4.0

    thumbnail of industry 4.0 white paper on tablet and print
    The Thermal Loop & Industry 4.0

    Industry 4.0 technology enables the capture and processing of data in real time, both where its generated and where it is needed, to implement effective improvements to industrial processes. Capturing data, though, is not enough. The advantage Watlow® brings to an Industry 4.0 project are its thermal experts, who understand both the important role thermal loop systems play in key applications and industry 4.0 implementations.

    Learn More
  • Who We Are

    Who We Are

    About Us Core Values Sustainability News Events & Webinars
    About Us

    We solve the world's toughest and most important thermal problems.


    About Us Leadership Team Company History Watlow Worldwide
    Core Values

    core values compass
    The Watlow Way

    At Watlow, our lean journey, as well as our core organizational beliefs are aligned with the Watlow Way, a set of core principles, behaviors and values which guides our company and is woven through every decision we make.

    Learn More
    Sustainability

    sustainability graphic - green earth
    Some of our best work is performed in areas intended to protect and preserve our environment

    We believe protecting the environment is everyone's responsibility and both our products and our own lean manufacturing processes are designed to address these challenges.

    Learn More
    News

    Find the latest news, press releases and annoucements.


    News
    Shiyi Zhou Joins Watlow® as Regional President for Asia Watlow® Welcomes Klaus Aarestrup as New Regional President of Europe Watlow’s New Large and Extra Large WATCONNECT® Control Panels Maximize Process Uptime with a Small Footprint Watlow’s New PM PLUS® 1/8 DIN PID Controller Watlow® Obtains KGS Certification on Flange and Circulation Heaters Watlow® Completes Acquisition of Eurotherm®
    View All News 
    Events

    Watlow & Eurotherm tradeshow booth at SPS 2024
    Events & Webinars

    Stay connected with Watlow through a variety of events, including upcoming trade shows, webinars, corporate and community involvement activities.

    Learn More

    About Us

    About Us Leadership Team Company History Watlow Worldwide

    Core Values

    core values compass
    The Watlow Way

    At Watlow, our lean journey, as well as our core organizational beliefs are aligned with the Watlow Way, a set of core principles, behaviors and values which guides our company and is woven through every decision we make.

    Learn More

    Sustainability

    sustainability graphic - green earth
    Some of our best work is performed in areas intended to protect and preserve our environment

    We believe protecting the environment is everyone's responsibility and both our products and our own lean manufacturing processes are designed to address these challenges.

    Learn More

    News

    News
    Shiyi Zhou Joins Watlow® as Regional President for Asia Watlow® Welcomes Klaus Aarestrup as New Regional President of Europe Watlow’s New Large and Extra Large WATCONNECT® Control Panels Maximize Process Uptime with a Small Footprint Watlow’s New PM PLUS® 1/8 DIN PID Controller Watlow® Obtains KGS Certification on Flange and Circulation Heaters Watlow® Completes Acquisition of Eurotherm®
    View All News 

    Events

    Watlow & Eurotherm tradeshow booth at SPS 2024
    Events & Webinars

    Stay connected with Watlow through a variety of events, including upcoming trade shows, webinars, corporate and community involvement activities.

    Learn More
  • Resources

    Resources

    Product Documentation Tools and Calculators Customer Service Knowledge and Insights CMRT/EMRT & Russian Material Disclosure Events & Webinars
    Product Documents

    Watlow Catalogs Specification Sheets User Manuals Software and Demos Brochures
    CAD Drawings Mobile Applications Watlow Patents Certifications & Approvals Retrofit Guides
    Tools and Calculators
     

    Wattage Calculator Ohm's Law Calculator 3-Phase Delta / Wye Calculator Glossary Equations Reference Data
    Customer Service Documents

    Invoice Payment Options Supplier Requirements Environmental Polices and Statements Copyright and Trademark Information Certifications & Approvals Policies Return Materials Authorization (RMA)
    Knowledge and Insights

    thumbnails of white papers relating to electrification and decarbonization
    White Papers
      Browse White Papers
    Tech Tips logo
    Tech Tips
      Browse Articles
    CMRT/EMRT & Russian Material Disclosure
     

    Conflict/Extended Mineral Russian Material Disclosure [.PDF]
    Events

    Watlow & Eurotherm tradeshow booth at SPS 2024
    Events & Webinars

    Stay connected with Watlow through a variety of events, including upcoming trade shows, webinars, corporate and community involvement activities.

    Learn More

    Product Documents

    Watlow Catalogs Specification Sheets User Manuals Software and Demos Brochures
    CAD Drawings Mobile Applications Watlow Patents Certifications & Approvals Retrofit Guides

    Tools and Calculators

    Wattage Calculator Ohm's Law Calculator 3-Phase Delta / Wye Calculator Glossary Equations Reference Data

    Customer Service Documents

    Invoice Payment Options Supplier Requirements Environmental Polices and Statements Copyright and Trademark Information Certifications & Approvals Policies Return Materials Authorization (RMA)

    Knowledge and Insights

    thumbnails of white papers relating to electrification and decarbonization
    White Papers
      Browse White Papers
    Tech Tips logo
    Tech Tips
      Browse Articles

    CMRT/EMRT & Russian Material Disclosure

    Conflict/Extended Mineral Russian Material Disclosure [.PDF]

    Events

    Watlow & Eurotherm tradeshow booth at SPS 2024
    Events & Webinars

    Stay connected with Watlow through a variety of events, including upcoming trade shows, webinars, corporate and community involvement activities.

    Learn More
  • Careers

    Careers

    Careers
    Career Opportunities

    Are you looking for an opportunity to make a great living and be part of a thriving cross functional community? Select an option below to view opportunities in your region.


    View Openings
    United States Europe Asia Mexico
    STM
    Student Programs
    At Watlow®, we recognize the importance of learning, experimenting, and building your career. Our student programs are a great way for you to gain hands-on experience and on-the-job learning from the start. Learn More

    Career Opportunities

    View Openings
    United States Europe Asia Mexico
    STM
    Student Programs
    At Watlow®, we recognize the importance of learning, experimenting, and building your career. Our student programs are a great way for you to gain hands-on experience and on-the-job learning from the start. Learn More
  • English
    • Español
    • Français
    • Italia
    • Dutch
    • 中文
    • Deutsch
  • Contact Us
    • Contact Watlow
    • Locate a Partner

Search

  1. Resources and Support
  2. Engineering Tools
  3. Knowledge Base

General Method for Determining Heater Requirements

Most electrical heating problems can be readily solved by determining the heat required to do the job. To do this, the heat requirement must be converted to electrical Power and the most practical heater can then be selected for the job. Whether the problem is heating solids, liquids or gases, the method, or approach, to determining the Power requirement is the same.

All heating problems involve the following steps to their solution:

Step 1: Define the Heating Problem

  • Gather application information
  • Sketch problem for visual reference

Step 2: Calculate Power Requirements

  • System start-up power requirement
  • System maintenance power requirements
  • Operating heat losses

Step 3: Review System Application Factors

  • Operating temperature
  • Operating efficiency
  • Safe/permissible watt densities
  • Mechanical considerations
  • Operating environment factors
  • Heater life requirements
  • Electrical lead considerations

Step 4: Select Heater

  • Type
  • Size
  • Quantity

Step 5: Select Control System

  • Type of temperature sensor and location
  • Type of temperature controller
  • Type of power controller

Defining the Problem

Your heating problem must be clearly stated, paying careful attention to defining operating parameters. Take these into consideration:

  • Minimum start and finish temperatures expected
  • Maximum flow rate of material(s) being heated
  • Required time for start-up heating and process cycle times
  • Weights and dimensions of both heated material(s) and containing vessel(s)
  • Effects of insulation and its thermal properties
  • Electrical requirements — voltage
  • Temperature sensing methods and location(s)
  • Temperature controller type
  • Power controller type
  • Electrical limitations
  • And since the thermal system you're creating may not take into account all the possible or unforeseen heating requirements, don't forget a safety factor. A safety factor increases heater capacity beyond calculated requirements.

Calculations for Required Heat Energy

When performing your own calculations, refer to Equations for values of materials covered by these equations.

The total heat energy (kWh or Btu) required to satisfy the system needs will be either of the two values shown below depending on which calculated result is larger.

  • Heat required for start-up
  • Heat required to maintain the desired temperature

The power required (kW) will be the heat energy value (kWh) divided by the required start-up or working cycle time.

The kW rating of the heater will be the greater of these values plus a safety factor.

The calculation of start-up and operating requirements consist of several distinct parts that are best handled separately. However, a short method can also be used for a quick estimate of heat energy required.

Safety Factor Calculation

You should always include a safety factor of varying size to allow for unknown or unexpected conditions. The size of the safety factor is dependent on the accuracy of the wattage calculation. Heaters should always be sized for a higher value than the calculated figure. A factor of 10% is adequate for small systems that are closely calculated; 20% additional wattage is more common. Safety factors of 20% and 35% are not uncommon, and should be considered for large systems, such as those containing doors that open or are large radiant heat applications. You'll also want to predict how long your system will operate without failure, so examine the amount of heater life you'll be needing. And because electricity costs money, take efficiency factors into account so your system will cost as little as possible to operate.

With these considerations in mind, carefully review them all to be sure you do, in fact, have definitive information to decide on a particular solution to your heating problem. Some of this supporting information may not be readily available or apparent to you. You may find it necessary to consult the reference tables and charts in this reference data section, or reference a book that deals with the particular parameter you need to define. At the minimum, the thermal properties of both the material(s) being processed/heated and their containing vessel(s) will be required.

Figuring a safety factor requires some intuition on your part. The list of possible influences can be great. From changing ambient operating temperatures, caused by seasonal changes, to a change in material or material temperature being processed, you must carefully examine all the influences.

Generally speaking, the smaller the system with fewer variables and outside influences---the smaller the safety factor. Conversely, the larger the system and the greater the variables and outside influences — the greater the safety factor.

Here are some general guidelines:

  • 10% safety factor for small systems with closely calculated power requirements
  • 20% safety factor is average20% to 35% for large systems

The safety factor should be higher for systems that have production operations that contain equipment cycles subjecting them to excessive heat dissipations, e.g.: opening doors on furnaces, introducing new batches of material that can be of varying temperatures, large radiant applications and the like.

Back to top
About Us
  • Core Values
  • Environmental Sustainability
  • Social Responsibility
  • Governance
  • Watlow Worldwide
  • Company History
  • News
Contact Us
  • Submit an Inquiry
  • Locate a Partner
  • Locate a Sales Office
  • Application Assistance
  • e-Solutions Login
Industries We Serve
  • Heat Treatment
  • Energy and Environmental Technologies
  • Semiconductor Processing
  • Clinical Equipment
  • Foodservice Equipment
  • Life Sciences
Resources & Support
  • Customer Service & Support
  • Engineering Tools
  • Technical Library
  • Know Your Rights: Workplace Discrimination is Illegal
  • OFCCP Pay Transparency Non-Discrimination Provision
  • Environmental Product Information Request Portal
    • Core Values
    • Environmental Sustainability
    • Social Responsibility
    • Governance
    • Watlow Worldwide
    • Company History
    • News
    • Submit an Inquiry
    • Locate a Partner
    • Locate a Sales Office
    • Application Assistance
    • e-Solutions Login
    • Heat Treatment
    • Energy and Environmental Technologies
    • Semiconductor Processing
    • Clinical Equipment
    • Foodservice Equipment
    • Life Sciences
    • Customer Service & Support
    • Engineering Tools
    • Technical Library
    • Know Your Rights: Workplace Discrimination is Illegal
    • OFCCP Pay Transparency Non-Discrimination Provision
    • Environmental Product Information Request Portal
Policies Privacy Policy Terms of Use Data Protection Policy - GDPR
© 2025 Watlow Electric Manufacturing Company. All Rights Reserved.