An immersion heater transfers heat directly into a liquid, so design must begin with the fluid. Chemistry, viscosity, circulation, minimum level and scale formation influence material and surface loading.
Use this guide to prepare a design review or RFQ. Final ratings depend on the complete product, installation, controls and operating environment.
Selection inputs that change the design
| Decision | Information to provide | Why it matters |
|---|---|---|
| Fluid | Composition, concentration and contamination | Determines corrosion risk and material compatibility. |
| Tank | Volume, dimensions, insulation and losses | Sets energy demand and insertion length. |
| Mounting | Thread, flange or over-the-side assembly | Affects sealing, access and active immersion. |
| Protection | Process sensor, high limit and level interlock | Prevents overheating during low level or stagnant flow. |
Match materials to the liquid
Provide full chemistry, concentration and temperature. The word water is insufficient when chlorides or cleaning chemicals are present.
Material selection includes sheath, connection, welds and exposed fasteners. Request a documented materials review where compatibility is uncertain.
Calculate power and heat-up time
Required energy depends on liquid mass, specific heat and temperature rise. Include wall losses, evaporation and cold material added during the cycle.
Split large loads into stages when electrical service, stability or geometry benefits. Oil often requires lower surface loading and circulation.
Prevent dry firing and local boiling
Keep the active section below minimum level. Add a low-level interlock where exposure is possible and use an independent high limit.
Consider scale, sediment and sludge. Include inspection and cleaning access because deposits insulate the sheath.
Common specification mistakes
- Choosing stainless steel without checking chemistry
- Allowing the active section above minimum level
- Using water watt density for viscous oil
- Ignoring deposits and stagnant zones
RFQ checklist
- Fluid, concentration, contaminants and temperature
- Tank volume, insulation and heat-up time
- Voltage, phase, current and control stages
- Connection, insertion and enclosure
- Level protection, sensors and maintenance access
Review the matching Immersion Heaters product range, then send this checklist with your drawing for an engineer-reviewed quotation.
Frequently asked questions
How is power estimated?
Calculate energy for the liquid temperature rise over time, then add realistic tank and process losses.
Why does scale cause failure?
Scale insulates the sheath, raising its temperature while less heat reaches the liquid.
Can the element touch the tank?
Maintain appropriate clearance from walls and deposits according to the installation drawing.