Technical content reviewed November 12, 2026 · Tillman & Associates
Where XDF and RXDF fit
Thermon’s Caloritech XDF and Ruffneck RXDF catalogs describe duct heaters for air or gas containing potentially explosive substances. These are duct-mounted electric heaters; they are different from space heaters such as XB.
The family name is a starting point, not approval for a particular process. Give Tillman the site classification, stream composition and complete operating envelope so the exact heater and documentation can be reviewed.
Classification, materials and orientation
The catalogs list temperature-code and construction choices. Confirm the complete class/division/group and required temperature code against the selected assembly’s nameplate. A room-heater approval or a generic explosion-proof description is not a duct-heater selection.
Standard catalog elements are nickel-plated carbon steel with fins. A stainless duct-section option does not make the elements stainless or Incoloy. Identify required wetted materials and corrosion concerns. Standard catalog arrangements mount in a horizontal duct section; confirm any proposed custom orientation.
Minimum airflow and outlet temperature
Each catalog model has a minimum airflow. A small required kW or a transition to a smaller connection does not remove that limit. The XDF catalog’s lowest listed T3B minimum is 1,107 SCFM, so a substantially lower-flow stream cannot be matched to that standard rating.
The linked XDF manual limits outlet air to 104°F (40°C) and requires the nameplate minimum airflow to be maintained. The selected unit’s supplied instructions govern. Wet, saturated, corrosive, vacuum or higher-temperature duties require explicit factory engineering review; no suitable model is established here for those conditions.
Control package and process information
CPXD literature distinguishes moisture-resistant enclosures from hazardous-location enclosures, and offers on/off, built-in temperature-control and SCR packages. Package 3 accepts a remote 4–20 mA temperature-control signal; confirm the complete panel rating and heater compatibility.
Include airflow proving, high-limit protection, operating sequence and shutdown conditions in the inquiry. Send normal and worst-case temperatures, pressure or vacuum, minimum flow and any liquid carryover. Tillman can coordinate the application questions and manufacturer review before a final ordering code is assigned.
What to send Tillman
- Complete hazardous classification, required temperature code and stream composition
- Minimum/maximum airflow and whether stated as SCFM or ACFM
- Inlet/outlet temperature range, heat duty and operating/design pressure or vacuum
- Humidity, condensation, carryover, corrosion and required wetted materials
- Duct dimensions, transitions, horizontal mounting and service space
- Electrical supply, panel location/rating, control signal, interlocks and quantity
Common questions
Can a transition make a standard heater suitable for very low airflow?
No. The selected heater’s minimum airflow still applies.
Does a stainless duct option mean stainless elements?
No. Confirm the element material separately from the duct-section material.
Does a 4–20 mA control signal establish safe operation?
No. The heater, panel, airflow proving, limits and complete application must all be reviewed.