Technical content reviewed November 13, 2026 · Tillman & Associates
Where HP fits
HP is a heavy-duty heat-exchanger unit-heater family. The catalog describes industrial space heating and liquid cooling, with fluid choices including steam, hot water, glycol and oil. Fluid and material compatibility still require review.
This is a fluid-to-air selection: the fan moves air across the core while the fluid supplies or rejects heat. A motor rating or fan size alone does not establish the thermal duty.
Single-pass versus multi-pass
Single-pass and multi-pass refer to the fluid path through the core. The HP catalog explains that additional passes route liquid through groups of tubes in sequence and can increase heat transfer while increasing pressure drop.
For steam, the current owner’s manual requires a single-pass model. Multi-pass HP configurations are for liquid service. For liquid applications, submit the allowable pressure drop with the required output so both constraints can be assessed.
Conditions and pressure ratings
Send the fluid identity, concentration or property data, flow, inlet temperature, desired outlet temperature and entering-air range. Clarify which requirements are fixed and which may vary; this is especially useful when a cooler has a minimum duty and limited pump pressure.
The manual directs users to the exchanger data plate for pressure and temperature limits. Broad catalog family ratings do not replace the selected model’s rating. Oil and other proposed fluids need explicit compatibility and application review against the current manual.
Complete assembly and service access
General-purpose and hazardous-location motor/construction choices are separate. The exact assembly, fluid temperature and location classification must be reviewed together; an explosion-proof motor alone does not establish approval of every heater configuration.
Include piping connections, support, core-removal access and controls. The catalog notes that optional male or flanged connections can make core removal more difficult. A replacement inquiry should include both exchanger and motor nameplates.
What to send Tillman
- Steam or liquid service, fluid identity and compatibility information
- Required output, flow and fluid inlet/outlet temperatures
- Entering-air range, elevation and allowable pressure drop
- Selected exchanger design pressure/temperature requirements
- Motor electrical service and complete site classification
- Connections, support, service clearances, labels and quantity
Common questions
Can a multi-pass HP be used for steam?
No. The current manual requires single-pass models for steam.
Is every HP configuration approved for a hazardous location?
No. Confirm the exact rated assembly, motor and operating conditions.
Does the builder confirm capacity or pressure drop?
No. Those results require a reviewed performance selection using the project conditions.