Industrial Heating: Unit Heaters, Vents and Controls

Gas or electric heat: reading output and supply

Gas unit heaters are usually rated by heat input in BTU per hour, as in a 45,000 BTU/h model, and deliver somewhat less heat depending on their efficiency, while electric models are rated in watts. Gas units are built for natural gas or propane and need correct venting and clearances, so confirm the fuel type before anything else. Electric heaters list watts and volts: 4,000 W at 240 V draws about 17 A, which calls for a circuit sized by an electrician.

Supply voltage changes output. A 240 V heater run on a 208 V supply delivers only about three-quarters of its rated watts, because power falls with the square of the voltage. Heaters for 120 V, 208 V, 240 V and 277 V are not interchangeable. Check whether the unit has a built-in thermostat or needs a separate wall control, and whether it is rated for the damp or dusty room.

Vents, grilles and limit controls: parts that must match

Vent caps and intake terminations are sized to the pipe, for example a 6 inch cap on 6 inch ducting, and the material must suit the application: aluminum for outdoor terminations, plastic grilles for sidewall registers in low-temperature air. Surface-mount wall grilles and sidewall grills are sold by width and height, such as 12 inch or 18 by 6 inch, so measure the opening before choosing.

Limit and safety controls list their opening and reset temperatures, and a replacement must match the original because it protects the appliance from overheating. Boiler stop-leak products are temporary treatments for small leaks, formulated for a particular system type and water volume. They do not repair a failing boiler, and the cause of the leak should still be found and fixed. Gas and flue work belongs to a qualified installer.

Questions about Industrial Heating: Unit Heaters, Vents and Controls

How big an electric heater do I need for a room?

A rough starting point is about 10 watts per square foot for a well-insulated room with standard ceilings. Poor insulation, high ceilings, drafts and cold climates need more. Check the voltage and the circuit capacity before choosing, since larger heaters need their own circuits.

Can a natural gas unit heater run on propane?

Only if the manufacturer supplies a conversion kit for that exact model and it is fitted by a qualified person. The burner orifices and gas valve settings differ between the two fuels, and running the wrong fuel is a fire and carbon monoxide hazard.

Is boiler stop leak a permanent repair?

No. It is a short-term measure for minor weeps, and it can clog small passages or sensors in some systems. Read the label for the system types it suits, drain and flush as instructed, and have the leaking part repaired or replaced.