Description
Sunstar SPU Positive Pressure U-Tube Heater | SPU50-20-N7
The Sunstar SPU50-20-N7 is a 50,000 BTU/hr natural gas infrared tube heater with 20 feet of radiant emitter folded into a U-tube, so the heater itself is only about 12' 5" long. It is part of Sunstar’s SPU positive pressure U-tube line, built for warehouses, maintenance shops, loading docks, fire stations and other high-ceiling spaces where doors open often and heated air is lost the moment they do.
SPS and SPU heaters use a push-through (positive pressure) burner: a blower sealed inside the burner box drives combustion through the tube, so the heater runs quietly, and Sunstar’s Tube Integrity Safety System (TISS) continuously monitors the space above the reflector for overheating or a compromised tube.
With the firing leg running beside the cooler return leg, a U-tube spreads its heat more evenly than a straight tube of the same length, which makes it the go-to choice for spot heating a bay, work cell or dock door.
This is a two-stage model: it fires at 50,000 BTU/hr on high and drops to 30,000 BTU/hr on low, so it can hold temperature on milder days with less gas and fewer on/off cycles. Control it with a two-stage 24V thermostat or a three-position High/Low/Off switch.
For planning, mount it at least 11 feet above the floor when level or 10 feet when tilted 45 degrees, and keep 56 inches clear below it and 22 inches to the sides. It can be vented on its own, common vented with other heaters, or run indirect vented with building exhaust, and it can draw outside combustion air through its fresh air collar in dusty or humid buildings. Installation must be done by a licensed contractor to the manufacturer’s instructions and local codes.
Key Features
- 50,000 BTU/hr natural gas input, 30,000 BTU/hr on low fire
- 20' U-tube emitter, about 12' 5" overall
- Quiet push-through burner with Tube Integrity Safety System
- Direct spark ignition with 100% gas shut-off
Frequently Asked Questions
How high should the SPU50-20-N7 be mounted?
Sunstar lists a minimum of 11 feet above the floor with the heater level and 10 feet at a 45-degree tilt. Mount it as high as the space allows for even coverage; going below the minimum can make the area right underneath uncomfortably hot.
What clearance does it need from combustibles?
Keep at least 56 inches below the heater and 22 inches to the sides clear of anything that can burn, including stacked materials and vehicles parked underneath. The full clearance chart, including ceiling and end distances, is in the installation manual.
Can I convert it to propane?
Yes. Sunstar makes a conversion kit matched to this model, offered in the gas conversion kit option above, and it must be installed by a qualified technician.
How do I control the two stages?
Use a two-stage 24V thermostat to switch between low and high fire automatically, or a three-position High/Low/Off switch for manual control. Several heaters can share one control with a two-stage relay kit at each heater.
