High Temperature Exhaust
Generator, boiler and water heater flue systems rated for positive pressure and continuous high flue-gas temperature.
Codes and listings
- UL 103
- UL 1738
- UL 1425
- NFPA 37
- NFPA 54
- CMC
Once flue gas is hot, positive pressure, or both, ordinary venting stops being a duct problem and becomes a structural and thermal one. That is the range this category is built for.
EXD engineers factory-built, positive-pressure flue for standby generators, prime power, combined boiler flues, and turbine exhaust, listed to UL 103, UL 1738, and UL 1425. Systems are tested to 60 in. w.c. internal pressure and 1,400°F continuous flue gas, with 1,800°F intermittent capacity.
Double-wall configurations carry 1 in. to 4 in. of high-density fiber insulation, which is how clearance to combustibles and personnel-contact skin temperature get solved without adding field labor. Heavy-duty thermal expansion bellows and inline pressure relief are engineered in per NFPA 37 and NFPA 54, so thermal cycling and pressure pulses are handled by design rather than absorbed by joints.
The category also covers commercial boiler and water heater venting across Category I through IV draft environments, including rigid and flexible stainless liners that restore an existing masonry or factory-built chimney on retrofit work.
Where it shows up
- Data center and hospital standby generator plants
- Central boiler and central utility plants
- Prime power and cogeneration installations
- High-rise mechanical penthouses
- Masonry chimney retrofits
Pressure and temperature rated
Listed assemblies verified at 60 in. w.c. with 1,400°F continuous and 1,800°F intermittent flue gas.
Thermal movement engineered
Expansion bellows, guides, and relief devices placed per NFPA 37 and NFPA 54, not improvised in the field.
Clearance reduction
Selectable 1 in. to 4 in. insulation profiles lower skin temperature and shrink required clearances.
Retrofit liners
Category III and IV rigid and flexible stainless liners bring existing chimneys back into compliance.
Positive-Pressure Flue
1 system
High Temperature Exhaust, answered plainly.
- What listing applies to generator exhaust venting?
- Positive-pressure factory-built generator flue is listed to UL 103, UL 1738, and UL 1425, and installed per NFPA 37 for engine exhaust.
- Can factory-built flue replace field-welded carbon steel stack?
- In most cases yes, and it is usually the cheaper installed answer. A listed multi-wall system removes field welding, cuts structural weight, and arrives with the thermal expansion and pressure relief already engineered.
- What draft categories are covered for boilers and water heaters?
- Category I, II, III, and IV, including condensing appliances that require liquid-tight gasketed joints and managed condensate drainage.