On the surveyed Bosch boiler the front door measured 96 °C and the burner flange around the throat reached 146 °C — FLIR-measured, bare. The door also hinges open for burner service.
FLIR-measured surface tempsCAD areas × 1.4 bolt/irregularityISO 12241 · v = 0.5 m/s
This view. Visible in this angle: front (boiler) door (96 °C) and burner flange (146 °C) — bare.3D model: Inzonex · equipment rights belong to the manufacturer
Peak surface
146 °C
Bare, FLIR-measured
Largest loss
2.5 kW
Front (boiler) door
This view, bare
4.3 kW
2 element group(s)
After insulation
≈95%
Surface drops to ≤45 °C
Figures are for one boiler. Surface temperatures from a real FLIR survey of a UK commercial boiler house; CAD surface areas uplifted ×1.4 for bolts and irregular geometry; ISO 12241 steady-state (50 mm core, ambient 28 °C, air movement 0.5 m/s).
What you are looking at
How hot is a Bosch boiler front door
The front of a Bosch package boiler is large, hot and movable — the three properties that defeat rigid insulation. The door runs at 96 °C over a 2.3 m² face and the burner flange at 146 °C, yet both have to open for burner service.
A buttoned removable panel is made to the door and hinges with it: insulated when closed, out of the way when open. The burner mounting and sight port stay clear.
Element (this view)
Temp °C
Area m²
Bare W
Insulated W
Surface °C
Cut
Front (boiler) door
96
2.33
2,530
150
30
−94%
Burner flange
146
0.85
1,780
60
30
−97%
Front / burner door, per boiler
3.18
4,310
210
≤45
−95%
ISO 12241, 50 mm Inzonex modular core, ε(bare)=0.9, ε(jacket)=0.85, hconv at 0.5 m/s. Insulated figures are conservative steady-state, not best-case.
Element by element
Why each one is left bare — and how it gets insulated
Front (boiler) door · 96 °C · 2.5 kW bare
The front door carries the burner and closes onto the furnace tube — a 2.3 m² face the FLIR survey measured at 96 °C. It hinges open for burner service, so a fixed jacket fails here; a buttoned removable panel insulates it and opens with the door.
Burner flange · 146 °C · 1.8 kW bare
The burner mounting flange ran hottest on the front at 146 °C — a concentrated ring of loss around the burner throat. A shaped removable collar insulates the flange while leaving the burner and sight port clear.
Geometry that re-opens for access is the core idea behind the Inzonex modular design (UK patent application GB2508992.1).
