Cochran shell boiler · Rear / back-plate view

How hot is a Cochran boiler back plate?

On a working Cochran package boiler the rear back plate and the economizer behind it run at 126–130 °C — FLIR-measured, bare. Together they are the single largest uninsulated heat loss in the boiler house.

FLIR-measured surface temps CAD areas × 1.4 bolt/irregularity ISO 12241 · v = 0.5 m/s

Bare · up to 130 °C Insulated · ≤45 °C

Drag-free toggle. Visible in this view: back plate (130 °C), economizer (126 °C), behind it — both bare.3D model: Inzonex · equipment rights belong to the manufacturer

Peak surface

130 °C

Bare, FLIR-measured

Largest loss

18.3 kW

Economizer

This view, bare

27.4 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 Cochran boiler back plate

The rear (back) plate of a Cochran shell boiler closes the reversal chamber, so the full flue-gas temperature presses against it — 130 °C across a 5.3 m² face. Bolted directly behind it sits the economizer, an 11.3 m² finned block at 126 °C that recovers flue heat but is almost always left completely bare because its shape resists rigid cladding.

These surfaces are the largest avoidable loss in the room. Running 8,000+ hours a year, the back of one boiler radiates tens of kilowatts continuously into the boiler-house air.

Element (this view)	Temp °C	Area m²	Bare W	Insulated W	Surface °C	Cut
Rear (back) plate	130	5.32	9,063	471	35	−95%
Economizer	126	11.31	18,327	954	34	−95%
Rear / back-plate view view, per boiler		16.6	27,390	1,425	≤45	−95%

ISO 12241, 50 mm Inzonex modular core, ε(bare)=0.9, ε(jacket)=0.85, h_conv 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

Rear (back) plate · 130 °C · 9.1 kW bare

A large, mostly flat face carrying the reversal-chamber heat. Easy to insulate, high payback — but usually left bare because it is “just the back”. A removable panel drops it from 130 °C to ≈35 °C and removes a burn hazard behind the boiler.

Cover: Silicone shell + PAROC stone-wool core (50 mm) · touch-safe ≤45 °C (ISO 13732-1)

Economizer · 126 °C · 18.3 kW bare

The biggest prize and the most-skipped surface. Finned tube blocks and access doors make rigid lagging impractical, so economizers run uninsulated for their whole life. An Inzonex panel is shaped to the casing and re-opens for tube access, keeping recovered heat in the gas path.

Cover: Silicone shell + PAROC stone-wool core (50 mm) · touch-safe ≤45 °C (ISO 13732-1)

Geometry that re-opens for access is the core idea behind the Inzonex modular design.

Materials & standards

What the cover is — and what it meets

Every surface on this view is covered by an Inzonex modular removable panel: a PAROC stone-wool core (50 mm) in a silicone outer shell — or a more durable PTFE shell as an option. The form-fitting build unbuttons for access and refits after each maintenance cycle. The outer surface drops to a touch-safe ≤45 °C.

ISO 12241 heat-loss methodISO 13732-1 ≤45 °C touch-safeEN 13501-1 reaction to fireASTM C680 heat-loss method

Industries that run this boiler

Brewery & beverageFood processingDairySugar & confectioneryDistillingChemical & petrochemicalPharmaceuticalTextile & dyeingPaper, pulp & packagingRubber & tyrePlasticsTobaccoPower & CHPOil & gas / refiningHospitals & healthcareCommercial laundryHotels & hospitalityUniversities & district heatingEdible oilAnimal feed

Take it further

From this surface to the number that matters

Calculator

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Put in your boiler count, fuel price and running hours — get energy, £ and payback for the whole room.

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Heat loss → CO₂ → EU ETS

Every bare kilowatt is real fuel and real carbon. See the tonnes and the EU-ETS cost behind it.

Carbon hub → 3D model

See it on the boiler

Rotate the Cochran model, toggle bare vs insulated, and jump to every other surveyed surface.

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FAQ

Quick answers

How hot is a Cochran boiler back plate?

On the surveyed boiler the rear back plate measured 130 °C bare (FLIR) over a 5.3 m² face; the economizer behind it ran at 126 °C.

How much heat does a bare economizer lose?

About 18 kW continuously — 126 °C over 11.3 m² (CAD ×1.4) by ISO 12241 — the largest single avoidable loss on the boiler.

Can an economizer be insulated if it needs tube access?

Yes. A modular removable panel is shaped to the casing and unbuttons for inspection, so it insulates without losing access, unlike rigid cladding.

What surface temperature do you reach after insulation?

About 34–39 °C — below the 45 °C touch-safe threshold — with roughly a 95% cut in heat loss.

More of this boiler

Other surveyed views

Every face of the Cochran model has its own measured surfaces. Explore them from the 3D hub.

↺ 3D model (hub)Iso rear Feedwater Boiler door