Volute and flanges
A squat horizontal body with two flanged connections, each with its own bolting. Small area, awkward shape, and warm around the clock.
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Inzonex Modular Insulation · Hot-water skid
Pumps
The casing stays hot. The motor must not. Drag the divider: the right-hand side is a fitted removable module on this exact geometry.
Energy cost saving / year€69960 €/MWh fuel
Heat retained / year10.5 MWhAt 8,000 operating hours
Emissions avoided / year2.35 t CO₂e201.6 kg CO₂e/MWh fuel
Modelled outer surface23.5 °CBelow the 45 °C design target
Estimate: 3 × 0.900 m² · 60 °C bare surface · 8,000 operating hours/year.
€699energy cost saving / year10.5 MWhretainedPumps,
01 / Energy 02 / Surface 03 / Maintenance 04 / Layout
For your operating conditions
Your savings
Change any input and every figure recomputes. The defaults describe the equipment modelled here.
What this is
Pumps,
and what it costs bare.
The casing stays hot. The motor must not.
A circulation pump on a hot-water circuit is a motor-driven impeller in a cast volute. It keeps water moving round the loop, so every outlet stays at temperature without waiting for the draw-off.
On this hot-water skid there are 3, each about 0.9 m² of surface above room temperature. At 60 °C they shed 1.4 kW into the plant room. With 50 mm of removable insulation the same surfaces shed 79 W, 94.3 % less. The module settles at 23.5 °C, at or under our 45 °C touch-safe target. We set that target against the burn thresholds in EN ISO 13732-1.
These are steady-state model estimates using the stated areas and class assumptions. Agreement with site measurements or a survey report has not been established.
Inzonex benefits
Where the heat goes.
Circulation duty on the hot-water circuit. Modules unclip for operation and inspection, then refit onto the same geometry.
The motor is off limits
Covering a motor traps its own losses and cooks the windings. This is the single most common reason a pump is found bare after its first service.
Duty and standby
A standby pump still sits full of hot water. It loses heat all year while producing nothing at all.
Coupling guard clear
The module stops at the coupling. Gland, vent and drain stay reachable without removing the whole cover.
Area and temperature scenarios
Area at each service temperature.
Bare surface loss per item. Nothing here is interpolated — each cell is a separate solution of the same balance, at 20 °C ambient.
| Casing area | Area m² | 50 °C | 55 °C | 60 °C | 65 °C | Insulated 60 °C | Cut |
|---|---|---|---|---|---|---|---|
| 0.3 m²volute and both flanges | 0.3000 | 109 W | 131 W | 154 W | 179 W | 9 W | 94.3 % |
| 0.4 m²volute and both flanges | 0.4000 | 145 W | 175 W | 206 W | 238 W | 12 W | 94.3 % |
| 0.5 m²volute and both flanges | 0.5000 | 181 W | 218 W | 257 W | 298 W | 15 W | 94.3 % |
| 0.6 m²volute and both flanges | 0.6000 | 217 W | 262 W | 309 W | 357 W | 17 W | 94.3 % |
| 0.8 m²volute and both flanges | 0.8000 | 290 W | 350 W | 412 W | 476 W | 23 W | 94.3 % |
| 0.9 m²volute and both flanges | 0.9000 | 326 W | 393 W | 463 W | 536 W | 26 W | 94.3 % |
| 1.2 m²volute and both flanges | 1.20 | 435 W | 524 W | 617 W | 714 W | 35 W | 94.3 % |
| 1.5 m²volute and both flanges | 1.50 | 544 W | 655 W | 772 W | 893 W | 44 W | 94.3 % |
| 2.0 m²volute and both flanges | 2.00 | 725 W | 874 W | 1.0 kW | 1.2 kW | 58 W | 94.3 % |
| 2.5 m²volute and both flanges | 2.50 | 906 W | 1.1 kW | 1.3 kW | 1.5 kW | 73 W | 94.3 % |
| 3.0 m²volute and both flanges | 3.00 | 1.1 kW | 1.3 kW | 1.5 kW | 1.8 kW | 87 W | 94.3 % |
| 4.0 m²volute and both flanges | 4.00 | 1.4 kW | 1.7 kW | 2.1 kW | 2.4 kW | 116 W | 94.3 % |
Volute and both flanges only. The motor is excluded deliberately, because covering it traps its own losses and cooks the windings. It is the single most common reason a pump is found bare after its first service.
Insulated column: 50 mm lamella at λ 0.038 W/m·K. Outer surface calculated without clamping. Our 45 °C design target is checked against the burn thresholds in EN ISO 13732-1
What this means
What it comes to.
At the modelled defaults, on this equipment.
- Outer surface at 50 mm
- 23.5 °CMeets the 45 °C design target
- Bare metal at 60 °C
- Above the 45 °C study targetContact risk depends on material and duration; no burn time is calculated
- Simple payback
- 9 monthsAt 190 EUR/m² supply and fit, saving €699 a year
Asked about pumps
Questions.
Answers distinguish modelled heat-loss estimates from equipment selection and service guidance.
Why is a circulation pump insulated but not its motor?
The casing runs at water temperature and radiates; the motor makes its own heat and has to shed it. A cover over a motor traps that heat and shortens the winding life, so the module stops at the coupling.
Does a standby pump still lose heat?
Yes, and this is the loss operators miss. A standby pump sits full of water at circuit temperature all year and radiates the whole time while producing nothing.
How much heat does a hot-water circulation pump lose?
Modelled here: 3 pumps of 0.9 m² at 60 °C lose 1.4 kW bare, and 79 W insulated at 50 mm. That is 94.3 per cent less.
What the numbers mean
How the figure is produced.
Steady-state estimate using convection, radiation and an insulation energy balance. Equivalence to a surveyed equipment model has not been established.
- Shape
- Horizontal cylinder, characteristic length 0.300 m
- Convection
- Churchill–Chu on air properties at film temperature
- Radiation
- Stefan–Boltzmann at emissivity 0.85
- Bare-case allowance
- ×1.20, assumed class multiplier; not an inventory of actual thermal bridges
- Insulated case
- Outer-surface energy balance, without temperature clamping. 45 °C is a design target; plus an assumed 5% heat-loss allowance for seams. The exterior uses a 0.3 m vertical-plate approximation; conductivity is constant.
Going deeper
How to specify and service them.
The figures on this page say what the heat costs. These say which arrangement to order, and what it means when the pump is running but nothing is moving.
The rest of the skid
Other equipment
Hot water
Plate heat exchangers
A plate pack runs hot on every face.
OpenHot waterBall valves
The smallest surfaces lose the most.
OpenHot waterFlanged joints
Every joint is a fin the pipe did not ask for.
OpenHot waterY-strainers
A sieve in the line, and it is opened on a cycle.
OpenHot waterDirt separator
A separator holds its charge at line temperature.
Open