Halstock calorifier
Halstock stainless steel calorifier
Halstock stainless steel calorifier
Halstock stainless steel calorifiers
Halstock twin coil calorifier

Stainless steel single coil and twin coil calorifiers for indirect hot water.

5 unvented calorifier models and 4 open-vented calorifiers available with continuous outputs (@44°C ∆T) of 390, 527, 1,843 and 2,106 l/h.

Warranty 5 cylinder product item
ErP Part L Compliant product icon

Product information

    • Power outputs 20-108kW and storage capacities 305-965 litres
    • Indirect method of producing safe and hygienic domestic hot water  (want to understand the difference between Indirect vs Direct Hot Water Systems?)
    • Fast recovery for constant hot water – as little as 13 minutes (Recovery times for 70% of the cylinder volume to 50°C 13-22 minutes)
    • Hot water cylinder and coil made out of corrosion resistant stainless steel for a long life backed up by a 5 year cylinder warranty
    • Now available with twin coils for flexibility and high performance hot water (models 500-965 only)
    • Can be integrated with solar thermal for a renewable energy option
    • Minimal heat loss for maximum economy thanks to layer of CFC-free polyurethane tank insulation under protective plastisol cladding
    • Highly efficient heat transfer from a corrugated coil design 
    • Low maintenance as no sacrificial anodes or powered corrosion protection systems needed
    • Can be located wherever convenient
    • Versatility in use – coupled to Hamworthy commercial boilers or backup via immersion heater
    • UK manufactured hot water calorifiers
    • Compliant with Energy Labelling requirements of ErP
    • Available for next day delivery (dependent on stock availability, charges apply, order cut-off 12pm).

Technical data

Units HS305
Capacity, nominal litres 305
Capacity with coil litres 298
Continuous output @44°C ΔT l/h 390
Continuous output @50°C ΔT l/h 344
Maximum working pressure, tank bar 6
Hydraulic test pressure bar 9
Number of coils 1
Lower coil output kW 20
Heat up time @50°C ΔT,lower coil only min 54
Upper coil output kW N/A
Heat up time @50°C ΔT,top coil only min N/A
Heat up time @50°C ΔT,combined coils min N/A
Recovery time 70% @50°C ΔT, combined coils min 38
10 min peak output @50°C ΔT litres 361
Coil max operating temperature °C 100
Coil max operating pressure bar 3
Upper coil tube diameter DN NA
Upper coil surface area m2 NA
Lower coil tube diameter DN DN20
Lower coil surface area m2 0.75
Reheat total delta T 50degC lower mins 38
Reheat total delta T 50degC both mins N/A
Standby losses kW/24hr 1.77
ErP efficiency rating - C
Immersion heater option, power kW 3
Immersion heater option, phase ph 1ph
Heat up time, Immersion only hour 5.8
Recovery time, Immersion only hour 4.1
Expansion vessel size litres 24
Weight empty kg 75
Weight full kg 379


Halstock calorifier brochure

Product brochures 2677 kb

Halstock calorifier installation manual

Installers guides 4409 kb

Ideal uses/applications

  • To provide domestic hot water for any type of commercial building.
  • Designed for use with natural gas, LPG or oil-fired commercial boilers for primary heat source.
  • Direct heating via optional Incoloy 800 electrical immersion heaters.
  • Suited to all areas of the UK, particularly locations with soft water (read here why).

Optional extras

Often bought with

Halstock stainless steel storage tank

Learn more

Wessex ModuMax mk3 boiler

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Case studies

Riverside Children's Centre benefits from built-in boiler controls of their boiler to provide hot water efficiently.

Riverside Childrens Centre, Canterbury

Sector: Education and childcare

Project: The nursery provides childcare and cooked midday meals for children. A hot water priority strategy using built-in boiler controls made the combination of a hot water circuit with a low temperature underfloor heating circuit possible.

Building: Nursery refurbishment

Application: Space heating, 43kW, indirect fired DHW

Learn more