Hot Water Production

Modutherm offers comprehensive commercial hot water solutions including stainless steel and Polywarm® calorifiers (200-3000L), heat pump calorifiers (200-1000L), and plate heat exchangers for instantaneous hot water production.

Our Juniper range features tank-in-tank calorifiers, heat pump thermal exchange cylinders, and the Juniper HP Plus exhaust air heat pump water heater (200-300L). Combined with the CoilMaster gas-fired water heater and Juniper PRS plate heat exchangers, Modutherm delivers efficient large-scale domestic hot water storage and production for hotels, schools, apartment buildings, care facilities, and commercial properties across the UK.

Commercial Hot Water Calorifiers

Modutherm's commercial hot water calorifiers are available in stainless steel and Polywarm® enamel finishes, ranging from 200–3,000 litres. The range includes the Scimitar® tank-in-tank calorifier (200–500L) and the Juniper® SS and PW series (500–3,000L), providing reliable large-scale domestic hot water storage for hotels, schools, care facilities, and commercial buildings across the UK.

5

5 Year Tank
Warranty*

2

2 Year Parts
Warranty*

ErP

ErP Part L
Compliant

In Stock

Available in 5-7 working days.

Made to Order

Available in 5-6 weeks.

Scimitar

  • 316L stainless steel calorifier
  • Tank-in-tank design
B/C
Energy
Class
192-462 L
Capacity
Range

Juniper® PW

  • Polywarm® calorifier
  • 8 calorifier models
  • 7 storage vessel models
C
Energy
Class
498-2917 L
Capacity
Range

Juniper® SS

  • Stainless steel calorifier
  • 10 calorifier models
  • 7 storage vessel models
C
Energy
Class
503-2925 L
Capacity
Range

Heat Pump Calorifiers

Designed for use with heat pump systems, Modutherm's heat pump calorifiers are available in Polywarm® and stainless steel finishes from 200–1,000 litres. The Juniper® PW XL and SS XL offer optimised heat exchange for heat pump installations, whilst the Juniper® PDC thermal exchange calorifier (300–800L) provides enhanced performance for low-temperature primary circuits. Suitable for new builds, retrofit projects, and renewable heating systems.

5

5 Year Tank
Warranty*

2

2 Year Parts
Warranty*

ErP

ErP Part L
Compliant

Juniper® PW XL

  • Polywarm® heat pump calorifier
  • 6 calorifier models
B/C
Energy
Class
200-1000 L
Capacity
Range

Juniper® SS XL

  • Stainless steel calorifier
  • 10 calorifier models
B/C
Energy
Class
200-1000 L
Capacity
Range

Juniper® PDC

  • Polywarm® heat pump thermal exchange calorifier
  • 3 calorifier models
  • Unique patented heat
    exchange system
B/C
Energy
Class
300-800 L
Capacity
Range

Heat Pump Water Heater

An heat pump water heater provides energy-efficient domestic hot water by extracting heat from the air rather than generating it directly with electricity.

The Juniper HP Plus is a heat pump water heater that achieves a COP of up to 4.09, producing over four times more heat energy than the electricity it consumes – earning an A++ energy efficiency rating.

5

5 Year Tank
Warranty*

2

2 Year Parts
Warranty*

ErP

ErP Part L
Compliant

SG

Smart Grid
Ready

Juniper HP Plus

  • Left & right hand variants
  • Integrated 1.6kW back-up electric heater
R290 Natural Refrigerant
A++
Energy
Class (55°C)
4.09
COP
(max.)
200-300L
Capacity Range

Instantaneous Hot Water Production

For applications requiring on-demand hot water without storage, Modutherm offers the Juniper® PRS stainless steel plate heat exchanger and the CoilMaster floor-standing gas-fired water heater/boiler. These solutions provide efficient instantaneous domestic hot water production for hotels, leisure facilities, and large commercial buildings.

Juniper® PRS

  • Stainless steel hot water
    plate heat exchanger
  • Designed to rapidly prepare DHW for medium and large-scale facilities
16 bar
Maximum
Operating Pressure

CoilMaster

  • Floor standing gas fired water heater/boiler
  • Efficiency of up to 108% net
  • Stainless steel heat exchanger
  • Up to 1830 L/h of DHW at 60°C
C
Energy
Class
10:1
Modulation Ratio
37-124 kW
Output
Range

Case Studies

FAQs
What is a commercial calorifier?
A commercial calorifier is an indirect hot water storage vessel that heats mains cold water using a primary heat source — typically a boiler or heat pump — via an internal coil or heat exchanger. The primary and secondary circuits remain separate throughout, so the stored domestic hot water never comes into direct contact with the heating circuit water. Calorifiers are used in hotels, schools, care homes, leisure centres, and apartment buildings where large volumes of hot water are required on demand.
What is the difference between a stainless steel and a Polywarm® calorifier?
Stainless steel calorifiers use a grade 316L stainless steel inner vessel, which provides excellent corrosion resistance and is particularly well suited to areas with aggressive water chemistry. Polywarm® calorifiers use a vitreous enamel-lined mild steel vessel with a sacrificial magnesium anode, offering a cost-effective alternative for standard water conditions. Modutherm's Juniper® SS and Juniper® PW ranges are available in both finishes from 500–3,000 litres, allowing specification to be matched to site conditions and budget.
What is a tank-in-tank calorifier?
A tank-in-tank calorifier stores domestic hot water inside an inner vessel that sits within an outer vessel containing the primary heating water. This arrangement maximises the heat transfer surface area, enabling rapid recovery and a high simultaneous draw-off rate. The Scimitar® is Modutherm's tank-in-tank calorifier, available in stainless steel from 200–500 litres, and is well suited to applications where high instantaneous hot water demand must be met from a compact vessel.
What is a heat pump calorifier and how does it differ from a standard calorifier?
A heat pump calorifier is specifically configured to work efficiently with heat pump primary circuits, which typically operate at lower flow temperatures than gas boiler systems. Standard calorifier coils are designed around higher primary temperatures and may not transfer heat effectively at the lower temperatures heat pumps produce. Modutherm's Juniper® PW XL and SS XL heat pump calorifiers feature enlarged coil surface areas optimised for low-temperature operation, and are available from 200–1,000 litres. The Juniper® PDC thermal exchange calorifier (300–800L) offers a further option for heat pump applications requiring enhanced performance.
What maintenance does a commercial calorifier require?
Commercial calorifiers should be inspected and serviced regularly in accordance with the manufacturer's recommendations and the relevant water hygiene regulations. Key maintenance tasks include inspection of the vessel interior for scale or corrosion, checking and replacing the sacrificial anode in Polywarm® models, verifying thermostat and temperature sensor accuracy, and carrying out Legionella risk management procedures including periodic thermal disinfection. The frequency of inspection will depend on local water conditions, system usage, and the requirements of the site's water safety plan.
What is a plate heat exchanger and when is it used instead of a storage calorifier?
A plate heat exchanger transfers heat between two fluid circuits across a series of corrugated metal plates, producing hot water instantaneously without the need for storage. This approach eliminates the risk of stored water becoming stagnant and reduces the space required in the plant room. The Juniper® PRS is Modutherm's stainless steel plate heat exchanger, suitable for applications where instantaneous hot water production is preferred and sufficient primary flow capacity is available to meet peak demand.

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