Grouped Renewables Limited

Phone +44 (0)1561 362227  Email

Buffers, Accumulators, Thermal Stores, Intermediate Vessels

High quality buffer vessels from copper, mild steel, stainless steel  and galvanised mild steel materials.

Our buffer vessels can be connected to many different types of systems ranging from air conditioning chillers, biomass boilers, heat pump boilers, solar thermal or a combination of these. Our vessels range from 10 litre all the way up to 10,000 litres meaning we can cater for any building from a small canal boat to a large office block, school or hospital

Bespoke service by availlable on reques

Buffer vessels as vented or pressurised as well as direct, indirect and twin coiled.

Various thermal insulation types to suit your specific requirements


buffer vessel
buffer vessel
buffer vessel
thermal store

Thermal store units designed to supply mains pressure hot water with high flow rates to all outlets whilst also providing excellent response to your heating demands.

The design gives the advantage of mains pressure hot water but with the safety of a traditional open vented storage system. The units are supplied in various sizes and complete with all the required components required making them simple and easy to install.

We can assist in the design of complex systems where multiple heat sources may be available, such as biomass, wood burners, heat pumps and solar thermal systems ensuring maximum efficiency is always achieved.

As with all our products we can manufacture to meet the requirements of your specification. Please contact us for more information.

  • Tel: +44(0)1561 362227 
  • E-mail:

Cylinders and Calorifiers

UK approved vented and unvented cylinders made in standard or non standard sizes to your specification. 

The cylinders are available in direct, indirect, combi direct and indirect including models for Economy 7High recovery and rapid recovery models are also available.

These may be manufactured in stainless steel or copper and may be insulated to your specification if the standard insulation does not meet your requirements.

vented cylinder
specioal cylinder
unvented cylinder
  • Tel: +44(0)1561 362227 
storage calorifier

Non storage (shell and tube) and storage  calorifiers 

Manufactured in copper, stainless steel or galvanised mild steel for both vented and unvented applications.

Our non storage calorifers, are designed to heat a fluid (usually water) instantaneously as it passes through the heat exchanger. The primary heat exchanger is usually a U-tube removable battery which allows the primary heating medium to pass along to the end of the exchanger and then back again producing maximum efficiency.

Heat exchangers are usually manufactured with a mild steel body and the primary exchangers are copper integron tubes expanded into a brass or steel plate. H

Storage calorifiers come with a range of inner heaters from basic plain tube coils,  integron (finned tube) removable batteries which can be maintained and replaced quickly and easily.  These inner heaters can be heated by steam, HTHW, MTHW or LTHW from primary heat sources such as steam, gas, biomass or oil boilers or even new innovative technologies such as air and ground source heat pumps. The option for the inclusion of additional heat sources such as solar panels is also available.

Storage calorifiers can be supplied with an inspection opening which is used to view and clean the inside of the vessels to prevent the growth of legionella bacteria, these are available in 3 sizes, 250mm,350mm and 450mm. Pre-plumbed de-statrification pump sets are also available which circulated the stored water to ensure there are no cold spots and prevents the water from stagnation which is again a safety feature to help prevent the growth of legionaires bacteria. Our insulation factory line can even pre-insulate the vessels before they leave us with 50mm Rockwool insulation clad with stucco aluminium, also available is spray foam insulation which is subject to size. Lagging jackets to BS5615 also available.

Intermediate vessels

Intermediate Vessel Drawing
Intermediate vessel features
Intermediate Vessel Standard Sizes