Today we take a look at commercial-grade indirect-fired water heaters, and ask is a calorifier the right choice for your hot water or heating system?
A calorifier is a commercial-grade indirect-fired water heater that provides hot water in a heating and hot water system.
It is designed for projects requiring large volume storage of water at high temperatures, but rather than using a burner, the water is heated by heat exchanger coils containing liquid from another heat source, such as a boiler.
In a typical application, the hot water directly heated by a gas or electric boiler passes through the calorifier and is used, via heat exchange, to heat up the cold water in a separate system of pipework. This does mean that a calorifier cannot react as quickly to demand as a direct-fired water heater, however, with the calorifier working as a buffer and storing the hot water, it reduces the operational demand placed on the boiler. With the boiler no longer required to work as hard to meet the domestic hot water needs (DHW) of a building, energy is saved, costs are reduced and emissions fall.
With the increased efficiency of modern condensing gas boilers, having a dedicated hot water boiler to heat the calorifier is no longer a requirement as they can easily supply heat to both the calorifier and the heating system. The compact Adveco MD range of gas condensing boilers, for example, are both high capacity and can be arranged in cascade to scale to provide both heating and, with an indirect calorifier, the DHW needs of a wide variety of commercial projects. It must be noted that when space heating is not required, such as during the summer months, the boiler will still be required to provide heat for the hot water system.
Another advantage of the indirect approach to heating is that due to the transferral of heat through the walls of the heat exchanger element the two fluids do not mix. This allows for more options in terms of the external heat supply and introduces a range of renewable technologies that use other fluids for heat transfer including solar thermal collectors and Air Source Heat Pumps. At Adveco, these options are supported by a variety of calorifiers. The Stainless Steel Indirect (SSI) range, for example, is supplied with a single high-output internal heat exchange coil at a low level to serve as an indirect calorifier in DHW installations. The ATSx range provides water heaters designed to be used with indirect heat sources as calorifiers across a range of DHW installations exhibiting smaller demands but requiring more than six bar pressure. For more complex and renewable-based systems, the Stainless Steel Twin-Coil (SST) or ATSR ranges offer a pair of independent internal heat exchange coils to serve DHW systems. Each high-output coil can be used with a separate heat source, enabling effective integration of renewable technologies or multiple heat sources, or alternatively can be combined to increase the heat transfer capacity from a single high-output source.
Also, by separating the supplies you reduce the risks of external contamination, a build-up of scale in hard water areas or the corrosive effects of soft water.
Calorifiers are also simple to install. Since there is no burner, there is no need for the gas supply to be directly connected to the appliance and the is no requirement for a flue.
So is a calorifier the right choice?
As with any hot water application, understanding the relationship between storage and recovery, and correct sizing is extremely important for efficient and cost-effective operation. Integrating a calorifier within a hot water system gives you a number of design options, as a larger calorifier means the boiler can be smaller, or the reverse if the existing system has a large efficient boiler. Understanding the hot water demand is critical. If demand is not so great, then using a larger calorifier can lead to unnecessary capital and ongoing operational expenditure. Go too small and the storage could prove inadequate and the system will not achieve its operational requirements.
Attaining the correct balance of demand and efficient, cost-effective supply is what ultimately defines a successful system, whether it be for a hotel, hospital, school, office or leisure facility. Each will have its own parameters to be met, and Adveco specialises in providing the widest range of calorifiers, boilers and renewables to meet the bespoke needs of any project.
The patterns of hot water usage and recognition of periods of peak demands often make sizing a complicated process, with many systems overcompensating and, by being oversized becoming more costly and less efficient. At its simplest, a commercial system should hold an hour of hot water output in storage, but the function of the building, its population and activities will adjust requirements, for example, where hospitals will typically exhibit a 24/7 demand for hot water, schools and offices may be limited to just 7½ hours per day. In some refurbishment scenarios, we will also see a physical limitation of space available for DHW storage, in which case a system will put more demand on the boiler or renewable to increase the output for preheating, reducing the required size of the calorifier.
If there is an availability of space, or a prefabricated packaged plant room approach can be used to relocate plant to previously unused space – such as a rooftop or car park – there is an opportunity to incorporate multiple calorifiers and thereby divide the total storage demand. This approach not only provides system resilience, but for commercial sites that exhibit predictable seasonal demands such as leisure centres, campsites and hotels, it allows for elements of the system to be shut down during off-peak periods. The other real advantage of adopting a packaged plant room approach to a DHW system is that the boiler or ASHP providing the preheat can be located in close association with the calorifier. The physical proximity helps negate problems of heat loss between the boiler, pipework and calorifier which can be detrimental if more widely separated in a system.